The evolution of the structure and functions of the musculoskeletal system. Objectives: introduce students with the structure and function of the musculoskeletal system in different groups of animals, with the direction of evolution of the musculoskeletal system. Features of a skeleton of man associated

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The main thing…

The human musculoskeletal system is a functional set of skeleton bones, tendons, joints, carrying out the nervous regulation of locomotion, maintaining postures and other motor actions, along with other system systems forms a human body.

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Human skeleton

The skeleton of the person is a set of bones, the passive part of the musculoskeletal system. Serves as a support soft tissue, the point of the muscle app (lever system), the extensive and protection of the internal organs.

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More about the skeleton ...

The human skeleton consists of two hundred and small bones, and almost all of them are connected to one integer with the help of joints, ligaments and other connections. During life, the skeleton constantly undergoes changes. During the intrauterine development, the cartilage skeleton of the fetus is gradually replaced by bone. This process continues also for several years after birth. A newborn baby in a skeleton is almost 270 bones, which is much more than an adult. Such a difference arose due to the fact that the children's skeleton contains a large number of small bones, which grow into large bones only to a certain age. This, for example, bones of the skull, pelvis and spine. Sleep vertebrae, for example, they grow into a single bone (crescents) only aged 18-25 years. Directly to the skeleton do not include 6 special bones (three on each side) located in the middle ear; Hearing bones are connected only to each other and participate in the work of the hearing body, carrying out the transmission of oscillations from the eardrum into the inner ear. Podium bone is the only bone that is not directly associated with others, is topographically on the neck, but traditionally refers to the bones of the facial skull. It is suspended with muscles to the bones of the skull and is connected to the larynx. The longest bone of the skeleton is the femoral bone, and the smallest - stirring in the middle ear.

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Functions ...

The bones of the facial skull are their main function - participation in food chewing. The brain skull bones - a cerebral skull consists of eight flat bones that protect the brain connected motionless. Ribs are bones that, together with the sternum, form a chest, the necessary element of the protection of internal organs placed in it. The vertebral pillar is the axis, or the support of our body, consisting of 33 or 34 vertebrae, is placed spinal cord. The femoral bone is the longest bone of the human body. Allows you to make a variety of movements with your foot due to its connection with the knee. Foot bones are a group of 26 bones, among which the largest, heel bone forming the heel is distinguished.

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The highest person in the world was an American, the growth of which was 2.72 m. By the time of his death, in 1940, when he was 22 years old, he continued to grow. The lowest person was 19-year-old Holland: her growth was only 59 cm, she died in 1895. The skeleton of the newborn baby consists of more than three hundred bones, but as a result of the fact that many of them grow together in the process of growing up, in the skeleton of adult they remain only 206

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The longest bones about which there are information is the bones of the Brachiosaurus - a dinosaur, the remains of which were found in Colorado (USA). Its blades reached the length of 2.4 m, and some ribs exceeded 3 m. Among modern living beings, the highest animal of the Earth is a giraffe, its growth can reach 6 m. Long, more than 2 meters of neck, the necessary giraffe to eat trees with branches of trees, has Only seven cervical vertebrae, as much as the mouse. Perhaps the most small are the temporal bones of the hummingbird - birds, the length of which does not exceed 2-3 cm, but in which there are muscles on the wings, allowing it to do up to 90 cracks per second. Hummingbirds may hang in the air when it feeds on the nectar of colors, and even fly back.

Slide 10.

Skeleton Diseases ...

There are many diseases of the bone system. Many of them are accompanied by restriction of mobility, and some can lead to a complete immobilization of a person. Serious threat to life and health are malignant and benign bone tumors, requiring often radical surgical treatment; Usually the affected limb is amputated. In addition to bones, joints are often amazed. Diseases of the joints are often accompanied by a significant impaired mobility and strong pain. With osteoporosis, bone fragility increases, bones become fragile; This systemic skeletal disease most often occurs in the elderly and in women after menopause.

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Muscular system ...

The muscular system is one of the main biological subsystems in higher animals, thanks to which the body moves in all its manifestations. The muscular system is absent in unicellular and sponges, however, these animals are not deprived of the ability to move.

