Functions of the musculoskeletal system of birds. Musculoskeletal system

The skeleton and muscles make up the musculoskeletal system of birds. Birds are similar in structure to reptiles. However, there are significant differences associated with adaptation to flight.

Skeleton

Bones are the support of the body, allowing movement and protecting internal organs. The light but strong skeleton consists of four sections and makes up 9-12% of the body weight.

Rice. 1. General structure of the bird’s skeleton.

Table “Birds' musculoskeletal system”

Department	Subdivision	Description
	Cerebral	No cranial sutures
		The eye sockets are separated by a bony septum. The beak protrudes in front, consisting of the mandible and mandible and covered with rhamphotheca - a horny sheath.
Spine		Contains 11-25 vertebrae that rotate the head 180-270°. The only movable part of the spine
		It consists of 3-10 fused vertebrae that form the dorsal bone, from which movable ribs extend (according to the number of vertebrae), connecting to the sternum. The keel is attached to it
	Lumbar	Fused into a single bone - a complex sacrum
	Sacral
	Tail	Inactive, has 5-9 free vertebrae. The last vertebrae form the pygostyle - the coccygeal bone
Skeleton of the thoracic limbs	Shoulder girdle	Includes elongated coracoids (crow bones), connected by the upper part to the fork (fused clavicles) and narrow shoulder blades, and the lower part to the sternum
	Skeleton of the forelimbs	Consists of a hollow humerus, radius and ulna (forearm), reduced hand. The fused metacarpus and wrist form a buckle on which are located three vestigial fingers
Skeleton of the pelvic limbs	Pelvic girdle	Consists of the ischial and pubic open bones, which allows for the laying of eggs. The pelvis is connected to the complex sacrum
	Skeleton of the hind limbs	Includes the femur and tibiotarsus (tibia) connected by the knee, the tarsus (the bone between the tibia and the toes) and the foot (toes with claws) connected by the ankle joint

Some bird bones are pneumatic, that is, hollow inside, filled with air coming from air sacs. Between the cavities there are bone beams - partitions that give the bones strength.

Rice. 2. Internal structure of bird bones.

Muscles

The muscles are characterized by high density and mobility. The most developed:

• neck muscles - turn their head in any position;
• pectoral and subclavian muscles - raise and lower wings;
• tail muscles - control the tail feathers;
• leg muscles with long tendons - move through trees, take off and land.

Rice. 3. Bird musculature.

The pectoral muscles of birds are conventionally white (lighten after heat treatment) and are adapted for intense short-term work. Dark red fibers are stronger, perform longer work and are less tired.

Adaptation to flight

Progressive structural features that allow birds to fly include:

• thin, hollow bones that reduce overall body weight;
• lack of teeth;
• transformation of scales into light wide feathers;
• streamlined head and body shape;
• a fork that softens the movement of the wings;
• fusion of vertebrae that form support during flight;
• tarsus that softens the landing.

Musculoskeletal system of birds consists of 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 is achieved by 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 braincase in a bird's skull is much larger than in the skull of reptiles;
• The skull of birds is lighter than that of reptiles;
• Bird skull braincase ends beak, and on the sides of the box there are large eye sockets;
• Adult birds have a skull whose bones are completely fused until the sutures disappear.

Bird spine, like other land animals, has 5 divisions: cervical, thoracic, lumbar, sacral and caudal. The most mobile department is cervical region. Thoracic vertebrae sedentary, and The vertebrae of the lumbar and sacral regions form a complex sacrum, merging with each other.

Some may also grow together shoulder girdle bones, for example, collarbones one next to the other, a saber-shaped shoulder blade with a raven bone - all this provides the shoulder girdle with strength sufficient for the normal operation of the wings attached to it. The wings are made up of typical for the upper extremities: humerus, ulna and radius bones 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 are not fused and have a wide gap, birds are able to lay fairly large eggs.

The powerful hind limbs consist of bones typical of all land animals, but the fibula is attached to the tibia to strengthen the tibia. The metatarsal bones are fused with part of the tarsal bones, and form a bone characteristic only of birds - tarsus. Three of the four fingers usually point forward, one - back.

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

A high level of mobility and variety of movements ensures 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 pectoral muscles, provide lifting of the wings. Bird flight speed can be different: 60-70 km/h for ducks and 65-100 km/h for the peregrine falcon. Maximum flight speed among birds noted in the black swift - 110-150 km/h. The powerful leg muscles of birds that have lost the ability to fly make it possible to move quickly on land (ostriches move at an average speed of 30 km/h).

