Outer part of the eye. The human eye as an optical system

Anatomy is the first science, without it there is nothing in medicine.

Old Russian handwritten medical book according to the list of the 17th century.

A doctor who is not an anatomist is not only useless, but also harmful.

E. O. Mukhin (1815)

The human visual analyzer belongs to the sensory systems of the body and, in anatomical and functional terms, consists of several interconnected, but different in purpose structural units (Fig. 3.1):

Two eyeballs located in the frontal plane in the right and left eye sockets, with their optical system allowing focusing on the retina (the actual receptor part of the analyzer) images of all environmental objects located within the area of ​​​​clear vision of each of them;

Systems for processing, encoding and transmitting perceived images through neural communication channels to the cortical section of the analyzer;

Accessory organs, similar for both eyeballs (eyelids, conjunctiva, lacrimal apparatus, extraocular muscles, orbital fascia);

Life support systems of the analyzer structures (blood supply, innervation, production of intraocular fluid, regulation of hydro- and hemodynamics).

3.1. Eyeball

The eye (bulbus oculi) of a person, approximately 2/3 located in

cavities of the eye sockets, has not quite correct spherical shape. In healthy newborns, its dimensions, determined by calculations, are (on average) 17 mm along the sagittal axis, 17 mm in the transverse axis, and 16.5 mm in the vertical axis. In adults with commensurate eye refraction, these figures are 24.4; 23.8 and 23.5 mm respectively. The weight of the eyeball of a newborn is up to 3 g, of an adult - up to 7-8 g.

Anatomical landmarks of the eye: the anterior pole corresponds to the apex of the cornea, the posterior pole corresponds to its opposite point on the sclera. The line connecting these poles is called the outer axis of the eyeball. The straight line mentally drawn to connect the posterior surface of the cornea with the retina in the projection of the indicated poles is called its internal (sagittal) axis. The limbus - the place of transition of the cornea into the sclera - is used as a reference point for the precise localization characteristics of the detected pathological focus in an hourly display (meridian indicator) and in linear values, which are an indicator of the distance from the point of intersection of the meridian with the limbus (Fig. 3.2).

In general, the macroscopic structure of the eye seems, at first glance, deceptively simple: two integumentary layers (conjunctiva and vagina

Rice. 3.1. The structure of the human visual analyzer (diagram).

eyeball) and three main membranes (fibrous, vascular, reticular), as well as the contents of its cavity in the form of the anterior and posterior chambers (filled with aqueous humor), the lens and the vitreous body. However, the histological structure of most tissues is quite complex.

The fine structure of the membranes and optical media of the eye is presented in the relevant sections of the textbook. This chapter makes it possible to see the structure of the eye as a whole, to understand

functional interaction of individual parts of the eye and its appendages, features of blood supply and innervation that explain the occurrence and course various types pathology.

3.1.1. Fibrous membrane of the eye

The fibrous membrane of the eye (tunica fibrosa bulbi) consists of the cornea and sclera, which, according to their anatomical structure and functional properties,

Rice. 3.2. The structure of the human eyeball.

stvam differ sharply from each other.

Cornea(cornea) - the anterior transparent part (~ 1/6) of the fibrous membrane. The place where it transitions into the sclera (limb) looks like a translucent ring up to 1 mm wide. Its presence is explained by the fact that the deep layers of the cornea extend posteriorly somewhat further than the anterior ones. Distinctive qualities of the cornea: spherical (radius of curvature of the anterior surface ~ 7.7 mm, posterior 6.8 mm), mirror-shiny, devoid of blood vessels, has high tactile and pain, but low temperature sensitivity, refracts light rays with a force of 40.0- 43.0 diopters

The horizontal diameter of the cornea in healthy newborns is 9.62 ± 0.1 mm, in adults it is

It measures 11 mm (the vertical diameter is usually ~1 mm less). In the center it is always thinner than at the periphery. This indicator correlates with age: for example, at 20-30 years old, the thickness of the cornea is 0.534 and 0.707 mm, respectively, and at 71-80 years old - 0.518 and 0.618 mm.

With closed eyelids, the temperature of the cornea at the limbus is 35.4 °C, and in the center - 35.1 °C (with open eyelids - 30 °C). In this regard, the growth of mold fungi with the development of specific keratitis is possible.

As for the nutrition of the cornea, it is carried out in two ways: due to diffusion from the perilimbal vascular network formed by the anterior ciliary arteries, and osmosis from the moisture of the anterior chamber and tear fluid (see Chapter 11).

Sclera(sclera) - the opaque part (5/6) of the outer (fibrous) membrane of the eyeball with a thickness of 0.3-1 mm. It is thinnest (0.3-0.5 mm) at the equator and at the point where the optic nerve exits the eye. Here, the inner layers of the sclera form the lamina cribrosa, through which the axons of the retinal ganglion cells pass, forming the disc and stem part of the optic nerve.

Areas of scleral thinning are vulnerable to the effects of increased intraocular pressure (development of staphylomas, excavation of the optic nerve head) and damaging factors, primarily mechanical (subconjunctival tears in typical places, usually in areas between the attachment sites of extraocular muscles). Near the cornea, the thickness of the sclera is 0.6-0.8 mm.

In the limbus region, three completely different structures merge - the cornea, sclera and conjunctiva of the eyeball. As a result, this zone can be the starting point for the development of polymorphic pathological processes - from inflammatory and allergic to tumor (papilloma, melanoma) and associated with developmental anomalies (dermoid). The limbal zone is richly vascularized due to the anterior ciliary arteries (branches of the muscular arteries), which at a distance of 2-3 mm from it give off branches not only into the eye, but also in three more directions: directly to the limbus (forming the marginal vascular network), episclera and adjacent conjunctiva. Along the circumference of the limbus there is a thick nerve plexus, formed by long and short ciliary nerves. Branches extend from it, which then enter the cornea.

The scleral tissue has few vessels, it is almost devoid of sensory nerve endings and is prone to

to the development of pathological processes characteristic of collagenosis.

Six extraocular muscles are attached to the surface of the sclera. In addition, it has special channels (graduates, emissaries). Along some of them, arteries and nerves pass to the choroid, and along others, venous trunks of various calibers exit.

On the inner surface of the anterior edge of the sclera there is a circular groove up to 0.75 mm wide. Its posterior edge protrudes somewhat anteriorly in the form of a spur, to which the ciliary body is attached (the anterior ring of attachment of the choroid). The anterior edge of the groove borders the Descemet's membrane of the cornea. At its bottom, at the posterior edge, there is the venous sinus of the sclera (Schlemm’s canal). The rest of the scleral recess is occupied by the trabecular meshwork (reticulum trabeculare) (see Chapter 10).

3.1.2. Choroid of the eye

The choroid of the eye (tunica vasculosa bulbi) consists of three closely interconnected parts - the iris, the ciliary body and the choroid.

Iris(iris) - the anterior part of the choroid and, unlike its other two sections, is not located parietally, but in the frontal plane relative to the limbus; has the shape of a disk with a hole (pupil) in the center (see Fig. 14.1).

Along the edge of the pupil there is a ring-shaped sphincter, which is innervated by the oculomotor nerve. The radially oriented dilator is innervated by the sympathetic nerve.

Iris thickness 0.2-0.4 mm; it is especially thin in the root zone, i.e. at the border with the ciliary body. It is here that, with severe contusions of the eyeball, its separation (iridodialys) can occur.

Ciliary (ciliary) body(corpus ciliare) - the middle part of the choroid - is located behind the iris, therefore inaccessible to direct inspection. The ciliary body is projected onto the surface of the sclera in the form of a belt 6-7 mm wide, starting at the scleral spur, i.e., at a distance of 2 mm from the limbus. Macroscopically, two parts can be distinguished in this ring - flat (orbiculus ciliaris) 4 mm wide, which borders on the dentate line (ora serrata) of the retina, and ciliary (corona ciliaris) 2-3 mm wide with 70-80 whitish ciliary processes (processus ciliares ). Each part looks like a roller or plate about 0.8 mm high, up to 2 mm wide and long.

The inner surface of the ciliary body is connected to the lens through the so-called ciliary girdle (zonula ciliaris), consisting of many very thin glassy fibers (fibrae zonulares). This belt acts as a ligament that suspends the lens. It connects the ciliary muscle with the lens into a single accommodative apparatus of the eye.

The vascular network of the ciliary body is formed by two long posterior ciliary arteries (branches of the ophthalmic artery), which pass through the sclera at the posterior pole of the eye, and then run in the suprachoroidal space along the 3 and 9 o'clock meridian; anastomose with the branches of the anterior and posterior short ciliary arteries. Sensitive innervation of the ciliary body is the same as that of the iris, motor innervation (for different portions of the accommodative muscle) - from the oculomotor nerve.

Choroid(chorioidea), or the choroid proper, lines the entire posterior section sclera along the length from the dentate line to the optic nerve, is formed by the posterior short ciliary arteries

ria (6-12), which pass through the sclera at the posterior pole of the eye.

The choroid has a number of anatomical features:

It is devoid of sensitive nerve endings, so the pathological processes developing in it do not cause pain;

Its vascular network does not anastomose with the anterior ciliary arteries; as a result, with choroiditis, the anterior part of the eye remains intact;

An extensive vascular bed with a small number of drainage vessels (4 vorticose veins) helps slow blood flow and allow pathogens of various diseases to settle here;

Organically connected with the retina, which in diseases of the choroid, as a rule, is also involved in the pathological process;

Due to the presence of the perichoroidal space, it is quite easily exfoliated from the sclera. It is maintained in its normal position mainly due to the draining venous vessels that perforate it in the equator region. Vessels and nerves penetrating the choroid from the same space also play a stabilizing role (see section 14.2).

3.1.3. Inner (sensitive) layer of the eye

The inner lining of the eye is retina(retina) - lines the entire surface of the choroid from the inside. In accordance with the structure, and therefore the function, two parts are distinguished in it - the optical (pars optica retinae) and the ciliary-iris (pars ciliaris et iridica retinae). The first is a highly differentiated nervous tissue with photoreceptors that perceive

providing adequate light rays with a wavelength from 380 to 770 nm. This part of the retina extends from the optic disc to the pars plana of the ciliary body, where it ends in the dentate line. Further, in a form reduced to two epithelial layers, having lost its optical properties, it covers the inner surface of the ciliary body and iris. Retinal thickness different areas unequal: at the edge of the optic nerve head 0.4-0.5 mm, in the area of ​​the foveola macular spot 0.07-0.08 mm, at the jagged line 0.14 mm. The retina is firmly attached to the underlying choroid only in a few areas: along the dentate line, around the optic disc and along the edge of the macula. In other areas, the connection is loose, so it is here that it easily peels off from its pigment epithelium.

Almost throughout, the optical part of the retina consists of 10 layers (see Fig. 15.1). Its photoreceptors facing the pigment epithelium are represented by cones (about 7 million) and rods (100-120 million). The former are grouped in the central sections of the shell, the latter are absent in the center, and their maximum density is noted 10-13 o from it. Further to the periphery, the number of rods gradually decreases. The main elements of the retina are in a stable position thanks to the vertically located supporting Müller cells and interstitial tissue. The retinal limiting membranes (membrana limitans interna et externa) also perform a stabilizing function.

Anatomically and with ophthalmoscopy, two functionally very important areas are clearly identified in the retina - the optic disc and the macula, the center of which is located at a distance of 3.5 mm from the temporal edge of the disc. As we approach the yellow spot

the structure of the retina changes significantly: first, the layer of nerve fibers disappears, then the ganglion cells, then the inner plexiform layer, the layer of internal nuclei and the outer plexiform layer. The foveola of the macula is represented only by a layer of cones, and therefore has the highest resolution (the area of ​​central vision, occupying ~1.2° in object space).

Photoreceptor parameters. Rods: length 0.06 mm, diameter 2 microns. The outer segments contain a pigment - rhodopsin, which absorbs part of the spectrum of electromagnetic light radiation in the range of green rays (maximum 510 nm).

Cones: length 0.035 mm, diameter 6 µm. Three different types of cones (red, green and blue) contain visual pigment with different light absorption rates. In red cones, it (iodopsin) adsorbs spectral rays with a wavelength of -565 nm, in green cones - 500 nm, in blue - 450 nm.

The pigments of cones and rods are “built-in” into the membranes - discs of their outer segments and are integral protein substances.

