Musculoskeletal system of birds table. Summary of a lesson in biology "the musculoskeletal system of birds"

§ 44. Habitat and external structure of birds. Questions What are the features external structure birds confirm their ability to fly? Describe the types of feathers and their purpose in the life of birds. What are the common signs and differences in the structure of the integument of birds and reptiles? What does this indicate?

Skeleton. Birds have a strong and lightweight skeleton (Fig. 159). Their bones are light: all long bones are tubular, have air cavities; some flat bones also have small air cavities. The strength of the skeleton is given by the fusion of many bones. A single bone is a skull, only the lower jaw is movably connected to it.

The spine consists of five sections: cervical (9-25 vertebrae), thoracic (3-10 vertebrae), lumbar (6 vertebrae), sacral (2 vertebrae) and caudal (5 vertebrae fused with a complex sacrum, 6 remained free and the last 4 fused into the coccygeal bone).

The thoracic vertebrae grow together to form a single dorsal bone. It is connected by a joint to a complex sacrum. The ribs are attached to the thoracic vertebrae. Each rib consists of a dorsal and abdominal sections, connected movably. The abdominal ribs are connected to the sternum. The thoracic vertebrae, ribs and sternum form the ribcage that protects the internal organs.

In flying birds, the large sternum has a high keel, to which strong pectoral muscles are attached, which move the wings. The pelvic bones grow together with the spine. The lumbar, sacral and part of the caudal vertebrae form a complex sacrum that provides reliable support for the hind limbs.

The rudiments of the second, third and fourth fingers are preserved. The skeleton of the free hind limb consists of the femur, the bones of the leg and foot fused together. Part of the tarsal bones and all the metatarsal bones fused together and formed a single bone - the tarsus.

Muscles. The large pectoral muscles that lower the wing are of great importance for the flight of birds (Fig. 160). They attach to the keel of the sternum and end in tendons on the wing bones. The subclavian muscles that lift the wings are located under the pectoralis major muscles. The muscles of the neck and hind limbs are well developed.

More than 30 muscles provide movement of the hind limbs. They begin on the bones of the pelvis, thigh, and lower leg. Long tendons fit to the fingers, which, when the bird lands on a branch, stretch, squeezing the fingers, so the birds do not fall from the branches during sleep. Intercostal and other muscles in the body walls provide mobility chest... There are several muscles that move the feathers.

Conclusions Reference propulsion system most fully reflects the adaptation of birds to flight. The skeleton is lightweight and durable. Lightness is ensured by the pneumaticity (filling with air) of the bones, strength - by their fusion. The wing bones are connected in large sections. The largest and strongest muscles are flight muscles, they attach to the keel of the sternum.

23 May 2012

Birds are animals that not only move along the ground, but also took off into the air, soar in the sky. Therefore, as a result of evolutionary development, a change in the mass and shape of their bodies was observed. At the same time, there was an accumulation of fat - an energy reserve, friction decreased during movement, muscle mass... At the same time, their skeleton and muscles changed, i.e. the musculoskeletal system of birds.
In many ways, it is the same as that of mammals. The musculoskeletal system of birds consists of an axial skeleton, skull, humerus and forearm, scapula, thoracic vertebrae, pelvic and femur, etc.
At the same time, it is completely different from the musculoskeletal system of mammals. For example, birds have a shallow head. all the bones of the cerebral skull have grown together, and their number has decreased. The skull is greatly lightened due to the fact that the bones are mostly hollow, and there is a toothless beak that is covered only by the cornea. Birds do not have spinal curves like humans. The "human" chest is expanded, while in animals and birds it is compressed from the sides.
Cervical the skeleton of birds is represented by 11-25 free vertebrae, but the vertebrae thoracic firmly fastened together and at the same time with the vertebrae of the lumbar spine. The sacral region fused with the girdle of the hind limbs, and the sacrum was formed.
There is a difference in the facial skeleton, and in the girdle of the limbs, and in the limbs themselves. For example, only birds have a keel - a cartilaginous outgrowth that was formed when the collarbone fusion with the sternum. In flying birds, the sternum is well developed, and the keel is large.
The musculoskeletal system of birds includes the hind limbs, which are two large, powerful pelvic bones fused with a complex sacrum. And since the bird walks on two legs, the sacrum itself is also powerful. The sacrum is formed by fused sacral, lumbar, caudal vertebrae, therefore, it is believed that birds do not have a lumbar region.
The skeleton of a bird differs from the skeletons of other living creatures in that it is durable and lightweight. This is achieved, firstly, because the bones of birds are tubular. Secondly, the lightness is due to the cavity of the bones. Therefore, the mass of a bird's skeleton is somewhere between 5-15% of its body weight. With the exception of the cervical spine, the entire spine is motionless.
Since the forelimbs have evolved into wings as a result of evolutionary development, the hand is almost undeveloped. But in birds that fly well, large pectoral muscles make up somewhere 15-20% of the mass, and their special location contributes to the stability of birds in the air.

