During veterinary-sanitary or forensic examinations, the doctor has to determine the type of animal from the carcass, corpse, their parts or individual bones. Often the decisive factor is the presence or absence of some detail or shape feature. Knowledge of the comparative anatomical features of the bone structure allows us to confidently draw a conclusion about the type of animal.

CERVICAL VERTEBRA - vertebrae cervicales.

Atlas - atlas - first cervical vertebra (Fig. 22).

At the large cattle The transverse processes (wings of the atlas) are flat, massive, set horizontally, their caudolateral acute angle is pulled back, the dorsal arch is wide. The wing has an intervertebral and alar foramen, but no transverse one.

The ovine caudal margin of the dorsal arch has a deeper, gentle notch, and there are also only two openings on the wing.

Rice. 22. Atlas cows (I), sheep Ш), goats (III), horses (IV), pigs (V), dogs (VI)

In goats, the lateral edges of the wings are slightly rounded, and the caudal notch of the dorsal arch is deeper and narrower than in sheep and cattle, and there is no transverse foramen.

In horses, on significantly developed, thinner, inclined wings, in addition to the alar and intervertebral foramina, there is a transverse foramen. The caudal edge of the dorsal arch has a deep, gently sloping notch.

In pigs, all cervical vertebrae are very short. Atlas has massive narrow wings with thickened rounded edges. The wing has all three openings, but the transverse one can be seen only along the caudal edge of the atlas wings, where it forms a small canal.

In dogs, the atlas has widely spaced lamellar wings with a deep triangular notch along its caudal margin. There are both intervertebral and transverse foramina, but instead of the alar foramen there is an alar notch - incisure alaris.

Axis, or epistropheus, - axis s. epistropheus - second cervical vertebra (Fig. 23).

Rice. 23. Axis (epistrophe) of a cow (1), sheep (II), goat (III), horse (IV), pig (V), dog (VI)

Rice. 24. Cervical vertebrae (middle) cow* (O, horses (II), pigs (III), dogs (IV)

In cattle, the axial vertebra (epistropheus) is massive. The odontoid process is lamellar, semi-cylindrical in shape. The crest of the axial vertebra is thickened along the dorsal edge, and the caudal articular processes at its base project independently.

In horses, the axial vertebra is long, the odontoid process is wide, flattened, the crest of the axial vertebra bifurcates in the caudal part, and on the ventral side of this bifurcation lie the articular surfaces of the caudal articular processes.

In pigs, the epistrophy is short, the odontoid process in the form of a wedge has a conical shape, the ridge is high (increases in the caudal part).

In dogs, the axial vertebra is long, with a long wedge-shaped odontoid process; the crest is large, lamellar, protrudes forward and hangs over the odontoid process.

Typical cervical vertebrae - vertebrae cervicales - third, fourth and fifth (Fig. 24).

In cattle, the typical cervical vertebrae are shorter than in the horse, the fossa and head are well defined. In the bifurcated transverse process, its cranioventral part (costal process) is large, lamellar, extended downward, the caudodorsal branch is directed laterally. The spinous processes are round, well defined and directed cephalad.

Horses have long vertebrae with a well-defined head, fossa and ventral ridge. The transverse process is bifurcated along the sagittal plane, both parts of the process are approximately equal in size. There are no spinous processes (in their place there are scallops).

Pig vertebrae are short, the head and fossa are flat. The costal processes are wide below, oval-rounded, drawn down, and the caudodorsal plate is directed laterally. There are spinous processes. An additional cranial intervertebral foramen is very typical for the cervical vertebrae of pigs.

Dogs have typical cervical vertebrae that are longer than pigs, but the head and fossa are also flat. The plates of the transverse costal process are almost identical and bifurcate along the same sagittal plane (as in the horse). Instead of spinous processes there are low ridges.

Sixth and seventh cervical vertebrae.

In cattle, on the sixth cervical vertebra, a powerful plate of the costal process extended ventrally has square shape, on the body of the seventh there is a pair of caudal costal facets, the transverse process is not bifurcated. The lamellar spinous process is high. There is no transverse hole, like the horse and pig.

In horses, the sixth vertebra has three small plates on the transverse process, the seventh is massive, does not have a transverse foramen, is shaped like the first thoracic vertebra of a horse, but has only one pair of caudal costal facets and a low spinous process on the body.

Rice. 25. Thoracic vertebrae of a cow (I), horse (II), pig (III), dog (IV)

The sixth vertebra of the pig has a wide powerful plate of the transverse process extended ventrally oval shape, on the seventh, the intervertebral foramina are double and the spinous process is high, lamellar, set vertically.

In dogs, the sixth vertebra has a wide plate of the costal process beveled from front to back and downwards; on the seventh, the spinous process is set perpendicularly, has an awl-shaped shape, caudal costal facets may be absent.

Thoracic vertebrae - vertebrae thoracicae (Fig. 25).

Cattle have 13 vertebrae. In the area of ​​the withers, the spinous processes are wide, lamellar, and caudally inclined. Instead of a caudal vertebral notch, there may be an intervertebral foramen. The diaphragmatic vertebra is the 13th with a vertical spinous process.

Horses have 18-19 vertebrae. In the area of ​​the withers, the 3rd, 4th and 5th spinous processes have club-shaped thickenings. The articular processes (except the 1st) have the appearance of small contiguous articular surfaces. Diaphragmatic vertebra - 15th (sometimes 14th or 16th).

Pigs have 14-15 vertebrae, maybe 16. The spinous processes are wide, lamellar, vertically set. At the base of the transverse processes there are lateral openings running from top to bottom (dorsoventrally). There are no ventral ridges. Diaphragmatic vertebra - 11th.

Dogs have 13 vertebrae, rarely 12. The spinous processes in the withers area at the base are curved and directed caudally. The first spinous process is the highest; on the latter, accessory and mastoid processes run ventrally from the caudal articular processes. Diaphragmatic vertebra - 11th.

Lumbar vertebrae - vertebrae lumbales (Fig. 26).

Cattle have 6 vertebrae. They have a long body, slightly narrowed in the middle part. ventral ridge. The transverse costal (transverse) processes are dorsally (horizontally) located, long, lamellar, with pointed, uneven edges and ends curved cranially. The articular processes are powerful, widely spaced, with strongly concave or convex articular surfaces.