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More about the muscles ...

The muscular system is a combination of muscle fibers combined to reduce the muscle fibers, which form special organs - muscles or independently included in the internal organs. Muscle mass is much larger than the mass of other organs: vertebrate animals it can reach up to 50% of the mass of the whole body, in an adult - up to 40%. Muscular tissue of animals is also called meat and, on a row with some other components of animal bodies, is eaten. In muscle tissues there is a transformation of chemical energy into mechanical energy and heat.

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For vertebrates, three types of muscles are distinguished:

Skeletal muscles (they are transverse, or arbitrary) smooth muscles (involuntary) heart muscle. It is only in the heart. Skeletal muscles heart muscle smooth muscles

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Muscle functions ...

The muscles of the face - allow you to take various expressions of our face: laughter, anger, etc. The two-headed shoulder muscles - together with its antagonist, the three-headed muscle of the shoulder - ensures the bending and extension of the forearm. The outer oblique muscles are allowed to reduce the air from the lungs. Perform work opposite to the operation of the diaphragm, which is not visible here, as it is inside the abdominal cavity. Fouring the thigh muscle - as in the case of the upper limbs, the four-headed muscles of the hip also has an antagonist muscle - the two-headed thigh muscle. Both are flex and infringement of the thigh.

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Evolution posture

The evolution of the posture is one of the important aspects of "posture", the improvement of the human musculoskeletal system in the process of historical development. The posture is a property inherent in a person only, the product of the evolutionary process is straightening. The main historical milestones of the evolution of the posture are: strain (2 million years ago); invention of stool (XV century); Mass school learning (XIX century); The emergence of a new mass profession is an office worker (XXI century). An outstanding Canadian physiologist Baschajan so described the value of this process

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"Among the mammals, by going once a vertical posture, has the most economical antigravitational mechanisms. The cost of muscle energy with this seemingly the least convenient posture, extremely economical "S-shaped spine - a kind of axial load shock absorber

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Evolution…

In the process of man's evolution, signs of straightening were gradually formed: a balanced head fit, S-shaped spine, vaulted foot, wide pelvis, wide and flat thoracic, massive lower limb bones, orientation of the blades in the front plane. S-shaped spine is a kind of shock absorber with axial loads. As you know, the bend is distinguished forward in the cervical department - the cervical lordosis, bending back in the thoracic - chest kyphosis, bending forward in the lumbar department - Lumbar Lordoz. Due to the natural bends, the strength of the spine to the axial load increases. With sharp and excessive loads, the spine, as it were, "folds" in the S-shaped form, preventing discs and bundles of the spine from the injury, and then parsing as a spring.

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A reprehensive skeleton allows a person to move, unlike other animals, on two legs, carrying weight from the heel to the front of the foot, which turns each step into the balancing exercise. The load is transmitted through the tibia. The Point of Support falls on the sock The force is created by Achilles tendon, which, when cutting the muscles of the caviar, raises the heel of the arrow arms of the "Gas" inertial loads during landing, which reach up to 200% body weight. Natural, balanced head fit, allows the long axes of the orbits to be facing forward. This is a distinctive sign of a person from his humanlike "counterparts", in which the head is suspended on the occipital muscles (anthropologists determine the position of the head on the structure of the base of the skull and the cervical vertebrae). The balanced position of the head eliminates the stretching of the rear bundles of the neck and the need for constant tension of the neck muscles, mainly, in contrast to animals, the muscles - the upper trapezium. In the process of historical development, humanity has passed a difficult path.