Standing lower in developmental level than birds and mammals is the class of reptiles. The body of such a reptile consists of a head, neck, torso and limbs, except for snakes and legless lizards, which are devoid of limbs. In structure, the musculoskeletal system of reptiles is close to amphibians, but unlike them, it has a more ossified skeleton. The more progressive structure of the skeleton and muscles of such animals determined their mobility. The skeleton of reptiles, like the musculoskeletal system of birds, also consists of their cervical, thoracic, sacral and tail sections. The long ribs are connected to the sternum to form the ribcage.
Reptiles, unlike other animals, have more dissected muscles, in particular, the intercostal muscles. They can regulate the volume of the chest, compress and expand it, thereby performing the breathing process. Since the ribs of reptiles end freely, this allows them to swallow rather large food. They have a well-developed tail section.
Summing up, it can be noted that the skeletons of all animals have distinctive features but perform similar functions. They serve as a support for the body, protect internal organs and help move all living things in space.

Source: fb.ru

Actual

Musculoskeletal system of birds consists of a skeleton and muscles. Skeleton has high strength with low weight, which is vital for birds to be able to fly. Strength is achieved due to the fusion of a number of bones, and low weight - the presence of cavities with air in the tubular bones.

Bird skull has a structure similar to the structure of the skull of reptiles, but there are a number of differences:

The cranium in a bird's skull is much larger than in the skull of reptiles;
The skull of birds is lighter than the skull of reptiles;
Bird Skull Brain Box Ending Out beak, and on the sides of the box have large eye sockets;
Adult birds have a skull, the bones of which are completely fused before the sutures disappear.

Spine of birds, like other land animals, it has 5 departments: cervical, thoracic, lumbar, sacral and caudal. The most mobile department is cervical spine. Thoracic vertebrae are inactive, and lumbar vertebrae and sacral divisions form a complex sacrum merging with each other.

Some may also grow together. bones of the shoulder girdle, for example, the clavicles are one with the other, the saber-shaped scapula with the crow's bone - all this provides the shoulder girdle with strength sufficient for the normal operation of the wings attached to it. The wings are composed of sections typical for the upper extremities: humerus, ulna and radius of the forearm, as well as fused bones of the hand. Of the 5 fingers, only three remain.

The pelvic girdle serves reliable support for the hind limbs, which is ensured by the fusion of the iliac bones with the complex sacrum. Due to the fact that the pelvic bones do not grow together and have a wide gap, birds are able to lay rather large eggs.

The powerful hind limbs consist of bones typical of all terrestrial animals, but at the same time the fibula is accreted to the tibia to strengthen the tibia. The bones of the metatarsus are fused with part of the bones of the tarsus, and form a bone characteristic only of birds - tarsus. Three of the four fingers are usually forward, one is backward.