Horses have 6 vertebrae. Their bodies are shorter than those of cattle, the transverse costal processes are thickened, especially the last two or three, on which flat articular surfaces are located along the cranial and caudal edges (in old horses they often synostose). The caudal surface of the transverse costal process of the sixth vertebra is connected by a joint to the cranial edge of the wing of the sacral bone. Normally, there is never synostosis here. The articular processes are triangular in shape, less powerful, closer together, with flatter articular surfaces.

Rice. 26. Lumbar vertebrae of a cow (I), horse (I), pig (III), dog (IV)

Pigs have 7, sometimes 6-8 vertebrae. The bodies are long. The transverse costal processes are horizontally located, lamellar, slightly curved, have lateral notches at the base of the caudal edge and lateral openings closer to the sacrum. The articular processes, like those of ruminants, are powerful, widely spaced, strongly concave or convex, but, unlike ruminants, they have mastoid processes, making them more massive.

Dogs have 7 vertebrae. The transverse costal processes are lamellar and directed cranioventrally. The articular processes have flat articular, slightly inclined surfaces. The accessory and mastoid (on the cranial) processes are strongly pronounced on the articular processes.

The sacral bone is os sacrum (Fig. 27).

In cattle, 5 vertebrae are fused. They have massive quadrangular wings located almost on a horizontal plane, with a slightly raised cranial edge. The spinous processes have fused to form a powerful dorsal ridge with a thickened edge. The ventral (or pelvic) sacral foramina are extensive. Complete synostosis of the vertebral bodies and arches normally occurs by 3-3.5 years.

In horses, 5 fused vertebrae have horizontally located triangular-shaped wings with two articular surfaces - auricular, dorsal for connection with the wing of the iliac bone of the pelvis and cranial for connection with the transverse costal process of the sixth lumbar vertebra. The spinous processes grow together only at the base.

In pigs, 4 vertebrae are fused. The wings are rounded, placed along the sagittal plane, the articular (ear-shaped) surface is on their lateral side. There are no spinous processes. Interarch openings are visible between the arches. Normally, synostosis occurs by 1.5-2 years.

In dogs, 3 vertebrae are fused. The wings are rounded, set, like those of a pig, in the sagittal plane with a laterally located articular surface. In the 2nd and 3rd vertebrae the spinous processes are fused. Synostosis is normal by 6-8 months.

Tail vertebrae - vertebrae caudales s. coccygeae (Fig. 28),

Cattle have 18-20 vertebrae. Long, on the dorsal side of the first vertebrae rudiments of arches are visible, and on the ventral side (on the first 9-10) there are paired hemal processes, which can form hemal arches on the 3rd-5th vertebrae. "The transverse processes are wide, lamellar, curved ventrally.

Fig 27. Sacral bone of a cow (1), sheep (I), goat (III), horse (IV), pig (V), dog (VI)

Horses have 18-20 vertebrae. They are short, massive, retain arches without spinous processes; only on the first three vertebrae the transverse processes are flat and wide, disappearing on the last vertebrae.

Pigs have 20-23 vertebrae. They are long, arched with spinous processes, inclined caudally, preserved on the first five to six vertebrae, which are flatter, then become cylindrical. The transverse processes are wide.

Rice. 28. Caudal vertebrae of a cow (I), horse (II), pig (III), dog (IV)

Dogs have 20-23 vertebrae. On the first five to six vertebrae, the arches, cranial and caudal articular processes are preserved. The transverse processes are large, long, extended caudoventrally.

Ribs - costae (Fig. 29, 30).

Cattle have 13 pairs of ribs. They have a long neck. The first ribs are the strongest and the shortest and straightest. The middle ones are lamellar, widening significantly downwards. They have a thinner caudal edge. The hind ones are more convex, curved, with the head and tubercle of the ribs closer together. The last rib is short, thins downward, and may be hanging. It can be felt in the upper third of the costal arch.

Synostosis of the head and tubercle of the rib with the body in young animals does not occur simultaneously and goes from front to back. The first to fuse with the body is the head and tubercle of the first rib. The articular surface of the tubercle is saddle-shaped. The sternal ends of the ribs (2nd to 10th) have articular surfaces for connection with the costal cartilages, which have articular surfaces at both ends. There are 8 pairs of sternal ribs.

Horses have 18-19 pairs of ribs. Most of them are of uniform size along the entire length, the first is significantly expanded ventrally, up to the tenth the curvature and length of the ribs increase, then begin to decrease. The first 6-7 ribs are the widest and most lamellar. Unlike ruminants, their caudal edges are thicker and their neck is shorter. The tenth rib is almost tetrahedral. There are 8 pairs of sternal ribs.

Pigs often have 14, maybe 12 or up to 17 pairs of ribs. They are narrow, from the first to the third or fourth the width increases slightly. They have articular surfaces for connection with the costal cartilages. In adults, the sternal ends are narrowed, in piglets they are slightly widened. On the tubercles of the ribs there are small flat statutory facets; the bodies of the ribs have a faintly visible spiral turn. There are 7 (6 or 8) pairs of sternal ribs.

Dogs have 13 pairs of ribs. They are arched, especially in the middle part. Their length increases to the seventh rib, their width to the third or fourth, and their curvature to the eighth rib. On the tubercles the facet ribs are convex, there are 9 pairs of sternal ribs.

The breast bone is sternum (Fig. 31).

In cattle it is powerful and flat. The handle is rounded, raised, does not protrude beyond the first ribs, and is connected to the body by a joint. The body expands caudally. On the xiphoid process there is a significant plate of xiphoid cartilage. Along the edges there are 7 pairs of articular costal fossae.

In horses it is laterally compressed. It has a significant cartilaginous addition on the ventral edge, forming a ventral ridge, which protrudes on the handle, rounding, and is called a hawk. In adult animals, the manubrium and body are fused. Cartilage without xiphoid process. Along the dorsal edge of the sternum there are 8 pairs of articular costal fossae.