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With the development of civilization, the requirements for the musculoskeletal system changed. If ancient people were or vertical or horizontal (hunted, collected, fought, lay, resting), then in the XVII century, 10% of the population was performed by a sedentary work. In the XXI century, the number of such workers increased to 90%. In the process of evolution, the person stopped adapting to the environment and began to adapt the environment to himself, and this could not but affect the posture. The invention of benches, chair (this is probably the XV century) significantly changed a human biomechanic, a new problem has appeared - "the posture of sitting on a chair". Modern man spends most of his time sitting at work, at home, in transport, working, learning, resting, waiting, taking food. Pose "Sitting" - optimal for the fulfillment of office work and learning, is a serious test for the musculoskeletal system. It is in this posture that the posture is most often suffering. It is the long posture sitting that is the cause of pain in the back, and the cause of various diseases. 18th century - century of mass school learning. This progressive historical process has a reverse side

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According to the Russian Institute of Children's Orthopedics, 40-80% of children detect disorders of posture, and in 3% -10% of them - various spinal curvatures are so-called school scoliosis. With the development of civilization, the content, organization and methods of human labor are changed. Office workers are a new mass profession, the number of which is more than 60% of the entire working population. The need for long-term observance of sedentary working poses (working at a computer, with documents, with clients) leads to an increase in the number of diseases of the musculoskeletal system of the adult population. The number of such diseases is steadily growing, they are young and this trend is likely to be preserved in the foreseeable future.

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Thanks for attention…

Good Bye ... Sources: Basmajian, J.V. (1985) 5th Edition. Muscles Alive, Their Function Revealed by Electromyography. Williams & Wilkins, Baltimore. 1985.

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The development of the musculoskeletal system largely depends on the degree of motor activity, nutrition, activities of the internal secretion glands. Of particular importance for the formation of the skeleton and development of muscles are exercise and labor. Upon constant load on the body, the muscles of the body are developing stronger, the bones of the skeleton are stronger. With regular practices, physical labor, physical education, man becomes more robust, efficiently thanks to the best blood supply to the muscles and the development of their physical qualities. Work, physical exercises develop internal muscles, leads to the improvement of all the functions of the body and the activities of organ systems. Physical work is the only physiological means of removing emotional stress, so that the nervous system will be in an optimal state and will be able to provide a clear regulation of the muscles. Systematic physical education classes increase the protective properties of blood and skin, the body's stability to the lack of oxygen, to low and high temperatures, to penetrating radiation.

Remember ! Exercise classes and the associated physical activity have a beneficial effect on the body only when their volume, intensity, duration correspond to age and health status.

One of the most harmful factors, negatively affects the processes of growth and human development, for the duration of its life, the condition of the body is hydodina - reduced motor activity. In our time, it is mainly a consequence of the liberation of a person from severe physical labor and the development of transport. Especially negatively continued hypodynamine affects the cardiovascular system (the strength of the reduction of the heart is weakened, its performance decreases, the tone of vessels decreases), as well as on metabolism and energy. Hydodine lands not only physical, but also mental performance, vital tone, and this leads to a limitation of social activity, the desire to overcome difficulties. The influence of hypodynamine affects each human body system.

A certain posture is characteristic of each person, that is, body position during standing, seating, walking, work. The posture is determined by the development of the skeleton and muscles. Signs of proper posture is moderate spinal bends, deployed shoulders, straight legs with a normal foot arch. There is a posture in children and youthful age and can change during life. Disadvantages of posture arise mainly due to non-compliance with hygienic rules.

Rachiocampsis - This is a violation in which the physiological bends of the spine is increasing or new ones. A healthy spine has four moderate bends that help him be elastic and balancing the center of gravity. The cervical and lumbar departments are curved several forward, both breast and sacral curved backwards. Enlarged or abnormal bends can be congenital disadvantage, consequence of the weakening of the musculoskeletal system or bone diseases. The following main types of posture disorders are distinguished: lumbar lordosis - excess bending of the spine forward in the lumbar department; breast kyphosis - excessive bending of the spine back in the thoracic department; scoliosis - Side spinal curvature.

Flatfoot - Flooding of the foot of the foot. Due to the flatfoot, blood vessels are compressed, the blood circulation of the foot is disturbed, its nervous endings are constantly annoyed, causes pain in the feet, bone, heads, and a change in gait. Flatfoot develops due to the weakness of the foot muscles, the large body weight, wearing the shoes on high heels.

The main diseases of the bone system is congenital, dystrophic, inflammatory And tumor.

