In the phylogenesis of chordates, the muscular system successively passes through a number of stages.

At the lancelet it is represented by a steam room longitudinal muscle(right and left), which runs along the body and is divided by connective tissue septa (myosepta) into short straight muscle bundles (myomeres). This (segmental) division of a single muscle layer is called metamerism.

With increased mobility, separation of the head and development of the limbs (in the form of fins) in fish the longitudinal muscle is divided by the horizontal septum into dorsal and ventral muscles, as well as isolation of the muscles of the head, body, tail and fins.

With access to land and an increase in the variety of movements in amphibians and reptiles the dorsal muscle, as well as the ventral one, is divided into two cords: lateral (transverse costalis muscle) and medial (transverse spinous muscle). In addition, in reptiles, subcutaneous muscles, which attach to the skin, first appear from the lateral cord.

In more highly organized animals ( birds and mammals) further differentiation of the muscular system occurs : lateral and medial cords, each of them is divided into two layers (superficial and deep). In addition, a diaphragm appears for the first time in mammals.

Phylogeny of the muscular system.

In ontogenesis, the muscular system mainly develops from the myotomes of the mesoderm, with the exception of some muscles of the head and neck, which are formed from the mesenchyme (trapezius, brachiocephalic).

At the beginning, a muscular longitudinal cord is formed, which immediately differentiates into dorsal and ventral layers; further, each of them is divided into lateral and medial layers, which, in turn, are differentiated into superficial and deep layers, the latter giving rise to certain muscle groups. For example, the iliocostal muscles develop from the superficial layer of the lateral layer, and the longissimus muscles of the back, neck, and head develop from the deep layer of the lateral layer.

3. Subcutaneous muscles – musculi cutanei

Subcutaneous muscles are attached to the skin, fascia and have no connection with the skeleton. Their contractions cause the skin to twitch and allow it to gather into small folds. These muscles include:

1) Subcutaneous muscle of the neck – m. Cutaneus colli (especially highly developed in dogs). It runs along the neck, closer to its ventral surface and passes to the facial surface to the muscles of the mouth and lower lip.

2) Subcutaneous muscle of the scapula and shoulder (scapulohumeral) – m. Cutaneus omobrachialis. It covers the area of the shoulder blade and part of the shoulder. Well expressed in horses and cattle.

3) Subcutaneous muscle of the trunk – m. Cutaneus trunci. It is located on the sides of the chest and abdominal walls and gives off bundles caudally into the knee fold.

4) In females, in the area of the mammary glands there are cranial and caudal muscles of the mammary gland (mm. Supramammilaris cranialis et caudalis), which give folding to the skin and help remove milk. Highly developed in carnivorous animals.

Males in this area have cranial and caudal preputial muscles (mm.preputialis cranialis et caudalis), which ensure the folding of the prepuce and act as its sphincter.

Skeletal muscles

Skeletal muscles are the active part of the musculoskeletal system. It consists of skeletal muscles and their auxiliary devices, which include fascia, bursae, synovial tendon sheaths, pulleys, and sesame bones.

In the body of an animal there are about 500 skeletal muscles. Most of them are arous and are located symmetrically on both sides of the animal’s body. Their total mass is 38-42% for a horse of body weight, in cattle 42-47%, in pigs 30-35% of body weight.

The muscles in the animal’s body are not located randomly, but in a regular manner, depending on the effect of the animal’s gravity and the work performed. They exert their effect on those parts of the skeleton that are movably connected, i.e. muscles act on joints and syndesmoses.

The main places of muscle attachment are bones, but sometimes they are attached to cartilage, ligaments, fascia, and skin. They cover the skeleton so that the bones only in some places lie directly under the skin. Fixed on the skeleton, as on a system of levers, the muscles, when contracted, cause various movements of the body, fix the skeleton in a certain position and give shape to the animal’s body.

The main functions of skeletal muscles:

1) The main function of muscles is dynamic. When contracting, the muscle shortens by 20-50% of its length and thereby changes the position of the bones associated with it. Work is performed, the result of which is movement.

2) Another muscle function - static. It manifests itself in fixing the body in a certain position, in maintaining the shape of the body and its parts. One of the manifestations of this function is the ability to sleep standing (horse).

3) Participation in metabolism and energy. Skeletal muscles are “heat sources” because when they contract, about 70% of the energy is converted into heat and only 30% of the energy provides movement. Skeletal muscles hold about 70% of the body's water, which is why they are also called “water sources.” In addition, adipose tissue can accumulate between muscle bundles and inside them (especially during fattening pigs).

4) At the same time, during their work, skeletal muscles help the heart function by pushing venous blood through the vessels. In experiments, it was possible to find out that skeletal muscles act like a pump, ensuring the movement of blood through the venous bed. Therefore, skeletal muscles are also called “peripheral muscle hearts.”

