Occipital protuberances: normal and pathological variants. Anatomy of the human occipital bone - information Occipital bone internal view

Occipital bone, os occipitale - odd, participates in the formation of the base and roof of the skull. The upper part of the scales of the occipital bone ossifies on the basis of connective tissue, the remaining parts (main and lateral) - on the basis of cartilage. The outer surface of the occipital bone is convex, the inner surface is concave. The anterior inferior section contains the foramen magnum, foramen magnum. The occipital bone has four parts: the main one, pars basilaris, two lateral parts, partes lateralis, and the occipital scales, squama occipitalis. Until 3-6 years of a child’s life, these parts are separate bones, and then, fused, they form one bone.
Main part, pars basilaris - short, thick, quadrangular. It limits the large (occipital) foramen, foramen magnum, of oval or round shape (Yu. V. Zadvornov, 1972). The upper surface of the main part is concave in the form of a groove and faces the cranial cavity; it forms a slope, clivus, to which the medulla oblongata is adjacent. In the middle of the lower outer surface there is a small pharyngeal tubercle, tuberculum pharyngeum. The outer, slightly uneven edges of the main part, together with the stony parts of the temporal bones, form the petrooccipital fissures, which are filled with cartilage in childhood and ossify with age.
Side parts, partes lateralis - form the lateral sides of the foramen magnum and connect the main part with the scales. On the inner, cerebral surface, at the outer edge there is a narrow groove of the petrosal sinus, which, together with the same groove of the temporal bone, forms something like a canal where the inferior petrosal sinus, sul, lies. sinus petrosi inferioris.
On the lower outer surface of each lateral part is the occipital process, condylus occipitalis, for connection with the upper articular surface of the atlas. Behind the occipital condyle there is a condylar fossa, fossa condylaris, with an opening in the bottom, which leads into the unstable condylar canal, canalis condylaris. On the outer edge of the lateral part there is a jugular notch, incisura jugularis, on which a small internal jugular process, processus jugularis, protrudes. The jugular notch with the notch of the same name on the temporal bone forms the jugular foramen, foramen jugularis, which is divided by the intrajugular process into anterior and posterior sections. The jugular vein originates in the anterior one, and the cranial nerves (IX-XI pair) pass through the posterior one. Along the jugular processes from the inner surface of the lateral part there is a deep groove of the transverse sinus, sul. sinus transversus. The anterior section of the lateral part contains the jugular tubercle, tuberculum jugulare, back and down from which, between the jugular and occipital processes, lies the canal of the hypoglossal nerve, canalis nervi hypoglossi.
Occipital scales, squama occipitalis - has a triangular shape, curved, limiting the foramen magnum at the back. The lateral edge of the scales is divided into two sections: the upper (lambda-like margo lambdoideus) and the lower (mastoid, margo mastoideus). In the middle of the outer surface of the scales there is an external occipital protrusion, protuberantia occipitale externa. The upper cervical lines, linea nuchalis supreior, diverge from it. Above them are additional high cervical lines, linea nuchalis suprema. From the external occipital protrusion down to the foramen magnum, the external nuchal crest, crista occipitalis externa, is directed. In the middle of the segment connecting the foramen magnum and the external occipital protrusion, the lower cervical lines, linea nuchalis inferior, diverge in different directions. Muscles are attached to these lines. On the inner surface of the scales there is a cruciform eminence, eminentia cruciformis, in which the internal occipital protrusion, protuberantia occipitalis interna, is located. A cruciform eminence divides the inner surface of the scales into four fossae; the two lower ones contain the cerebellar hemispheres, and the upper ones contain the occipital lobes of the brain. From the cruciform eminence, grooves of the transverse sinus, sul. sinus transversa - the groove of the superior sagittal sinus goes upward, sul. sinus sagittalis superior, and downwards - the internal occipital crest, crista occipitalis interna.
Ossification. The first points of ossification in the occipital bone appear at the beginning of the 3rd month of the intrauterine period of development in the connective tissue and cartilaginous parts. In the cartilaginous part there are five points of ossification: one in the main part, two in the lateral parts and two in the cartilaginous part of the scales. In the connective tissue part of the scales there are two points of ossification. At the end of 3 months, the upper and lower sections of the scales grow together, and the main part, scales and side parts grow together at 3-6 years of life. The main part fuses with the body of the sphenoid bone mainly at the age of twenty.