Congenital diseases A group of lesions, the main sign of which is the violation of the development of individual bones or the entire skeleton in intrauterine development and after birth. The reasons for these lesions are not fully understood, but it is known that they are often associated with related marriages; These diseases arise and as a result of the impact on the body of pregnant women of harmful factors (injuries, chemical agents, nervous overloads, smoking, alcohol).

Dystrophic diseases Develop in disruption of bone tissue. An example of such lesions is rahit, Arthrosis, Osteochondrosis and others. To dystrophic diseases include a large group of so-called osteochondropathy, which are observed mainly in children and adolescents. They are due to a disruption of the nutrition of this or another area of \u200b\u200bthe bone system, as a result, she donates, softened and under the action of the load is deformed. Later it is replaced by a healthy bone tissue, but the curvature remains. An example of such diseases is scoliosis, Lordoz, Kyphos, flatfoot.

FROM inflammatory diseases Most often found osteomyelitis and tuberculosis bones and joints. The inflammation of bone tissue can also develop as complications of transferred infectious diseases. Sometimes they occur when the causative agents of infection on the naked bone surface with open fractures.

Mechanical damage The bone system is often observed. These include various bone fractures, dislocations of joints, stretching ligaments. Hit - These are damage to soft tissues, often accompanied by hemorrhages under the skin. Signs of strikes are swelling, pain, hemorrhage under the skin. When hitting, it is necessary to immediately make something cold, then tightly bandaged the joint and consult a doctor. Dislocation - The yield of the articular head of the articular depression. Signs of dislocation is the change in the shape of the joint, pain. When first aid first apply the cold, then the joint is fixed motionless and deliver the victim to the hospital. Exercises of dislocation without a doctor is not allowed. Bone fracture This is a violation of the integrity of bones. Distinguish between traumatic and pathological fractures:

■ traumatic fractures - arise due to the unexpected action of significant mechanical force on a healthy bone; are divided into closed (without leaning the skin) and open (There is injured skin in the fracture zone)

■ pathological fractures - There are bones, weakened by any pathological process, in case of insignificant injury and even spontaneously.

For fractures are characterized by sharp pain, increasing with movements and loads, appearance of edema, pathological mobility of bones, change their position. According to the open bone fracture can be stitching from the wound.

Muscle diseases may arise as a result of metabolic disorders, inflammatory processes, injuries, during the blockage of large arteries and others. Minor motor activity can lead to atrophy muscles. Muscle inflammation belongs to the most common diseases of the muscular system - miost. Muscle damage is also in the form of bruises and breaks.

Blood, you need to know, this is a special juice ...

"Evolution of the reference - motor system of animals."

In order to survive, animals needed to look for food, it is better to hide or defend against enemies, moving faster. By changing together with the body, the musculoskeletal system was supposed to provide all these evolutionary changes.

The most primitive - nuts, which have no reference system. Move slowly, flowing with falselyones, while constantly change the shape.

For the first time the speed of movement varies with flagelon and infusories.

The outer skeleton was formed in crustaceans, spider and insects. It is represented by the chitinular cuticle, a chitine shell, which is saturated with lime. Muscles are attached to this cover, which allows you to move around this animal rather quickly. It should be noted that the outer skeleton has its drawbacks: it does not grow with the animals, and during growth it is necessary to lift the animal several times, while the animal becomes completely defenseless and becomes easy prey for enemies.

The inner skeleton is deprived of such drawbacks - it grows with animals and allows you to even more specialize individual muscles and their groups, while achieving record velocities of the body movement. All chordic inner skeleton.

The skeleton of most vertebrate animals is formed by bones, cartilage, tendons. The skeletal bones can be connected either motionless - fuse, either moving with a joint.

The following parts are distinguished in the skeleton: axial skeleton; The skeleton of the limbs; Skeleton skull.

In fish, amphibious, reptiles, birds and mammals are well developed by the spine, which consists of vertebrae.

The spine of fish consists of a torso and tail departments.

At the amphibians, in connection with the water-terrestrial lifestyle, the axial skeleton was complicated and presented with a cervical department consisting of one vertebra, torso - from seven vertebrae with edges that end freely. The sacral division consists of one vertebra, the bones of the pelvis are attached to it. Tailed amphibians have several vertebrae in the tail section.