The structure of muscle as an organ

The structure of muscle from a biochemist's point of view

Skeletal muscle is composed of organic and inorganic compounds. Inorganic compounds include water and mineral salts (calcium, phosphorus, magnesium salts). Organic matter is mainly represented by proteins, carbohydrates (glycogen), lipids (phosphatides, cholesterol).

Table 2.

Chemical composition of skeletal muscle

The chemical composition of skeletal muscles is subject to significant age-related and, to a lesser extent, species, breed and gender differences, which is primarily due to the unequal water content in them (% of water decreases with age).

These are located at the distal end of the anti-back surface of the bones of the metacarpus, metatarsus and distal phalanges of the fingers (see skeleton). The sesamoid bones include the patella and accessory carpal bone.

BRIEF INFORMATION ON PHYLO AND ONTOGENESIS OF MUSCULARITY

Phylogenetic transformations. Muscle elements in a number of sizes

The developments of living beings appear early in coelenterates. They are not yet isolated into independent morphological units, but are only contractile muscle elements of epithelial cells. Subsequently, they separate from the epithelium, forming several layers of smooth muscle cells closely connected to the skin, resulting in the formation of the so-called musculocutaneous sac (flatworms). The source of muscle cell formation is the mesoderm.

WITH with the appearance of a secondary body cavity, the muscles are divided into somatic muscles, which are part of skin-muscular sac, and visceral, surrounding the intestines and blood vessels. Despite this division, it can be either all smooth (annelids) or all striated (insects). This indicates that in phylogeny, striated muscles are almost no different from smooth muscles either in origin or function. With further complication of organization, somatic and visceral muscles develop divergently, increasingly diverging from each other structurally and functionally.

U In primitive chordates (lancelet, cyclostomes), all somatic muscles develop from mesoderm somites and are striated. It is a pair of right and left longitudinal muscles running along the entire body, divided by connective tissue septa - myosepta into a number of myomeres - short segments of straight muscle bundles. This (segmental) division of a single muscle layer is called metamerism (Fig. 73).

WITH By separating the head and developing the limbs (in the form of fins), the muscles are also differentiated. The longitudinal muscle in fish is divided by a horizontal septum into dorsal and ventral muscles. They are innervated by the dorsal and ventral branches of the spinal nerves, respectively. This innervation is preserved during all further muscle transformations. Due to the uniformity of movements of proto-aquatic animals, the dorsal and ventral longitudinal muscles have a myomeric structure. Each myomere usually corresponds to its own vertebra and paired spinal nerve. In higher fish (herrings, etc.), one can see their longitudinal splitting into separate layers. The muscles of the fins are also distinct, however, compared to the muscles of the body trunk, they are poorly developed, since the main load during movement in aquatic animals falls on the tail and torso.

Vrakin V.F., Sidorova M.V.	MORPHOLOGY OF FARM ANIMALS

Rice. 73. Muscles of the body of chordates:

A - lancelet; 5 - fish; B - tailed amphibian; G - reptile; 1 - myomeres (myotomes); 2- myosepta; 3- dorsal m.. of the trunk; 4- longitudinal side partition; 5 - dorsal m. of the tail; 6 - surface compressor; 7- trapezoidal m.; 8 - ventral m. of the trunk; 9 - ventral tail m.; 10 - mm. thoracic limb; 11 - widest m, back; 12, 13, 14 - ventral mm. (12 - external oblique, 13 internal oblique, 14 - straight); 15 - mm. pelvic limb.

With access to land and an increase in the variety of movements, the division of muscle layers into individual muscles, both along and across, increases. In this case, metamerism gradually disappears. It is clearly visible in the muscles of fish, is also noticeable in amphibians, and weakly in reptiles. In mammals, it is preserved only in the deep layers, where short muscles connect the elements of two adjacent bone segments (interspinous, intertransverse, intercostal muscles).

Vrakin V.F., Sidorova M.V.	MORPHOLOGY OF FARM ANIMALS

First of all, metamerism begins to disappear in the abdominal part of the body, where already in amphibians, individual myomeres merge to form wide, lamellar-shaped abdominal muscles. Along with this, there is a longitudinal splitting of the muscular abdominal wall with the formation of a four-layer abdominal press. In the dorsal muscles of the amphibian body, two cords can be distinguished: lateral and medial, the metamerism of which is obscured only in the cervical region, where independent muscles are isolated.

U In reptiles, the muscle bundles of the lateral and medial muscle cords acquire different directions. Myomeria persists only in the deep layers. The closer to the head, the clearer the fragmentation of the dorsal cords into individual muscles.

U In mammals, the somatic muscles are differentiated to the greatest extent. In the dorsal muscles, 4 layers are formed due to the separation of the lateral and medial muscle strands. In this case, a clear pattern is observed: the deeper the muscle is, the better its metamerism is expressed; The closer to the outer surface of the body a muscle lies, the more it loses metamerism, spreading throughout the body in a wide layer. The disarticulation of the dorsal muscles also increases in the cranial direction, which is associated with the degree of mobility of the spine. If in the area of the sacrum - the most immobile part of the stem skeleton

- the dorsal muscles are absolutely not dissected, then in the area of the withers, and especially the neck, the muscle complexes consist of a large number of independent muscles.