Occipital bone, os occipitale, forms the posterior and lower walls of the cranium, participating simultaneously in both the cranial vault and its base. Accordingly, it (being a mixed bone) ossifies both as a covering bone on the basis of connective tissue (the upper part of the occipital scales), as well as on the basis of cartilage (the remaining parts of the bone). In humans, it is the result of the fusion of several bones that exist independently in some animals. Therefore, it consists of 4 separately laid parts that grow together into a single bone only at the age of 3-6 years. These parts, closing the foramen magnum, foramen magnum (the place of transition of the spinal cord into the medulla from the spinal canal into the cranial cavity), are as follows: in front - the basilar part, pars basilaris, on the sides - the lateral parts, partes laterales, and behind - the occipital scales, squama occipitalis. The upper part of the scales, wedged between the parietal bones, ossifies separately and often remains separated for life by a transverse suture, which is also a reflection of the existence in some animals of an independent interparietal bone, os interparietale, as it is called in humans.

The occipital scales, squama occipitalis, as a covering bone, have the appearance of a plate, convex on the outside and concave on the inside. Its external relief is due to the attachment of muscles and ligaments. Thus, in the center of the outer surface there is the external occipital protuberance, protuberantia occipitalis externa (the place where the ossification point appears). From the protrusion, it runs laterally on each side along a curved line - the upper nuchal line, linea nuchae superior. A little higher there is a less noticeable one - linea nuchе suprema (highest). From the occipital protrusion down to the posterior edge of the foramen magnum, the external nuchal crest, crista occipitalis externa, runs along the midline. From the middle of the ridge to the sides there are lower and other lines, lipae nuchae inferiores.

The relief of the internal surface is determined by the shape of the brain and the attachment of its membranes, as a result of which this surface is divided by two ridges intersecting at right angles into four pits; both of these ridges together form a cruciform eminence, eminentia cruciformis, and at the site of their intersection - the internal occipital protuberance, protuberantia occipitalis interna. The lower half of the longitudinal ridge is sharper and is called crista occipitalis interna, while the upper and both halves (usually the right) of the transverse ridge are equipped with well-defined grooves: sagittal, sulcus sinus sagittalis superioris, and transverse, sulcus sinus transversi (traces of the junction of the venous sinuses of the same name). Each of the lateral parts, partes laterales, is involved in the connection of the skull with the vertebral column, therefore, on its lower surface it bears the occipital condyle, condylus occipitalis - the place of articulation with the atlas.

Approximately near the middle of the condylus occipitalis, the hypoglossal canal canalis hypoglossalis passes through the bone. On the upper surface of the pars lateralis there is the sulcus sinus sigmoidei (a trace of the so-called venous sinus). The basilar part, pars basilaris, fuses with the sphenoid bone by the age of 18, forming a single bone in the center of the base of the skull, os basilare. On the upper surface of this bone there is a slope, clivus, fused from two parts, on which the medulla oblongata and the pons lie. On the lower surface protrudes the pharyngeal tubercle, tuberculum pharyngeum, to which the fibrous membrane of the pharynx is attached.