Rice. 29. Ribs of a cow (I), horse (II)

Rice. 30. Vertebral end of horse ribs

Rice. 31. Cow breast bone (I). sheep (II), goats (III), horses (IV), pigs (V), dogs (VI)

In pigs, like in cattle, it is flat, connected to the handle by a joint. The handle, unlike ruminants, in the form of a rounded wedge protrudes in front of the first pairs of ribs. The xiphoid cartilage is elongated. On the sides there are (7-8) pairs of articular costal fossae.

In dogs, it is in the form of a round, bead-shaped stick. The handle protrudes in front of the first ribs with a small tubercle. The xiphoid cartilage is rounded, on the sides there are 9 pairs of articular costal fossae.

Chest - thorax.

In cattle it is very voluminous, in the front part it is laterally compressed, and has a triangular exit. Behind the shoulder blades it expands strongly in the caudal direction.

In horses, it is cone-shaped, long, slightly compressed from the sides, especially in the area where the shoulder girdles are attached.

In pigs, it is long, laterally compressed, the height and width vary among different breeds.

Dogs are cone-shaped with steep sides, the inlet is rounded, the intercostal spaces - spatia intercostalia - are large and wide.

Self-test questions

1. What is the importance of the movement apparatus in the life of the body?

2. What functions does the skeleton perform in the body in mammals and birds?

3. What stages of development in phylo- and ontogenesis do the internal and external skeletons of vertebrates go through?

4. What changes occur in the bones with increasing static load (with limited motor activity)?

5. How is bone built as an organ and what differences are there in its structure in young growing organisms?

6. What sections is the vertebral column divided into in terrestrial vertebrates and how many vertebrae are there in each section in mammals?

7. In which part of the axial skeleton is there a complete bone segment?

8. What are the main parts of a vertebra and what parts are located on each part?

9. In which parts of the spinal column did the vertebrae undergo reduction?

10. By what features will you distinguish the vertebrae of each section of the spinal column and by what features will you determine the species characteristics of the vertebrae of each section?

11. What characteristic features structures have an atlas and an axial vertebra (epistropheus) in domestic animals? What is the difference between the atlas of pigs and the axial vertebra of ruminants?

12. By what feature can you distinguish the thoracic vertebra from the other vertebrae of the spinal column?

13. By what features can you distinguish the sacral bone of cattle, horses, pigs and dogs?

14. Name the main features of the structure of a typical cervical vertebra in ruminants, pigs/horses and dogs.

15. Which one is the best? characteristic feature have lumbar vertebrae? How do they differ between ruminants, pigs, horses and dogs?

2.1. Origin and functions of the animal skeleton.

The supporting structures in invertebrate animals that provide them with a permanent body shape are very diverse. They are of ecto-, ento- and mesodermal origin. In vertebrates, the skeleton is mainly of mesodermal origin.

The skeleton in the animal body performs various functions:

Ensuring constant body shape;

Passive part of the musculoskeletal system;

Protection from mechanical and other influences;

Hematopoietic function.

2.2. Evolution of the skeleton in the series of invertebrate animals.

In sponges, the supporting structures are represented by needles having different chemical compositions.

In coelenterates, a dense supporting plate (mesoglea) appears, which occupies the space between the ecto- and endoderm. The skeleton of coral polyps develops from the ectoderm. In arthropods, the exoskeleton is represented by a chitinized cover, which includes functions of protection against mechanical damage and the exoskeleton, to which the striated muscles that first appeared in arthropods are attached.

Bivalves and gastropods have shells formed by secretions of the mantle. Cephalopods have complex cartilaginous structures that protect nerve centers and sense organs.

2.3. Evolution of the skeleton in chordates.

As in invertebrates, the skeleton of chordates serves as a protection for organs and serves as a support for organs of locomotion.

Axial skeleton has undergone great changes in the process of evolution.

In lower chordates, the axial skeleton is the notochord, and in higher chordates it is gradually replaced by developing vertebrae. The vertebrae are divided into a body, upper and lower arches.

Thus, in cyclostomes, the notochord is preserved throughout life, but vertebral anlages appear, which are small cartilaginous formations metamerically located above the notochord. They are called the upper arcs.

In primitive fish, in addition to the upper arches, lower arches appear, and in higher fish, vertebral bodies appear. The vertebral bodies in most fish and higher animals are formed from the tissue surrounding the notochord, as well as from the bases of the arches. The upper and lower arches are fused with the vertebral bodies. The ends of the upper arches grow together, forming the spinal canal. On the lower arches, processes appear to which the ribs are attached. Fish have two sections of the spine - the trunk and the caudal. The remains of the notochord in fish are preserved between the vertebral bodies.

In amphibians early stages development, the notochord is replaced by the spine. The spine already has four sections: cervical, thoracic, sacral and caudal. The cervical region has only one vertebra, the thoracic region consists of five vertebrae. Small ribs ending freely are attached to the thoracic vertebrae. The sacral region, like the cervical region, includes one vertebra, which is a support for the bones of the pelvis and hind limbs. The caudal region in tailless amphibians is fused into one bone, while in tailed amphibians it consists of a large number of vertebrae.

Reptiles have five sections in the spine: cervical, thoracic, lumbar, sacral and caudal. In the cervical region, different species of reptiles have different numbers of vertebrae, but the maximum is eight. The first vertebra is called the atlas and has the shape of a ring, and the second is called the epistropheus and has an odontoid process on which the first vertebra rotates. In the thoracic region, the number of vertebrae is not constant; ribs are attached to them, most of which are connected to the sternum, forming the rib cage for the first time in higher animals. There are only 22 vertebrae in the thoracolumbar region, and two in the sacral region. Ribs are also attached to the lumbar and sacral vertebrae. In the caudal region the number of vertebrae varies, sometimes there are several dozen.

In birds, the vertebral column is similar to that of reptiles, but has a certain specialization in the caudal connection. and the spine - the trunk ribs. It is found from the IVDr surrounding the notochord, as well as from the base of the arc formation, with the way of life. Cervical region includes up to 25 vertebrae, which provides greater mobility.

In mammals, the spine has five sections: cervical thoracic, lumbar, sacral and caudal. There are seven vertebrae in the cervical region, and a variable number of vertebrae in the thoracic region (from 9 to 24, but more often 12-13). The thoracic vertebrae are joined by ribs, a large number of which are connected to the sternum. The lumbar region includes from three to nine vertebrae. The sacral vertebrae are fused to form the sacrum, and the caudal spine contains varying numbers of vertebrae in different mammal species.