Rods and cones have different light sensitivity. The first ones operate at brightness environment up to 1kd? m -2 (night, scotopic vision), the second - over 10 cd? m -2 (daytime, photopic vision). When brightness ranges from 1 to 10 cd?m -2, all photoreceptors function at a certain level (twilight, mesopic vision) 1.

The optic disc is located in the nasal half of the retina (at a distance of 4 mm from the posterior pole

1 Candela (cd) is a unit of luminous intensity equivalent to the brightness of a completely black body at the solidification temperature of platinum (60 cd per 1 cm2).

eyes). It lacks photoreceptors, so there is a blind spot in the field of view corresponding to the location of its projection.

The retina receives nutrition from two sources: the six inner layers receive it from the central retinal artery (a branch of the ophthalmic branch), and the neuroepithelium - from the choriocapillaris layer of the choroid proper.

The branches of the central arteries and veins of the retina pass in the layer of nerve fibers and partly in the layer of ganglion cells. They form a layered capillary network, which is absent only in the foveola of the macula (see Fig. 3.10).

An important anatomical feature of the retina is that the axons of its ganglion cells throughout their entire length are devoid of myelin sheath (one of the factors determining the transparency of the tissue). In addition, it, like the choroid, is devoid of sensory nerve endings (see Chapter 15).

3.1.4. Inner nucleus (cavity) of the eye

The cavity of the eye contains light-conducting and light-refracting media: aqueous humor that fills its anterior and posterior chambers, the lens and the vitreous body.

Anterior chamber of the eye(camera anterior bulbi) is a space limited by the posterior surface of the cornea, the anterior surface of the iris and the central part of the anterior capsule of the lens. The place where the cornea meets the sclera and the iris meets the ciliary body is called the anterior chamber angle (angulus iridocornealis). In its outer wall there is a drainage system (for aqueous humor) of the eye, consisting of a trabecular meshwork, scleral venous sinus (Schlemm's canal) and collector tubules (graduates). Through

The pupil of the anterior chamber communicates freely with the posterior one. In this place it has the greatest depth (2.75-3.5 mm), which then gradually decreases towards the periphery (see Fig. 3.2).

Posterior chamber of the eye(camera bulbi) is located behind the iris, which is its anterior wall, and is limited externally by the ciliary body and posteriorly by the vitreous body. The inner wall is formed by the equator of the lens. The entire space of the posterior chamber is penetrated by ligaments of the ciliary girdle.

Normally, both chambers of the eye are filled with aqueous humor, which in its composition resembles blood plasma dialysate. Aqueous humor contains nutrients, in particular glucose, ascorbic acid and oxygen consumed by the lens and cornea, and removes waste metabolic products from the eye - lactic acid, carbon dioxide, exfoliated pigment and other cells.

Both chambers of the eye contain 1.23-1.32 cm 3 of fluid, which is 4% of the total contents of the eye. The minute volume of chamber moisture is on average 2 mm 3, the daily volume is 2.9 cm 3. In other words, complete exchange of chamber moisture occurs within

10 o'clock

There is an equilibrium between the inflow and outflow of intraocular fluid. If for any reason it is violated, this leads to a change in the level of intraocular pressure, the upper limit of which normally does not exceed 27 mm Hg. Art. (when measured with a Maklakov tonometer weighing 10 g).

The main driving force that ensures the continuous flow of fluid from the posterior chamber to the anterior chamber, and then through the angle of the anterior chamber outside the eye, is the pressure difference in the eye cavity and the venous sinus of the sclera (about 10 mm Hg), as well as in the said sinus and anterior ciliary veins.

Lens(lens) is a transparent semi-solid avascular body in the form of a biconvex lens, enclosed in a transparent capsule, with a diameter of 9-10 mm and a thickness (depending on accommodation) of 3.6-5 mm. The radius of curvature of its anterior surface at rest of accommodation is 10 mm, the posterior surface is 6 mm (with a maximum accommodation voltage of 5.33 and 5.33 mm, respectively), therefore, in the first case, the refractive power of the lens averages 19.11 diopters, in the second - 33.06 diopters. In newborns, the lens is almost spherical, has a soft consistency and a refractive power of up to 35.0 diopters.

In the eye, the lens is located immediately behind the iris in a depression on the anterior surface of the vitreous body - in the vitreous fossa (fossa hyaloidea). In this position it is held by numerous glassy fibers, which together form the suspensory ligament (ciliary band) (see Fig.

12.1).

The posterior surface of the lens, like the anterior one, is washed by aqueous humor, since it is separated from the vitreous body almost along its entire length by a narrow gap (retrolental space - spatium retrolentale). However, along the outer edge of the vitreous fossa, this space is limited by the delicate annular ligament of Wieger, located between the lens and the vitreous body. The lens is nourished through exchange processes with chamber moisture.

Vitreous chamber of the eye(camera vitrea bulbi) occupies the posterior part of its cavity and is filled with the vitreous body (corpus vitreum), which is adjacent to the lens in front, forming a small depression in this place (fossa hyaloidea), and throughout the rest of its length it is in contact with the retina. Vitreous

the body is a transparent gelatinous mass (gel-type) with a volume of 3.5-4 ml and a weight of approximately 4 g. It contains large quantities hyaluronic acid and water (up to 98%). However, only 10% of water is associated with the components of the vitreous body, so fluid exchange in it occurs quite actively and, according to some data, reaches 250 ml per day.

Macroscopically, the vitreous stroma itself (stroma vitreum), which is penetrated by the vitreous (clockets) canal, and the hyaloid membrane surrounding it from the outside are isolated (Fig. 3.3).

The vitreous stroma consists of a fairly loose central substance, in which there are optically empty zones filled with liquid (humor vitreus) and collagen fibrils. The latter, becoming denser, form several vitreal tracts and a denser cortical layer.

The hyaloid membrane consists of two parts - anterior and posterior. The border between them runs along the dentate line of the retina. In turn, the anterior limiting membrane has two anatomically separate parts - lenticular and zonular. The boundary between them is the circular hyaloidocapsular ligament of Wieger, which is strong only in childhood.

The vitreous body is tightly connected to the retina only in the region of its so-called anterior and posterior bases. The first refers to the area where the vitreous body is simultaneously attached to the epithelium of the ciliary body at a distance of 1-2 mm anterior to the serrated edge (ora serrata) of the retina and 2-3 mm posterior to it. The posterior base of the vitreous body is the zone of its fixation around the optic nerve head. It is believed that the vitreous body also has a connection with the retina in the area of ​​the macula.

Rice. 3.3. Vitreous body of the human eye (sagittal section) [according to N. S. Jaffe, 1969].

The vitreous canal (canalis hyaloideus) of the vitreous body begins as a funnel-shaped expansion from the edges of the optic nerve head and passes through its stroma towards the posterior capsule of the lens. The maximum channel width is 1-2 mm. In the embryonic period, the vitreous artery passes through it, which is empty by the time the child is born.

As already noted, there is a constant flow of fluid in the vitreous body. From the posterior chamber of the eye, the fluid produced by the ciliary body enters the anterior part of the vitreous through the zonular fissure. Next, the fluid that has entered the vitreous body moves to the retina and the prepapillary opening in the hyaloid membrane and flows out of the eye both through the structures of the optic nerve and along the perivascular processes.

wanderings of the retinal vessels (see Chapter 13).

3.1.5. Visual pathway and pupillary reflex pathway

The anatomical structure of the visual pathway is quite complex and includes a number of neural links. Within the retina of each eye there is a layer of rods and cones (photoreceptors - I neuron), then a layer of bipolar (II neuron) and ganglion cells with their long axons (III neuron). Together they form the peripheral part of the visual analyzer. The pathways are represented by the optic nerves, chiasm and optic tracts. The latter end in the cells of the external geniculate body, which plays the role of the primary visual center. From them originate the fibers of the central

Rice. 3.4. Visual and pupillary pathways (diagram) [according to C. Behr, 1931, with modifications].

Explanation in the text.

neurons of the visual pathway (radiatio optica), which reach the area striata of the occipital lobe of the brain. The primary core is localized here.

tic center of the visual analyzer (Fig. 3.4).

Optic nerve(n. opticus) formed by axons of ganglion cells

retina and ends in the chiasm. In adults, its total length varies from 35 to 55 mm. A significant part of the nerve is the orbital segment (25-30 mm), which in the horizontal plane has an S-shaped bend, due to which it does not experience tension during movements of the eyeball.

Over a considerable distance (from the exit from the eyeball to the entrance to the optic canal - canalis opticus), the nerve, like the brain, has three membranes: hard, arachnoid and soft (see Fig. 3.9). Together with them, its thickness is 4-4.5 mm, without them - 3-3.5 mm. At the eyeball, the dura mater fuses with the sclera and Tenon's capsule, and at the optic canal, with the periosteum. The intracranial segment of the nerve and the chiasm, located in the subarachnoid chiasmatic cistern, are dressed only in a soft shell.

The intrathecal spaces of the orbital part of the nerve (subdural and subarachnoid) are connected to similar spaces in the brain, but are isolated from each other. They are filled with fluid of complex composition (intraocular, tissue, cerebrospinal). Because the intraocular pressure normally 2 times higher than intracranial (10-12 mm Hg), the direction of its current coincides with the pressure gradient. The exception is cases when the intracranial pressure(for example, with the development of a brain tumor, hemorrhages in the cranial cavity) or, conversely, the tone of the eye is significantly reduced.

All nerve fibers that make up the optic nerve are grouped into three main bundles. The axons of ganglion cells extending from the central (macular) region of the retina constitute the papillomacular fascicle, which enters the temporal half of the optic nerve head. Fibers from ganglionic

The cells of the nasal half of the retina run along radial lines into the nasal half of the disc. Similar fibers, but from the temporal half of the retina, on the way to the optic nerve head “flow around” the papillomacular bundle from above and below.

In the orbital segment of the optic nerve near the eyeball, the relationships between nerve fibers remain the same as in its disk. Next, the papillomacular bundle moves to the axial position, and the fibers from the temporal quadrants of the retina move to the entire corresponding half of the optic nerve. Thus, the optic nerve is clearly divided into right and left halves. Less pronounced is its division into upper and lower half. An important clinical feature is that the nerve is devoid of sensory nerve endings.

In the cranial cavity, the optic nerves connect above the area of ​​the sella turcica, forming a chiasma (chiasma opticum), which is covered with the pia mater and has the following dimensions: length 4-10 mm, width 9-11 mm, thickness 5 mm. The chiasma borders below with the diaphragm of the sella turcica (the preserved portion of the dura mater), above (in the posterior section) with the bottom of the third ventricle of the brain, on the sides with the internal carotid arteries, and behind with the pituitary infundibulum.

In the area of ​​the chiasm, the fibers of the optic nerves partially intersect due to portions associated with the nasal halves of the retinas. Moving to the opposite side, they connect with fibers coming from the temporal halves of the retinas of the other eye and form the visual tracts. The papillomacular bundles also partially intersect here.

The visual tracts (tractus opticus) begin at the posterior surface of the chiasm and, going around from the outside

sides of the cerebral peduncle, ending in the external geniculate body (corpus geniculatum laterale), the posterior part of the visual thalamus (thalamus opticus) and the anterior quadrigeminum (corpus quadrigeminum anterius) of the corresponding side. However, only the external geniculate bodies are an unconditional subcortical visual center. The remaining two entities perform other functions.

In the optic tracts, the length of which in an adult reaches 30-40 mm, the papillomacular bundle also occupies a central position, and crossed and uncrossed fibers still run in separate bundles. Moreover, the first of them are located ventromedially, and the second - dorsolaterally.

The optic radiation (central neuron fibers) originates from the ganglion cells of the fifth and sixth layers of the lateral geniculate body. First, the axons of these cells form the so-called Wernicke's field, and then, passing through the posterior thigh of the internal capsule, they fan out in the white matter of the occipital lobe of the brain. The central neuron ends in the sulcus of the bird's spur (sulcus calcarinus). This area represents the sensory visual center - cortical area 17 according to Brodmann.

The path of the pupillary reflex - light and for placing the eyes at a close distance - is quite complex (see Fig. 3.4). The afferent part of the reflex arc (a) of the first of them starts from the cones and rods of the retina in the form of autonomous fibers running as part of the optic nerve. In the chiasm they intersect in the same way as the optic fibers and pass into the optic tracts. In front of the external geniculate bodies, the pupillomotor fibers leave them and, after partial decussation, continue into the brachium quadrigeminum, where

end at the cells (b) of the so-called pretectal area (area pretectalis). Next, new interstitial neurons, after partial decussation, are sent to the corresponding nuclei (Yakubovich - Edinger - Westphal) of the oculomotor nerve (c). Afferent fibers from the macula of the retina of each eye are represented in both oculomotor nuclei (d).