The spine reptiles has five departments: cervical; chest; lumbar; sacral; tail. In the cervical vertebrae is connected by moving. They provide head mobility - a necessary condition for existence on Earth. Breast and lumbar vertebrae carry ribs. Some ribs are connected to the sternum, forming a chest, provides protection to organs and better air flow into the lungs. The sacral division consists of two vertebrae. Well developed tail department.

In the serpent, all departments of the spine carry ribs, except for the tail. It should be noted that the edges end freely, which allows them to collect large food.

The spine birds has five departments, as in reptiles. In the cervical department from 9 to 25 vertebrae, connected moving. Comedy breast vertebrae and ribs connected to the sternum form the chest. Breasts of many birds has a special ledge - Kiel. Muscles are attached to the keel, actively working during flight. The final thoracic, lumbar, sacral and first tail vertebrae grown, creating a powerful crescent, serving for the support of the rear limbs, which increases the strength of the skeleton - the fitness to flight. The bones of the birds are light, many of them are hollow inside.

The spine mammals also consists of five departments. The forelimbs consist of a shoulder, forearm, brushes. The hind limbs consist of hips, legs, feet. The front limb shoulder bone is attached to the chest using the belt of the front limbs, in some animals it consists of a clavicle and blades (primates), in other blades only, as the clavits are missing (dogs and non-parnye).

With the help of the belt of the hind limbs consisting of pelvic bones, who have grown up with the sacrum of the spine, the hind limbs are attached to the spine. The skull consists of brain and facial departments. In the brain department is a brain.

Despite some differences, the skeleton performs similar functions: body support; protection of internal organs; Moving the body in space.

Philogenesis of the motor function underlies the progressive evolution of animals. Therefore, the level of their organization primarily depends on the nature of the motor activity, which is determined by the characteristics of the organization musculoskeletal systemwe have undergogered in the type of chord large evolutionary transformations in connection with the change of habitat and changes in the molds of locomotion. Indeed, the water environment in animals that do not have an outer skeleton involves monotonous movements due to the bends of the entire body, while life on land more contributes to their movement using the limbs.

Skeleton

At chordovy the skeleton is internal. The structure and functions are divided into the axial, the skeleton of the limbs and head.

Axial skeleton

In the subtype there are uncertain axial skeleton in the form of chord. It is built of strongly vacuated cells, tightly adjacent to each other and covered with common elastic and fibrous shells outside. The elasticity of chord is attached to the tour pressure of its cells and the strength of the shells.

Throughout the life of the vertebrates of chord, only the head and some lower fish is maintained. All other animals, it is reduced. In a person in the posthambrional period, chord rudiments in the form of Nucleus pulposus intervertebral disks are preserved.

All vertebrates are gradually displaced vertebraedeveloping from the sclerotoms of somites, and is functionally replaced vertebral post. This is one of the pronounced examples of the homotopic substitution of the bodies. The formation of vertebrae in phylogenesis begins with the development of their arcs covering the nervous tube and places of muscle attachment. Starting from cartilage fish detects the hid of the chord shell and the growth of the bases of the vertebral arcs, as a result of which the body of the vertebrae is formed. The fastening of the upper vertebral arcs above the nervous tube forms the ostic processes and the vertebral channel in which the nervous tube is enclosed.

Horde replacement by a vertebral pillar - a more powerful support organ with a segmental structure - allows you to increase the total body sizes and activates the motor function.

Fish has only two spinal deposits: torch and tail.This is due to moving them in water due to body bends.

Amphibians acquire also cervical and sacral Departments represented by each one vertebra. The first provides greater mobility of the head, and the second is a reverse limbs.

The cervical spine is extended in the reptiles, the first two vertebra of which is movably connected to the skull and provide greater mobility of the head. Appears lumbar The department is still weakly excluded from the thoracic, and the crescents are already from two vertebrae.

Mammals are characterized by a steady amount of vertebrae in the cervical region, equal to 7. Due to the large value in the movement of the hind limbs, the crushes is formed by 5-10 vertebrae. Lumbar and chest departments are clearly excluded from each other.

