Functions of the vertebrate skeleton. Abstracts for state exams for students of biology. Skeleton of chordates

The musculoskeletal system ensures the movement and preservation of the position of the animal's body 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.

Conditionally, the musculoskeletal system is divided into passive and active parts. To passive part include bones and their joints, on which the nature of the mobility of bone levers and links of the animal's body depends (15%). active part make up skeletal muscles and their auxiliary attachments, due to the contractions of which, the bones of the skeleton are set in motion (45%). Both the active and passive parts have a common origin (mesoderm) and are closely related.

Functions of the apparatus of movement:

1) Motor activity is a manifestation of the vital activity of the organism, it is it that distinguishes animal organisms from plant organisms and causes 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 took place under the influence of the gravitational field of the Earth, then its size and shape in vertebrates differ in significant diversity, which is explained by different conditions of their habitat (terrestrial, terrestrial-tree, air, water).

3) In addition, the apparatus of movement provides a number of vital functions of the body: the search for and capture of food; attack and active defense; carries out the respiratory function of the lungs (respiratory motility); helps the heart with the promotion of blood and lymph in the vessels ("peripheral heart").

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

The functions of the apparatus of movement are provided by the nervous and cardiovascular systems., respiratory organs, digestion and urination, skin, endocrine glands. Since the development of the apparatus of movement is inextricably linked with the development of the nervous system, when these connections are violated, first paresis and then paralysis movement apparatus (the animal cannot move). With a decrease in physical activity, there is a violation of metabolic processes and atrophy of muscle and bone tissues.

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 be carried out. The energy of elastic deformations in the bones is converted into piezoelectric, and in the muscles - into heat. 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 the vascular system, in turn, cannot function normally without the movement apparatus.

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

The skeleton consists of about 200-300 bones (Horse, k.s. -207-214; pig, dog, cat -271-288), which are interconnected by means of connective, cartilaginous or bone tissue. The mass of the skeleton in an adult animal is from 6% (pig) to 15% (horse, k.r.s.).

Everybody 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 the vital organs are located. So, for example, in the cranial cavity is the brain, in the chest - the heart and lungs, in the pelvic cavity - the genitourinary organs.

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

3) The locomotor function of the skeleton is manifested in the fact that the bones are levers that are set in motion by the 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 tremors (cartilaginous pads, etc.).

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

6) Participation in metabolism, especially in 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 body's internal environment (homeostasis).

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

DIVISION OF THE SKELETON

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

to the axial skeleton include the skeleton of the head (cranial cranium), the skeleton of the neck, trunk and tail. The skull has the most complex structure, since it contains the brain, organs of vision, smell, balance and hearing, oral and nasal cavities. The main part of the skeleton of the neck, trunk and tail is the spinal 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); the thoracic region - from the thoracic vertebrae (v.thoracica), ribs (costa) and sternum (sternum); lumbar - from the lumbar vertebrae (v.lumbalis); sacral - from the sacrum (os sacrum); tail - from the tail vertebrae (v.caudalis). The thoracic region of the body has the most complete structure, where there are thoracic vertebrae, ribs, breast bone, which together form the chest (thorax), in which the heart, lungs, and mediastinal organs are located. The smallest development, in terrestrial animals, is the tail section, 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 patterns of body structure, which ensure the mobility of the animal. They include :

1) Bipolarity (uniaxiality) is expressed in the fact that all sections of the axial skeleton are located on the same axis of the body, moreover, the skull is on the cranial pole, and the tail is on the opposite. The sign of uniaxiality makes it possible 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, as well as the trunk, 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 (antimeria) makes it possible to distinguish lateral (lateral, external) and medial (internal) directions on the body of an animal.

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

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

5) And the last pattern is, due to gravity, the location in the spinal canal of the neural tube, and under it the intestinal tube with all its derivatives. In this regard, a dorsal direction is planned on the body - towards the back and a 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 regularity - bilaterality (antimerism). The limbs are paired, there are left and right limbs. The rest of the elements are asymmetrical. On the limbs, belts (thoracic and pelvic) and the skeleton of free limbs are distinguished.