Rib cage formed by the thoracic vertebrae, ribs and sternum. Each rib covers two sections at once - the dorsal and the abdominal, movably articulated with each other. This provides movement of the sternum relative to the spine during breathing. The sternum of birds is large in comparison with other animals, and also has one feature - keel, to which the pectoral muscles join, lowering and raising the wings.

A high level of mobility and a variety of movements provide differentiation of the muscular system of birds. The most developed are pectoral muscles(1/5 of the total mass of the bird), growing from the keel of the sternum and serving to lower the wings. The subclavian muscles, which are located under the pectoralis, provide the lifting of the wings. Bird speed can be different: 60-70 km / h for ducks and 65-100 km / h for a peregrine falcon. Maximum flight speed among birds observed in the black swift - 110-150 km / h. Powerful leg muscles in birds that have lost the ability to fly make it possible to move quickly over land (ostriches move at an average speed of 30 km / h).

Birds are vertebrates adapted to flight, their forelimbs turned into wings, the body is covered with feathers, and have a streamlined body shape. There are more than 9000 living species. Birds live in virtually all climatic zones and occupy various ecological niches.

Compared to reptiles, a number of large aromorphoses occurred in birds, which allowed them to become more active and less dependent on conditions. environment... This is the emergence of thermoregulation (warm-bloodedness), complete separation of venous and arterial blood flow, the emergence of a four-chambered heart. Other multiple adaptations of birds are more appropriate to consider as adaptations to flight.

Feather cover of birds

The feather cover of birds evolved from the horny scales of reptiles. Each feather develops in a feather bag, in which the lower end of the feather (quill) remains, through which the feather is fed.

In the plume, the trunk and the fan are distinguished. The fan consists of horny barbs of the first order and those extending from them of the second order. Second-order barbs have hooks with which they engage adjacent second-order barbs. Thus, the fan becomes monolithic, does not allow air flows through itself, which plays an important role in the ability of birds to fly.

The feather cover of birds does not grow over their entire body, but only in the so-called pterilia... V pharmacies feathers do not grow, but they are covered with feathers that have grown in the pterilia. In birds, only the lower legs and beak are not covered with feathers (in some species, the neck is also).

Bird feathers are not the same. Distinguish between contour feathers, down feathers, down, etc. Contour feathers are cover, tail feathers (located on the tail), flight feathers (on the wings). Flight and tail feathers are essential for flight. Down serves as thermal insulation.

For birds, molt is characteristic when the feather cover is replaced. In some species, this happens in such a way that they immediately lose almost all old feathers. In others, molting occurs gradually.

The skin of birds is dry, thin. They have only one gland - the coccygeal gland. Well developed in waterfowl. Birds lubricate feathers with its fatty secretion, which prevents them from getting wet.

Musculoskeletal system of birds

The musculoskeletal system of birds undergoes a number of significant changes associated with flight. This applies to both the skeleton and the muscular system.

The bones of birds become lighter, many have cavities. Many bones in the skeleton grow together to provide additional strength during flight.

The bird's skull is robust with large eye sockets. The beak is formed by jaws covered with horny sheaths ( beak and mandible). Beak different types birds are adapted to the acquisition and processing of certain types of food. All birds have missing teeth.

The cervical spine is highly mobile. The number of vertebrae depends on the species of bird. The thoracic vertebrae grow together. The lumbar, sacral and first caudal vertebrae also grow together, forming complex sacrum giving powerful support to the pelvic girdle and hind limbs. The last caudal vertebrae also grow together; tail feathers are attached to them.

The ribs extend from the thoracic vertebrae. Each rib of the bird consists of an upper and lower part, movably connected to each other. The lower parts of the ribs are attached to a fairly large sternum. The ribs of birds have hook-shaped processes. In the vast majority of birds, the sternum leaves keel, to which are attached powerful muscles that ensure the raising and lowering of the wings in flight.