The efferent pathway of innervation of the iris sphincter begins from the already mentioned nuclei and runs as a separate bundle as part of the oculomotor nerve (n. oculomotorius) (e). In the orbit, the sphincter fibers enter its lower branch, and then through the oculomotor root (radix oculomotoria) into the ciliary ganglion (e). Here the first neuron of the path under consideration ends and the second begins. Upon leaving the ciliary ganglion, the sphincter fibers as part of the short ciliary nerves (nn. ciliares breves), passing through the sclera, enter the perichoroidal space, where they form a nerve plexus (g). Its terminal branches penetrate the iris and enter the muscle in separate radial bundles, i.e., innervate it sectorally. In total, there are 70-80 such segments in the sphincter of the pupil.

The efferent pathway of the pupillary dilator (m. dilatator pupillae), which receives sympathetic innervation, begins from the ciliospinal center of Budge. The latter is located in the anterior horns of the spinal cord (h) between C VII and Th II. From here connective branches depart, which through the borderline trunk of the sympathetic nerve (l), and then the lower and middle sympathetic cervical ganglia (t 1 and t 2) reach the superior ganglion (t 3) (level C II - C IV). Here the first neuron of the pathway ends and the second, which is part of the plexus of the internal carotid artery (m), begins. In the cranial cavity, fibers innervating the dilatation

torus of the pupil, exit from the mentioned plexus, enter the trigeminal (Gasserian) node (gangl. trigeminal), and then leave it as part of the optic nerve (n. ophthalmicus). Already at the apex of the orbit, they pass into the nasociliary nerve (n. nasociliaris) and then, together with the long ciliary nerves (nn. ciliares longi), penetrate the eyeball 1.

Regulation of the function of the pupillary dilator occurs with the help of the supranuclear hypothalamic center, located at the level of the bottom of the third ventricle of the brain in front of the pituitary infundibulum. Through the reticular formation it is connected with the ciliospinal center of Budge.

The reaction of the pupils to convergence and accommodation has its own characteristics, and the reflex arcs in this case differ from those described above.

During convergence, the stimulus for pupil constriction is proprioceptive impulses coming from the contracting internal rectus muscles of the eye. Accommodation is stimulated by the blurriness (defocusing) of images of external objects on the retina. The efferent part of the arc of the pupillary reflex is the same in both cases.

The center for setting the eye to close distance is believed to be in Brodmann's cortical area 18.

3.2. The eye socket and its contents

The orbita is the bony container for the eyeball. Through its cavity, the posterior (retrobulbar) section of which is filled with the fatty body (corpus adiposum orbitae), pass the optic nerve, motor and sensory nerves, oculomotor muscles.

1 In addition, the central sympathetic pathway(s) departs from the Budge center, ending in the occipital cortex of the brain. From here begins the corticonuclear pathway of inhibition of the sphincter of the pupil.

tsy, muscle that lifts the upper eyelid, fascial formations, blood vessels. Each eye socket has the shape of a truncated tetrahedral pyramid, with its apex facing the skull at an angle of 45 o to the sagittal plane. In an adult, the depth of the orbit is 4-5 cm, the horizontal diameter at the entrance (aditus orbitae) is about 4 cm, and the vertical diameter is 3.5 cm (Fig. 3.5). Three of the four walls of the orbit (except the outer one) border the paranasal sinuses. This neighborhood often serves as the initial cause of the development of certain pathological processes in it, often of an inflammatory nature. It is also possible for tumors to grow from the ethmoid, frontal and maxillary sinuses (see Chapter 19).

The outer, most durable and least vulnerable to diseases and injuries, the wall of the orbit is formed by the zygomatic, partly the frontal bone and the greater wing of the sphenoid bone. This wall separates the contents of the orbit from the temporal fossa.

The upper wall of the orbit is formed mainly by the frontal bone, in the thickness of which, as a rule, there is a sinus (sinus frontalis), and partly (in the posterior section) by the small wing of the sphenoid bone; borders on the anterior cranial fossa, and this circumstance determines the severity possible complications if it is damaged. On the inner surface of the orbital part of the frontal bone, at its lower edge, there is a small bony protrusion (spina trochlearis), to which a tendon loop is attached. The tendon of the superior oblique muscle passes through it, which then abruptly changes the direction of its course. In the upper outer part of the frontal bone there is a fossa for the lacrimal gland (fossa glandulae lacrimalis).

The inner wall of the orbit is formed over a large area by a very thin bone plate - lam. orbitalis (rarugacea) re-

Rice. 3.5. Eye socket (right).

ethmoid bone. In front it is adjacent to the lacrimal bone with the posterior lacrimal crest and the frontal process upper jaw with the anterior lacrimal crest, behind - the body of the sphenoid bone, above - part of the frontal bone, and below - part of the upper jaw and palatine bone. Between the crests of the lacrimal bone and the frontal process of the upper jaw there is a depression - the lacrimal fossa (fossa sacci lacrimalis) measuring 7 x 13 mm, in which the lacrimal sac (saccus lacrimalis) is located. Below this fossa passes into the nasolacrimal canal (canalis nasolacrimalis), located in the wall of the maxillary bone. It contains the nasolacrimal duct (ductus nasolacrimalis), which ends at a distance of 1.5-2 cm posterior to the anterior edge of the inferior turbinate. Due to its fragility, the medial wall of the orbit is easily damaged even with blunt trauma with the development of emphysema of the eyelids (more often) and the orbit itself (less often). In addition, patho-

logical processes arising in the ethmoid sinus spread quite freely towards the orbit, resulting in the development of inflammatory swelling of its soft tissues (cellulitis), phlegmon or optic neuritis.

The lower wall of the orbit is also the upper wall of the maxillary sinus. This wall is formed mainly by the orbital surface of the upper jaw, partly also zygomatic bone and the orbital process of the palatine bone. In case of injury, fractures of the lower wall are possible, which are sometimes accompanied by drooping of the eyeball and limitation of its upward and outward mobility when the inferior oblique muscle is pinched. The lower wall of the orbit begins from the bone wall, slightly lateral to the entrance to the nasolacrimal canal. Inflammatory and tumor processes, developing in maxillary sinus, spread quite easily towards the orbit.

At the apex, in the walls of the orbit, there are several holes and slits through which a number of large nerves and blood vessels pass into its cavity.

1. Bony canal of the optic nerve (canalis opticus) 5-6 mm long. It begins in the orbit with a round hole (foramen opticum) with a diameter of about 4 mm, connecting its cavity with the middle cranial fossa. Through this canal, the optic nerve (n. opticus) and the ophthalmic artery (a. ophthalmica) enter the orbit.

2. Superior orbital fissure (fissura orbitalis superior). Formed by the body of the sphenoid bone and its wings, it connects the orbit with the middle cranial fossa. Covered with a thin connective tissue film, through which three main branches of the optic nerve pass into the orbit (n. ophthalmicus 1 - lacrimal, nasociliary and frontal nerves (nn. lacrimalis, nasociliaris et frontalis), as well as the trunks of the trochlear, abducens and oculomotor nerves (nn. trochlearis, abducens and oculomotorius). Through the same gap, the superior ophthalmic vein (v. ophthalmica superior) leaves it. With damage to this area, a characteristic symptom complex develops: complete ophthalmoplegia, i.e. immobility of the eyeball, drooping (ptosis) of the upper eyelid, mydriasis, decreased tactile sensitivity of the cornea and skin of the eyelids, dilatation of the retinal veins and slight exophthalmos.However, the “superior orbital fissure syndrome” may not be fully expressed when not all, but only individual nerve trunks passing through this fissure are damaged.

3. Lower orbital fissure (fissura orbitalis inferior). Formed by the lower edge of the greater wing of the sphenoid bone and the body of the upper jaw, it provides communication

1 First branch trigeminal nerve(n. trigeminus).

orbits with pterygopalatine (in the posterior half) and temporal fossae. This gap is also closed by a connective tissue membrane into which the fibers of the orbital muscle (m. orbitalis), innervated by the sympathetic nerve, are woven. Through it, one of the two branches of the inferior ophthalmic vein leaves the orbit (the other flows into the superior ophthalmic vein), which then anastomoses with the pterygoid venous plexus (et plexus venosus pterygoideus), and the infraorbital nerve and artery (n. a. infraorbital), zygomatic nerve (n. zygomaticus) enter ) and orbital branches of the pterygopalatine ganglion (ganglion pterygopalatinum).

4. The round hole (foramen rotundum) is located in the large wing of the sphenoid bone. It connects the middle cranial fossa with the pterygopalatine fossa. The second branch of the trigeminal nerve (n. maxillaris) passes through this hole, from which the infraorbital nerve (n. infraorbitalis) departs in the pterygopalatine fossa, and the zygomatic nerve (n. zygomaticus) in the inferotemporal fossa. Both nerves then enter the orbital cavity (the first is subperiosteal) through the inferior orbital fissure.

5. Lattice openings on the medial wall of the orbit (foramen ethmoidale anterius et posterius), through which the nerves of the same name (branches of the nasociliary nerve), arteries and veins pass.

In addition, in the large wing of the sphenoid bone there is another hole - oval (foramen ovale), connecting the middle cranial fossa with the infratemporal fossa. The third branch of the trigeminal nerve (n. mandibularis) passes through it, but it does not take part in the innervation of the organ of vision.

Behind the eyeball, at a distance of 18-20 mm from its posterior pole, there is a ciliary node (ganglion ciliare) measuring 2x1 mm. It is located under the external rectus muscle, adjacent in this area to the

superiority of the optic nerve. The ciliary ganglion is a peripheral nerve ganglion, the cells of which are connected to the fibers of the corresponding nerves through three roots (radix nasociliaris, oculomotoria et sympathicus).

The bone walls of the orbit are covered with a thin but strong periosteum (periorbita), which is tightly fused with them in the area of ​​​​the bone sutures and the optic canal. The opening of the latter is surrounded by a tendon ring (annulus tendineus communis Zinni), from which all oculomotor muscles begin, with the exception of the inferior oblique. It originates from the lower bony wall of the orbit, near the inlet of the nasolacrimal canal.

In addition to the periosteum, the orbital fascia, according to the International Anatomical Nomenclature, includes the eyeball sheath, muscular fascia, orbital septum and orbital fat body (corpus adiposum orbitae).

The vagina of the eyeball (vagina bulbi, former name - fascia bulbi s. Tenoni) covers almost the entire eyeball, with the exception of the cornea and the place where the optic nerve exits it. The greatest density and thickness of this fascia are observed in the area of ​​the equator of the eye, where the tendons of the extraocular muscles pass through it on the way to the places of attachment to the surface of the sclera. As the limbus approaches, the vaginal tissue becomes thinner and is eventually gradually lost into the subconjunctival tissue. In places where the extraocular muscles are cut through, it gives them a fairly dense connective tissue coating. Dense cords (fasciae musculares) also extend from this same zone, connecting the vagina of the eye with the periosteum of the walls and edges of the orbit. In general, these cords form a ring-shaped membrane, which is parallel to the equator of the eye

and holds it in the eye socket in a stable position.

The subvaginal space of the eye (formerly called spatium tenoni) is a system of slits in the loose episcleral tissue. It ensures free movement of the eyeball to a certain extent. This space is often used for surgical and therapeutic purposes (performing implant-type sclero-strengthening operations, introducing medicines by injection).

The orbital septum (septum orbitale) is a well-defined fascial-type structure located in the frontal plane. Connects the orbital edges of the cartilage of the eyelids with the bony edges of the orbit. Together they form, as it were, its fifth, movable wall, which, when the eyelids are closed, completely isolates the cavity of the orbit. It is important to keep in mind that in the area of ​​the medial wall of the orbit, this septum, which is also called the tarso-orbital fascia, is attached to the posterior lacrimal crest of the lacrimal bone, as a result of which the lacrimal sac, which lies closer to the surface, is partially located in the preseptal space, i.e., outside the cavity eye sockets.

The cavity of the orbit is filled with a fatty body (corpus adiposum orbitae), which is enclosed in a thin aponeurosis and penetrated by connective tissue bridges dividing it into small segments. Due to its plasticity, adipose tissue does not interfere with the free movement of the extraocular muscles passing through it (during their contraction) and the optic nerve (during movements of the eyeball). The fat body is separated from the periosteum by a slit-like space.