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

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

PHYLOGENESIS OF THE SKELETON

In the phylogeny of vertebrates, the skeleton develops in two directions: external and internal.

The external skeleton performs a protective function, is characteristic of lower vertebrates and is located on the body in the form of scales or shells (tortoise, armadillo). In higher vertebrates, the external skeleton disappears, but some of its elements remain, changing their purpose and location, becoming the integumentary bones of the skull and, located already under the skin, are associated 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 bones of the skull are injured, they are forced to be replaced with artificial plates.

The internal skeleton performs mainly a supporting function. In the course of development under the influence of biomechanical load, it constantly changes. If we consider invertebrates, then their internal skeleton looks like partitions to which muscles are attached.

The primitive chordates animals (lancelet ), along with partitions, an axis appears - a chord (cell strand), dressed in connective tissue membranes.

At cartilaginous fish(sharks, rays), cartilaginous arches are segmentally formed around the notochord, which later form the vertebrae. Cartilaginous vertebrae, connecting with each other, form the spinal column, ventrally, ribs join it. Thus, the notochord remains in the form of nucleus pulposus between the vertebral bodies. At the cranial end of the body, a skull is formed and, together with the spinal column, participates in the formation of the axial skeleton. In the future, the cartilaginous skeleton is replaced by a bone, less flexible, but more durable.

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

With the transition of animals to a terrestrial way of life, amphibian 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, the peripheral skeleton (the skeleton of the limbs) is also formed. In amphibians, 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 passes 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, the skeleton also goes through three stages of development in ontogenesis: membranous (connective tissue), cartilaginous and bone.

At the earliest stage of development of the embryo, the supporting part of its body is dense connective tissue, which forms a membranous skeleton. Then a chord appears in the embryo, and around it the cartilaginous, and later the bony vertebral column and skull, and then the 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 body weight. Each cartilage has the shape of a future bone and is covered with a perichondrium (dense connective tissue sheath). 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 - I do) occurs both from the outer surface (perichondral ossification) and from the inside (endochondral ossification). In place of the cartilage, coarse-fibrous bone tissue is formed. As a result of this, the skeleton of the fetus is built of coarse fibrous bone tissue.

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



Skeleton - the skeleton of domestic animals includes two sections (Fig. 15): axial and limbs (peripheral).
The axial skeleton in domestic animals is represented by metamerically arranged vertebrae that form the spinal column, the thorax, and the skull. Its bones are secondary and develop due to the elements of the internal skeleton. Only the integumentary bones of the skull and the clavicle develop at the expense of the elements of the external skeleton - the primary bones.
Along the body of the animal, along the median plane, there is a spine, in which two parts are distinguished: the spinal column - columna vertebralis, formed by the bodies of the vertebrae, - the supporting part, connecting the work of the limbs in the form of a kinematic arc, and the spinal canal - canalis vertebralis, which is formed by the arches of the vertebrae surrounding the spinal cord.

With the appearance in terrestrial animals of limbs fixed on the axial skeleton, the spine is differentiated into sections that coincide with the direction of action of the forces of gravity of the body of tetrapods. In those places where the limb belts are attached to it, the thoracic and sacral sections stand out, the lumbar section remains between them: The cervical section forms in front of the thoracic and the tail section behind the sacral (Fig. 16). So the spine was divided into cervical, thoracic, lumbar, sacral and caudal sections, in which the vertebrae acquired some differences related to their function. The thoracic region, together with the lumbar, is also distinguished as the skeleton of the body.
Ribs - costae are preserved in higher vertebrates completely only in the thoracic region, forming a complete bone segment where the ribs are connected to the sternum with the help of costal cartilages, or incomplete, formed only by the thoracic vertebrae, bone ribs and costal cartilages. In other sections, the ribs remain in the form of rudiments fused with the transverse processes.
With the development of the limbs in terrestrial vertebrates, the sternum (breast bone) appears in the thoracic region, on which the lower ends of the costal cartilages rest.
The number of vertebrae in the thoracic region is from 12 to 19, in the caudal region - from 12 to 24. In mammals, there are 7 vertebrae in the cervical region, and 6 or 7 in the lumbar region, and less in the sacral region - only 3-5 (Table 3).