The shoulder girdle of birds consists of elongated shoulder blades (lying along the spine), powerful coracoids (connected to the beginning of the sternum) and collarbones. The clavicles grow together and form fork, which plays the role of a kind of spacer when the wings move. The bones of the forelimbs are homologous to those of reptiles. In the wing of birds, the humerus, ulna and radius are preserved. However, a number of bones in the wrist and metacarpus grow together to form buckle... The fingers on the wings of birds are reduced, only three remain, of which only one is well developed.

The bones of the pelvic girdle (iliac, sciatic and pubic) are spliced together on each side and are motionlessly accreted to the complex sacrum. Both pubic bones do not grow together with each other. Also, the ischial bones do not grow together. This makes the pelvis of the bird open, which makes it possible to lay large eggs. The skeleton of the hind limb consists of the femur, the bones of the lower leg, tarsus, fingers (usually four, three of which are turned forward). The tarsus is formed by a series of bones in the tarsus and metatarsus.

The muscles of birds are more differentiated than those of reptiles. In addition, in a number of departments, the muscular system is very powerful. So in birds, the pectoral and subclavian muscles are highly developed, which are responsible for raising and lowering the wings. The muscles of the neck and tail are well developed.

Respiratory system of birds

The respiratory system of birds is in many ways unique, they are characterized by the so-called double breathing... With him, it passes through the lungs Fresh air and during inhalation and exhalation. To carry out such breathing, birds have air bags(several pairs can also be unpaired).

On inhalation, air enters the lungs and back air sacs. On exhalation, air from the lungs predominantly passes into the anterior air sacs, and enters the lungs from the rear. From the anterior sacs, air is removed through the trachea.

The lungs of birds are dense, spongy tissue that increases their surface.

Air bags filled with air reduce the density of the bird's body, making it lighter.

At rest, birds breathe due to the expansion and contraction of the pectoral muscles. In flight, the bird's chest remains almost motionless and provides additional support for the wings. Therefore, the expansion and contraction of the air sacs occurs due to the movement of the wings. Moreover, the more often and more powerful the flapping of the wings, the more often the birds breathe, and the more their air sacs are filled with air.

The circulatory system of birds

In the circulatory system of birds, venous and arterial blood do not mix. Unlike reptiles in birds, only one (right) aorta emerges from the left ventricle of the heart.

The heart is four-chambered. The right atrium and ventricle contain only venous blood. Left - only arterial. The systemic circulation begins in the left ventricle and ends in the right atrium. The small (pulmonary) circle of blood circulation begins in the right ventricle and ends in the left atrium.

The large heart of birds beats often, very often in flight (hundreds of times per minute).

Digestive system of birds

Fast digestion is characteristic of birds. For many, food passes through their digestive tract in less than an hour.

In many birds, the esophagus has an enlargement (goiter), where swallowed food is temporarily deposited. There are salivary glands.

A feature of the digestive system of birds is the presence of two stomachs. In the first (glandular), enzymatic processing of food takes place. In the second (muscular), food is rubbed both by the powerful walls of the stomach and by swallowed stones.

The large intestine in birds is short, opens into the cloaca, the rectum is absent. Thus, the remains are not retained in the body, which makes it easier for the bird's body to fly.

Excretory system of birds

The main product of excretion in birds is uric acid, as in reptiles. It requires little water to release it. Removal of harmful substances from the body occurs quickly, which is associated with an intensive metabolism.

Birds have large enough kidneys, the ureters open directly into the cloaca. Bladder absent.

The nervous system and sensory organs of birds

V nervous system birds, a stronger development of the forebrain hemispheres occurs (they are responsible for complex behavior and the development of conditioned reflexes), the midbrain also increases (associated with the improvement of vision) and the cerebellum (is responsible for coordination of movements, which is of great importance for birds in connection with flight).

The main sense organ of birds is vision. This is due to the fact that when flying, you need to see objects from a distant distance, birds clearly distinguish colors and their shades. There are more sensitive cells in the eyes of birds than in mammals.

Hearing is also important in the life of birds. In a number of birds (for example, owls), it is very thin, allowing you to catch the sounds made by prey at night.