Skeleton of the head. The skeleton of the head is the skull. It is located at the anterior end of the skeleton and consists of two parts: the cranium and the visceral skeleton, which differ from each other both in origin and in function. The cranium serves as a container for the brain, and the visceral skeleton provides support for the organs of the anterior part of the digestive canal.

During the process of evolution, the greatest changes occur in the visceral region. In the embryos of all vertebrates, and in lower vertebrates throughout life, the visceral skeleton consists of arches covering the anterior part of the digestive tube. In fish, they are differentiated into the jaw arch (food capture), hyoid arch (attachment to the skull) and branchial arch (gill attachment).

In terrestrial animals, the visceral skeleton is greatly transformed and reduced: top part The jaw arch fuses with the bottom of the skull; small bones are formed from the hyoid arch, which are part of the middle ear. The second and third branchial arches in mammals form the thyroid cartilage, and the fourth and fifth arches form the remaining cartilages of the larynx.

Skeleton of limbs. There are two types of free limbs. These are the fins of fish and the five-fingered limbs of mammals. The five-fingered limbs of vertebrates have a very diverse structure, which is associated with their performance various functions. For example, the burrowing limbs of a mole, the swimming limbs of a seal, the climbing limbs of monkeys, etc. But nevertheless, despite the differences, the limbs of vertebrates retain a general structural plan, which proves their common origin.

For the first time, limbs appeared in fish and were represented by fins. These are paired pectoral and ventral fins. In most fish, fins consist of radial thin bony rays and serve the function of changing the direction of swimming, rather than supporting the body. In lobe-finned fish, the rays are expected to enlarge due to the fusion and use of fins as support and movement along the solid base of drying up water bodies. Therefore, the fins of ancient lobe-finned fish formed the basis for the development of the limbs of vertebrates. An important feature of the transformation of fins into the limbs of terrestrial vertebrates was the replacement of the strong connection of skeletal elements with a movable connection in the form of joints. As a result of this, the limb has turned into a complex movable lever, in which three bones are distinguished: the shoulder, forearm and hand. There are two limb girdles - shoulder and pelvic.

Further, the evolution of the forelimb followed the path of lengthening the shoulder and forearm, shortening the wrist, reducing the number of bones in the carpal region (in amphibians - 3 rows, in mammals - 2 rows) and lengthening of the distal sections, i.e. phalanges of fingers.

The skeleton of the human hand is also characterized by a general structural plan with the forelimbs of vertebrates, but along with this it also has important differences, since the human hands are not only weapons of labor, but also the result of it and are capable of performing a variety of actions.

2.4. Anomalies and malformations of the human skeleton.

1. The presence of ribs at the lower cervical or first lumbar vertebrae. In accordance with the evolution of vertebrates in humans, during embryonic development, ribs are formed in all parts of the spine, but subsequently they are preserved only in the thoracic region, and in other parts the ribs are reduced. But sometimes a person experiences similar atavisms.

2. Presence of caudal vertebrae. During embryogenesis in humans, like vertebrates, 8-11 caudal vertebrae are formed, then they are reduced and 4-5 underdeveloped vertebrae remain, forming the coccyx. Sometimes atavistic signs appear in the form of the presence of the caudal spine.

3. Spina bifida- This is a common anomaly that occurs when the fusion of the upper vertebral arches is disrupted. It most often manifests itself in the lumbosacral region of the spine and, depending on the depth and extent of the cleft, can have varying degrees gravity.

4. The presence in the tympanic cavity of only one auditory ossicle - the column. This disorder, corresponding to the structure of the sound-transmitting apparatus of amphibians and reptiles, is the result of incorrect differentiation of the elements of the maxillary gill arch into the auditory ossicles. This is a recapitulation of the main stages of phylogeny of the visceral skull in ontogenesis.

5. Heterotopia of the upper limb girdle. This is the movement of the upper limb girdle from the cervical region to the level of 1-2 thoracic vertebrae. This anomaly is called Sprengel's disease or congenital high scapula. It is expressed in the fact that the shoulder girdle on one or both sides is several centimeters higher than the normal position. The mechanism of such a disorder is associated both with a violation of the movement of organs and with a violation of morphogenetic correlations.

6. Polydactyly- the result of the development of the anlages of additional fingers, characteristic of distant ancestral forms.

7. Flat feet, club feet, narrow chest, lack of chin protuberance– atavistic skeletal anomalies, which are often found and are anobolias (superstensions) that arose during the phylogenesis of primates.

The musculoskeletal system ensures movement and preservation of the animal’s body position in space, forms the external shape of the body and participates in metabolic processes. It accounts for about 60% of the body weight of an adult animal.

Conventionally, the musculoskeletal system is divided into passive and active parts. TO passive part include bones and their connections, on which the nature of the mobility of bone levers and links of the animal’s body depends (15%). Active part consists of skeletal muscles and their auxiliary attachments, thanks to the contractions of which the bones of the skeleton are set in motion (45%). Both active and passive parts have a common origin (mesoderm) and are closely interconnected.

Functions of the motion apparatus:

1) Motor activity is a manifestation of the vital activity of the organism; it is what distinguishes animal organisms from plant organisms and determines the emergence of a wide variety of modes of movement (walking, running, climbing, swimming, flying).

2) The musculoskeletal system forms the shape of the body - exterior animal, since its formation occurred under the influence of the Earth’s gravitational field, its size and shape in vertebrate animals are distinguished by significant diversity, which is explained by different living conditions (terrestrial, terrestrial-woody, airy, aquatic).

3) In addition, the movement apparatus provides a number of vital functions of the body: searching and capturing food; attack and active defense; carries out respiratory function lungs (respiratory motor skills); Helps the heart move blood and lymph through the vessels (“peripheral heart”).

4) In warm-blooded animals (birds and mammals), the movement apparatus ensures the maintenance of a constant body temperature;

The functions of the movement apparatus are provided by the nervous and cardiovascular systems, respiratory, digestive and urinary organs, skin, glands internal secretion. Since the development of the movement apparatus is inextricably linked with the development nervous system, then when these connections are broken, first paresis, and then paralysis movement apparatus (the animal cannot move). With a decrease in physical activity, a violation occurs metabolic processes and atrophy of muscle and bone tissue.