The concept of " phylogenesis”(from the Greek phyle - “genus, tribe” and genesis - “birth, origin”) was introduced in 1866 by the German biologist Ernst Haeckel to denote the historical development of organisms in the process of evolution.

Consider how the spine developed and improved from the simplest organisms to humans. It is necessary to distinguish between the external and internal skeleton.

Exterior skeleton performs a protective function. It is inherent in lower vertebrates and is located on the body in the form of scales or shells (tortoise, armadillo). In higher vertebrates, the external skeleton disappears, but its individual elements remain, changing their purpose and location, becoming the integumentary bones of the skull. Located already under the skin, they are connected with the internal skeleton.

Internal skeleton performs mainly a supporting function. In the course of development, under the influence of a biomechanical load, it constantly changes. In invertebrates, it looks like partitions to which muscles are attached.

In primitive chordates (lancelets), along with partitions, an axis appears - a chord (cell cord), dressed in connective tissue membranes. In fish, the spine is relatively simple and consists of two sections (trunk and tail). Their soft cartilaginous spine is more functional than that of chordates; the spinal cord is located in the vertebral canal. The skeleton of fish is more perfect, allowing for faster and more precise movements with a smaller mass.

With the transition to a terrestrial way of life, a new part of the skeleton is formed - the skeleton of the limbs. And if in amphibians the skeleton is made of coarse fibrous bone tissue, then in more highly organized terrestrial animals it is already built from lamellar bone tissue, consisting of bone plates containing ordered collagen fibers.

The internal skeleton of vertebrates passes through three stages of development in phylogenesis: connective tissue (membranous), cartilaginous and bone.

Mammal skeleton (left) and fish (right)

The deciphering of the lancelet genome, completed in 2008, confirmed the proximity of the lancelets to the common ancestor of vertebrates. According to the latest scientific data, lancelets are relatives of vertebrates, although the most distant.

The mammalian spine consists of the cervical, thoracic, lumbar, sacral, and caudal regions. Its characteristic feature is the platycelial (having flat surfaces) shape of the vertebrae, between which cartilaginous intervertebral discs are located. The upper arches are well defined.

In the cervical region, all mammals have 7 vertebrae, the length of which depends on the length of the neck. The only exceptions are two animals: the manatee has 6 of these vertebrae, and in different species of sloths - from 8 to 10. The giraffe has very long cervical vertebrae, while cetaceans that do not have a cervical interception, on the contrary, are extremely short.

The ribs are attached to the vertebrae of the thoracic region, forming the chest. The sternum closing it is flat and only in bats and in representatives of burrowing species with powerful forelimbs (for example, moles) has a small crest (keel), to which the pectoral muscles are attached. In the thoracic region there are 9-24 (usually 12-15) vertebrae, the last 2-5 bear false ribs that do not reach the sternum.

In the lumbar region from 2 to 9 vertebrae; rudimentary ribs merge with their large transverse processes. The sacral region is formed by 4-10 fused vertebrae, of which only the first two are truly sacral, and the rest are caudal. The number of free tail vertebrae ranges from 3 (in the gibbon) to 49 (in the long-tailed pangolin).

The mobility of individual vertebrae depends on lifestyle. So, in small running and climbing animals, it is high along the entire length of the spine, so their body can bend in different directions and even curl up into a ball. The thoracic and lumbar vertebrae are less mobile in large, rapidly moving animals. In mammals moving on their hind legs (kangaroos, jerboas, jumpers), the largest vertebrae are located at the base of the tail and sacrum, and then their size consistently decreases. In ungulates, on the contrary, the vertebrae and especially their spinous processes are larger in the anterior part of the thoracic region, where the powerful muscles of the neck and partly of the forelimbs are attached to them.