Various blood vessels, motor, sensory and sympathetic, pass through the orbit in the direction from its apex to the entrance.

tic nerves, which has already been partially mentioned above, and is described in detail in the corresponding section of this chapter. The same applies to the optic nerve.

3.3. Accessory organs of the eye

The auxiliary organs of the eye (organa oculi accesoria) include the eyelids, conjunctiva, muscles of the eyeball, lacrimal apparatus and the fascia of the orbit already described above.

3.3.1. Eyelids

The eyelids (palpebrae), upper and lower, are mobile structural formations that cover the eyeballs in front (Fig. 3.6). Thanks to blinking movements, they contribute to the uniform distribution of tear fluid over their surface. The upper and lower eyelids at the medial and lateral corners are connected to each other by means of adhesions (comissura palpebralis medialis et lateralis). Approximately for

Rice. 3.6. Eyelids and anterior segment of the eyeball (sagittal section).

5 mm before merging, the inner edges of the eyelids change the direction of their course and form an arched bend. The space outlined by them is called the lake of tears (lacus lacrimalis). There is also a small pinkish-colored elevation - the lacrimal caruncle (caruncula lacrimalis) and the adjacent semilunar fold of the conjunctiva (plica semilunaris conjunctivae).

When the eyelids are open, their edges are limited by an almond-shaped space called the palpebral fissure (rima palpebrarum). Its horizontal length is 30 mm (in an adult), and its height in the central section ranges from 10 to 14 mm. Within the palpebral fissure, almost the entire cornea is visible, with the exception of the upper segment, and the areas of the sclera bordering it white. When the eyelids are closed, the palpebral fissure disappears.

Each eyelid consists of two plates: the outer (musculocutaneous) and the inner (tarsal-conjunctival).

The skin of the eyelids is delicate, easily folds and is equipped with sebaceous and sweat glands. The underlying tissue is devoid of fat and very loose, which contributes to the rapid spread of edema and hemorrhage in this area. Usually, two orbital-palpebral folds are clearly visible on the skin surface - upper and lower. As a rule, they coincide with the corresponding edges of the cartilages.

The cartilages of the eyelids (tarsus superior et inferior) look like horizontal plates slightly convex outward with rounded edges, about 20 mm long, 10-12 and 5-6 mm high, respectively, and 1 mm thick. They consist of very dense connective tissue. With the help of powerful ligaments (lig. palpebrale mediate et laterale), the ends of the cartilages are connected to the corresponding walls of the orbit. In turn, the orbital edges of the cartilages are firmly connected

connected to the edges of the orbit through fascial tissue (septum orbitale).

In the thickness of the cartilage there are elongated alveolar meibomian glands (glandulae tarsales) - about 25 in the upper cartilage and 20 in the lower. They run in parallel rows and open into excretory ducts near the posterior edge of the eyelids. These glands produce a lipid secretion that forms the outer layer of the precorneal tear film.

The back surface of the eyelids is covered with a connective membrane (conjunctiva), which is tightly fused with cartilage, and beyond them forms mobile vaults - a deep upper one and a shallower lower one, easily accessible for inspection.

The free edges of the eyelids are limited by the anterior and posterior ridges (limbi palpebrales anteriores et posteriores), between which there is a space about 2 mm wide. The anterior ridges contain the roots of numerous eyelashes (located in 2-3 rows), into the hair follicles of which the sebaceous (Zeiss) and modified sweat (Moll) glands open. On the posterior ridges of the lower and upper eyelids, in their medial part, there are small elevations - lacrimal papillae (papilli lacrimales). They are immersed in the lacrimal lake and are equipped with pinholes (punctum lacrimale) leading to the corresponding lacrimal canaliculi (canaliculi lacrimales).

The mobility of the eyelids is ensured by the action of two antagonistic groups of muscles - closing and opening them. The first function is realized with the help of the circular muscle of the eye (m. orbicularis oculi), the second - the muscle that lifts the upper eyelid (m. levator palpebrae superioris) and the lower tarsal muscle (m. tarsalis inferior).

The orbicularis oculi muscle consists of three parts: the orbital (pars orbitalis), the age-old (pars palpebralis) and the lacrimal (pars lacrimalis) (Fig. 3.7).

Rice. 3.7. Orbicularis oculi muscle.

The orbital part of the muscle is a circular sphincter, the fibers of which begin and are attached to the medial ligament of the eyelids (lig. palpebrale mediale) and the frontal process of the upper jaw. Contraction of the muscle leads to a tight closure of the eyelids.

The fibers of the secular part of the orbicularis muscle also originate from the medial ligament of the eyelids. Then the course of these fibers becomes arched and they reach the outer corner of the palpebral fissure, where they are attached to the lateral ligament of the eyelids (lig. palpebrale laterale). The contraction of this group of fibers ensures the closure of the eyelids and their blinking movements.

The lacrimal part of the circular muscle of the eyelid is represented by a deeply located portion of muscle fibers that begin somewhat posterior to the posterior lacrimal crest of the lacrimal bone. Then they pass behind the lacrimal sac and are woven into the fibers of the secular part of the orbicularis muscle, coming from the anterior lacrimal crest. As a result, the lacrimal sac becomes enclosed in a muscle loop, which, during contractions and relaxations,

the time of blinking movements of the eyelids either expands or narrows the lumen of the lacrimal sac. Due to this, tear fluid is absorbed from the conjunctival cavity (through the lacrimal openings) and moves along the lacrimal ducts into the nasal cavity. This process is also facilitated by contractions of those bundles of lacrimal muscle that surround the lacrimal canaliculi.

Particularly distinguished are those muscle fibers of the circular muscle of the eyelid, which are located between the roots of the eyelashes around the ducts of the meibomian glands (m. ciliaris Riolani). The contraction of these fibers helps to secrete secretions from the mentioned glands and press the edges of the eyelids to the eyeball.

The orbicularis oculi muscle is innervated by the zygomatic and anterior temporal branches of the facial nerve, which lie quite deep and enter it mainly from the inferolateral side. This circumstance should be taken into account if it is necessary to perform akinesia of the muscle (usually when performing abdominal operations on the eyeball).

The muscle that lifts the upper eyelid begins near the optic canal, then goes under the roof of the orbit and ends in three portions - superficial, middle and deep. The first of them, turning into a wide aponeurosis, passes through the orbital septum, between the fibers of the age-old part of the circular muscle and ends under the skin of the eyelid. The middle portion, consisting of a thin layer of smooth fibers (m. tarsalis superior, m. Mülleri), is woven into the upper edge of the cartilage. The deep plate, like the superficial one, also ends with a tendon stretch, which reaches the upper fornix of the conjunctiva and is attached to it. Two portions of the levator (superficial and deep) are innervated by the oculomotor nerve, the middle one by the cervical sympathetic nerve.

The lower eyelid is pulled down by a poorly developed eye muscle (m. tarsalis inferior), which connects the cartilage to the lower fornix of the conjunctiva. Special processes of the sheath of the inferior rectus muscle are also woven into the latter.

The eyelids are richly supplied with vessels due to the branches of the ophthalmic artery (a. ophthalmica), which is part of the internal carotid artery system, as well as anastomoses from the facial and maxillary arteries (aa. facialis et maxillaris). The last two arteries already belong to the external carotid artery. Branching out, all these vessels form arterial arches - two on the upper eyelid and one on the lower.

The eyelids also have a well-developed lymphatic network, which is located at two levels - on the anterior and posterior surfaces of the cartilage. In this case, the lymphatic vessels of the upper eyelid flow into the pre-auricular lymph nodes, and the lower - into the submandibular ones.

Sensitive innervation of the facial skin is carried out by three branches of the trigeminal nerve and branches of the facial nerve (see Chapter 7).

3.3.2. Conjunctiva

Conjunctiva (tunica conjunctiva) is a thin (0.05-0.1 mm) mucous membrane that covers the entire back surface of the eyelids (tunica conjunctiva palpebrarum), and then, forming the arches of the conjunctival sac (fornix conjunctivae superior et inferior), passes to the front the surface of the eyeball (tunica conjunctiva bulbi) and ends at the limbus (see Fig. 3.6). It is called the connective membrane because it connects the eyelid and eye.

In the conjunctiva of the eyelids, two parts are distinguished - the tarsal, tightly fused with the underlying tissue, and the mobile orbital in the form of a transitional (to the fornix) fold.

When the eyelids are closed, a slit-like cavity is formed between the layers of the conjunctiva, deeper at the top, resembling a bag. When the eyelids are open, its volume decreases noticeably (by the size of the palpebral fissure). The volume and configuration of the conjunctival sac also change significantly with eye movements.

The conjunctiva of the cartilage is covered with stratified columnar epithelium and contains goblet cells at the edge of the eyelids, and crypts of Henle near the distal end of the cartilage. Both of them secrete mucin. Normally, the meibomian glands are visible through the conjunctiva, forming a pattern in the form of a vertical picket fence. Under the epithelium there is reticular tissue, firmly fused to the cartilage. At the free edge of the eyelid, the conjunctiva is smooth, but already at a distance of 2-3 mm from it it becomes rough, due to the presence of papillae here.

The conjunctiva of the transitional fold is smooth and covered with 5-6-layer squamous epithelium with a large number of goblet mucous cells (they secrete mucin). Its subepithelial loose connector is

This tissue, consisting of elastic fibers, contains plasma cells and lymphocytes that can form clusters in the form of follicles or lymphomas. Due to the presence of well-developed subconjunctival tissue, this part of the conjunctiva is very mobile.

On the border between the tarsal and orbital parts of the conjunctiva there are additional Wolfring lacrimal glands (3 at the upper edge of the upper cartilage and one more below the lower cartilage), and in the area of ​​the fornix - Krause's glands, the number of which is 6-8 in the lower eyelid and 15-40 - on the top. They are similar in structure to the main lacrimal gland, the excretory ducts of which open in the lateral part of the superior conjunctival fornix.

The conjunctiva of the eyeball is covered with stratified squamous non-keratinizing epithelium and is loosely connected to the sclera, so it can easily move along its surface. The limbal part of the conjunctiva contains islands of columnar epithelium with secreting Becher cells. In the same zone, radially to the limbus (in the form of a belt 1-1.5 mm wide), Manz cells producing mucin are located.

The blood supply to the conjunctiva of the eyelids is carried out by vascular trunks extending from the arterial arches of the palpebral arteries (see Fig. 3.13). The conjunctiva of the eyeball contains two layers of vessels - superficial and deep. The superficial one is formed by branches arising from the arteries of the eyelids, as well as by the anterior ciliary arteries (branches of the muscular arteries). The first of them go in the direction from the conjunctival arches to the cornea, the second - towards them. The deep (episcleral) vessels of the conjunctiva are branches of only the anterior ciliary arteries. They are directed towards the cornea and form a dense network around it. Os-

the new trunks of the anterior ciliary arteries, before reaching the limbus, go inside the eye and participate in the blood supply to the ciliary body.

The veins of the conjunctiva accompany the corresponding arteries. The outflow of blood occurs mainly through the palpebral vascular system into the facial veins. The conjunctiva also has a rich network of lymphatic vessels. The outflow of lymph from the mucous membrane of the upper eyelid occurs in the pre-auricular lymph nodes, and from the lower - in the submandibular.

Sensitive innervation of the conjunctiva is provided by the lacrimal, subtrochlear and infraorbital nerves (nn. lacrimalis, infratrochlearis et n. infraorbitalis) (see Chapter 9).

3.3.3. Muscles of the eyeball

The muscular apparatus of each eye (musculus bulbi) consists of three pairs of antagonistically acting oculomotor muscles: the superior and inferior straight lines (mm. rectus oculi superior et inferior), the internal and external straight lines (mm. rectus oculi medialis et lataralis), the superior and inferior oblique (mm. rectus oculi superior et inferior). mm. obliquus superior et inferior) (see Chapter 18 and Fig. 18.1).

All muscles, with the exception of the inferior oblique, begin, like the levator palpebrae superioris muscle, from the tendon ring located around the optic canal of the orbit. Then the four rectus muscles are directed, gradually diverging, anteriorly and, after perforating Tenon’s capsule, their tendons are woven into the sclera. The lines of their attachment are at different distances from the limbus: internal straight - 5.5-5.75 mm, lower - 6-6.5 mm, external 6.9-7 mm, upper - 7.7-8 mm.