The organs of the musculoskeletal system have properties of elastic deformations, when moving, mechanical energy arises in them in the form of elastic deformations, without which normal blood circulation and impulses of the brain and spinal cord cannot occur. The energy of elastic deformations in bones is converted into piezoelectric energy, and in muscles into thermal energy. The energy released during movement displaces blood from the vessels and causes irritation of the receptor apparatus, from which nerve impulses enter the central nervous system. Thus, the work of the movement apparatus is closely connected and cannot be carried out without the nervous system, and vascular system in turn, cannot function normally without a movement apparatus.

The basis of the passive part of the movement apparatus is the skeleton. Skeleton (Greek sceletos - dried, dried; lat. Skeleton) are bones connected in a certain order that form a solid frame (skeleton) of the animal’s body. Since the Greek word for bone is “os,” the science of the skeleton is called osteology.

The skeleton includes about 200-300 bones (Horse, r.s. -207-214; pig, dog, cat -271-288), which are connected to each other using connective, cartilaginous or bone tissue. The skeletal mass of an adult animal ranges from 6% (pig) to 15% (horse, cattle).

All skeletal functions can be divided into two large groups: mechanical and biological. TO mechanical functions include: protective, support, locomotor, spring, anti-gravity, and biological – metabolism and hematopoiesis (hemocytopoiesis).

1) The protective function is that the skeleton forms the walls of the body cavities in which vital important organs. For example, the cranial cavity contains the brain, the chest contains the heart and lungs, and the pelvic cavity contains the genitourinary organs.

2) The supporting function is that the skeleton provides support for muscles and internal organs, which are attached to the bones and are held in their position.

3) The locomotor function of the skeleton is manifested in the fact that the bones are levers that are driven by muscles and ensure the movement of the animal.

4) The spring function is due to the presence in the skeleton of formations that soften shocks and shocks (cartilaginous pads, etc.).

5) The anti-gravity function is manifested in the fact that the skeleton creates support for the stability of the body rising above the ground.

6) Participation in metabolism, especially mineral metabolism, since bones are a depot of mineral salts of phosphorus, calcium, magnesium, sodium, barium, iron, copper and other elements.

7) Buffer function. The skeleton acts as a buffer that stabilizes and maintains a constant ionic composition of the internal environment of the body (homeostasis).

8) Participation in hemocytopoiesis. Red located in the bone marrow cavities Bone marrow produces blood cells. The mass of bone marrow in relation to the mass of bones in adult animals is approximately 40-45%.

SKELETAL DIVISION

The skeleton is the frame of an animal's body. It is usually divided into main and peripheral.

To the axial skeleton include the skeleton of the head (skull-cranium), the skeleton of the neck, torso and tail. The most complex structure has a skull, since it houses the brain, organs of vision, smell, balance and hearing, mouth and nasal cavity. The main part of the skeleton of the neck, body and tail is the vertebral column (columna vertebralis).

The spinal column is divided into 5 sections: cervical, thoracic, lumbar, sacral and caudal. The cervical region consists of the cervical vertebrae (v.cervicalis); thoracic region - from the thoracic vertebrae (v.thoracica), ribs (costa) and sternum (sternum); lumbar - from the lumbar vertebrae (v.lumbalis); sacrum - from the sacrum bone (os sacrum); caudal - from the caudal vertebrae (v.caudalis). The most complete structure has the thoracic section of the body, where there are thoracic vertebrae, ribs, and breast bone, which together form the chest (thorax), in which the heart, lungs, and mediastinal organs are located. The tail region is the least developed in terrestrial animals, which is associated with the loss of the locomotor function of the tail during the transition of animals to a terrestrial lifestyle.

The axial skeleton is subject to the following laws of body structure, which ensure the mobility of the animal. These include :

1) Bipolarity (uniaxiality) is expressed in the fact that all parts of the axial skeleton are located on the same axis of the body, with the skull on the cranial pole and the tail on the opposite pole. The sign of uniaxiality allows us to establish two directions in the animal’s body: cranial - towards the head and caudal - towards the tail.

2) Bilaterality (bilateral symmetry) is characterized by the fact that the skeleton, like the torso, can be divided by the sagittal, medial plane into two symmetrical halves (right and left), in accordance with this the vertebrae will be divided into two symmetrical halves. Bilaterality (antimerism) makes it possible to distinguish lateral (lateral, external) and medial (internal) directions on the animal’s body.

3) Segmentation (metamerism) lies in the fact that the body can be divided by segmental planes into a certain number of relatively identical metamers - segments. Metameres follow an axis from front to back. On the skeleton, such metameres are vertebrae with ribs.

4) Tetrapodium is the presence of 4 limbs (2 thoracic and 2 pelvic)

5) And the last regularity is, due to the force of gravity, the location in the spinal canal of the neural tube, and below it the intestinal tube with all its derivatives. In this regard, the dorsal direction is marked on the body - towards the back and the ventral direction - towards the abdomen.

Peripheral skeleton represented by two pairs of limbs: thoracic and pelvic. In the skeleton of the limbs there is only one pattern - bilaterality (antimerism). The limbs are paired, there are left and right limbs. The remaining elements are asymmetrical. On the limbs there are girdles (thoracic and pelvic) and a skeleton of free limbs.

Using a belt, the free limb is attached to the spinal column. Initially, the limb girdles had three pairs of bones: a scapula, a clavicle and a coracoid bone (all preserved in birds); in animals, only one scapula remained; from the coracoid bone, only a process on the tubercle of the scapula on the medial side was preserved; rudiments of the clavicle are present in predators (dogs) and cat). In the pelvic girdle, all three bones (iliac, pubic and ischial) are well developed, which grow together.

The skeleton of the free limbs has three links. The first link (stilopodium) has one ray (Greek stilos - column, podos - leg): on thoracic limb- this is the humerus, on the pelvic bone - the femur. The second links (zeugopodium) are represented by two rays (zeugos - pair): on the thoracic limb there are the radius and ulna bones (bones of the forearm), on the pelvic limb there are the tibia and fibula bones (tibia bones). The third links (autipodium) form: on the thoracic limb - the hand, on the pelvic limb - the foot. They distinguish between basipodia (the upper section - the bones of the wrist and, accordingly, the tarsus), metapodium (middle - the bones of the metacarpus and metatarsus) and acropodium (the outermost section - the phalanges of the fingers).