In birds, the forelimbs (wings) are adapted for flying, and the hind limbs for moving on the ground. A peculiar feature of the skeleton is the pneumaticity of the bones: they are lighter because they contain air. The bones of birds are also quite fragile, as they are rich in lime salts, and therefore the strength of the skeleton is largely achieved by the fusion of many bones.

Vertebrate skeleton formed not only by bones: it includes cartilage and connective tissue, and sometimes it includes various skin formations.

In vertebrates, it is customary to distinguish axial skeleton(skull, notochord, spine, ribs) and limb skeleton, including their belts (shoulder and pelvic) and free departments. Snakes, legless lizards and caecilians lack the skeleton of limbs, although some species of the first two groups retain their rudiments. In eels, the ventral fins corresponding to the hind limbs have disappeared. In whales and sirens, there are no external signs of hind legs either.

Scull. By origin, there are three categories of skull bones:

• cartilage replacement,
• integumentary (overhead, or skin)
• visceral.

Sharks and their relatives may have once had bones in it, but now its box is a single monolith of cartilage with no seams between the elements. Bony fishes have more bones in their skulls than any other class of vertebrates. In them, as in all higher groups, the central bones of the head are laid in the cartilage and replace it, and therefore are homologous to the cartilaginous skull of sharks.

Visceral elements of the skull- derivatives of cartilaginous gill arches that arose in the walls of the pharynx during the development of vertebral gills. In fish, the first two arcs have changed and turned into jaw and hyoid apparatus. In typical cases, they still have 5 gill arches, but in some genera their number has decreased. The primitive modern sevengill shark (Heptanchus) has as many as seven gill arches behind the jaw and hyoid arches. In bony fish, the jaw cartilages are lined with numerous integumentary bones; the latter also form gill covers that protect the delicate gill filaments. In the course of vertebrate evolution, the original jaw cartilages were steadily reduced until they completely disappeared. If in crocodiles the remnant of the original cartilage in the lower jaw is lined with 5 paired integumentary bones, then in mammals only one of them remains - the tooth, which completely forms the skeleton of the lower jaw.

The skull of ancient amphibians contained heavy integumentary plates and was similar in this respect to the typical lobe-finned fish skull. In modern amphibians, both superimposed and replacement bones are greatly reduced. In the skull of frogs and salamanders, there are fewer of them than in other vertebrates with a bony skeleton, and in the latter group, many elements remain cartilaginous. In turtles and crocodiles, the skull bones are numerous and tightly fused together. In lizards and snakes, they are relatively small, and the outer elements are separated by wide intervals, like in frogs or toads. In birds, the skull bones are thin but very hard; in adults, they have fused so completely that several sutures have disappeared. The orbital cavities are very large; the roof of the relatively huge braincase is formed by thin integumentary bones; light jaws are covered with horny sheaths. In mammals, the skull is heavy and includes powerful jaws with teeth. The remains of the cartilaginous jaws moved to the middle ear and formed its bones - the hammer and anvil.

In birds and reptiles, the skull is attached to the spine with the help of one of its condyle(articular tubercle). In modern amphibians and all mammals, two condyles are used for this, located on the sides of the spinal cord.

Spine, in embryonic development it is always preceded by chord, which persists for life in the lancelet and cyclostomes. In fish, it is surrounded by vertebrae (in sharks and their closest relatives, it is cartilaginous) and looks beaded. In mammals, only rudiments of the notochord are preserved in the intervertebral discs. The notochord is not transformed into vertebrae, but is replaced by them. They arise during embryonic development as curved plates, gradually surrounding the notochord with rings and, as they grow, almost completely displacing it.

In a typical spine, 5 sections are distinguished:

• cervical,
• thoracic (corresponding to the chest),
• lumbar,
• sacral
• tail.