The ventral muscles of the trunk part of the body also have 4 layers, although not fully expressed everywhere. In the chest these are the internal and external intercostal, rectus and transverse pectoral muscles, in the lumbar-abdominal region - the abdominal muscles.

The locomotor function of the tail muscles becomes less and less as they go onto land and is completely lost in mammals. This leads to a significant decrease in muscle mass while maintaining a high degree of differentiation due to the mobility of the tail.

The limbs of terrestrial vertebrates originate from lobe-finned fins, which are very mobile, with a well-developed skeleton and strong muscles (coelacanth). The metamerism of the muscles of the limbs, clearly visible in ray-finned fish, is lost very early in phylogenesis, especially with access to land. With the transformation of a limb into a complex lever that supports and moves the animal’s body on land, a large number of muscles are separated.

Primitive tetrapods are characterized by the projection of the humerus and femur to the side and upward from the girdle. With this arrangement of the limbs, large amounts of muscle energy are required to maintain the body hanging. On the thoracic limb, the greatest load falls on the coracoid bone, to which, as a result, the bulk of the muscles of the shoulder and elbow joints are attached.

Vrakin V.F., Sidorova M.V.	MORPHOLOGY OF FARM ANIMALS

Adaptations for fast running, manipulation of the thoracic limb and the ability to rest while standing, which developed in mammals, were accompanied by rotation of the limb from the segmental to the sagittal plane, opening of the joints and an increasingly higher elevation of the body above the ground. At the same time, the conditions of the action of gravity and the work of muscles when the animal stood and moved changed. In ungulates, the adaptation of the limbs to rapid forward movement and to the economical expenditure of muscle energy when standing has led to a loss of variety of movement. This was expressed in an even greater reduction of the shoulder girdle (disappearance of the collarbone) and straightening of the free limb. The shoulder girdle lost its bony connection with the axial part of the body and acquired a vast area of support with the help of muscles that connected it with the head, neck, withers, back and chest. So the muscles of the limbs began to dominate in mass over the muscles of the torso. The muscles of the girdles and proximal limbs largely cover the trunk muscles on top and partially displace them. The development of the muscles of the distal links is largely determined by the characteristics of the mechanics of movement and ecology of the animal (walking, crawling, jumping, digging, etc.). In ungulates, due to the reduction of the fingers and straightening of the joints, there was a decrease in the number and complexity of the structure of the muscles of the distal parts of the limbs.

And finally, the most superficial and least dissected muscle layer is the subcutaneous musculature - a part of the somatic musculature that first appeared in reptiles. In mammals it is highly developed, especially in animals that can curl up (hedgehog, armadillo). Among domestic animals, it is well developed in the horse and has the appearance of wide layers lying under the skin in the neck, withers, shoulder blades, chest and belly (see Fig. 72). On the head, the subcutaneous muscles come into close contact with the visceral muscles and are an integral part of the muscles of the face, eyelids, nose, and auricle.

Complex transformations in the musculature of the head occur in parallel with complex phylogenetic transformations of the skull. As a result, the somatic muscles in the head region are largely replaced by the visceral muscles surrounding the head. The somatic muscles of the head are narrower in fish, represented only by the muscles of the eye and some supra- and subbranchial muscles with longitudinal direction of muscle fibers (participate in the respiratory movements of the gill apparatus).

The visceral muscles surrounding the head end of the intestinal tube have undergone significant differentiation, acquired the properties of striated muscle tissue, but retained their circular direction of fibers. It forms the circular muscle layers of the jaw, hyoid and gill arches, on the basis of which the bulk of the muscles of the head develop: jaw, hyoid, gill, some muscles of the shoulder girdle with grasping, chewing and other functions.

Vrakin V.F., Sidorova M.V.	MORPHOLOGY OF FARM ANIMALS

In mammals, the somatic muscles of the head are represented by the muscles of the eye, middle ear, tongue and some muscles of the hyoid bone. The visceral muscles form the facial (facial) and masticatory (jaw) muscles.

And finally, only mammals have a muscular thoraco-abdominal barrier - the diaphragm.

Ontogenetic development. Somatic muscles mainly originate from the myotomes of the somites of the mesoderm (Fig. 74). In the head region, the muscles of the eyeball are formed from three pre-auricular myotomes. The anterior postauricular myotomes disappear, and from the posterior (occipital) myotomes the sublingual muscles develop. The visceral muscles of the head are of mesenchymal origin. Cervical, thoracic, lumbar, sacral and caudal myotomes are formed in accordance with the number of metameric segments of the body. They grow in the dorsal and ventral directions and give rise to all the somatic muscles of the neck, trunk and tail. The muscles of the limbs are formed by outgrowths of the ventral sections of the myotomes, to which are attached cellular material evicted from the parietal layer of the mesoderm splanchnotome. The formation of muscles lags somewhat behind the formation of the skeleton and to a certain extent depends on it.