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Lesson topic:Features of the musculoskeletal system of birds in connection with their adaptation to flight.

Lesson objectives:To familiarize students with the features of the musculoskeletal system of birds in connection with their adaptation to flight;

Equipment:Skeleton of a bony fish, frog, bird, table “Dove”. Handout card-photocopies of the drawing “Structure of the skeleton of a bird” without markings.

I.Organizing time

I. Updating of basic knowledge.

1.Individual survey: work on cards 1--5.

What feathers form the flying surface of a bird's wing? What bones of the skeleton are they attached to?

By what signs of external structure can a bird be recognized among other vertebrates?

How do birds differ from each other?

1. What types of feathers do you know?

2. How do they differ from each other?

3. What are their functions?

1. The bird's body is not completely covered with feathers. Bare or almost bare areas of the body are present on the abdomen, sides of the body and neck. How can we explain the presence of areas of skin devoid of feathers in birds?

2. What is the role of feather cover in the life of a bird? __________

How are birds' bodies adapted for flight?

2.Frontal survey.

-Where do birds live?

-How do birds differ in external structure from reptiles?

-What signs of similarity can be noted in their structure?

3.Test.

Write down the numbers of the correct judgments.

1.All birds are capable of flight.

2.Birds are the largest class in terms of the number of species among other classes of terrestrial vertebrates.

3.Birds usually have 4 toes on their feet: three of them point forward and one points back.

4.The bird's beak consists of modified upper and lower jaws, devoid of teeth.

5.The flying surface of the wing is formed by contour feathers.

6.The feather cover of a pigeon has no down.

7.Down feathers and down are the same thing.

8.The contour feather consists of a shaft and a fan.

9.The body of the bird is covered with coverts and down feathers.

10.The flight feathers of most birds are attached to the ulna and hand bones.

Answer: 2, 3, 4, 5, 6, 9, 10.

III. Studying new Topics

Let's move on to studying our topic - getting to know the features of the musculoskeletal system of birds and trying to remember how these devices are related to flight. To do this, let's do the laboratory work “Structure of the skeleton of a bird” (p. 253.).

-Why do birds belong to the phylum Chordata, subphylum Vertebrata?

-What is the significance of the skeleton for animals?

-List the main parts of the vertebrate skeleton.

The skeleton of a bird is generally similar to the skeleton of other vertebrates known to you, but it also has a number of distinctive features. Pay attention to the skeleton of the pigeon. It is very light due to the presence of airways in the bones. The total mass of the skeleton is 8-18% of the mass of the entire body, at the same time, the bird’s skeleton is strong due to the fusion of a number of bones with each other.

The axial skeleton - the spinal column - is divided into five sections: cervical, thoracic, lumbar, sacral, caudal. The number of cervical vertebrae varies depending on the type of bird from 11 (pigeon) to 23-25 ​​(swan). The first vertebra is the atlas, in most birds it has the shape of a bony ring, the second, the epistropheus, is articulated with it by an odontoid process, which provides a movable connection between the head and the body. The remaining cervical vertebrae are saddle-shaped, which causes significant mobility of the vertebrae relative to each other. The peculiarities of the cervical vertebrae allow birds to freely turn their heads 180°, and some (owls, parrots) even 270°. This makes it possible to make complex and rapid movements of the head when grasping moving prey, cleaning plumage, building nests, etc.

Birds have 3-10 thoracic vertebrae. Fusing together, they form the dorsal bone and are connected to the complex sacrum by a very strong joint. Thanks to this, the trunk section of the axial skeleton is motionless, which is important when flying.

The ribs are attached to the thoracic vertebrae. Each rib consists of two sections - dorsal and abdominal, movably connecting with each other and forming an angle with the apex directed backwards. The ribs articulate with the vertebrae and sternum through movable joints, which, along with the developed intercostal muscles, ensures a change in the volume of the body cavity (which is important for breathing). The strength of the chest is increased by hook-shaped processes, strengthened on the dorsal sections and overlapping the subsequent rib. The sternum is large and has a keel to which the muscles that lower the wings are attached.

All lumbar, sacral (there are two of them) and part of the caudal vertebrae are motionlessly fused to each other into a monolithic bone - a complex sacrum. In total, it includes 10-22 vertebrae, the boundaries between which are not visible. The bones of the pelvic girdle (ischial, pubic and iliac) are fixedly connected to it. This ensures the immobility of the trunk, which is very important when walking.

The free caudal vertebrae (5-9 of them) are fused into the coccygeal bone - the pygostyle, to which the tail feathers are attached like a fan.