Number cervical vertebrae varies greatly depending on the group of animals. Modern amphibians have only one such vertebra. Small birds can have as few as 5 vertebrae, while swans can have up to 25. The Mesozoic marine reptile plesiosaur had 72 cervical vertebrae. Mammals almost always have 7; the exception is sloths (from 6 to 9). The first cervical vertebra is called atlas. In mammals and amphibians, it has two articular surfaces, which include the occipital condyles. In mammals, the second cervical vertebra ( epistrophy) forms an axis on which the atlas and skull rotate.

To chest the vertebrae are usually attached to the ribs. Birds have about five, mammals have 12 or 13; there are a lot of snakes. The bodies of these vertebrae are usually small, and the spinous processes of their superior arches are long and tilt backwards.Lumbar vertebrae usually from 5 to 8; in most reptiles and all birds and mammals, they do not bear ribs. The spinous and transverse processes of the lumbar vertebrae are very powerful and, as a rule, are directed forward. In snakes and many fish, the ribs are attached to all the trunk vertebrae, and it is difficult to draw a border between the thoracic and lumbar regions. In birds, the lumbar vertebrae are fused with the sacral vertebrae to form a complex sacrum, which makes their backs more rigid than those of other vertebrates, with the exception of turtles, in which the thoracic, lumbar, and sacral regions are connected to the carapace.

Number sacral vertebrae varies from one in amphibians to 13 in birds.Structure tail department is also very diverse; in frogs, birds, great apes, and humans, it contains only a few partially or completely fused vertebrae, and in some sharks, up to two hundred. Toward the end of the tail, the vertebrae lose their arches and are represented by one body.

Ribs first appear in sharks in the form of small cartilaginous processes in the connective tissue between the muscle segments. In bony fish, they are bony and homologous to the hemal arches located below on the caudal vertebrae. In quadrupeds, such ribs of the "fish" type, called the lower ones, are replaced by the upper ones and are used for breathing. They are laid in the same connective tissue partitions between the muscle blocks as in fish, but are located higher in the body wall.

Skeleton limbs. The limbs of tetrapods developed from the paired fins of lobe-finned fish, in the skeleton of which there were elements homologous to the bones of the shoulder and pelvic girdle, as well as the front and hind legs.Originally there were at least five separate ossifications in the shoulder girdle, however modern animals usually have only three: scapula, clavicle and coracoid. In almost all mammals, the coracoid is reduced, attached to the scapula, or absent altogether. In some animals, the shoulder blade remains the only functional element of the shoulder girdle.

Pelvic girdle includes three bones:

• iliac,
• ischial
• pubic.

In birds and mammals, they completely merged with each other, in the latter case forming the so-called nameless bone. In fish, snakes, whales, and sirens, the pelvic girdle is not attached to the spine, which therefore lacks the typical sacral vertebrae. In some animals, both the shoulder and pelvic girdle include accessory bones.

Bones anterior free limb and in quadrupeds, in principle, the same as in the back, but they are called differently. In the forelimb, if counted from the body, first comes shoulder bone behind it radial and ulnar bones, then carpal, metacarpal and phalanges of fingers.

AT hind limb they correspond femoral, then big and small tibia, tarsal, metatarsal bones and phalanges of fingers. The initial number of fingers is 5 on each limb. Amphibians have only 4 toes on their front paws. In birds, the forelimbs are modified into wings; the bones of the wrist, metacarpus and fingers are reduced in number and partially fused together, the fifth toe is lost on the legs. Horses have only the middle finger left. Cows and their closest relatives rely on the third and fourth fingers, while the rest are lost or reduced. Ungulates move on their fingertips and are called phalanx walking. Cats and many other animals, when walking, rely on the entire surface of the fingers and belong to digitigrade type. Bears and humans, when moving, press the entire sole to the ground and are called plantigrade.