The occipital bone, os occipitalae, unpaired, forms the posterior part of the base and roof of the skull. There are four parts in it: the main part, pars basilaris, two lateral parts, partes laterales, and the scales, squama. In a child, these parts are separate bones connected by cartilage. In the 3rd to 6th year of life, the cartilage ossifies and they grow together into one bone. All these parts, joining together, limit a large hole, foramen magnum. In this case, the scales lie behind this hole, the main part is in front, and the side ones are on the sides. The scales are mainly involved in the formation of the posterior part of the roof of the skull, and the main and lateral parts are the base of the skull.
The main part of the occipital bone is shaped like a wedge, the base of which faces forward toward the sphenoid bone, and the apex faces posteriorly, delimiting the large foramen in front. In the main part, five surfaces are distinguished, of which the upper and lower are connected at the back at the anterior edge of the occipital foramen. The anterior surface is connected by the sphenoid bone until the age of 18–20 with the help of cartilage, which subsequently ossifies. The upper surface, the slope, clivus, is concave in the form of a groove, which is located in the sagittal direction. The medulla oblongata, pons, vessels and nerves are adjacent to the clivus. In the middle of the lower surface there is a pharyngeal tubercle, tuberculum pharyngeum, to which the initial part of the pharynx is attached. On each side of the pharyngeal tubercle, two transverse ridges extend from each side, of which m. is attached to the anterior one. longus capitis, and to the rear - m. rectus capitis anterior. The lateral rough surfaces of the main part are connected through cartilage to the petrous part of the temporal bone. On their upper surface, near the lateral edge, there is a small groove of the inferior petrosal sinus, sulcus sinus petrosi inferioris. It is in contact with a similar groove in the petrous part of the temporal bone and serves as the place to which the inferior petrosal venous sinus of the dura mater is adjacent.
The lateral part is located on both sides of the occipital foramen and connects the main part with the scales. Its medial edge faces the foramen magnum, the lateral edge faces the temporal bone. The lateral margin bears the jugular notch, incisura jugularis, which, with the corresponding notch of the temporal bone, limits the jugular foramen. The intrajugular process, processus intrajugularis, located along the edge of the notch of the occipital bone, divides the foramen into anterior and posterior. The internal jugular vein runs in the anterior one, and the IX, X, IX pairs of cranial nerves pass in the posterior. The posterior part of the jugular notch is limited by the base of the jugular process, processus jugularis, which faces the cranial cavity. Posterior and inside of the jugular process, on the inner surface of the lateral part there is a deep groove of the transverse sinus, sulcus sinus transverse. In the anterior section of the lateral part, on the border with the main part, there is a jugular tubercle, tuberculum jugulare, and on the lower surface there is an occipital condyle, condylus occipitalis, with which the skull articulates with the first cervical vertebra. The condyles, according to the shape of the upper articular surface of the atlas, form oblong ridges with convex oval articular surfaces. Behind each condyle there is a condylar fossa, fossa condylaris, at the bottom of which there is a visible opening of the outlet channel connecting the veins of the meninges with the external veins of the head. In half of the cases this hole is absent on both sides or on one side. Its width is very variable. The base of the occipital condyle is penetrated by the hypoglossal nerve canal, canalis hypoglossi.
The occipital scales, squama oscipitalis, are triangular in shape, curved, its base faces the occipital foramen, and its apex faces the parietal bones. The upper edge of the scales is connected to the parietal bones through the lambdoid suture, and the lower edge is connected to the mastoid parts of the temporal bones. In this regard, the upper edge of the scales is called lambdoid, margo lambdoideus, and the lower edge is called mastoid, margo mastoideus. The outer surface of the scales is convex, in its middle the external occipital protrusion, protuberantia occipitalis externa, rises, from which the external occipital crest, crista occipitalis externa, intersected in pairs by two nuchal lines, lineae nuchae superior et inferior, descends vertically towards the occipital foramen. In some cases, there is also a higher nuchal line, lineae nuchae suprema. Muscles and ligaments are attached to these lines. The inner surface of the occipital scales is concave, forming in the center the internal occipital protuberance, protuberantia occipitalis interna, which is the center of the cruciform eminence, eminentia cruciformis. This elevation divides the inner surface of the scales into four separate depressions. The upper two of them are adjacent to the occipital lobes of the brain, and the two lower ones are adjacent to the cerebellar hemispheres.
Ossification. It begins at the beginning of the 3rd month of intrauterine development, when islands of ossification appear in both the cartilaginous and connective tissue parts of the occipital bone. Five ossification points appear in the cartilaginous part, of which one is located in the main part, two in the lateral parts and two in the cartilaginous part of the scales. Two ossification points appear in the connective tissue upper part of the scales. By the end of the 3rd month, the upper and lower sections of the scales grow together; in the 3rd-6th year, the main part, lateral parts and scales grow together.

The occipital bone of the skull, a photo of which is presented in the article, is unpaired. It is located in the lower back. This element forms part of the arch and participates in the formation of the base. You can often hear the question from schoolchildren: “Is the occipital bone of the skull flat or tubular?” In general, all solid elements of the head have the same structure. The occipital bone, like the others, is flat. It includes several elements. Let's take a closer look at them.