SKELETAL PHYLOGENESIS

In vertebrate phylogenesis, the skeleton develops in two directions: external and internal.

The exoskeleton performs a protective function, is characteristic of lower vertebrates and is located on the body in the form of scales or shell (turtle, armadillo). In higher vertebrates, the external skeleton disappears, but its individual elements remain, changing their purpose and location, becoming the covering bones of the skull and, located under the skin, connected with the internal skeleton. In phylo-ontogenesis, such bones go through only two stages of development (connective tissue and bone) and are called primary. They are not able to regenerate; if the skull bones are injured, they are forced to be replaced with artificial plates.

The internal skeleton performs mainly a supporting function. During development, under the influence of biomechanical load, it constantly changes. If we consider invertebrate animals, then their internal skeleton has the form of partitions to which muscles are attached.

In primitive chordates animals (lancelet ), Along with the septa, an axis appears - the notochord (cellular cord), covered with connective tissue membranes.

U cartilaginous fish(sharks, rays) cartilaginous arches are formed segmentally around the notochord, which subsequently form vertebrae. The cartilaginous vertebrae, connecting to each other, form the spinal column, and the ribs are attached to it ventrally. Thus, the notochord remains in the form of nuclei pulposus between the vertebral bodies. The skull is formed at the cranial end of the body and, together with the vertebral column, participates in the formation of the axial skeleton. Subsequently, the cartilaginous skeleton is replaced by a bone one, less flexible, but more durable.

U bony fish the axial skeleton is built from stronger, coarse-fibrous bone tissue, which is characterized by the presence of mineral salts and a random arrangement of collagen (ossein) fibers in the amorphous component.

With the transition of animals to a terrestrial lifestyle, amphibians a new part of the skeleton is formed - the skeleton of the limbs. As a result of this, in terrestrial animals, in addition to the axial skeleton, a peripheral skeleton (the skeleton of the limbs) is also formed. In amphibians, as well as in bony fish, the skeleton is built of coarse fibrous bone tissue, but in more highly organized terrestrial animals (reptiles, birds and mammals) the skeleton is already built from lamellar bone tissue, consisting of bone plates containing collagen (ossein) fibers arranged in an orderly manner.

Thus, the internal skeleton of vertebrates goes through three stages of development in phylogenesis: connective tissue (membranous), cartilaginous and bone. The bones of the internal skeleton that go through all these three stages are called secondary (primordial).

ONTOGENESIS OF THE SKELETON

In accordance with the basic biogenetic law of Baer and E. Haeckel, in ontogenesis the skeleton also goes through three stages of development: membranous (connective tissue), cartilaginous and bone.

At the earliest stage of embryonic development, the supporting part of its body is dense connective tissue, which forms the membranous skeleton. Then a notochord appears in the embryo, and around it, first a cartilaginous, and later a bony spinal column and skull, and then limbs begin to form.

In the prefetal period, the entire skeleton, with the exception of the primary integumentary bones of the skull, is cartilaginous and makes up about 50% of the body weight. Each cartilage has the shape of a future bone and is covered with perichondrium (a dense connective tissue membrane). During this period, ossification of the skeleton begins, i.e. formation of bone tissue in place of cartilage. Ossification or ossification (Latin os - bone, facio - do) occurs both from the outer surface (perichondral ossification) and from the inside (enchondral ossification). In place of the cartilage, coarse fibrous bone tissue is formed. As a result of this, in fruits the skeleton is built of coarse fibrous bone tissue.

Only in the neonatal period is coarse fibrous bone tissue replaced by more advanced lamellar bone tissue. During this period, special attention to newborns is required, since their skeleton is not yet strong. As for the chord, its remains are located in the center intervertebral discs in the form of nucleus pulposus. During this period, special attention should be paid to the integumentary bones of the skull (occipital, parietal and temporal), as they bypass the cartilaginous stage. Between them in ontogenesis, significant connective tissue spaces called fontanelles (fonticulus) are formed; only in old age do they completely undergo ossification (endesmal ossification).



Question 1.
Skeleton performs the following functions:
1) supporting - for all other systems and organs;
2) motor - ensures the movement of the body and its parts in space;
3) protective - protects against external influences organs of the chest and abdominal cavity, brain, nerves, blood vessels.

Question 2.
Distinguish two types of skeleton– external and internal. Some protozoa, many mollusks, arthropods have an exoskeleton - these are the shells of snails, mussels, oysters, the hard shells of crayfish, crabs, and the light but durable chitinous coverings of insects. Invertebrate radiolarians, cephalopods and vertebrates have an internal skeleton.

Question 3.
The body of mollusks is usually enclosed in a shell. The sink may consist of two doors or be of another shape in the form of a cap, curl, spiral, etc. The shell is formed by two layers - the outer, organic, and the inner, made of calcium carbonate. The calcareous layer is divided into two layers: behind the organic layer lies a porcelain-like layer formed by prismatic crystals of calcium carbonate, and below it is a mother-of-pearl layer, the crystals of which have the shape of thin plates on which light interference occurs.
The shell is an external hard skeleton.

Question 4.
The body and limbs of insects have a chitinized cover - the cuticle, which is the exoskeleton. The cuticle of many insects is equipped big amount hairs that perform the function of touch.

Question 5.
Protozoa can form external skeletons in the form of shells or shells (foraminifera, radiolarians, armored flagellates), as well as internal skeletons of various shapes. Main function protozoan skeleton, protective.

Question 6.
The presence of hard covers in arthropods prevents the continuous growth of animals. Therefore, the growth and development of arthropods is accompanied by periodic molting. The old cuticle is shed, and until the new one hardens, the animal grows.

Question 7.
Vertebrates have an internal skeleton, the main axial element of which is the notochord. In vertebrates, the internal skeleton consists of three sections - the skeleton of the head, the skeleton of the trunk and the skeleton of the limbs. Vertebrates (amphibian fish, reptiles, birds, mammals) have an internal skeleton.