External skeleton. In vertebrates of all classes, one way or another, the external skeleton is represented. The head plates of scutes (extinct jawless), ancient fish and amphibians, as well as the scales, feathers and hair of higher tetrapods, are skin formations. The shell of turtles is of the same origin - a highly specialized skeletal formation. Their skin bony plates (osteoderms) approached the vertebrae and ribs and merged with them. It is noteworthy that the shoulder and pelvic girdle parallel to this shifted inside the chest. In the crest on the back of crocodiles and armadillo shells, there are bone plates of the same origin as the shell of turtles.

Topic 1. Diversity of animals

Practical work No. 5. Comparison of the structure of the skeletons of vertebrates

Target: consider the skeletons of vertebrates, find similarities and differences.

Working process.

			reptiles		mammals
Head skeleton (skull)	The bones are rigidly connected to each other. The lower jaw is movably connected. There are gill arches	Cartilaginous skull	Bone skull	The bones of the skull fuse together. Has a large brain box, large eye sockets	The skull is the brain region, which consists of bones that grow together, the facial region (jaws)
Trunk skeleton (spine)	Two departments: tulubovy, tail. The tubular vertebrae bear ribs	Departments: cervical, tulubovy, sacral, caudal. One cervical vertebra. no ribs	Sections (5): cervical, thoracic, lumbar, sacral, caudal. The cervical region provides head mobility. Ribs are well developed. There is a chest - thoracic vertebrae, ribs, sternum	Sections (5): cervical, thoracic, lumbar, sacral, caudal. The cervical region has a large number of vertebrae (11-25). The vertebrae of the thoracic, lumbar, sacral sections are fixedly connected (strong base). Ribs are developed. There is a chest - thoracic vertebrae, ribs, sternum has a keel	Sections (5): cervical, thoracic, lumbar, sacral, caudal. The cervical region (7 vertebrae) provides the mobility of the head. Ribs are well developed. There is a chest - thoracic vertebrae, ribs, sternum
limb skeleton	Paired fins (pectoral, ventral) are represented by bone rays	Anterior - bones of the shoulder, forearm, hand. Posterior - bones of the thigh, lower leg, foot. Limbs end in fingers (5)	Anterior - humerus, ulna and radius, hand. Back - femur, lower leg, foot. Limbs end in fingers (5)	Limbs are wings. Anterior - humerus, ulna and radius, the hand has three fingers. Back - femur, lower leg, foot. The bones of the foot fuse and form the forearm. Limbs end in fingers	Anterior - humerus, ulna and radius, bones of the hand. Posterior - femur, small and large tibia, foot bones. Limbs end in fingers (5)
Skeleton of limb girdle	Muscles join to the bones	Belt of the forelimbs - shoulder blades (2), crow bones (2), collarbones (2). Belt of the hind limbs - three pairs of pelvic bones fused together	Belt of the forelimbs - shoulder blades (2), collarbones (2). Belt of the hind limbs - three pairs of pelvic bones fused together	Belt of the forelimbs - shoulder blades (2), collarbones (2) fused together and formed a fork Belt of the hind limbs - three pairs of pelvic bones fused together
Way to travel	The fish are swimming. Movements are provided by fins: caudal - active forward movement, paired (abdominal, pectoral) - slow movement	Provide jumping locomotion. Animals can swim thanks to the membranes between the fingers of the hind limbs.	During movement, the body crawls along the substrate. Crocodiles, snakes can swim	The main mode of transportation is flight. The skeleton is characterized by lightness - the bones have cavities filled with air. The skeleton is strong - the growth of bones.	Different modes of movement - run, jump, fly (terrestrial environment), dig holes in the soil (soil), swim and dive (aquatic environment)

findings. 1. All vertebrates have an internal skeleton, which has a general structural plan - the skeleton of the head (skull), the skeleton of the body (spine), the skeleton of the limbs, the skeleton of the limb belts. 2. The skeleton performs a protective function, serves as an attachment site for muscles that provide movement for animals. 3. Features of the structure of the skeletons of vertebrates provide certain ways of movement of these animals in space.