Occipital bone of the skull: anatomy

This element is connected to the temporal and parietal ones through sutures. The occipital bone of the human skull includes 4 parts. It is of cartilaginous and membranous origin. The occipital bone of the animal's skull includes:

1. Scales.
2. Two articular condyles.
3. Body.
4. Two jugular processes.

Between these parts there is a large hole. Through it there is communication between the brain cavity and the spinal canal. The occipital bone of the human skull articulates with the sphenoid element and the 1st cervical vertebra. It includes:

1. Scales.
2. Condyles (lateral masses).
3. Body (basilar part).

There is also a large hole between them. It connects the cranial cavity with the spinal canal.

Scales

It is a spherical plate. Its outer surface is convex, and its inner surface is concave. When considering the structure of the occipital bone of the skull, one should study the structure of the plate. On its outer surface there are:

1. Projection (inion). It is presented in the form of an elevation in the center of the scales. When palpated, it can be felt quite well.
2. Occipital platform. It is represented by a section of scales above the protrusion.
3. Nuchal highest line. It starts from the upper boundary of the inion.
4. Nuchal upper line. It runs at the level of the protrusion between the lower and highest edges.
5. Bottom line. It passes between the upper edge and the occipital foramen.

Inner surface

It contains:

1. Cross-shaped elevation. It is located at the intersection of the internal ridge and grooves of the transverse and superior sagittal sinuses.
2. Inner ledge. It is located at the junction of the venous sinuses.
3. Inner ridge.
4. Grooves: one sagittal and two transverse sinuses.
5. Opistion. This is an identification point. It corresponds to the center of the posterior edge of the occipital foramen.
6. Bazion. This is a conditional stitch that corresponds to the center of the anterior edge of the occipital foramen.

The inner surface of the scales has a relief, which is determined by the shape of the brain and the membranes adjacent to it.

Lateral masses

They contain:

1. Jugular processes. They limit the hole of the same name on the sides. These elements correspond to the transverse vertebral processes.
2. Sublingual canal. It is located lateral and anterior to the foramen magnum. It contains the XII nerve.
3. Condylar canal located behind the condyle. It contains an emissary vein.
4. Jugular tubercle. It is located above the channel

Body

It represents the very front part. The body is sloping at the top and front. It distinguishes:

1. Bottom surface. It has a pharyngeal tubercle, the site of attachment of the pharyngeal suture.
2. Two outer lines (edges). They are connected to the pyramids of the temporal element.
3. Slope (upper surface). It is directed into the cranial cavity.

In the lateral part the groove of the petrosal inferior sinus is distinguished.

Articulations

The occipital bone of the skull is connected to the elements of the vault and base. It acts as a link between the head and the spine. As mentioned above, in the part of the head under consideration, the sphenoid element and the occipital bone of the skull are connected. Type of articulation - synchondrosis. The connection is made using the front surface of the body. It articulates with the occipital by a suture. At the junction there is a conditional point. It is called "lambda". In some cases, the interparietal bone is found here. It is formed from the upper part of the scales and is separated from it using a transverse seam. The occipital bone of the skull articulates with the temporal element by sutures:

1. Petro-jugular. The jugular process articulates with the notch of the same name in the temporal bone.
2. Petro-basilar. The lateral part of the base is connected to the pyramid of the temporal element.
3. Occipitomastoid. The mastoid part articulates with the posteroinferior plane of the temporal element.

With the atlas, the lower convex surface of the condyles connects with the concave parts of the 1st vertebra of the neck. Here a joint of the diarthrosis type is formed. It contains a capsule, synovium, and cartilage.

Ligaments

They are presented in the form of membranes:

1. Front. It is located between the base of the bone and the arch of the atlas.
2. Rear. This ligament is stretched between the back parts of the first vertebra of the neck and the foramen magnum. It is included in the composition of the corresponding surface of the spinal canal.
3. Lateral. This membrane connects the jugular process to the transverse vertebral process.
4. Pokrovnoy. It is a continuation of the longitudinal posterior membrane towards the front of the large hole. This ligament passes into the periosteum of the elements

In addition, there are:

1. Pterygoid ligaments. They go to the lateral parts of the foramen magnum.
2. Tooth ligament. It runs from the process of the 2nd cervical vertebra to the anterior border of the foramen magnum.
3. Superficial aponeurosis. It is attached along the nuchal superior line.
4. Deep aponeurosis. It is attached to the base of the occipital bone.