At fish, all the torso vertebra carry ribs, not fastening with each other and with sternum. They give the body a steady shape and provide support to the muscles, bending the body in the horizontal plane. This function of the ribs remains in all vertebrates that make snake-shaped movements - in tailed amphibians and reptiles, so they also have ribs on all vertebrae, except for the tail.

In the reptiles, the ribs of the breasts are growing with the sternum, forming a chest, and in mammals in the chest, 12-13 pairs of ribs are included.

Skeleton head

Continuation of the axial skeleton in front is axial, or brain, skull, Officer to protect the brain and senses. Next to it develops visceral, or facial skull Forming the support of the front of the digestive tube. Both parts of the skull develop differently from different adventures. In the early stages of evolution and ontogenesis, they are not interconnected.

In the rear of the axial skull, traces of segmentation are found in the development process, therefore it is believed that it represents the result of merging with each other front vertebrae bookmarks. The composition of the brain skull includes bookmarks of cartilage capsules of mesenchymal origin, surrounding hearing organs, smell and vision. In addition, a portion of the brain skull (lying the Kepende from the Turkish saddle), which does not have segmentation, develops, apparently, as a neoplasm due to an increase in the size of the front brain.

Phylogenetically, the brain skull was three stages of development: merfaculate, cartilage and bone.

He has almost the entire membrane and no front, non-segmented, part.

The skull of cartilage fish is almost completely cartilage, and includes both the rear, primary segmented, part and the front.

In bone fish and other vertebrates axial skull, it becomes bone due to the processes of charging in the region of its base (basic, wedge-shaped, lattice bones) and due to the occurrence of cover bones in the upper part of it (dark, frontal, nasal bones).

Visceral skull for the first time appears also at the lower vertebrates. It is formed from the mesenchymis of ectodermal origin, which is grouped in the form of thickening having a form of a forehead, in between gill groats of the pharynx. The first two arrangements get a particularly strong development and give the beginning of the jaw and sub-language arcs of adult animals. The following arcs, among 4-5 steam, perform the reference function for the gills and are called gill.

In cartilage fish, ahead of the jewish arc usually contains another 1-2 pairs of pre-trial arcs, having a rudimentary character.

The jewish arc consists of two cartilage. Upper called square, he Performs the function of the primary upper jaw. Nizhny, or meckelev, cartilage - primary lower jaw.

In bone fish, the substitution of primary jaws begins with secondary, consisting of overhead bones - a jaw and foremaster from above and a dental at thenime. Labor-square and meckel cartilage are reduced in size and shifted by the stop.

Amphibians in connection with the transition to the ground existence have undergone significant changes in the visceral skull. The gill arches are partially reduced, and partly, changing the functions, part of the cartilage apparatus of the larynx. Jewish arc with its upper element - a silly-square cartilage - it grows completely with the base of the brain skull . Giomandibular cartilage performs the function of the hearing bone - the column, - transmitting sound oscillations from the outdoor to the inner ear.

For the maxillary apparatus of reptiles, a higher degree of ossification is characterized than amphibians. Part of the cartilaginous material of gill arcs is part of not only the larynx, but also the trachea.

The lower jaw of mammals is articulated with the temporal bone with a complex joint, which allows not only to capture food, but also to make complex chewable movements.

One hearing bone - column,- characteristic of amphibious and reptiles, decreasing in size, turns into stapes, and the rudiments of the roasting and square and meckoeleva cartilage, fully emerging from the composition of the jaw apparatus, are converted according to okovalenka. and hammer. Thus, a single functional chain of three auditory bones in the middle ear, characteristic only for mammals, is created.

Skeleton limbs

Chordovy has unpaid and paired limbs. Unpaired (spine, tail "and anal fins) are the main organs of movement from undepair, fish and to a lesser extent in tailed amphibians. Fish also has paired limbs - breast and abdominal fins, on the basis of which pair limbs of terrestrial four-legged animals are developing.