Question 8.
Plants then they also have supporting structures with the help of which they carry the leaves towards the sun and support them in such a position that the leaf blades are illuminated as best as possible sunlight. In woody plants, the main support is mechanical tissue. There are three types of mechanical fabrics:
1) collenchyma is formed from living cells of various shapes. They are found in young plant stems and leaves;
2) the fibers are represented by dead elongated cells with uniformly thickened membranes. Fibers are part of wood and bast. An example of non-lignified bast fibers is flax;
3) stony cells have irregular shape and highly thickened lignified shells. These cells form nut shells, stones of drupes, etc. Stony cells are found in the pulp of pear and quince fruits.
In combination with other tissues, mechanical tissue forms a kind of “skeleton” of the plant, especially developed in the stem. Here it often forms a kind of cylinder running inside the stem, or is located along it in separate strands, providing bending strength to the stem. In the root, on the contrary, the mechanical tissue is concentrated in the center, increasing the root's tensile strength. Wood also plays a mechanical role; even after dying, wood cells continue to perform a supporting function.

Phylogeny of the vertebrate skeleton.

The vertebrate skeleton is formed from the mesoderm and consists of 3 sections: the skeleton of the head (skull), the axial skeleton of the body (chord, spine and ribs), the skeleton of the limbs and their girdles.

The main directions of evolution of the axial skeleton:

1. Replacement of the chord with the spine, cartilage tissue with bone.

2. Differentiation of the spine into sections (from two to five).

3. Increase in the number of vertebrae in departments.

4. Formation chest.

Cyclostomes and lower fish retain the notochord throughout their lives, but they already have vertebral primordia (paired cartilaginous formations located above and below the notochord): the upper arches in cyclostomes, and the lower arches in fish.

In bony fishes, vertebral bodies develop, spinous and transverse processes appear, and the spinal cord canal is formed. The spine consists of 2 sections: trunk and caudal. The trunk region has ribs that end freely on the ventral side of the body.

In amphibians, 2 new sections appear: cervical and sacral, each of them containing one vertebra. There is a cartilaginous sternum. The ribs of tailed amphibians are of insignificant length and never reach the sternum; tailless amphibians have no ribs.

The reptile spine is divided into the cervical region, which contains 8-10 vertebrae, the thoracic, lumbar (in these regions - 22 vertebrae), the sacral - 2 and the caudal, which can contain several dozen vertebrae. First two cervical vertebrae have special structure, resulting in greater head mobility. The last three cervical vertebrae each have a pair of ribs. First five pairs of ribs thoracolumbar region join the cartilaginous sternum to form the rib cage.

In mammals, the spine consists of 5 sections. The cervical region has 7 vertebrae, the thoracic region - from 9 to 24, the lumbar region - from 2 to 9, the sacral region - 4-10 or more, and in the caudal region there are very large variations. There is a reduction of the ribs in the cervical and lumbar regions. The sternum is bony. 10 pairs of ribs extend to the sternum, forming the rib cage.

Ontophylogenetically determined skeletal anomalies: additional ribs at the seventh cervical or first lumbar vertebra, splitting of the posterior arch of the vertebrae, non-fusion of the spinous processes of the vertebrae ( Spinabifida), an increase in the number of sacral vertebrae, the presence of a tail, etc.

The vertebrate skull develops as an extension of the axial skeleton ( brain section) and as a support for the respiratory and anterior digestive systems ( visceral section).

The main directions of skull evolution:

1. Combining the visceral (facial) part with the cerebral part, increasing the volume of the cerebral part.

2. Reducing the number of skull bones due to their fusion.

3. Replacement of a cartilaginous skull with a bone one.

4. Movable connection of the skull with the spine.

The origin of the axial skull is associated with metamerism (segmentation) of the head. Its laying comes from two main sections: chordal– on the sides of the chord, which maintains division into segments ( parachordalia), prechordal– ahead of the chord ( trabeculae).

The trabeculae and parachordalia grow and fuse together, forming the braincase from below and from the sides. The olfactory and auditory capsules grow to it. The lateral walls are filled with orbital cartilages. The axial and visceral skull develop differently and on early stages Phylo- and ontogeny are not related to each other. The brain skull goes through three stages of development: membranous, cartilaginous and bony.

Cyclostomes have a roof brain skull connective tissue (membranous), and the base is formed by cartilaginous tissue. The visceral skull is represented by the skeleton of the preoral funnel and the gill, which in lampreys consists of a series of seven cartilages.

In lower fish, the axial skull is cartilaginous (Figure 8). The occipital region appears. The visceral skull consists of 5-6 metamerically located cartilaginous arches that cover the anterior section of the digestive tube. The first arch, the largest, is called the maxillary arch. It consists of the upper cartilage, the palatoquadrate, which forms the primary maxilla. The lower cartilage, Meckel's cartilage, forms the primary mandible. The second branchial arch is the hyoid (hyoid), consists of two upper hyomandibular cartilages and two lower ones - hyoids. The hyomandibular cartilage on each side fuses with the base of the skull, the hyoid is connected to Meckel's cartilage. Thus, the jaw arch connects to the brain skull and this type of connection of the visceral and brain skull is called hyostylous.

Figure 8. Jaws (after Romer and Parsons, 1992). A-B – modification of the first two pairs of gill arches in the jaw of fish; G – skeleton of the shark’s head: 1 - skull, 2 - olfactory capsule, 3 - auditory capsule, 4 - spine, 5 - palatoquadrate cartilage (upper jaw), 6 - Meckel’s cartilage, 7 - hyomandibular, 8 - hyoid, 9 - squirt (the first underdeveloped gill slit), 10 - the first complete gill slit: D - cross section of the shark in the head area.

Bony fish develop a secondary bony skull. It consists partly of bones that develop from the cartilage of the primary skull, as well as of the integumentary bones that are adjacent to the primary skull. The roof of the skull consists of paired frontal, parietal and nasal bones. IN occipital region available occipital bones. In the visceral skull, secondary jaws develop from the integumentary bones. The role of the upper jaw passes to the integumentary bones, which develop in upper lip, lower jaw, as well as to the integumentary bones developing in the lower lip. On other visceral arches, integumentary bones do not develop. The type of connection between the brain and visceral skull is hyostylous. The skull of all fish is firmly connected to the spine.