Rice. 74. Metameric anlage of muscles in the mammalian embryo myotoma:

1- occipital. 2 - cervical, 3 - chest. 4 - lumbar, 5 - sacral, 6 - caudal.

During the embryonic period, from the 20-22nd day of development, myoblasts multiply in the myotomes of cattle. In the prefetal period, anatomical differentiation begins: muscles and muscle groups are separated. In parallel with this, but much longer, the histogenesis of muscle tissue occurs. Myoblasts merge into myotubes, and myofibrils appear in them. Anatomical differentiation mainly ends in the prefetal period - by the 50-55th day. The formation and differentiation of muscles occurs in a certain sequence. The axial muscles are formed earlier than others. In it, differentiation proceeds from the head end to the tail end. At the same time, deep muscles differentiate earlier

Vrakin V.F., Sidorova M.V.	MORPHOLOGY OF FARM ANIMALS

superficial. During the process of muscle differentiation, the corresponding cranial or spinal nerves grow into them. This connection is established very early and remains throughout life. The anlage of the limbs appears in the form of roller-like thickenings near the ventral sections from the 5th cervical to the 1st thoracic myotome - the rudiment of the thoracic limb and from the 1st lumbar to the 3rd sacral myotome - the rudiment of the pelvic limb. Soon the ridges contract and take the form of flattened conical outgrowths - buds. The formation of muscles on the thoracic limb in a calf embryo begins on the 32nd day, and on the posterior limb - on the 34th day of embryonic development. The muscles of the belts are formed first, then the free limb, where the process spreads from the proximal to the distal links. As in the axial part of the body, differentiation of deep muscles occurs earlier, superficial muscles - later. Extensors, abductors and supinators are located on the lateral side of the limb, and flexors, adductors and pronators are located on the medial side. The muscle bellies are formed before the tendons. By the end of the prefetal period, the muscles of the limbs are anatomically formed, but histologically they are immature - they consist of muscular tubes lying in bundles. During the fetal period, histological differentiation of muscles continues: the number and size of myotubes increase, the tubes transform into muscle fibers, and the number of myofibrils in them increases; the endomysium and perimysium of the muscles are formed, capillary networks develop, and bundles of the first, second and third orders are formed.

As a result of anatomical and histological differentiation, the dorsal muscles of the spinal column are formed from the dorsal areas of the myotomes, lying above the vertebral bodies. It is innervated by the dorsal rami of the spinal nerves. From the ventral sections of the myotomes, the ventral muscles of the spinal column are formed, lying under the vertebral bodies, the muscles of the chest, abdominal wall and diaphragm. All the muscles of the limbs develop from the muscle buds.

IN In the process of organogenesis, muscles become separated in length, thickness, fragmentation or fusion, the formation of complex and multifidus muscles, and the formation of their feathery structure. In the early fetal period, the muscles of the trunk grow faster, and in the late period, the muscles of the limbs, especially their most distal links - the paws.

At birth, ungulates have a fully formed movement apparatus, which immediately begins to function: after a few hours, a newborn calf, lamb, foal, or piglet can follow its mother. However, this does not mean that the processes of growth and differentiation in the locomotor apparatus are completed. They continue until the age of morphophysiological maturity, and adaptive restructuring of the movement apparatus occurs throughout life.

Postnatal muscle growth. After birth, intensive growth of muscles continues, which outpaces the skeleton in terms of growth rate. This process is especially intense in the first two months after birth.

Vrakin V.F., Sidorova M.V.	MORPHOLOGY OF FARM ANIMALS

Denia. The next growth peaks in cattle occur in the 6th and 12th months of life, in sheep - in the 3rd and 9th months. The axial muscles grow faster than the muscles of the limbs, especially with the onset of puberty. In newborn calves, the mass of the axial muscles is 46%. and for 14-month-olds - 53%. In the limbs, there is a greater rate of muscle growth in the proximal links (compared to the distal ones). On the thoracic limb they grow somewhat more intensely, but complete growth faster than the muscles of the pelvic limb. Extensors grow faster than flexors, and the periods of increase in their growth rate do not coincide.

With age, the number of muscle fibers per unit area in the muscles and in the primary muscle bundles decreases, since along with the thickening of the muscle fibers (about 15-20 times), the muscles grow with connective tissue, it becomes denser, the muscle bundles. I order include fewer fibers. However, the relative amount of connective tissue in muscle decreases with age, and muscle

Increasing. Thus, over 18 months, the amount of connective tissue in bulls increases by 8 times, and muscle tissue by 17 times. The chemical composition also changes: the amount of protein and fat increases, and water becomes less. Each muscle type has its own dynamics of chemical parameters.

Not only muscle groups, but also each muscle has its own growth pattern, which is associated both with the characteristics of its internal structure and functioning. The highest growth rates are in muscles of the dynamic type. The unevenness of muscle growth largely determines the change in proportions and body shapes.