In the larvae of fish, as well as in modern undepair along the body on both sides, the side skin folds are drawn, called metapleral . They do not have a skeleton or own musculature, performing a passive role - stabilization of the position of the body and an increase in the area of \u200b\u200bthe abdominal surface, facilitating movement in the aquatic environment. Evolution went along the way to intensify the functions of extreme departments and the weakening of the functions of the central parts.

As a result, breastfish developed from the front departments of the folds, and from the rear - abdominal fins due to the merge of the bases of cartilage rays arose brachial and pelvic belt. Resttheir sections were differentiated in skeleton free limbs.

In the skeleton of the wrist, the correct radial location of the bone elements in 3-4 rows is preserved, 7-5 bones are located in the mixture, and then the phalanges of 7-5 fingers are also radially lying.

In modern amphibians, the amount of fingers in the limbs is five or oligomerization to four.

Further progressive transformation of the limbs is expressed in increasing the degree of mobility of bone compounds, in reducing the number of bones in the wrist, at first up to three rows of amphibians and then up to two - in reptiles and mammals. In parallel, the number of finger phalanges is also reduced. It is also characteristic of the elongation of the proximal sections of the limb and the shortening of distal.

The location of the limbs during evolution also changes. If fish fingers are at the level of the first vertebrae and facing the parties, then the ground vertebrates as a result of the complication of the orientation in the space appears the neck and the mobility of the head appears, and in the reptiles and especially in mammals in connection with the body of the body above the Earth, the forelimbs are moved by the Forward And not horizontally oriented, but vertically. The same applies to the hind limbs.

2. Muscular system

Representatives of the type chordic muscles are divided into the nature of the development and innervation on somatic and visceral.

Somatic muscles It develops from the miotomes and is innervated by nerves whose fibers come from the spinal cord in the composition of the abdominal roots of the spinal nerves. Visceral muscles It develops from other sections of the mesoderm and is innervated by the nerves of the vegetative nervous system. All somatic muscles of the transverse striped, and visceral can be both cross-striped and smooth.

The most significant changes have undergone visceral muscles associated with visceral arcs of the front of the digestive tube. In the lower vertebrate, most of this musculature is represented by a common compressor of the visceral apparatus - m. Constrictor Superficialis covering the entire area of \u200b\u200bgill arcs from all sides. In the area of \u200b\u200bthe jewish arc, this muscle is innervated tripher nerve (V) in the region of the sub-surround arc - facial(VII), in the field of the first gill arc - language (IX) Finally, its part lying caudal - wandering nerve (x). In this regard, all derivatives of the respective visceral arcs and muscles associated with them are innervated by all vertebrates listed nerves.

In the front of the compressor, a large muscular mass serving the jaw machine is isolated. Behind the visceral apparatus, the trapezoid muscle M is differentiated. Trapezius, with separate beams attached to the last gill slots and the front edge of the dorsal belt of the shoulder belt. The part of the surface compressor in the region of the sub-speaking arc in the reptiles grows, covers the neck from the bottom and from the sides and forms a squeezel of the neck M. Sphincter Colli. In mammals, this muscle is divided into two layers: deep and superficial. Deep retains the former name, and the surface is called Platysma Myoides and is subcutaneously. These two muscles grow up to the entire area of \u200b\u200bthe head and give rise to a complex system of facial subcutaneous muscles, which primates and a person call mimic. Therefore, all mimic muscles are inexvained in the same way as the muscle from which it happens is the face nerve.

The muscles of the gummy apparatus with a loss of gill breathing are reduced, but their individual elements are preserved in the form of muscles of the sub-speaking apparatus, pharynx and larynx. The trapezoidal muscle completely loses with a gill with a gill and becomes exclusively the muscle of the shoulder belt. Part of it in mammals is departed from the cottage swelling of the skull and rises to the clavicle and the sternum, is isolated - the breast-curable-large muscle t. Sternocleidomastoideus. Innervating this muscle The back of the wandering nerve becomes an independent brain-brain nerve XI pair, extreme - p. Accessorius.