Muscles

They are attached to:

On the bottom line are recorded:

1. Rectus capitis posterior minor muscle. It is attached to the spinous process of the 1st vertebra of the neck.
2. The back is a big straight line. They are attached to the 2nd vertebra of the neck.
3. Oblique superior capitis muscle. It is attached to the transverse process of the 2nd cervical vertebra.

and nerves

The tentorium of the cerebellum is attached to the edges of the transverse sulcus. The falx cerebri is fixed by its posterior part. It is attached to the edges of the groove on the superior sagittal sinus. The cerebellar falx is fixed on the occipital internal crest. Pairs of nerves pass through the jugular foramen:

1. Glossopharyngeal (IX).
2. Wandering (X).
3. Additional (XI). Its spinal roots pass through the foramen magnum.

At the level of the condyles, the XII pair of nerves passes through the hypoglossal canal.

Injuries

The structure of the occipital bone of the skull is such that it is highly susceptible to mechanical damage. Moreover, they can be accompanied by serious, in some cases, fatal consequences. This is because the occipital bone of the skull protects the optic nerve. And its damage can lead to complete or partial loss of the ability to see.

Types of injuries

The following damages exist:

1. Depressed fracture of the occipital bone of the skull. It appears from mechanical impact with a blunt object. In such situations, the brain usually bears most of the load.
2. Splinter damage. It represents a violation of the integrity of the element, accompanied by the formation of fragments of various sizes. This can cause damage to the brain structure.
3. Linear fracture of the occipital bone of the skull. It also represents a violation of the integrity of the element. In this case, the damage is often accompanied by fractures of other bones, concussion and brain contusion. Such an injury appears as a thin strip on an x-ray. It divides the skull, namely its occipital bone.

The last damage is different in that the displacement of the elements relative to each other is no more than a centimeter. This fracture may go unnoticed and not manifest itself in any way. This injury occurs especially often in children during active play. If your child experiences headaches and nausea after a fall, you should consult a doctor.

A special case

The skull may suffer damage involving the foramen magnum. In this case, the brain nerves will also be injured. The clinical picture is characterized by bulbar symptoms. It is accompanied by disorders of the respiratory and cardiovascular systems. The consequences of such an injury are quite serious. This can be a violation of certain brain functions, osteoma of the occipital bone, and even death.

TBI

There are three main types of brain damage:

1. Shake.
2. Squeezing.
3. Injury.

The most common signs of a concussion include fainting lasting 30 seconds or more. up to half an hour. In addition, a person experiences nausea, vomiting, dizziness, and headaches. Short-term memory loss and irritability to noise and light are possible. With simultaneous damage to the occipital bone and concussion, a complex of symptoms is observed. A slight bruise is manifested by loss of consciousness. It can be short-lived (a few minutes) or last several hours. Paralysis and speech impairment are often observed. With a moderate injury, there is a poor reaction of the pupils to light, and nystagmus occurs - involuntary twitching of the eyes. If the damage is severe, the victim may fall into a coma for several days. In this case, compression of the brain may also occur. This occurs due to the development of a hematoma. However, in some cases, compression can cause swelling or bone fragments. This condition usually requires emergency surgery.

Consequences

Injuries to the occipital bone can cause unilateral visuospatial agnosia. Doctors call this condition disturbances of various types of perception. The victim, in particular, cannot see or understand the space to his left. In some cases, people believe that what they received does not pose a danger to them. However, for any damage, regardless of severity, you must go to the hospital. A condition that does not show any symptoms in the early stages can cause serious consequences.

Development and age-related features of the occipital bone

Anatomy and clinical biomechanics of the occipital bone

The occipital bone is a flat, unpaired spherical bone, bordering: in front - with the sphenoid bone, in front and above - with the parietal bones, in front and below - with the temporal bones, below - with the first cervical vertebra.