The influence of internal and external factors on muscle growth. The animal's lifestyle, the method of production and the nature of the food leave an imprint on the growth and differentiation of muscles. Thus, pigs develop more dorsal muscles, especially the neck. Horses have better developed chewing muscles than cattle. The abdominal muscles, on the contrary, are more developed in cattle.

The nature of muscle growth is also influenced by the sex of the animal. With the same fatness, the muscles in steers are better developed and make up a larger percentage of the carcass than in heifers and castrated bulls. In addition, bulls continue to grow muscle for longer, meaning they can ultimately produce more meat. In bulls, the muscles of the neck, withers and shoulder girdle are more developed (which is important for the strength of the animal when establishing hierarchy in the herd). Heifers have more developed abdominal and posterior musculature. In terms of the nature of muscle growth, castrates are close to heifers, but in terms of the growth of the longissimus and semispinalis muscles they lag behind animals of both sexes. Bulls have fewer fatty inclusions in their muscles, while heifers and castrates have thinner muscle fibers and well-marked meat.

There are also some differences in the rates of growth and muscle development between breeds with different areas of productivity. Early maturing breeds are characterized by high growth energy, but late maturing ones

LECTURE MYOLOGY PHYLOGENESIS, ONTOGENESIS AND FUNCTIONAL ANATOMY OF THE MUSCULAR SYSTEM Performed by: Vladimirova Ya. B. Kokoreva T. V.

Muscles or muscles (from Latin musculus - mouse, small mouse) are organs of the body of animals and humans, consisting of elastic, elastic muscle tissue, capable of contracting under the influence of nerve impulses. Designed to perform various actions: body movements, contraction of vocal cords, breathing. Muscles consist of 86.3% water. There are 640 muscles in the human body

Motivation: - - - possibilities of the movement performed, volume of movement; active or passive movements are triggered by one or another muscle group; by influencing the muscular system, we change the general condition; muscle relief is a guide for the topography of blood vessels and nerves; muscle transplantation, that is, the muscle can be “relearned”.

Development of muscles of cranial origin - from the head myotomes (sclerotomes) and mesenchyme of the branchial arches. Innervated by branches of cranial nerves of spinal origin - from the myotomes of the trunk of the embryo: from the ventral myotomes they are innervated by the anterior branches of the SMN; - from the dorsal myotomes they are innervated by the posterior branches of the SMN - Autochthonous muscles - muscles that remain at the site of their primary anlage. Truncofugal muscles are muscles that have moved from the trunk to the limbs. Truncopetal muscles are muscles that have moved from the limbs to the torso.

Striated Smooth 1. The unit of organization is the myocyte. Length about 50 microns. Width from 6 microns. 2. Involuntary contraction Control by the autonomic nervous system The movement is wave-like, works slowly, since the nerve fiber does NOT approach every cell They come into action slowly, but remain for a long time Does not have an exact spatial orientation of cells 3. 4. 5. 6. 1 2. 3. 4. 5. 6. Cardiac The unit of organization is the muscle fiber - a set of myoblasts floating in the common cytoplasm (sarcoplasm). They have a common sarcolemma. Length about 40 -100 mm. Width from 7 mm. Voluntary contraction Control by the somatic nervous system Fast contraction, quick reaction, so each muscle fiber has a neuromuscular synapse Switch on quickly, but have a short-term effect Clear orientation of muscle fibers

Between the muscle fibers there are thin layers of loose fibrous connective tissue - endomysium. The collagen fibers of the outer layer of the basement membrane are woven into it, which helps to combine forces during contraction of the myosymplasts. Thicker layers of loose connective tissue surround several muscle fibers, forming the perimysium and dividing the muscle into bundles. Several bundles are combined into larger groups, separated by thicker connective tissue layers. The connective tissue surrounding the surface of the muscle is called the epimysium.

Muscle as an organ contains connective tissue. Endomysium is a thin connective tissue that surrounds each muscle fiber and small groups of fibers. Perimysium – covers larger complexes of muscle fibers and muscle bundles.

Significance of endomysium and perimysium 1. Through the endomysium and perimysium, vessels and nerves approach the muscle fiber. They form the stroma of the organ; 2. Muscle fibers are formed into bundles, bundles into muscles; 3. Since the endomysium is fused with the sarcolemma of the muscle fiber, therefore, the contracting muscle fiber can only stretch to a certain limit

The myofibrils in the fiber are surrounded by a shell - sarcolemma, and immersed in a special medium - sarcoplasm. Depending on the pigment and oxygen content, the fibers are divided into white and red. White fibers are anaerobic, contain more myofibrils and less sarcoplasm. They start up quickly, but cannot work for a long time. Example: sternocleidomastoid, gastrocnemius muscles. Red fibers are thick fibers. There is a lot of myoglobin in the sarcoplasm and cytochrome in the mitochondria, but fewer myofibrils. Slow to start, but last a long time. Example: back muscles, diaphragm.