The main stages of the phylogenesis of the visceral muscles of the Zhumnoy region are recompidulating in the embryogenesis of mammals and man. Knowledge of these recapitulation allows you to explain the complexity of the innervation of the muscles of the face and neck, combined with them the generality of origin.

Somatic muscles

Musculatory head. In all vertebrate animals, in the process of embryogenesis, the lower ends of the ends of the ends are formed in the ventral directions, covering the body cavity outside and firing along the central line on the abdominal side. Thus, the bookmarks of somatic muscles become segmental not only on the dorsal side in connection with the segmentation of somites, but also on central. In myotomas and in their ventral processing, longitudinal muscular fibers is based on.

Miotoma lying on the head end of the body disintegrate on the mesenchym and form the primitives of individual muscles. From the first miotoma of the head, the upper inner and lower straight and lower oblique muscles of the eye are formed, innervated overallian nerve p. Oculomotorius (III Couple). From the second Miotoma - the upper oblique muscle, innervated block nerve p. Trochlearis (IV steam); and from the third - outer straight muscle receiving innervation from distolishing nerve P. Abducens (VI steam).

The rear miotomes of the head, forming powerful ventral processes, propagating around the visceral muscles of the pharyngeal region, form an approximate muscles, which in fish is weakly differentiated, and starting with amphibians decomposed on m. Sternohyoideus, t. Omohyoideus, etc. Geniohyoideus. In terrestrial vertebrals, due to the last muscle, its own musculature of the language is formed - m. Genioglossus and m. Hyoglossus. All sub-band muscles are inexvained subject nerve P. Hypoglossus, which amniota becomes a typical brain nerve.

Musculatory torso and limbs. Urgent, as well as fish, the whole muscles of the body consists of a number of muscular segments, or momers, the right and left sides, which together form the so-called so-called side muscles. Each mixer develops from the myotoma of one somite and is innervated by the original motor branch of one cerebrospinal nerve. Momers are separated from each other by Miosepts - connecting partitions. The same partition running longitudinally, the live muscle is divided into spinal and abdominal muscles.

Already at the fish, the direction of muscle bunches in the momers begins to change at different depths of the muscular layer. This differentiation is significantly more pronounced in terrestrial vertebrates and leads to the gradual separation of various layers of abdominal and spinal muscles. As a result, complex muscle groups arise, from the initial clear metamery of which only traces in the form of deep muscles of the back and neck, connecting the adjacent vertebrae with each other. The value of the spine muscles of ground vertebrates is reduced due to the movement of most of them using the limbs, and the abdominal muscles undergo the change of functions: initially participating in body movements, they are served in reptiles and mammals to change the volume of the thoracic and abdominal cavities in the process of breathing.

Musculature of pair fins of fish is laid in the form of a number of muscular kidneys growing from the ventral ends of the Miotomes. Each of these kidneys is divided into two muscular incarnation, growing at the base of the fins of the fins from its spinal and abdominal sides. The first functionally become muscles, reducing the fin, the second - leading. In the terrestrial vertebrates of the muscular incarnation, the homologous discharge muscle of the fin, the group of extensors of the five-panel limb develops, and from the advent of its antagonists - a group of flexors. Within each group, differentiation on surface and deep muscle bundles that become independent muscles are different. In general, the muscles of terrestrial vertebrates, homologous muscles of fin fish, form primary muscles of limbs. It is innervated by the nerves of the shoulder and lumbar-sacral plexuses formed in the process of moving limb belts during embryogenesis.

With further differentiation of the Miotomes of the chest develops a group of muscles, leading the shoulder belt itself, or secondary muscles. It includes the widest muscle of the back, greater and small breasts, as well as gear muscles. They are innervated directly by the spinal nerves of the spinal cord segments located caudal than its sites that carry out the innervation of primary muscles. The rear pair of limbs does not have secondary muscles due to the fact that the heterotopy of the pelvic belt relative to the spine in the process of evolution is less pronounced.

Changing the habitat and character of vertebrate movements led to the strengthening and separation of a large number of muscles, serving limbs, and to relative reduction of the muscles of the body. Such muscles like breast, wide back muscle and trapezoidal, largely cover the torso muscles and even partially displacing it functionally.

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