The vast majority of birds have poorly developed sense of smell.

Reproduction and development of birds

A pair of testes functions as reproductive organs in male birds. During the breeding season, they greatly increase. Through the vas deferens, sperm enters the cloaca and is subsequently injected into the female's cloaca. Birds only have internal fertilization.

Females retain only one ovary. This is due to the formation of large eggs (containing a large number of yolk), turning into large eggs in the genital tract of the female. Two such eggs would not be able to pass through the pelvis of a bird.

Fertilization of the egg takes place in the upper part of the oviduct. Moving to the cloaca, the egg is covered with shells: protein (contains a large supply of water), two shells, one shell (lime is later partially used to form the skeleton), one shell shell. The duration of egg formation is different for different bird species. On average, about a day.

An embryonic disc is formed on the surface of the yolk by crushing. The yolk is suspended in the egg on protein threads - chalases.

One of the manifestations of the complex behavior of birds is the expressed concern for the offspring. The birds incubate the clutch, after hatching the chicks take care of them for a long time. Chicks are of two types: brood and nest. The first ones, almost immediately after hatching, are able to follow their parents and feed on their own. When they hatch, they are already covered in fluff. Breeding chicks appear naked, blind and helpless. The parents feed them in the nest.

Bird ecology

The high metabolic rate due to the improvement, first of all, of the circulatory, respiratory and digestive systems led to the warm-bloodedness of birds (the ability to maintain a constant body temperature). This resulted in less dependence on environmental conditions than in reptiles. Birds are widely spread across the Earth; they are found in Antarctica as well.

Birds are characterized by seasonal migrations associated with moving to the best places for feeding, breeding, avoiding unfavorable conditions. Allocate sedentary, nomadic and migratory birds... Sedentary birds usually live all year round in the same place. In the post-nesting period, nomadic birds fly hundreds of kilometers away. Migratory birds fly thousands and tens of thousands of kilometers. Usually they fly away for the winter to those places where there is no severe cold (for example, from Europe to Africa).

Among the birds, there are three large groups: typical birds, penguins and ostriches. Representatives of the last two do not fly. Ostrich species are the largest living birds. Penguins are adapted to swimming. The vast majority of typical birds fly. They are the most numerous and varied (more than 20 orders).

There are various ecological groups of birds by habitats(birds of the forest, open spaces, waterfowl, living near water bodies), nesting sites(in crowns, bushes, ground, nesting in hollows, etc.), type of food(herbivores, insectivores, carnivores, scavengers, omnivores), etc.

Lesson number 5.

Theme: The evolution of the musculoskeletal system in animals.

Class: 7 B

Goals:

To study the features of the musculoskeletal system of mammals.

To study the complication of the musculoskeletal system in the course of evolution.

Tasks:

educational:

To study the structure and functions of the musculoskeletal system of mammals.

To study the structure and functions of the musculoskeletal system in the course of evolution.

Find out the features of complication in representatives of the musculoskeletal system of different taxa.

developing:

Formation of the ability to establish causal relationships.

Development of the ability to work with a book and tables.

educational:

To generalize the complex of knowledge about the evolution of the musculoskeletal system.

Lesson type: explanation of new material.

Method: descriptive and illustrative.

The form: group.

Should know after the lesson:

The structure and functions of the musculoskeletal system, ranging from unicellular to chordate.

Features of the complication of the structure of the musculoskeletal system in representatives of different taxa.

During the classes:

Organizational start:

Teacher: Hello guys, sit down! Please open your notebooks and write down the topic of our lesson: "The evolution of the musculoskeletal system."

Learning new material:

Teacher: During a long evolutionary path, animals have mastered new territories, types of food, constantly adapting to environmental conditions. In order to survive, animals had to look for food, better hide or defend themselves from enemies, move faster. Changing along with the body, the musculoskeletal system was supposed to provide all these evolutionary changes.

What do you think are the most remarkable animals?