Each muscle has a network of blood vessels. Muscle contractions promote blood flow. In a relaxed, non-working muscle, most of the blood capillaries are closed to blood flow. When a muscle contracts, all blood capillaries immediately open.

The structure of a muscle Each muscle is connected at one end to one bone (the origin of the muscle), and at the other end to the other (the attachment of the muscle). The muscle is divided into: head, abdomen, and tail.

Motor nerve fibers approach each muscle fiber and sensory nerve fibers depart. The number of nerve endings in a muscle depends on the degree of functional activity of the muscles.

Each muscle fiber is innervated independently and is surrounded by a network of hemocapillaries, forming a complex called a myon. A group of muscle fibers innervated by one motor neuron is called a motor unit. It is characteristic that muscle fibers belonging to one motor unit do not lie side by side, but are located mosaically among fibers belonging to other units.

A tendon is a dense fibrous connective tissue cord that connects a muscle to or attaches to the skeleton.

peritenonium type IV collagen fibers endotenonium Collagen fibers of the tendon, intertwined with collagen fibers of the periosteum, are woven into the ground substance of the bone tissue, forming ridges, tubercles, tubercles, depressions, and depressions on the bones.

Fascia is connective tissue collagen fibers with a small admixture of elastic fibers Superficial temporal fascia Deep fascia of the thigh

1. 2. 3. 4. 5. Fascia separates the muscles from the skin and eliminates the displacement of the skin during the movements of contracting muscles. Fascia conserves the force of muscle contraction by eliminating friction between muscles during contraction. Fascia stretches large veins under tension, as a result of which blood from the periphery is “sucked” into these veins. Fascia is important as barriers that prevent the spread of infection and tumors. During operations, fascia helps determine the location of muscles, blood vessels, and viscera.

Classification of muscles Skeletal muscles vary in shape, structure, position relative to the axes of the joints, etc., and therefore are classified differently.

III. According to the functional features, Static (strong) - short belly and long tendon. The muscles work with greater force, but with a smaller range of motion. Dynamic (dexterous) – long muscle bundles, short tendons. Muscles work with less force, but produce larger movements

Accessory apparatus of muscles Skeletal muscles have an accessory apparatus that facilitates their functioning. n n n Fascia; Osteofascial sheaths; Synovial bursae; Synovial tendon sheaths; Muscle blocks; Sesamoid bones.

Anomalies of muscle development are very common and are divided into three groups: 1. Absence of any muscle; 2. The presence of an additional muscle that does not exist in nature. 3. Additional bundles of existing muscle.

Developmental defects: Underdevelopment of the sternocleidomastoid muscle - Torticollis; Underdevelopment of the diaphragm. Cause of diaphragmatic hernia. Underdevelopment of the deltoid and trapezius muscles – Deformation of the shoulder girdle and shoulder

I. Shape: Fusiform; Ribbon-shaped; Flat wide; Serrated; Long; n n n Square; Triangular; Round; Deltoid; Soleus, etc.

II. In the direction of muscle fibers With straight parallel fibers; With transverse ones; With circular; Pinnate: A. Unipinnate; Bipinnate; C. Multipinnate. B.

IV. By function: Adductors; Diverters; Bending; Extensor; Pronators; n n Arch supports; Straining; Muscles are synergists; Muscles are antagonists.

V. In relation to the joint: Single-joint; Two-joint; Multi-joint.

Question 1. Phylogenesis of the muscular system: patterns of development.

Not an isolated muscular system

Single skin-muscle bag

Appearance of striated muscle tissue

Division of muscle cords into myotomes

Development of muscle groups

Development of limb muscles (change in environment)

Development of the diaphragm

Development of all muscle groups - performing differentiated movements

Question 2. Ontogenesis of the muscular system: sources and timing of development

Skeletal muscles develop from the mesoderm. In the human embryo, around the 20th day of development, somites appear on the sides of the neural groove. Somewhat later in the somites, one can distinguish their part - the myotomes. Myotome cells become spindle-shaped and develop into dividing myoblasts. Some myoblasts differentiate. The other part of myoblasts remains undifferentiated and

turns into myosatellite cells. Some myoblasts contact each other with their poles, then in the contact zones the plasma membranes are destroyed, and the cells unite with each other, forming symplasts. Undifferentiated myoblasts migrate to them, which are surrounded by the same basement membrane as the myosymplast. If the muscles of the trunk develop from the dorsal section of the mesoderm (segmented), then the visceral, facial, chewing and some muscles of the neck, as well as the perineum, develop from the unsegmented ventral section of the mesoderm, located respectively in the head or tail ends of the body (Table 33). From the mesoderm of the limb buds, their autochthonous (native) muscles are formed (Greek autos. himself, chton - earth). A number of muscles are also formed in the buds of the limbs, but subsequently their proximal ends are attached to the bones of the body - these are truncopetal (lat. truncus - torso, petere - to direct), for example, the pectoralis major and minor muscles. In contrast, truncofugal muscles (Latin fugere - to run) develop from the myotomes of the trunk, but their distal ends are attached to the bones of the limbs, for example, the rhomboid major and minor muscles.