The superior oblique muscle from the optic foramen is directed to the bone-tendon block, located at the upper inner corner of the orbit and, spreading across

it, goes posteriorly and outward in the form of a compact tendon; attaches to the sclera in the upper outer quadrant of the eyeball at a distance of 16 mm from the limbus.

The inferior oblique muscle begins from the inferior bony wall of the orbit somewhat lateral to the entry into the nasolacrimal canal, runs posteriorly and outward between the inferior wall of the orbit and the inferior rectus muscle; attaches to the sclera at a distance of 16 mm from the limbus (inferior outer quadrant of the eyeball).

The internal, superior and inferior rectus muscles, as well as the inferior oblique muscle, are innervated by branches of the oculomotor nerve (n. oculomotorius), the external rectus - by the abducens nerve (n. abducens), and the superior oblique - by the trochlear nerve (n. trochlearis).

When one muscle or another contracts, the eye moves around an axis that is perpendicular to its plane. The latter runs along the muscle fibers and crosses the rotation point of the eye. This means that for most oculomotor muscles (with the exception of the external and internal rectus muscles), the axes of rotation have one or another angle of inclination relative to the original coordinate axes. As a result, when such muscles contract, the eyeball makes a complex movement. So, for example, the superior rectus muscle, with the eye in the middle position, lifts it upward, rotates inwards and turns it slightly toward the nose. It is clear that the amplitude of vertical movements of the eye will increase as the angle of divergence between the sagittal and muscular planes decreases, i.e., when the eye turns outward.

All movements of the eyeballs are divided into combined (associated, conjugated) and convergent (fixation of objects at different distances due to convergence). Combined movements are those that are directed in one direction:

up, right, left, etc. These movements are performed by synergistic muscles. So, for example, when looking to the right, the external rectus muscle contracts in the right eye, and the internal rectus muscle contracts in the left eye. Convergent movements are realized through the action of the internal rectus muscles of each eye. A variety of them are fusion movements. Being very small, they carry out particularly precise fixation of the eyes, thereby creating conditions for the unhindered merging of two retinal images into one solid image in the cortical section of the analyzer.

3.3.4. Lacrimal apparatus

The production of tear fluid occurs in the lacrimal apparatus (apparatus lacrimalis), consisting of the lacrimal gland (glandula lacrimalis) and small accessory glands of Krause and Wolfring. The latter provide the eye's daily need for hydrating fluid. The main lacrimal gland actively functions only in conditions of emotional outbursts (positive and negative), as well as in response to irritation of sensitive nerve endings in the mucous membrane of the eye or nose (reflex lacrimation).

The lacrimal gland lies under the upper outer edge of the orbit in the recess of the frontal bone (fossa glandulae lacrimalis). The tendon of the levator palpebrae superioris muscle divides it into the greater orbital and lesser eyelid parts. The excretory ducts of the orbital lobe of the gland (3-5 in number) pass between the lobules of the secular gland, simultaneously receiving a number of its numerous small ducts, and open in the conjunctival fornix at a distance of several millimeters from the upper edge of the cartilage. In addition, the age-old part of the gland also has independent proto-

ki, the number of which is from 3 to 9. Since it lies immediately under the upper fornix of the conjunctiva, when the upper eyelid is everted, its lobular contours are usually clearly visible.

The lacrimal gland is innervated by secretory fibers of the facial nerve (n. facialis), which, having traveled a complex path, reach it as part of the lacrimal nerve (n. lacrimalis), which is a branch of the optic nerve (n. ophthalmicus).

In children, the lacrimal gland begins to function by the end of the 2nd month of life, so until this period expires, their eyes remain dry when they cry.

The tear fluid produced by the above-mentioned glands rolls down the surface of the eyeball from top to bottom into the capillary gap between the posterior ridge of the lower eyelid and the eyeball, where a tear stream (rivus lacrimalis) is formed, flowing into the tear lake (lacus lacrimalis). Blinking movements of the eyelids promote the movement of tear fluid. When they close, they not only move towards each other, but also shift inwards (especially the lower eyelid) by 1-2 mm, as a result of which the palpebral fissure shortens.

The lacrimal duct consists of the lacrimal canaliculi, lacrimal sac and nasolacrimal duct (see Chapter 8 and Fig. 8.1).

Lacrimal canaliculi (canaliculi lacrimales) begin with lacrimal puncta (punctum lacrimale), which are located at the top of the lacrimal papillae of both eyelids and are immersed in the lacrimal lake. The diameter of the points with open eyelids is 0.25-0.5 mm. They lead into the vertical part of the tubules (length 1.5-2 mm). Then their course changes to almost horizontal. Then, gradually drawing closer, they open into the lacrimal sac behind the internal commissure of the eyelids, each individually or having previously merged into a common opening. The length of this part of the tubules is 7-9 mm, diameter

0.6 mm. The walls of the tubules are covered with stratified squamous epithelium, under which there is a layer of elastic muscle fibers.

The lacrimal sac (saccus lacrimalis) is located in a bone, vertically elongated fossa between the anterior and posterior knees of the internal commissure of the eyelids and is covered by a muscle loop (m. Horneri). Its dome protrudes above this ligament and is located preseptally, that is, outside the orbital cavity. The inside of the sac is covered with stratified squamous epithelium, under which there is a layer of adenoid and then dense fibrous tissue.

The lacrimal sac opens into the nasolacrimal duct (ductus nasolacrimalis), which first passes through the bone canal (length about 12 mm). In the lower section it has a bone wall only on the lateral side; in the remaining sections it borders on the nasal mucosa and is surrounded by a dense venous plexus. The duct opens under the inferior turbinate at a distance of 3-3.5 cm from the external opening of the nose. Its total length is 15 mm, diameter 2-3 mm. In newborns, the outlet of the duct is often closed by a mucous plug or thin film, as a result of which conditions are created for the development of purulent or serous-purulent dacryocystitis. The wall of the duct has the same structure as the wall of the lacrimal sac. At the outlet of the duct, the mucous membrane forms a fold, which plays the role of a locking valve.

In general, we can assume that the lacrimal duct consists of small soft tubes of various lengths and shapes with varying diameters, which join at certain angles. They connect the conjunctival cavity with the nasal cavity, where there is a constant outflow of tear fluid. It is provided due to the blinking movements of the eyelids, the siphon effect with capillary

the tension of the fluid filling the lacrimal ducts, the peristaltic change in the diameter of the tubules, the suction ability of the lacrimal sac (due to the alternation of positive and negative pressure in it during blinking) and the negative pressure created in the nasal cavity during the aspiration movement of air.

3.4. Blood supply to the eye and its auxiliary organs

3.4.1. Arterial system of the organ of vision

The main role in the nutrition of the organ of vision is played by the ophthalmic artery (a. ophthalmica) - one of the main branches of the internal carotid artery. Through the optic canal, the ophthalmic artery penetrates the cavity of the orbit and, being first under the optic nerve, then rises from the outside upward and crosses it, forming an arch. From her and from-

all the main branches of the ophthalmic artery run (Fig. 3.8).

The central retinal artery (a. centralis retinae) is a small-diameter vessel coming from the initial part of the arch of the ophthalmic artery. At a distance of 7-12 mm from the posterior pole of the eye through hard shell it enters from below into the depths of the optic nerve and is directed towards its disc with a single trunk, giving off a thin horizontal branch in the opposite direction (Fig. 3.9). Often, however, there are cases where the orbital part of the nerve receives power from a small vascular branch, which is often called the central artery of the optic nerve (a. centralis nervi optici). Its topography is not constant: in some cases it departs in various ways from the central retinal artery, in others - directly from the ophthalmic artery. In the center of the nerve trunk this artery after the T-shaped division

Rice. 3.8. Blood vessels of the left orbit (top view) [from the work of M. L. Krasnov, 1952, with modifications].

Rice. 3.9. Blood supply to the optic nerve and retina (diagram) [according to H. Remky,

1975].

occupies a horizontal position and sends multiple capillaries towards the vascular network of the pia mater. The intracanalicular and peritubular parts of the optic nerve are supplied by r. recurrences a. ophthalmica, r. recurrences a. hypophysial

sup. ant. and rr. intracanaliculares a. ophthalmica.

The central retinal artery emerges from the stem part of the optic nerve, dichotomously divides up to the 3rd order arterioles (Fig. 3.10), forming vascular

Rice. 3.10. Topography of the terminal branches of the central arteries and veins of the retina of the right eye on the diagram and photograph of the fundus.

a dense network that nourishes the medulla of the retina and the intraocular part of the optic nerve head. It is not so rare that in the fundus of the eye during ophthalmoscopy one can see an additional source of nutrition for the macular zone of the retina in the form of a. cilioretinalis. However, it no longer departs from the ophthalmic artery, but from the posterior short ciliary or arterial circle of Zinn-Haller. Its role is very important in case of circulatory disorders in the central retinal artery system.

Posterior short ciliary arteries (aa. ciliares posteriores breves) are branches (6-12 mm long) of the ophthalmic artery that approach the sclera of the posterior pole of the eye and, perforating it around the optic nerve, form the intrascleral arterial circle of Zinn-Haller. They also form the vascular system itself

membrane - the choroid (Fig.

3.11). The latter, through its capillary plate, nourishes the neuroepithelial layer of the retina (from the layer of rods and cones to the outer plexiform layer inclusive). Individual branches of the posterior short ciliary arteries penetrate the ciliary body, but do not play a significant role in its nutrition. In general, the system of posterior short ciliary arteries does not anastomose with any other choroid plexuses of the eye. It is for this reason that inflammatory processes developing in the choroid itself are not accompanied by hyperemia of the eyeball. . Two posterior long ciliary arteries (aa. ciliares posteriores longae) arise from the trunk of the ophthalmic artery and are located distally

Rice. 3.11. Blood supply to the vascular tract of the eye [according to Spalteholz, 1923].

Rice. 3.12. Vascular system of the eye [according to Spalteholz, 1923].

posterior short ciliary arteries. The sclera is perforated at the level of the lateral sides of the optic nerve and, entering the suprachoroidal space at 3 and 9 o'clock, they reach the ciliary body, which is mainly nourished. They anastomose with the anterior ciliary arteries, which are branches of the muscular arteries (aa. musculares) (Fig. 3.12).

Near the root of the iris, the posterior long ciliary arteries divide dichotomously. The resulting branches connect with each other and form a large arterial

circle of the iris (circulus arteriosus iridis major). New branches extend from it in a radial direction, forming in turn a small arterial circle (circulus arteriosus iridis minor) at the border between the pupillary and ciliary belts of the iris.

The posterior long ciliary arteries are projected onto the sclera in the area of ​​passage of the internal and external rectus muscles of the eye. These guidelines should be kept in mind when planning operations.

Muscular arteries (aa. musculares) are usually represented by two

more or less large trunks - upper (for the muscle that lifts the upper eyelid, the superior rectus and superior oblique muscles) and the lower (for the remaining extraocular muscles). In this case, the arteries supplying the four rectus muscles of the eye, outside the tendon attachment, give branches to the sclera, called anterior ciliary arteries (aa. ciliares anteriores), two from each muscle branch, with the exception of the external rectus muscle, which has one branch.

At a distance of 3-4 mm from the limbus, the anterior ciliary arteries begin to divide into small branches. Some of them are directed to the limbus of the cornea and, through new branches, form a two-layer marginal looped network - superficial (plexus episcleralis) and deep (plexus scleralis). Other branches of the anterior ciliary arteries perforate the wall of the eye and, near the root of the iris, together with the posterior long ciliary arteries, form a large arterial circle of the iris.

The medial arteries of the eyelids (aa. palpebrales mediales) in the form of two branches (upper and lower) approach the skin of the eyelids in the area of ​​their internal ligament. Then, positioned horizontally, they widely anastomose with the lateral arteries of the eyelids (aa. palpebrales laterales), extending from the lacrimal artery (a. lacrimalis). As a result, arterial arches of the eyelids are formed - upper (arcus palpebralis superior) and lower (arcus palpebralis inferior) (Fig. 3.13). Anastomoses from a number of other arteries also participate in their formation: supraorbital (a. supraorbitalis) - branch of the ophthalmic (a. ophthalmica), infraorbital (a. infraorbitalis) - branch of the maxillary (a. maxillaris), angular (a. angularis) - facial branch (a. facialis), superficial temporal (a. temporalis superficialis) - branch of the external carotid (a. carotis externa).