The occipital bone has a double embryological origin: the basilar part is of cartilaginous origin, and the squama of the occipital bone is membranous (membranous). Thus, the occipital bone is involved in the formation of the base and vault of the skull. Prenatally, the occipital bone consists of 4 parts: the interparietal squama (2 ossification nuclei), the squama of the supraoccipital part of the occipital bone (2 ossification nuclei), 2 condyles (each with one ossification nucleus) and the basilar part (2 ossification nuclei). All parts of the bone are connected by cartilage.

At birth, the cartilaginous junction of the basilar part (body) and the condyles is often injured, involving the hypoglossal nerve in the canal of the same name. Clinically, damage to this level can be expressed by impaired sucking and regurgitation. It is also possible that there is a traumatic lesion of the foramen magnum with the development of bulbar disorders (R. Caporossi, 1996).

By about 5-6 years. fusion of the scales and condylar parts of the occipital bone occurs. At 7 years of age, the fusion of the condyles and the body of the occipital bone occurs. At the same time, the formation of the hypoglossal nerve canal is completed.

occipital scales, squama occipitalis limits the foramen magnum posteriorly.

On its outer surface there are: inion, inion(point corresponding to the external occipital protrusion); lower, upper and highest nuchal lines ( linea nuchalis inferior, superior et suprema); external nuchal crest, crista occipitalis externa.

On the inner surface of the occipital scales there are: internal occipital protrusion, protuberantia occipitalis interna; internal nuchal crest, crista occipitalis interna; groove of the superior sagittal sinus, sulcus sinus sagittalis superioris; transverse sinus groove (right and left), sulcus sinus transverse; groove of the sigmoid sinus (near the jugular notch), sulcus sinus sigmoidei; occipital sinus groove, sulcus sinus occipitalis.

The internal relief corresponds to the venous sinuses and separates the two upper, cerebral and two lower, cerebellar fossae.

Lateral part (right and left), pars lateralis located lateral to the foramen magnum, foramen magnum. It includes the occipital condyle (right and left), condilus occipitalis, convex and sloping anteriorly and inwardly. Here true rotation occurs, the condyles slide in all directions. Condylar canal containing the emissary vein. Hypoglossal canal, oblique anteriorly, perpendicular to the condyle and containing the hypoglossal nerve. Lateral to the jugular foramen is the jugular process, oriented outward. The jugular process corresponds to the transverse process of C1. The jugular processes are involved in the formation of petrojugular synchondrosis, which presumably ossifies at 5-6 years. The internal jugular vein passes through the jugular foramen, which drains approximately 95% of the venous blood from the skull. Thus, when the petrojugular suture is blocked, cephalalgia of venous stasis may occur.

Basilar part of the occipital bone, pars basilaris, located anterior to the large hole, square in shape, sloping from top to bottom and front to back. On the lower (outer) surface of the basilar part there is a pharyngeal tubercle, tuberculum pharyngeum. The beginning of the laryngeal-esophageal-pharyngeal fascia, which is a tube surrounding the formations of the same name in the neck, is attached to the pharyngeal tubercle. Osteopaths call it the central ligament, it continues to the thoraco-abdominal diaphragm. The consequence of its downward tension may be straightening of the cervical lordosis (reciprocal tension of the nuchal ligament), and one of the possible causes will be gastric dysfunction. On the upper (inner) surface, a slope is determined, clivus, bazion (the point corresponding to the middle of the anterior edge of the large foramen), two lateral edges, articulating with the pyramids of the temporal bones and, the anterior edge, articulating with the body of the sphenoid bone.

Rice. Occipital bone (according to H. Feneis, 1994): 1 – foramen magnum; 2 – bazion; 3 – condylar part; 4 – scales of the occipital bone; 5 – mastoid edge; 6 – parietal edge; 7 – occipital condyle; 8 – condylar canal; 9 – canal of the hypoglossal nerve; 10 – jugular process; 11 – intrajugular process; 12 – external occipital protuberance (inion); 13 – cruciform elevation; 14 – internal occipital protrusion; 15 – groove of the superior sagittal sinus; 16 – groove of the transverse sinus; 17 – groove of the sigmoid sinus.

From a mechanical point of view, the connection between the occipital bone and the eyes is revealed. With damage to the occipital bone, a violation of accommodation can often be observed. On the other hand, when the eyes are affected, dizziness, straightening of the cervical lordosis, and cervicalgia are often detected.