Development from mesoderm

Division into somites

Myotome derivatives: back muscles develop from the dorsal region

From the ventral - muscles of the chest and abdomen

Mesenchyme - muscles of the limbs

I visceral arch (VA) - masticatory muscles

II VD - facial muscles

III and IV VD - muscles of the soft palate, pharynx, larynx, upper esophagus

V VD - sternocleidomastoid and trapezius muscles

From the occipital myotomes - muscles of the tongue

From the preauricular myotomes - the muscles of the eyeball

Question 3. Muscle. Definition, structure.

A muscle as an organ consists of bundles of striated muscle fibers, each of which is covered with a connective tissue membrane (endomysium). Bunches of fibers of various sizes are separated from each other by layers of connective tissue that form the perimysium. The muscle as a whole is covered with an external perimysium (epimysium), which passes onto the tendon (Fig. 156). From the epimysium, blood vessels penetrate into the muscle, branching in the internal perimysium and endomysium, in the latter there are capillaries and nerve fibers. Muscles and tendons

are rich in sensitive nerve endings that perceive “muscle and tendon feeling” - information about the tone of muscle fibers, the degree of their contraction, tendon stretching - and transmit it along the nerves to the brain. These receptors form neuromuscular and neurotendon spindles surrounded by a connective tissue capsule. The motor endings of axons form motor plaques (axo-muscular synapses), which resemble synapses in their structure.

Muscle bundles form a belly, which passes into the tendon part. The proximal part of the muscle - its head - starts from the bone; the distal end - the tail (tendon) - is attached to another bone. The exception to this rule are the muscles of facial expression, the muscles of the floor of the mouth and the perineum, which are not attached to the bones. The tendons of different muscles differ from each other. The shape of a muscle is related to its function. Muscles have a number of auxiliary structures. Each muscle or group of muscles with similar functions is surrounded by its own fascia. Muscular septa separate groups of muscles that perform different functions. The synovial sheath separates the moving tendon from the motionless walls of the fibrous sheath and eliminates their friction.

I.M. Sechenov in the book “Reflexes of the Brain” writes: “All the infinite variety of external manifestations of brain activity is finally reduced to just one phenomenon - muscle movement.” Skeletal muscles move bones, actively change the position of the human body, participate in the formation of the walls of the oral, abdominal cavities, pelvis, are part of the walls of the pharynx, upper part of the esophagus, larynx, carry out movements of the eyeball and auditory ossicles, respiratory and swallowing movements. Skeletal muscles keep the human body in balance and move it in space. The total mass of skeletal muscles in a newborn child is 20 - 22% of body weight; in an adult it reaches 40%; in elderly and old people it decreases to 25 - 30%. A person has about 400 striated muscles that contract voluntarily under the influence of impulses coming through nerves from the central nervous system. Bundles of striated muscle fibers form skeletal muscles, which are innervated by motoneurons - motor neurons of the anterior horns of the spinal cord (see section Spinal cord). From a functional point of view, a muscle consists of motor units. Each motor unit is a group of muscle fibers (myosymplasts) innervated by one motor neuron of the anterior horn of the spinal cord, which contract simultaneously. Motor units are either fast or slow.

Somatic and visceral muscular system, its phylo-ontogenesis. Subcutaneous muscles. Skeletal muscles. The structure of muscle as an organ. Classification of muscles. Assistive devices of muscles.

Myology(Myologia) is a branch of domestic animal anatomy that studies the structure of the muscular system. Muscle tissue, which forms the basis of this system, carries out all motor processes in the animal body. Thanks to it, the body is fixed in a certain position and moves in space, respiratory movements of the chest and diaphragm, eye movement, swallowing, and motor functions of internal organs, including the work of the heart, are carried out.

Muscle has special contractile organelles - myofibrils . myofibrils, consisting of thin protein filaments (myofilaments), they can be unstriated or striated (cross-striped). Accordingly, a distinction is made between unstriated and striated muscle tissue.

1) Non-striated muscle tissue consists of spindle-shaped cells (smooth myocytes). These cells form muscle layers in the walls of blood and lymphatic vessels, in the walls of internal organs (stomach, intestines, urinary tract, uterus, etc.). The length of the cells ranges from 20 µm (in the wall of a blood vessel) to 500 µm (in the wall of the uterus of a pregnant cow), diameter from 2 to 20 µm. In functional terms, non-striated muscle tissue has a number of features: it has great strength (for example, significant masses of food are constantly moving in the intestines), has low fatigue, slow contraction and rhythmic movements (in the intestinal wall, non-striated muscle tissue contracts 12 times per minute, and in spleen - only 1 time).

2) Striated muscle tissue is characterized by the presence of striated myofibrils and has 2 types.