Both arches are located in the muscle layer of the eyelids at a distance of 3 mm from the ciliary edge. However, on the upper eyelid there is often not one, but two

Rice. 3.13. Arterial blood supply to the eyelids [according to S. S. Dutton, 1994].

arterial arches. The second of them (peripheral) is located above the upper edge of the cartilage and is connected to the first by vertical anastomoses. In addition, small perforating arteries (aa. perforantes) extend from these same arches to the posterior surface of the cartilage and conjunctiva. Together with the branches of the medial and lateral arteries of the eyelids, they form the posterior conjunctival arteries, which participate in the blood supply to the mucous membrane of the eyelids and, partially, the eyeball.

The conjunctiva of the eyeball is supplied by the anterior and posterior conjunctival arteries. The first depart from the anterior ciliary arteries and go towards the conjunctival fornix, and the second, being branches of the lacrimal and supraorbital arteries, go towards them. Both of these circulatory systems are connected by many anastomoses.

The lacrimal artery (a. lacrimalis) departs from the initial part of the arch of the ophthalmic artery and is located between the external and superior rectus muscles, giving them and the lacrimal gland multiple branches. In addition, as indicated above, with its branches (aa. palpebrales laterales) it takes part in the formation of the arterial arches of the eyelids.

The supraorbital artery (a. supraorbitalis), being a fairly large trunk of the ophthalmic artery, passes in the upper part of the orbit to the notch of the same name in the frontal bone. Here it, together with the lateral branch of the supraorbital nerve (r. lateralis n. supraorbitalis), exits under the skin, nourishing the muscles and soft tissues of the upper eyelid.

The supratrochlearis artery emerges from the orbit near the trochlea along with the nerve of the same name, having previously perforated the orbital septum (septum orbitale).

The ethmoidal arteries (aa. ethmoidales) are also independent branches of the ophthalmic artery, but their role in feeding the tissues of the orbit is insignificant.

From the external carotid artery system, some branches of the facial and maxillary arteries take part in the nutrition of the auxiliary organs of the eye.

The infraorbital artery (a. infraorbitalis), being a branch of the maxillary artery, penetrates the orbit through the inferior orbital fissure. Located subperiosteally, it passes through the canal of the same name on the lower wall of the infraorbital groove and exits onto the facial surface of the maxillary bone. Participates in the nutrition of the tissues of the lower eyelid. Small branches extending from the main arterial trunk are involved in the blood supply to the inferior rectus and inferior oblique muscles, the lacrimal gland and the lacrimal sac.

The facial artery (a. facialis) is a fairly large vessel located in the medial part of the entrance to the orbit. In the upper section it gives off a large branch - the angular artery (a. angularis).

3.4.2. Venous system of the organ of vision

The outflow of venous blood directly from the eyeball occurs mainly through the internal (retinal) and external (ciliary) vascular systems of the eye. The first is represented by the central retinal vein, the second by four vorticose veins (see Fig. 3.10; 3.11).

The central vein of the retina (v. centralis retinae) accompanies the corresponding artery and has the same distribution as it. In the optic nerve trunk it connects with the central artery of the network

Rice. 3.14. Deep veins of the orbit and face [according to R. Thiel, 1946].

buds into the so-called central connecting cord through processes extending from the pia mater. It flows either directly into the cavernous sinus (sinus cavernosa), or first into the superior ophthalmic vein (v. ophthalmica superior).

Vorticose veins (vv. vorticosae) drain blood from the choroid, ciliary processes and most of the muscles of the ciliary body, as well as the iris. They cut through the sclera in an oblique direction in each of the quadrants of the eyeball at the level of its equator. The upper pair of vorticose veins flows into the superior ophthalmic vein, the lower one into the inferior one.

The outflow of venous blood from the auxiliary organs of the eye and orbit occurs through the vascular system, which has complex structure And

is characterized by a number of clinically very important features (Fig. 3.14). All veins of this system are devoid of valves, as a result of which the outflow of blood through them can occur both towards the cavernous sinus, i.e., into the cranial cavity, and into the system of veins of the face, which are connected with the venous plexuses of the temporal region of the head, the pterygoid process, and the pterygopalatine fossa , condylar process of the mandible. In addition, the venous plexus of the orbit anastomoses with the veins of the ethmoid sinuses and the nasal cavity. All these features determine the possibility of dangerous spread purulent infection from the skin of the face (boils, abscesses, erysipelas) or from the paranasal sinuses into the cavernous sinus.

3.5. Motor

and sensory innervation

eyes and its auxiliary

organs

The motor innervation of the human organ of vision is realized through the III, IV, VI and VII pairs of cranial nerves, the sensory innervation - through the first (n. ophthalmicus) and partly the second (n. maxillaris) branches of the trigeminal nerve (V pair of cranial nerves).

The oculomotor nerve (n. oculomotorius, III pair of cranial nerves) begins from the nuclei lying at the bottom of the Sylvian aqueduct at the level of the anterior tubercles of the quadrigeminal. These nuclei are heterogeneous and consist of two main lateral ones (right and left), including five groups of large cells (nucl. oculomotorius), and additional small cell ones (nucl. oculomotorius accessorius) - two paired lateral ones (Yakubovich-Edinger-Westphal nucleus) and one unpaired (Perlia nucleus), located between

them (Fig. 3.15). The length of the nuclei of the oculomotor nerve in the anteroposterior direction is 5-6 mm.

From the paired lateral magnocellular nuclei (a-e) fibers depart for three rectus (superior, internal and inferior) and inferior oblique oculomotor muscles, as well as for two portions of the muscle that lifts the upper eyelid, and the fibers innervating the internal and inferior rectus, as well as the inferior oblique muscles immediately cross.

Fibers extending from the paired parvocellular nuclei innervate the sphincter muscle of the pupil (m. sphincter pupillae) through the ciliary ganglion, and those extending from the unpaired nucleus innervate the ciliary muscle.

Through the fibers of the medial longitudinal fasciculus, the nuclei of the oculomotor nerve are connected with the nuclei of the trochlear and abducens nerves, the system of vestibular and auditory nuclei, the nucleus of the facial nerve and the anterior horns of the spinal cord. Thanks to this, we provide

Rice. 3.15. Innervation of external and internal muscles eyes [according to R. Bing, B. Brückner, 1959].

coordinated reflex reactions of the eyeball, head, and torso to all kinds of impulses, in particular vestibular, auditory and visual.

Through the superior orbital fissure, the oculomotor nerve penetrates into the orbit, where, within the muscular funnel, it divides into two branches - superior and inferior. The superior thin branch is located between the superior rectus muscle and the muscle that lifts the upper eyelid, and innervates them. The lower, larger branch passes under the optic nerve and is divided into three branches - the external (the root to the ciliary ganglion and fibers for the inferior oblique muscle depart from it), the middle and internal (innervate the inferior and internal rectus muscles, respectively). The root (radix oculomotoria) carries fibers from the accessory nuclei of the oculomotor nerve. They innervate the ciliary muscle and the sphincter of the pupil.

The trochlear nerve (n. trochlearis, IV pair of cranial nerves) begins from the motor nucleus (length 1.5-2 mm), located at the bottom of the Sylvian aqueduct immediately behind the nucleus of the oculomotor nerve. Penetrates into the orbit through the superior orbital fissure lateral to the muscular infundibulum. Innervates the superior oblique muscle.

The abducens nerve (n. abducens, VI pair of cranial nerves) starts from the nucleus located in the pons at the bottom of the rhomboid fossa. It leaves the cranial cavity through the superior orbital fissure, located inside the muscular funnel between the two branches of the oculomotor nerve. Innervates the external rectus muscle of the eye.

The facial nerve (n. facialis, n. intermediofacialis, VII pair of cranial nerves) has mixed composition, i.e. includes not only motor, but also sensory, gustatory and secretory fibers that belong to the intermediate

nerve (n. intermedius Wrisbergi). The latter is closely adjacent to the facial nerve at the base of the brain from the outside and is its dorsal root.

The motor nucleus of the nerve (length 2-6 mm) is located in the lower part of the pons at the bottom of the IV ventricle. The fibers extending from it emerge in the form of a root at the base of the brain in the cerebellopontine angle. Then the facial nerve, together with the intermediate nerve, enters facial canal temporal bone. Here they merge into a common trunk, which further penetrates the parotid salivary gland and is divided into two branches that form the parotid plexus - plexus parotideus. Nerve trunks extend from it to the facial muscles, innervating, among other things, the orbicularis oculi muscle.

The intermediate nerve contains secretory fibers for the lacrimal gland. They depart from the lacrimal nucleus, located in the brain stem, and through the ganglion ganglion (gangl. geniculi) enter the greater petrosal nerve (n. petrosus major).

Afferent pathway for main and accessory lacrimal glands begins with the conjunctival and nasal branches of the trigeminal nerve. There are other areas of reflex stimulation of tear production - the retina, the anterior frontal lobe of the brain, the basal ganglia, the thalamus, the hypothalamus and the cervical sympathetic ganglion.

The level of damage to the facial nerve can be determined by the state of tear secretion. When it is not broken, the focus is located below the gangl. geniculi and vice versa.

The trigeminal nerve (n. trigeminus, V pair of cranial nerves) is mixed, that is, it contains sensory, motor, parasympathetic and sympathetic fibers. It contains nuclei (three sensitive - spinal, pontine, midbrain - and one motor), sensory and motor

body roots, as well as the trigeminal ganglion (on the sensitive root).

Sensitive nerve fibers begin from the bipolar cells of the powerful trigeminal ganglion (gangl. trigeminale) 14-29 mm wide and 5-10 mm long.

The axons of the trigeminal ganglion form the three main branches of the trigeminal nerve. Each of them is associated with certain nerve nodes: the optic nerve (n. ophthalmicus) - with the ciliary (gangl. ciliare), the maxillary (n. maxillaris) - with the pterygopalatine (gangl. pterygopalatinum) and the mandibular (n. mandibularis) - with the ear ( gangl. oticum), submandibular (gangl. submandibulare) and sublingual (gangl. sublihguale).

The first branch of the trigeminal nerve (n. ophthalmicus), being the thinnest (2-3 mm), exits the cranial cavity through the fissura orbitalis superior. When approaching it, the nerve is divided into three main branches: n. nasociliaris, n. frontalis and n. lacrimalis.

N. nasociliaris, located within the muscular funnel of the orbit, is in turn divided into long ciliary, ethmoidal and nasal branches and, in addition, gives off a root (radix nasociliaris) to the ciliary ganglion (gangl. ciliare).

Long ciliary nerves in the form of 3-4 thin trunks are directed to the posterior pole of the eye, perforate

the sclera around the optic nerve and along the suprachoroidal space are directed anteriorly. Together with short ciliary nerves extending from the ciliary ganglion, they form a dense nerve plexus in the region of the ciliary body (plexus ciliaris) and around the circumference of the cornea. The branches of these plexuses provide sensitive and trophic innervation to the corresponding structures of the eye and perilimbal conjunctiva. The rest of it receives sensory innervation from the palpebral branches of the trigeminal nerve, which should be kept in mind when planning anesthesia of the eyeball.

On the way to the eye, the long ciliary nerves are joined by sympathetic nerve fibers from the plexus of the internal carotid artery, which innervate the pupillary dilator.

Short ciliary nerves (4-6) extend from the ciliary ganglion, the cells of which are connected to the fibers of the corresponding nerves through the sensory, motor and sympathetic roots. It is located at a distance of 18-20 mm behind the posterior pole of the eye under the external rectus muscle, adjacent in this zone to the surface of the optic nerve (Fig. 3.16).

Like the long ciliary nerves, the short ones also approach the posterior

Rice. 3.16. The ciliary ganglion and its innervation connections (diagram).

pole of the eye, perforate the sclera around the circumference of the optic nerve and, increasing in number (up to 20-30), participate in the innervation of the tissues of the eye, primarily its choroid.

Long and short ciliary nerves are a source of sensitive (cornea, iris, ciliary body), vasomotor and trophic innervation.

The final branch n. nasociliaris is the subtrochlear nerve (n. infratrochlearis), which innervates the skin in the area of ​​the root of the nose, the inner corner of the eyelids and the corresponding parts of the conjunctiva.

The frontal nerve (n. frontalis), being the largest branch of the optic nerve, after entering the orbit, gives off two large branches - the supraorbital nerve (n. supraorbitalis) with medial and lateral branches (r. medialis et lateralis) and the supratrochlear nerve. The first of them, having perforated the tarso-orbital fascia, passes through the nasal orbital foramen (incisura supraorbital) of the frontal bone to the skin of the forehead, and the second comes out of the orbit at its inner wall and innervates a small area of ​​the eyelid skin above its internal ligament. In general, the frontal nerve provides sensory innervation to the middle part of the upper eyelid, including the conjunctiva, and the skin of the forehead.