Student: The most primitive are rhizomes, which do not have a support system, move slowly, flowing with the help of pseudopods, while constantly changing shape.

Teacher: For the first time, the speed of movement changes in flagellates and ciliates. Guys, you have to remember which animals have an external skeleton?

Student: The outer skeleton was formed in crustaceans, arachnids and insects. It is represented by a chitinous cuticle, a chitinous shell, which is impregnated with lime. Muscles are attached to this cover, which allows these animals to move rather quickly. Currently, arthropods are the most common type of animals.

Teacher: And what are the disadvantages of such a skeleton?

Student: It should be noted that the external skeleton also has its drawbacks: it does not grow with the animal, and during growth it is necessary to molt the animal several times, while the animal becomes completely defenseless and becomes an easy prey for enemies.

Teacher: Guys, let's write down the information that we talked to in the table:

Teacher: Guys, along with the outer one, there is an inner skeleton. Please tell me what are the advantages of the internal skeleton?

Student: The internal skeleton is devoid of such shortcomings - it grows with the animal and allows even more specialization of individual muscles and their groups, while reaching record speeds of body movement. All chordates have an internal skeleton.

Teacher: The skeleton of most vertebrates is formed by bones, cartilage, and tendons. The bones of the skeleton can be connected either motionlessly - fused together, or mobile - with the help of a joint. Muscles attach to bones in such a way that the bones are set in motion. The following parts are distinguished in the skeleton:

Axial skeleton;

Limb skeleton;

Skull skeleton.

Fish, amphibians, reptiles, birds and mammals have a well-developed spine, which consists of vertebrae. Each vertebra consists of a body, superior and inferior arches. The ends grow together and form a channel in which the spinal cord is located. Chorda persists throughout life in beluga and sturgeon.

Guys, what are the parts of the spine in fish?

Student: The spine in fish consists of the trunk and tail sections.

The spine is formed by biconcave vertebrae, between which the remains of the notochord are preserved. The vertebrae of the trunk region have an upper arch and an upper process, ribs are attached to them from below. In the caudal region, the vertebrae have superior, inferior arches and spinous processes.

The skull consists of the cerebral and facial regions. The facial region is represented by the jaws, the hyoid arch and the branchial apparatus.

The skeleton of the fins is represented by bony rays, the belt of the forelimbs is connected to the skull. In addition to paired fins - pectoral and pelvic fins, there are unpaired fins - dorsal and anal.

Teacher: Guys, let's write down what we just said.

Systematic group	Dept. Skeleton	Skeleton departments	Bones forming the skeleton
Superclass: Fish		Brain department	Consists of a multitude of fused bones that are not mobile.
		facial section	It is represented by the jaws, the hyoid arch and the branchial apparatus.
	Spine	Trunk department Tail section
	Skeleton free final	Unpaired fins (dorsal, caudal, anal)	Represented by the radius. In the nutria of the body there are support bones.
	Skeleton free final	Paired fins (pectoral and pelvic)	Presented by bone rays.
	Limb belts	Forelimb belt	The belt of the forelimbs is connected to the skull. Both the pectoral and pelvic fins are attached to both belts by means of small bones.
	Limb belts	Hind limb belt

What do you think are the main features of the skeleton in amphibians?

Student: In amphibians, due to the aquatic-terrestrial lifestyle, the axial skeleton has become more complicated and is represented by the cervical region, consisting of one vertebra, the trunk - from seven vertebrae with ribs that end freely. The sacral region consists of one vertebra, the bones of the pelvis are attached to it. Tailed amphibians have several vertebrae in the caudal region. The skull is movably articulated with the cervical vertebra.

The musculature loses its metameric structure and is represented by many separate muscles.

The skeleton of the frog, like in all vertebrates, is divided into four sections: the axial skeleton, the skeleton of the skull, the skeleton of the limbs and the skeleton of the girdles of the limbs.

The axial skeleton is represented by the spine, which, in addition to torso and tail divisions peculiar to fish appeared cervical and sacral departments.