Pay attention to the bird skull. It is formed by thin spongy bones, the boundaries between which are visible only in young birds. Compared to reptiles, the volume of the braincase in the skull of birds is much larger, the eye sockets are large, the jaws are devoid of teeth and form a beak.

In birds, compared to amphibians and reptiles, the skeleton of the fore and hind limbs has undergone significant changes. The skeleton of the forelimb is strengthened due to the fusion of the bones of the hand and a reduction in the number of fingers to three. The girdle of the forelimbs is also adapted for flight: powerful crow bones (coracoids), fused clavicles,

forming a fork, ensure the movement of the wings.

The structure of the skeleton of the hind limb allows birds to walk bipedally. The bones of the foot are fused into one bone - the tarsus, which is an additional lever that increases the length of the step. The phalanges of the fingers are movably attached to the tarsus.

Now, using the instructions, complete the proposed tasks in writing in 20 minutes, using the text of the textbook, drawing p. 236, the corresponding table on the board and fill out the table in your notebooks:

Skeletal departments	Bones department	Structural features in connection with flight

-So, what adaptations for flight are present in the bird’s skeleton?

& Missing teeth;

jsSthe presence of a sternum with a keel to which muscles are attached;

& ribs consisting of two parts - this articulation ensures their mobility when the bird breathes in flight;

& the reduction in the number of fingers and the fusion of small bones of the hand ensure the strength of this section of the wing, which bears the heaviest load in flight;

jssthe strong connection between the vertebrae of the thoracic and lumbosacral sections of the skeleton serves as reliable support for the body during flight.

The muscles of birds are also well developed. The most developed (up to 25% of the bird’s mass) are the muscles that move the wings. They are shifted to the chest, and this, on the one hand, facilitates the moving organ (wings), and on the other hand, makes the center of gravity of the body motionless, which is very important for straight flight. The most developed muscles in birds are the pectoralis major muscles, which lower the wings and make up 50% of the mass of the total muscles. The wings are raised by the subclavian muscles, which are also well developed and located under the pectoralis major. The muscles of the hind limbs and neck are highly developed in birds.

IV. Consolidation

1.Eliminate unnecessary things:

a) shoulder blades; c) crow bones;

b) collarbone; d) humerus.

2.There is a certain correspondence between the proposed first and second concepts. Find a similar correspondence between the third and one of the five given concepts:

Ulna - forearm<=>tibia - ?

a) tarsus; b) foot; c) lower leg; d) thigh; d) brush.

3.Summarize the following concepts into one:

ulna, humerus, hand bones - ...

4.The concepts “Atlas” and:

a) cervical spine; c) second cervical vertebra;

b) first cervical vertebra; d) sacrum.

5.Bird science is:

a) poultry farming; c) cynology;

b) ornithology; d) zoology.

Answers." 1 - g; 2 - A; 3 - forelimb; 4 - ; 5 B.

Homework

§ 54, answer questions 1.4 in the textbook, p. 165.

Musculoskeletal system. Skeleton and muscles of birds.

Subject: Skeleton of birds.

Target: study the skeleton of birds.

Tasks:

1. Educational: familiarize students with the features of the skeleton of birds in connection with their adaptation to flight; give the concepts of “tarsus” and “keel”.

2.Developing: development of concepts: “spine”, “pelvis”, “sacrum”, “sternum”; ability to work with a textbook; development of thinking.

3. Educational: formation of a scientific worldview, environmental education (using the example of identifying adaptations to environmental factors in the structure of the skeleton).

• The skull is a single bone; only the lower jaw is movably connected to it

The pelvic bones fuse with the spine. The lumbar, sacral and part of the caudal vertebrae form a complex sacrum.

1 - lumbar vertebrae, 2 - sacral vertebrae, 3 - caudal vertebrae,

4 - ilium, 5 - ischium, 6 - pubic bone

Bones are light: all long bones are tubular and have air cavities; some flat bones also have small air cavities.

• Skeleton of a crow's body from the side:
• 1 - last cervical vertebrae, 2 - fused thoracic vertebrae (dorsal bone),
• 3 - cervical ribs, 4 - thoracic ribs, 5 - uncinate process, 6 - body of the sternum,
• 7 - keel, sternum, 8 - complex sacrum, 9 - movable caudal vertebrae,
• 10 - pygostyle, 11 - coracoid, 12 - fork, 13 - scapula,
• 14 - articular cavity for the head of the humerus, 15 - ilium,
• 16 - ischium, 17 - pubic bone,
• 18 - acetabulum for articulation with the femoral head

Spinal sections

1. Cervical (9-25 vertebrae), 2. thoracic (3-10 vertebrae), 3. lumbar (6 vertebrae), 4. sacral (2 vertebrae), 5. caudal (5 fused with the complex sacrum, 6 remained free, 4 last fused into the coccygeal bone).