The lacrimal nerve (n. lacrimalis), entering the orbit, runs anteriorly above the external rectus muscle of the eye and is divided into two branches - the upper (larger) and the lower. Upper branch, being a continuation of the main nerve, gives branches to

lacrimal gland and conjunctiva. Some of them, after passing through the gland, perforate the tarso-orbital fascia and innervate the skin in the area of ​​the outer corner of the eye, including the area of ​​the upper eyelid. A small lower branch of the lacrimal nerve anastomoses with the zygomaticotemporal branch (r. zygomaticotemporalis) of the zygomatic nerve, which carries secretory fibers for the lacrimal gland.

The second branch of the trigeminal nerve (n. maxillaris) takes part in the sensitive innervation of only the auxiliary organs of the eye through its two branches - n. infraorbitalis and n. zygomaticus. Both of these nerves are separated from the main trunk in the pterygopalatine fossa and penetrate into the orbital cavity through the inferior orbital fissure.

The infraorbital nerve (n. infraorbitalis), entering the orbit, passes along the groove of its lower wall and enters the facial surface through the infraorbital canal. Innervates the central part of the lower eyelid (rr. palpebrales inferiores), the skin of the wings of the nose and the mucous membrane of its vestibule (rr. nasales interni et externi), as well as the mucous membrane of the upper lip (rr. labiales superiores), upper gums, alveolar recesses and, in addition In addition, the upper dentition.

The zygomatic nerve (n. zygomaticus) in the orbital cavity is divided into two branches - n. zygomaticotemporalis and n. zygomaticofacialis. Having passed through the corresponding channels in the zygomatic bone, they innervate the skin of the lateral forehead and a small area of ​​the zygomatic region.

Hello, dear friends!

I really like learning something new and interesting. My mother taught me to read and write at the age of 4, and for as long as I can remember, I read always and everywhere - in the toilet, at the dinner table, with a flashlight under the blanket.

And what a miracle the first e-book was for me! This is necessary - a device the size of a small notebook can hold thousands of books, and you can read them even at night in bed without light!

Precisely because excessive hobby It was through reading and ignorance of the basic rules of rest that I began to lose my sight during my school years. Now you have to read more about restoring vision and eye health.

But today I want to take a break from serious topics and treat you to an entertaining, and sometimes funny, article about the “mirror of the soul.” Give me a few minutes of your time, I’m sure you’ll like it :)

• Among all the sense organs, the eyes occupy special place. Up to 80% of the information the body receives from the outside passes through the eyes.
• It is known that Grigory Rasputin trained the expressiveness of his gaze, its rigidity and strength in order to assert himself in communication with people. And Emperor Augustus dreamed that those around him would find supernatural power in his gaze.



• Our eye color provides information about heredity. For example, blue eye color is more common in northern regions, brown in temperate climates, and black in the equator region.
• When exposed to daylight or too much cold, a person's eye color may change (this is called a chameleon)
• It is believed that people with dark eyes are persistent, resilient, but in crisis situations they are too irritable; gray-eyed - decisive; brown-eyed people are reserved, while blue-eyed people are hardy. Green-eyed people are stable and focused.
• There are approximately 1% of people on Earth whose iris color is different in their left and right eyes.



• A mechanism with a human eye - is it possible? Without a doubt! The most interesting thing is that such a device already exists! Mitsubishi Electric has developed an electronic eye on a chip that is already used in some products. This eye has the same functions as the human eye.
• Why do people close their eyes when they kiss? Scientists have found out! During a kiss, we lower our eyelids so as not to faint from an overabundance of feelings. During a kiss, the brain experiences sensory overload, so by closing your eyes, you subconsciously reduce the excess intensity of passions.



• The eye of large whales weighs about 1 kg. However, many whales do not see objects in front of their snout.
• The human eye distinguishes only seven primary colors - red, orange, yellow, green, blue, indigo and violet. But besides this, the eyes ordinary person are able to distinguish up to one hundred thousand shades, and the eyes of a professional (for example, an artist) up to a million shades!
• According to experts, what makes any eyes BEAUTIFUL is internal energy, health, kindness, interest in the world around you and people!
• Record: The Brazilian can bulge his eyes 10 mm! This man used to work at a commercial haunted attraction where he scared visitors. However, now he is seeking global recognition of his abilities. And he wants to get into the Guinness Book of Records!
• Clothes that are too tight have a negative impact on your eyesight! It interferes with blood circulation, and this affects the eyes.
• Man is the only creature with white eyes! Even monkeys have completely black eyes. This makes the ability to determine other people's intentions and emotions by their eyes an exclusively human privilege. From the eyes of a monkey it is completely impossible to understand not only its feelings, but even the direction of its gaze.



• Indian yogis treat their eyes by looking at the sun, stars and moon! They believe that there is no light equal in strength to that of the sun. The sun's rays revitalize vision, accelerate blood circulation, and neutralize infections. Yogis recommend looking at the sun in the morning, when it is not covered by clouds, with eyes wide open but relaxed for as long as possible or until tears appear in the eyes. This exercise is best done at sunrise or sunset. But you should not look at it at noon.
• Psychologists have discovered what attracts us to strangers. It turns out that most often we are attracted to - sparkling eyes emitting any emotions.
• It is impossible to sneeze with your eyes open!



• The iris of the eyes, like human fingerprints, are very rarely repeated in people. We decided to use this! Along with the usual passport control, in some places there is a checkpoint that determines the identity of a person by the iris of his eye.
• Computers of the future will be able to be controlled by eye movements! And not with a mouse and keyboard, as it is now. Scientists at College London are developing technology that will monitor pupil movement and analyze the mechanism of human vision.
• Eye turns 6 eye muscles. They provide eye mobility in all directions. Thanks to this, we quickly fix one point of an object after another, estimating the distances to objects.
• Greek philosophers believed that blue eyes owe their origin to fire. The Greek goddess of wisdom was often called "blue-eyed".
• It’s a paradox, but when reading quickly, eye fatigue is less than when reading slowly.
• Scientists believe that the golden color helps restore vision!

Source http://muz4in.net/news/interesnye_fakty_o_glazakh/2011-07-07-20932

Our amazing eyes

Few would argue that our lives would be unspeakably boring without our five senses. All of our senses are important to us, but if you asked a person which of them he is least willing to part with, then most likely you would choose vision.

Below are 10 weird and wonderful facts you may not know about your eyes.

1. The lens in your eye is faster than any photographic lens.

   Try looking around the room quickly and think about how many different distances you focus on.

   Every time you do this, the lens in your eye constantly changes focus even before you realize it.

   Compare this to a photographic lens, which takes several seconds to focus from one distance to another.

   If the lens in your eye didn't focus so quickly, objects around us would constantly move in and out of focus.



2. All people need reading glasses as they age.

   Let's assume that you have excellent distance vision. If you are now reading this article, you are over 40 and have good eyesight, then it is quite safe to say that in the future you will still need reading glasses.

   For 99 percent of people, the first time they need glasses occurs between the ages of 43 and 50. This happens because the lens inside your eyes loses its focusing ability as you age.

   To focus on objects near you, the lens in the eye must change shape from flat to more spherical, an ability that declines with age.

   After age 45, you will need to hold objects further away to focus on them.

3. Eyes are fully formed by age 7

   By the age of 7, our eyes are fully formed and, in physiological parameters, completely correspond to the eyes of an adult. That's why it's important to get the vision disorder known as lazy eye or amblyopia diagnosed before you turn 7.

   The sooner this disorder is detected, the higher the chances that it will respond to treatment, since the eyes are still in the developmental stage and vision can be corrected.

4. We blink about 15,000 times a day

   Blinking is a semi-reflexive function, which means we do it automatically but can also decide whether to blink if we need to.

   Blinking is an extremely important function of our eyes, as it helps eliminate any debris from the surface of the eye and coats the eye with fresh tears. These tears help oxygenate our eyes and have an antibacterial effect.

   The blinking function can be compared to the windshield wipers on a car, which clean and remove anything unnecessary to allow you to see clearly.



5. Everyone develops cataracts as they age.

   People often don't realize that cataracts are a normal part of aging, and everyone develops them at some point in their lives.

   The development of cataracts is like the appearance of gray hair; it is just an age-related change. Cataracts usually develop between 70 and 80 years of age.

   With cataracts, clouding of the lens occurs and, as a rule, it takes about 10 years from the onset of this disorder before treatment is needed.

6. Diabetes is often one of the first things diagnosed during an eye exam.

   People with type 2 diabetes, which develops throughout life, are often asymptomatic, meaning we often don't even realize we have diabetes.

   This type of diabetes is often discovered during an eye exam as small bleeds from the blood vessels at the back of the eye. This is another reason why you should have your eyes checked regularly.

7. You see with your brain, not your eyes

   The function of the eyes is to collect necessary information about the object you are looking at. This information is then sent to the brain through the optic nerve. All information is analyzed in the brain, in the visual cortex, to enable you to see objects in a complete form.

8. The eye can adapt to blind spots in the eye

   Certain disorders, such as glaucoma and common conditions such as stroke, can cause blind spots to develop in your eyes.

   This would seriously impair your vision if it weren't for the ability of our brains and eyes to adapt and help eliminate these blind spots.

   This occurs by suppressing the blind spot in the affected eye and the ability of the healthy eye to fill in the gaps in vision.

9. Visual acuity of 20/20 is not the limit of your vision

   Often people assume that visual acuity of 20/20, which refers to the distance in feet between the subject and the vision test chart, is an indicator of better vision.

   This actually refers to the normal vision that an adult should see.

   If you've seen an eye test chart, 20/20 acuity means you can see the second line from the bottom. The ability to read the line below indicates a visual acuity of 20/16.

10. Your eyes produce water when they start to dry out

    This may sound strange, but this is one of the amazing facts about eyes.

    Tears are made up of three different components: water, mucus and fat. If these three components are not in precise proportions, the eyes may become dry.

    The brain responds to dryness by producing tears.

Source http://interesting-facts.com/10-interesnyh-faktov-o-glazah/

Do you know that…

• We blink up to 10 million times a year.
• All children are colorblind when they are first born.
• A baby's eyes do not produce tears until he is 6 to 8 weeks old.
• Cosmetics cause the most damage to the eyes.
• Some people start sneezing when bright light enters their eyes.
• The space between the eyes is called the glabella.
• The examination of the iris of the eye is called iridology.
• The cornea of ​​a shark's eye is often used in surgical operations on the human eye, as it has a similar structure.
• The human eyeball weighs 28 grams.
• The human eye can distinguish up to 500 shades of gray.
• Sailors in ancient times thought that wearing gold earrings would improve their eyesight.
• People typically read text from a computer screen 25% slower than from paper.
• Men are able to read small print better than women.
• When crying profusely, tears flow down a straight channel directly into the nose. Apparently, this is why the expression “don’t make a fool of yourself” came about.

Source http://facte.ru/man/3549.html

A person sees not with his eyes, but through his eyes, from where information is transmitted through the optic nerve, chiasm, visual tracts to certain areas of the occipital lobes of the cerebral cortex, where the picture of the external world that we see is formed. All these organs make up our visual analyzer or visual system.

Having two eyes allows us to make our vision stereoscopic (that is, form a three-dimensional image). The right side of the retina of each eye transmits the “right side” of the image to the optic nerve. right side brain, acts similarly left-hand side retina. Then the brain connects two parts of the image - right and left - together.

Since each eye perceives “its own” picture, if the joint movement of the right and left eyes is disrupted, binocular vision may be disrupted. Simply put, you will begin to see double or see two completely different pictures at the same time.

Basic functions of the eye

• optical system that projects the image;
• a system that perceives and “encodes” the received information for the brain;
• "serving" life support system.

The eye can be called a complex optical device. Its main task is to “transmit” the correct image to the optic nerve.

Cornea- a transparent membrane covering the front of the eye. It lacks blood vessels and has great refractive power. Part of the optical system of the eye. The cornea borders the opaque outer layer of the eye, the sclera. See structure of the cornea.

Anterior chamber of the eye- This is the space between the cornea and the iris. It is filled with intraocular fluid.