The frog's skull is movably articulated with a single cervical vertebra, which ensures the movement of the head in the vertical plane (the head cannot move in the horizontal plane).

The number of vertebrae in the trunk of a frog is seven... The frog has no ribs, but in tailed amphibians, short upper ribs develop on the vertebrae of the trunk, and in legless ones, real ribs.

The sacral region includes one vertebra, bearing long transverse processes, to which the iliac bones of the pelvis are attached.

The tail section of the frog ends with a tail bone - urostyle- a bone, which is several vertebrae that have fused during embryonic development.

The forelimbs are four-fingered (the first toe is reduced) and consist of three sections: shoulder- brachial bone, forearm- fused radius and ulna and brush represented by bones wrists, pasterns and phalanges of the fingers.

The hind limbs are divided into three sections: hips, shins and feet... The thigh consists of the femur, the lower leg - from the fused tibia and fibula, the foot - from bones tarsus, metatarsus and phalanges.

Shoulder girdle the frog encircles the body in a wide semicircle and is fixed in the muscles. It is represented by several paired bones: scapulae ending in wide suprascapular cartilages, crow bones and clavicles, as well as one unpaired bone - the sternum.

Pelvic girdle consists of three paired, accreted due to heavy loads of bones: iliac, pubic and sciatic. With the help of the iliac bones, the pelvic girdle is attached to the transverse processes of the sacral vertebra.

Teacher: Guys, with the help, please fill in your plate.

Systematic group	Dept. Skeleton	Skeleton departments	Bones forming the skeleton
Class: Amphibians		Brain department Facial department	The number of bones is less, since there are no gill covers.
	Spine	Cervical department (1 pos.) Trunk department (7 pos.) Cross section (1 pos.) Tail section	Formed by vertebrae of different structures. (False) ribs are attached to the trunk vertebrae.
	Skeleton free final	Front limbs
	Skeleton free final	Hind limbs
	Limb belts	Forelimb belt
	Limb belts	Hind limb belt

Now, let's figure out what features the musculoskeletal system of reptiles has. I am listening to your answers.

Students: The spine of reptiles has five sections: cervical; chest; lumbar; sacral; tail.

In the cervical spine, the vertebrae are connected movably. They provide head mobility - necessary condition existence on earth. The thoracic and lumbar vertebrae bear the ribs. In some, the ribs connect to the sternum to form the rib cage, providing protection to the organs and better air flow to the lungs. The sacral region consists of two vertebrae. The tail section is well developed. In snakes, all parts of the spine bear ribs, except for the caudal. It should be noted that the ribs end freely, which allows them to swallow large food.

Teacher: With the help of the textbook, please write down the listed features on the plate.

Systematic group	Dept. Skeleton	Skeleton departments	Bones forming the skeleton
Class: Reptiles		There are no differences	There are no differences
	Spine	Cervical department (more than 1 pos.) Chest Lumbar region Sacral region (2 pos.) Tail section	Formed by vertebrae of different structures. Ribs are attached to the trunk vertebrae.
	Skeleton free final	Front limbs	Shoulder (humerus), forearm (radius and ulna), hand (wrist, metacarpus and 4th phalanges of the fingers).
	Skeleton free final	Hind limbs (There are no differences from amphibians)	Thigh (femur), lower leg (tibia and fibula), foot (tarsus, metatarsus and 5 phalanges of the fingers)
	Limb belts	Forelimb belt (There are no differences from amphibians)	The shoulder blades, to which the bones of the forelimbs are attached.
	Limb belts	Hind limb belt (There are no differences from amphibians)	Consists of 3 paired fused bones (ilium, pubic and sciatic)

Let's see, but what is the complication of the musculoskeletal system in birds?