• The sternum, or sternum (6) is a wide and long, concave bone plate from the inside, bearing a high bony ridge along the midline - the keel of the sternum (7). The sharp increase in the surface of the sternum, due to both its growth and the formation of a keel, is a direct adaptation to flight; it provides the possibility of attaching powerful muscles that move the wing. At the anterior end of the sternum, on the sides of the carina, there are large articular platforms that provide strong attachment of the coracoids to the body of the sternum (11). On the lateral edges of the sternum there are small depressions that serve for articulation with the lower ends of the abdominal ribs.

Forelimb belt

The girdle of the forelimbs consists of paired xiphoid blades, two clavicles fused into a fork, and two large caracoids resting on the sternum.

• 1.Collarbones. 2. Blade. 3, Crow bone. 4. Sternum. 5.Kiel.

Skeleton of the front free limb - wing

• Crow wing skeleton: 1 - humerus, 2 - radius, 3 - ulna, 4 - independent bones of the wrist, 5 - buckle (merged bones of the wrist and metacarpus), 6 - phalanges of the second finger, 7 - the only phalanx of the first finger, 8 - the only phalanx of the third finger

Changes due to adaptation to flight.

• The skeleton of the forelimb, which turned into a wing, has undergone significant changes. Shoulder ( 1 ) is a powerful tubular bone that fits into the glenoid cavity of the shoulder joint. The nature of the articular surfaces significantly limits the possibility of rotational movements in the shoulder joint, which ensures the stability of the wing in flight. The powerful epiphyses of the distal end of the humerus form articular surfaces for articulation with two bones of the forearm: the straighter and thinner radius (, 2 ) and a more powerful, slightly curved ulna ( 3 ). On the surface of the ulna, tubercles are visible - the attachment points of the rims of the secondary flight feathers. The nature of the articular surfaces of the elbow joint ensures a strong connection between the bones of the shoulder and forearm and limits rotational movements in this joint. At the same time, greater mobility is maintained in one plane - the plane of the wing, which allows the bird to fold its wing at rest and change its area when the flight mode changes. 4 Dramatic changes in connection with adaptation to flight occurred in the structure of the hand. In the proximal part of the wrist, only two independent bones are preserved (, 5 ). They are almost immovably connected by ligaments to the bones of the forearm. The movable joint is located between them and the rest of the bones of the wrist, which is why it is called the intercarpal joint. The remaining bones of the wrist and all the bones of the metacarpus merge into a single formation - a buckle ( 6 ). The skeleton of the fingers is sharply reduced. Two phalanges of the second finger are preserved ( 7 ), continuing the axis of the buckle. One phalanx is preserved from the first finger (Fig. 4 ), a bunch of feathers is attached to it, forming a wing (, 8 ). The third finger is also represented by one phalanx (), attached to the base of the first phalanx of the second finger.

These transformations in the skeleton of the hand provide a strong support for the primary flight feathers - the part of the wing that carries the greatest load in flight.

• Skeleton of the free hind limb.

The powerful long bones of the skeleton of the hind limbs, the appearance of an additional lever, the sharp relief of the articular surfaces - all this ensures the strength and mobility of the hind limbs. : Skeleton of the hind limb of a crow 1 - femur, 2 - patella, 3 - tibia-tarsus), 4 - fibula, 5 - tarsus (fused bones of the tarsus and metatarsus),

• Neck muscles are well developed. More than 30 muscles provide movement of the hind limbs. They begin on the bones of the pelvis, thigh, and leg. Long tendons come to the fingers, which, when the bird lands on a branch, stretch, squeezing the fingers, so the birds do not fall from the branches while sleeping. The intercostal and some other muscles provide mobility to the chest. There are special muscles that move feathers.

Muscle contraction pattern

Diagram of muscle contraction when raising (A) and lowering (B) the wings: 1 - pectoralis major muscles; 2 - subclavian muscles

• The large pectoral muscles that lower the wing are important for the flight of birds. They are attached to the keel of the sternum and end with tendons on the wing bones.

Ostriches are flightless birds.