Iris- shaped like a circle with a hole inside (pupil). The iris consists of muscles that, when contracted and relaxed, change the size of the pupil. It enters the choroid of the eye. The iris is responsible for the color of the eyes (if it is blue, it means there are few pigment cells, if it is brown, it means a lot). Performs the same function as the aperture in a camera, regulating the light flow.

Pupil- a hole in the iris. Its size usually depends on the light level. The more light, the smaller the pupil.

Lens- the “natural lens” of the eye. It is transparent, elastic - it can change its shape, almost instantly “focusing”, due to which a person sees well both near and far. Located in the capsule, held ciliary girdle. The lens, like the cornea, is part of the optical system of the eye.

Vitreous body- a gel-like transparent substance located in the back of the eye. The vitreous body maintains the shape of the eyeball and is involved in intraocular metabolism. Part of the optical system of the eye.

Retina- consists of photoreceptors (they are sensitive to light) and nerve cells. Receptor cells located in the retina are divided into two types: cones and rods. In these cells, which produce the enzyme rhodopsin, the energy of light (photons) is converted into electrical energy in nervous tissue, i.e. a photochemical reaction.

Rods are highly photosensitivity and allow you to see in low light; they are also responsible for peripheral vision. Cones, on the contrary, require more light, but they are the ones that allow you to see small details (responsible for central vision) and make it possible to distinguish colors. The largest concentration of cones is located in the central fossa (macula), which is responsible for the highest visual acuity. The retina is adjacent to the choroid, but in many areas it is loose. This is where it tends to flake off when various diseases retina.

Sclera- the opaque outer layer of the eyeball, which in front of the eyeball turns into a transparent cornea. 6 extraocular muscles are attached to the sclera. It contains a small number of nerve endings and blood vessels.

Choroid— lines the posterior part of the sclera, the retina is adjacent to it, with which it is closely connected. The choroid is responsible for the blood supply to intraocular structures. In diseases of the retina, it is very often involved in the pathological process. There are no nerve endings in the choroid, so when it is diseased, there is no pain, which usually signals some kind of problem.

Optic nerve- using the optic nerve, signals from nerve endings are transmitted to the brain.

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We are used to mercilessly straining our eyes while sitting in front of monitors. And few people think that in fact this is a unique organ, about which even science still knows not everything.

website invites all office workers to think more often about their vision and at least sometimes do eye exercises.

• The pupils of the eyes dilate almost half when we look at the one we love.
• The human cornea is so similar to the shark cornea that the latter is used as a substitute in eye surgery.
• Each eye contains 107 million cells, all of which are sensitive to light.
• Every 12th male representative is color blind.
• The human eye is capable of perceiving only three parts of the spectrum: red, blue and yellow. The remaining colors are a combination of these colors.
• Our eyes are about 2.5 cm in diameter and they weigh about 8 grams.
• Only 1/6 of the eyeball is visible.
• On average, we see about 24 million different images throughout our lives.
• Your fingerprints have 40 unique characteristics, while your iris has 256. This is the reason why retinal scans are used for security purposes.
• People say “in a blink of an eye” because it is the fastest muscle in the body. Blinking lasts about 100 - 150 milliseconds, and you can blink 5 times per second.
• The eyes transmit a huge amount of information to the brain every hour. The capacity of this channel is comparable to the channels of Internet providers in a large city.
• Brown eyes are actually blue under the brown pigment. There is even a laser procedure that can turn brown eyes blue forever.
• Our eyes focus on about 50 things per second.
• The images that are sent to our brain are actually upside down.
• The eyes load the brain with work more than any other part of the body.
• Each eyelash lives for about 5 months.
• The Mayans found squint attractive and tried to make sure their children were squinted.
• About 10,000 years ago, all people had brown eyes, until a person living in the Black Sea region developed a genetic mutation that resulted in blue eyes.
• If you only have one eye red in a flash photo, there is a chance that you have an eye tumor (if both eyes are looking in the same direction towards the camera). Fortunately, the cure rate is 95%.
• Schizophrenia can be detected with 98.3% accuracy using a conventional eye movement test.
• Humans and dogs are the only ones who look for visual cues in the eyes of others, and dogs only do this when interacting with humans.
• About 2% of women have a rare genetic mutation that causes them to have an extra cone retina. This allows them to see 100 million colors.
• Johnny Depp is blind in his left eye and nearsighted in his right.
• A case has been reported of conjoined twins from Canada who share a thalamus. Thanks to this, they could hear each other's thoughts and see through each other's eyes.
• The human eye can make smooth (not jerky) movements only if it is following a moving object.
• The story of the Cyclops comes from the peoples of the Mediterranean islands who discovered the remains of extinct pygmy elephants. Elephants' skulls were twice the size of a human's, and the central nasal cavity was often mistaken for the eye socket.
• Astronauts can't cry in space because of gravity. Tears gather in small balls and begin to sting your eyes.
• Pirates used blindfolds to quickly adapt their vision to the environment above and below deck. Thus, one eye got used to bright light, and the other to dim light.
• There are colors that are too “complex” for the human eye; they are called “impossible colors.”
• We see certain colors because this is the only spectrum of light that passes through water, the area where our eyes originate. There was no evolutionary reason on earth to see a wider spectrum.
• Eyes began to develop about 550 million years ago. The simplest eye was particles of photoreceptor proteins in single-celled animals.
• Sometimes people with aphakia, the absence of a lens, report seeing ultraviolet light.
• Bees have hairs in their eyes. They help determine wind direction and flight speed.
• Apollo mission astronauts reported seeing flashes and streaks of light when they closed their eyes. It was later discovered that this was caused by cosmic radiation irradiating their retinas outside of Earth's magnetosphere.
• We “see” with our brains, not with our eyes. Blurred and poor-quality images are a disease of the eyes, as the sensor receiving the distorted image. Then the brain will impose its distortions and “dead zones”.
• About 65-85% of white cats with blue eyes- deaf.

The eyes are a complex organ in structure, since they contain various working systems that perform many functions aimed at collecting information and transforming it.

The visual system as a whole, including the eyes and all their biological components, includes more than 2 million constituent units, which include the retina, lens, cornea, nerves, capillaries and vessels, iris, macula and optic nerve occupy an important place.

A person must know how to prevent diseases associated with ophthalmology in order to maintain visual acuity throughout his life.

In order to understand what the human eye is, it is best to compare the organ with a camera. The anatomical structure is presented:

1. Pupil;
2. Cornea (colorless, transparent part of the eye);
3. Iris (it determines the visual color of the eyes);
4. Lens (responsible for visual acuity);
5. Ciliary body;
6. Retina.

The following structures of the ocular apparatus also help ensure vision:

1. Choroid;
2. Optic nerve;
3. The blood supply is carried out by nerves and capillaries;
4. Motor functions are carried out by the eye muscles;
5. Sclera;
6. Vitreous body (main defense system).

Accordingly, elements such as the cornea, lens and pupil act as the “lens”. The light falling on them or Sun rays are refracted and then focused on the retina.

The lens is “autofocus”, since its main function is to change the curvature, due to which visual acuity is maintained at normal levels - the eyes are able to clearly see surrounding objects at different distances.

The retina acts as a kind of “photo film”. The image seen remains on it, which is then transmitted in the form of signals via the optic nerve to the brain, where processing and analysis takes place.

Knowing the general features of the structure of the human eye is necessary to understand the principles of operation, methods of prevention and treatment of diseases. It is no secret that the human body and each of its organs is constantly improving, which is why the eyes, in evolutionary terms, managed to achieve a complex structure.

Due to this, structures of different biology are closely interconnected in it - vessels, capillaries and nerves, pigment cells, and connective tissue also takes an active part in the structure of the eye. All these elements help the harmonious functioning of the organ of vision.

Anatomy of the eye: main structures

The eyeball, or the human eye itself, has round shape. It is located in a cavity in the skull called the orbit. This is necessary because the eye is a delicate structure that is very easy to damage.

The protective function is performed by the upper and lower eyelids. Visual movement of the eyes is provided by extrinsic muscles called the oculomotor muscles.

The eyes need constant hydration - this function is performed by the lacrimal glands. The film they form additionally protects the eyes. The glands also ensure the drainage of tears.

Another structure related to the structure of the eyes and providing their direct function is outer shell– conjunctiva. It is also located on the inner surface of the upper and lower eyelids, and is thin and transparent. Function: sliding during eye movement and blinking.

The anatomical structure of the human eye is such that it has another important membrane for the organ of vision - the sclera. It is located on the front surface, almost in the center of the organ of vision (eyeball). The color of this formation is completely transparent, the structure is convex.

The directly transparent part is called the cornea. She is the one who has hypersensitivity to various kinds of stimuli. This happens due to the presence of many nerve endings in the cornea. The lack of pigmentation (transparency) allows light to penetrate inside.

The next eye shell that forms this important organ is the choroid. In addition to providing the eyes with the necessary amount of blood, this element is also responsible for regulating tone. The structure is located from the inside of the sclera, lining it.

Every person's eyes have a certain color. A structure called the iris is responsible for this sign. Differences in shades are created due to the pigment content in the very first (outer) layer.

This is why eye color varies from person to person. The pupil is the hole in the center of the iris. Through it, light penetrates directly into each eye.

The retina, despite being the thinnest structure, is the most important structure for the quality and acuity of vision. At its core, the retina is a nervous tissue consisting of several layers.

The main optic nerve is formed from this element. That is why visual acuity and the presence of various defects such as farsightedness or myopia are determined by the condition of the retina.

The vitreous body is commonly called the cavity of the eye. It is transparent, soft, almost jelly-like in feel. The main function of the formation is to maintain and fix the retina in the position necessary for its operation.

Optical system of the eye

Eyes are one of the most anatomically complex organs. They are a “window” through which a person sees everything that surrounds him. This function can be performed by an optical system consisting of several complex, interconnected structures. The composition of “eye optics” includes:

1. Lens;

Accordingly, the visual functions they perform are the transmission of light, its refraction, and perception. It is important to remember that the degree of transparency depends on the state of all these elements, therefore, for example, if the lens is damaged, a person begins to see the picture unclearly, as if in a haze.

The main element of refraction is the cornea. The light flux hits it first, and only then enters the pupil. It, in turn, is a diaphragm on which light is additionally refracted and focused. As a result, the eye receives an image with high clarity and detail.

Additionally, the lens also performs the function of refraction. After the light flux hits it, the lens processes it, then transmits it further - to the retina. Here the image is “imprinted”.

The liquid and vitreous body present slightly contribute to refraction. However, the condition of these structures, their transparency, and sufficient quantity have a great influence on the quality of human vision.

The normal operation of the eye optical system leads to the fact that the light falling on it undergoes refraction and processing. As a result, the image on the retina is reduced in size, but completely identical to the real one.

Also note that it is upside down. A person sees objects correctly, since the finally “imprinted” information is processed in the corresponding parts of the brain. That is why all elements of the eyes, including blood vessels, are closely interconnected. Any minor violation leads to loss of visual acuity and quality.

How the human eye works

Based on the functions of each anatomical structure, we can compare the principle of operation of the eye to a camera. Light or an image first passes through the pupil, then penetrates the lens, and from it to the retina, where it is focused and processed.

The constituent elements - rods and cones - contribute to sensitivity to penetrating light. Cones, in turn, allow the eyes to perform the function of distinguishing colors and shades.

Violation of their work leads to color blindness. After refraction of the light flux, the retina translates the information imprinted on it into nerve impulses. They then enter the brain, which processes it and outputs the final image that a person sees.

Prevention of eye diseases

Eye health must be constantly maintained at a high level. That is why the issue of prevention is extremely important for any person. Checking visual acuity in medical office is not the only eye concern.

It is important to monitor the health of the circulatory system, as it ensures the functioning of all systems. Many of the irregularities identified are the result of a lack of blood or irregularities in the feeding process.

Nerves are elements that are also important. Their damage leads to impaired quality of vision, for example, the inability to distinguish the details of an object or small elements. That is why you should not overstrain your eyes.

At long work It is important to give them a rest every 15-30 minutes. Special gymnastics are recommended for those involved in work that involves prolonged examination of small objects.

In the process of prevention, one should Special attention pay attention to the illumination of the work space. Feeding the body with vitamins and minerals, eating fruits and vegetables helps prevent many eye diseases.

Inflammations should not be allowed to form, as this can cause suppuration, therefore proper hygiene the eye is a good way of preventive treatment.

Thus, the eyes are a complex object that allows us to see the world around us. It is necessary to take care and protect them from diseases, then their vision will retain its sharpness for a long period.

The structure of the eye is shown in great detail and clearly in the following video.