Students: The spine of birds has five sections, like that of reptiles. In the cervical spine there are 9 to 25 vertebrae, movably connected. Fused thoracic vertebrae and ribs, connected to the sternum, form the chest. The sternum of many birds has a special protrusion - the keel. Muscles are attached to the keel that actively work during flight. The terminal thoracic, lumbar, sacral and first caudal vertebrae have fused, creating a powerful sacrum that serves to support the hind limbs, which increases the strength of the skeleton - fitness for flight. The bones of birds are light, many of them are hollow inside.

Despite some differences, the skeleton performs similar functions:

body support;

protection of internal organs;

movement of the body in space.

But at the same time, the skeleton is light and strong due to the thinness of the bones and their pneumaticity.

Brain department the skull is large, articulated with the spine by one condyle, like in reptiles.

V facial department huge eye sockets and elongated jaws, modified into a beak.

The skeleton of the torso consists of spine and chest... The spine includes five sections: cervical, thoracic, lumbar, sacral and caudal. The cervical vertebrae are characterized by saddle joints, which provide greater mobility of the neck (in owls, the head rotation angle reaches 270 degrees).

The posterior thoracic, lumbar, 2 sacral and the anterior caudal have grown together into a complex sacrum.

The middle caudal remains free, the latter fused to form the coccygeal bone.

The rib cage is formed by ribs consisting of two bones connected by a joint at an angle to each other. Thanks to this structure of the ribs, the sternum can move in and out in relation to the spine during breathing movements.

On the top of the ribs, there are flat outgrowths overlapping the posterior ribs, which increases the strength of the chest.

Most birds have a keel on the sternum, to which the pectoral muscles are attached, which set the wings in motion.

The forelimbs consist of the humerus, the forearm is represented by the ulna and radius, the hand consists of the fused bones of the wrist and metacarpus, which form a common bone - buckle, and three fingers: second, third and fourth.

Bird pelvis open, the sciatic and pubic bones do not fuse, this is due to the laying of large eggs.

Due to the fact that the main load during walking falls on the hind limbs, the pelvic bones are massive, firmly grow together with the posterior thoracic, lumbar, sacral vertebrae, as well as with part of the caudal vertebrae, forming a complex sacrum.

Teacher: Well done guys, let's fill in the remaining columns of the table using your textbook.

Systematic group	Dept. Skeleton	Skeleton departments	Bones forming the skeleton
Class: Birds		Facial department Brain department	Formed by bones fused together. There are huge eye sockets and a horny beak without teeth.
	Spine	Cervical (from 9 to 25 vertebrae) Chest Lumbar Cross section Tail section	Formed by vertebrae of different structures. Ribs are attached to the trunk vertebrae, which fuse with the sternum, and it forms a keel, to which muscles are attached. In birds, the posterior thoracic, lumbar, 2 sacral and the anterior caudal are fused into a complex sacrum.
	Skeleton free final	Front limbs
	Skeleton free final	Hind limbs	Thigh (femur), tibia (tibia), the tarsus (fused bones of the tarsus and metatarsus) and from 1 to 4 phalanges of the fingers appear.
	Limb belts	Forelimb belt	The shoulder blades and collarbones have grown together and formed a fork.
	Limb belts	Hind limb belt	The pelvic bones are fused and adhered to the lumbosacral spine.

Teacher: Now guys, let's look at the skeleton of mammals and describe it in the same way:

Systematic group	Dept. Skeleton	Skeleton departments	Bones forming the skeleton
Class: Birds		Facial department Brain department	There is a movable mandibular bone. Formed by bones fused together.
	Spine	Cervical department (7 positions) Chest (from 9 to 24 pos.) Lumbar region (from 2 to 9 pos.) Cross section (3-4 pos.) Tail section	Formed by vertebrae of different structures. Ribs are attached to the trunk vertebrae, which grow together with the sternum, below there are false ribs. The crescent vertebrae grow together to form the sacrum.
	Skeleton free final	Front limbs (Like reptiles)	Shoulder (humerus), forearm (radius and ulna), the hand is modified. Bone reduction occurs and 1 phalanx remains.
	Skeleton free final	Hind limbs

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