The skull of terrestrial vertebrates changes mainly due to the loss of gill respiration. In amphibians, the brain skull still retains a lot of cartilage; it becomes lighter than the skull of fish. Characteristic of all terrestrial vertebrates is the movable connection of the skull with the spine. The greatest changes occur in the visceral skull. Amphibians have functioning secondary jaws. The first, the jaw arch, is partially reduced. The palatoquadrate cartilage of the first jaw arch fuses with the base of the cranium - this type of connection is called autostyle. In this regard, the hyomandibular cartilage of the hyoid arch loses its role as a suspension of the jaw arch. It is transformed into an auditory ossicle (column), located in the auditory capsule. The lower cartilage of the first branchial arch - Meckel's cartilage - is partially reduced, and the remaining part is surrounded by integumentary bones. The hyoid (lower cartilage of the second arch) is transformed into the anterior horns of the hyoid bone. The remaining visceral arches (there are 6 of them in amphibians) are preserved in the form of the hyoid bone and in the form of laryngeal cartilages.

In reptiles, the skull of an adult animal ossifies. There are a large number of integumentary bones. The connection of the visceral and cerebral skull occurs due to the quadrate bone (the ossified posterior part of the reduced palatoquadrate cartilage). Skull autostyle. The jaws are secondary. Changes in other parts of the visceral arches are the same as in amphibians. In reptiles, a secondary hard palate and zygomatic arches are formed.

In mammals, there is a decrease in the number of bones as a result of their fusion and an increase in the volume of the cranium. The roof of the skull is formed by the frontal and parietal bones, the temporal region is covered by the zygomatic arch. The secondary maxillae form the anterior bottom part skulls Lower jaw consists of one bone and its process forms a joint with which it connects to the brain skull.

The rudiments of the palatoquadrate and Meckel's cartilages are transformed, respectively, into the auditory ossicles - the incus and the malleus. Upper section the hyoid arch forms the stapes, lower section- sublingual apparatus. Parts of the 2nd and 3rd branchial arches form the thyroid cartilage of the larynx, the 4th and 5th arches are transformed into the remaining cartilages of the larynx. In higher mammals, the volume of the brain skull increases significantly. In humans, the size of the facial skull is significantly reduced compared to brain section, skull round and smooth. The zygomatic arch (synapsid type of skull) is formed.

Ontophylogenetically determined defects of the skull: an increase in the number of bone elements (each bone can consist of a large number of bones), nonunion hard palate– “cleft palate”, frontal suture, the upper part of the occipital scales can be separated from the rest by a transverse suture; in the upper jaw there is an unpaired incisor bone characteristic of other mammals, one auditory ossicle, the absence of a mental protuberance, etc.

The main directions of evolution of the skeleton of belts and free limbs:

1. From the skin (metapleural) folds of the lancelet to the paired fins of fish.

2. From the multi-rayed fin of fish to the five-fingered limb.

3. Increased mobility of the connection between the limbs and the belts.

4. Reducing the number of bones of the free limb and enlarging them through fusion.

The basis for the formation of vertebrate limbs are skin folds on the sides of the body (metapleural), which are found in lancelets and fish larvae.

Due to the change in function, the metapleural folds changed their structure. In fish, muscles and a skeleton appeared in them, in the form of a metameric series of cartilaginous rays that form the internal skeleton of the fins. In higher fish, the fin rays are bony. The primary anterior girdle is an arch (mostly bony) that covers the body from the sides and the ventral side. The belt lies superficially, covered with several bones homologous to the scapula and coracoid of higher vertebrates. It serves only to connect the fins with the secondary belt. The secondary girdle consists of a large paired bone, which is attached to the roof of the skull on the dorsal side, and connected to each other on the ventral side. The posterior belt of fish is poorly developed. It is represented by a small paired plate. In lobe-finned fish, the fins began to serve as a support when moving along the ground, and changes occurred in them that prepared them for transformation into the five-fingered limb of terrestrial vertebrates (Figure 9). The number of bone elements has decreased, they have become larger: the proximal section consists of one bone, the middle – two bones, the distal – radially located rays (7 – 12). The articulation of the skeleton of the free limb with the limb girdles became movable, which allowed lobe-finned fish to use their fins as a support for the body when moving along the ground.

Figure 9. Pectoral fin of a lobe-finned fish and the foreleg of an ancient amphibian (after Carroll, 1992). 1 - cleithrum, 2 - scapula, 3 - basalia, corresponding humerus, 4 - basalia, corresponding ulna, 5 - basalia, corresponding radius, 6 - radials, 7 - clavicle.

The next stage of evolution is the replacement of the strong connection of skeletal elements with movable joints, a decrease in the number of rows in the wrist and the number of bones in a row in higher vertebrates, a significant lengthening of the proximal (shoulder, forearm) and distal sections (fingers), as well as shortening of the bones of the middle section.

The limb of terrestrial vertebrates is a complex lever that serves to move the animal on land. The girdles of the limbs (scapulae, crow's, clavicle) have the form of an arc that covers the body from the sides and bottom (Figure 10). To attach a free limb, there is a depression on the scapula, and the belts themselves become wider, which is associated with a significant development of the muscles of the limbs. In terrestrial vertebrates, the pelvic girdle consists of 3 paired bones: the iliac, ischial and pubic (Figure 11). The ischial bones connect to the sacrum. All three bones form the acetabulum. Well developed dorsal region belts, which contributes to their stronger strengthening.

Figure 10. Comparison of the forelimb girdles of lobe-finned fish (left) and amphibians (right) (after Kvashenko, 2014). 1 - cleithrum, 2 - scapula, 3 - clavicle, 4 - sternum, 5 - coracoid, 6 - presternum, 7 - retrosternum.

In humans, ontophylogenetically determined anomalies of the skeleton of the limbs occur: flat feet, accessory bones of the wrist, tarsus, additional fingers or toes (polydactyly), etc.

Figure 11. Development of the pelvic girdle of terrestrial vertebrates in connection with the reduction of ribs (after Kvashenko, 2014). 1 - coelom, 2 - ribs, 3 - ventral spinous processes, 4 - pelvic plate of fish, 5 - fossa hip joint, 6 - ilium, 7 - pubic bone, 8 - ischium, 9 - femur, 10 - sacral vertebra.