A) Striated cardiac muscle tissue consists of elongated cells (cardiomyocytes) square shape. Their ends, connecting with each other in chains, form the so-called functional muscle “fibers” with a thickness of 10-20 microns. Closely interconnected, functional muscle “fibers” form the muscular layer of the heart ( myocardium), constant and rhythmic contractions of which set the blood in motion.

B) Striated skeletal muscle tissue, unlike cardiac tissue, does not consist of cells, but of multinucleated muscle formations (myosymplasts) of a cylindrical shape. The length of myosymplasts ranges from a few millimeters to 13-15 cm, diameter from 10 to 150 microns. The number of cores in them can reach several tens of thousands. Myosymplasts (they are also called “muscle fibers”) form skeletal muscles and are part of some organs (tongue, pharynx, larynx, esophagus, etc.). Functionally, skeletal muscle tissue is easily excitable and contracts faster than non-striated muscle tissue (for example, under normal conditions, skeletal muscle contracts within 0.1 s, and non-striated muscle within several seconds). But, unlike the smooth (non-striated) muscles of internal organs, skeletal muscles fatigue faster.

Muscular system Depending on the structural features, the nature of the motor function and innervation, they are divided into somatic and visceral.

Somatic muscular system makes up 40% of body weight and is built from myosymplasts. It is voluntary and innervated by the somatic nervous system. Somatic muscles contract quickly and energetically, but short-term and quickly fatigue. This type of contraction is called tetanic and it is characteristic of somatic muscles. These include:

1) subcutaneous muscles, which have no connection with the skeleton and are attached to the skin; their contractions cause the skin to twitch and allow it to gather into small folds;

2) skeletal muscles, which are attached to the skeleton;

3) diaphragm - a dome-shaped muscle that separates the chest cavity from the abdominal cavity;

4) muscles of the tongue, pharynx, larynx, auricle, eyeball, middle ear, esophagus and external reproductive organs.

Visceral muscular system makes up 8% of body weight and is built from smooth myocytes. It is involuntary and innervated by the autonomic nervous system. Smooth muscles contract slowly, for a long time and do not require a large amount of energy. This type of contraction is called tonic and it is characteristic of visceral muscles, which form muscle bundles, layers and membranes of internal organs.

Phylo-ontogenesis of the muscular system

In the phylogenesis of chordates, the muscular system successively passes through a number of stages.

At the lancelet it is represented by paired longitudinal muscles (right and left), which run along the body and are divided by connective tissue septa (myosepta) into short straight muscle bundles (myomeres). This (segmental) division of a single muscle layer is called metamerism.

With increased mobility, separation of the head and development of the limbs (in the form of fins) in fish the longitudinal muscle is divided by the horizontal septum into the dorsal and ventral muscles, as well as

Isolation of the muscles of the head, body, tail and fins.

With access to land and an increase in the variety of movements in amphibians and reptiles the dorsal muscle, as well as the ventral one, is divided into two cords: lateral (transverse costal muscle) and medial (transverse spinous muscle). In addition, in reptiles, subcutaneous muscles, which attach to the skin, first appear from the lateral cord.

In more highly organized animals ( birds and mammals) further differentiation of the muscular system occurs: the lateral and medial cords, each of them, are divided into two layers (superficial and deep). In addition, a diaphragm appears for the first time in mammals.

Phylogeny of the muscular system.

Chordata	Muscular system
Lancelet	Longitudinal muscle
Fish	Dorsal				Ventral
Amphibians, reptiles	Lateral		Medial		Lateral		Medial
Birds, mammals	Power	Deep	P	G	P	G	P	G

Subcutaneous muscles – musculi cutanei

3) Subcutaneous muscle of the trunk – m. Cutaneus trunci. It is located on the sides of the chest and abdominal walls and gives off bundles caudally into the knee fold.

Males in this area have cranial and caudal preputial muscles (mm.preputialis cranialis et caudalis), which ensure the folding of the prepuce and act as its sphincter.

Skeletal muscles

There are about 500 skeletal muscles in the animal's body. Most of them are paired and are located symmetrically on both sides of the animal’s body. Their total mass is 38-42% of body weight in horses, 42-47% in cattle, and 30-35% of body weight in pigs.

The main functions of skeletal muscles:

2) Another muscle function is static. It manifests itself in fixing the body in a certain position, in maintaining the shape of the body and its parts. One of the manifestations of this function is the ability to sleep standing (horse).

4) At the same time, during their work, skeletal muscles help the heart work, pushing venous blood through the vessels. In experiments, it was possible to find out that skeletal muscles act like a pump, ensuring the movement of blood through the venous bed. Therefore, skeletal muscles are also called “peripheral muscle hearts.”

The structure of muscle from a biochemist's point of view

Table 2. Chemical composition of skeletal muscle

Lecture on biology on the topic "phylogeny of the musculoskeletal and nervous systems." Anatomy of domestic animals Subcutaneous muscles - musculi cutanei

BRIEF INFORMATION ON PHYLO AND ONTOGENESIS OF MUSCULARITY