Ostriches are flightless birds. They are characterized by a complete absence of a keel and underdeveloped pectoral muscles; the skeleton is not pneumatic, with the exception of the femurs. The wings of ostriches are underdeveloped; two fingers on them end in claws, or spurs. The hind limbs are long and strong, with only two toes. One of the fingers ends in something like a horny hoof (an overgrown claw) - the bird leans on it when running. When running, an ostrich can reach speeds of up to 60-70 km/h.

Penguins or penguins- a family of flightless seabirds, the only one in the order penguin-like (Sphenisciformes). There are about 20 modern species in the family (according to various sources - from 18 to 20). All representatives of this family swim and dive well.

• The forelimbs of penguins are modified into elastic flippers, which, thanks to the special structure of the skeleton, are in a semi-extended state and, while swimming underwater, rotate in the shoulder joint almost like a screw. The wings of these birds practically do not bend, since they are flippers covered with scaly short feathers. They only help penguins row while swimming and diving. Some species of penguins are capable of making up to 120 swing movements per minute. The penguins' webbed feet and tail serve as a kind of rudder.

Attached to the well-developed keel of the sternum are powerful pectoral muscles that control the movement of the wing-flippers. In some species of penguins, the pectoral muscles make up a quarter of the total body weight, which is significantly more than in many flying birds. The bones forming the skeleton of the wings are flattened like planks. Penguins are very different from other birds in bone density and are similar to marine mammals.

• What changes in the skeletal structure of birds compared to reptiles occurred in connection with their adaptation to flight?
• What are the features of the location and structure of the muscles of birds? Explain your reasons.
• Why do flying birds have a high keel?
• What are the structural features of the pelvis of birds? What is the reason for this structure?

Homework: § 45, fill out the table

Skeletal departments

Bones forming the compartment

Peculiarities

• Presentation. Biology teacher - N.F. Neverova. MBOU secondary school No. 10 city of Dimitrovgrad, Ulyanovsk region.

Task 1. Do laboratory work.

Subject: "The external structure of a bird. The structure of feathers."

Goal of the work: study the features of the external structure of birds in connection with flight.

2. Using the instructions given in paragraph 44 of the textbook, do laboratory work, sketch the structure of feathers and make an explanation for the drawings.

3. Make a conclusion about the features of the external structure of birds.

The feathers of birds develop from the same epithelial embryos as the scales of reptiles. Birds are well adapted for flight: the forelimbs are turned into wings, the body is streamlined and covered with feathers. The main role in flight is played by flapping movements and tail feathers.

Task 2. Fill out the table.

Task 3. Write down the numbers of the correct statements.

Statements:

1. All birds are capable of flight.

2. Birds are the largest class of terrestrial vertebrates in terms of the number of species.

3. Birds usually have four toes on their feet.

4. The flying surface of the wing is formed by contour feathers.

5. There is no down in the feather cover of a pigeon.

6.Down feathers and down are the same thing.

7.The contour feather consists of a shaft and a fan.

8. The skin of birds is thin and dry (there is only a coccygeal gland).

Correct statements: 4, 7, 8.

Task 4. Do laboratory work.

Subject: "Structure of a bird's skeleton."

Goal of the work: study the structural features of the bird skeleton; note features associated with flight.

1. Make sure that the workplace has everything necessary to perform laboratory work.

2. Using the instructions given in paragraph 45 of the textbook, complete the laboratory work.

3. Color the bones of the bird's skeleton (green - bones of the spine, blue - bones of the forelimb belt, brown - forelimbs, red - hind limbs, yellow - hind limbs) and label them.

4. Note how the structure of the bird’s skeleton is adapted to flight.

The musculoskeletal system well reflects the adaptations of birds to flight. The skeleton is light and durable. Lightness is ensured by the pneumaticity of the bones, strength by their fusion. in the hand the bones have fused into a buckle, in the foot - into a tarsus.

Task 5. Write down the numbers of the correct statements.

Statements:

1. The keel (outgrowth of the sternum) of birds helps to cut through the air in flight.

2. The tarsus in birds was formed as a result of the fusion of several bones of the foot.

3. The skeleton of a bird's wing is similar to the skeleton of the wing of an ancient flying lizard.

4. The beak of a bird is a modified upper and lower jaw, devoid of teeth.

5.The wings of a bird rise and fall due to the action of the pectoral muscles.

6. The girdle of the forelimbs in birds consists of two shoulder blades and two clavicles.

7. One finger is well preserved in the bird's wing hand.

8.The position of the wings provides birds with stability in flight.

9. The presence of horny scales is a common feature of reptiles and birds.

10. The length of the neck in birds depends on the number of vertebrae.

Correct statements: 1, 3, 4, 5, 8, 9.