Onto and phylogenesis of skeletal muscles. myology

The phylogeny of the organ systems of chordates is considered in accordance with the progressive direction of evolution of this type of animals from the subtype Cranial to the class Mammals. The organization of organ systems of the class Birds has not been described due to the fact that birds evolved from reptiles much later than mammals and are a side branch of the evolution of chordates.

Covers

covers any animals always perform the function of perceiving external irritations, and also protect the body from the harmful effects of the environment. The intensification of the first function of the integument leads in the process of evolution of multicellular animals to the emergence of the nervous system and sensory organs. The intensification of the second function is accompanied by differentiation. The expansion of functions is also characteristic, as a result of which the skin, as an organ of protection, is also involved in gas exchange, thermoregulation and excretion, and feeding offspring. This is due to the complication of the structure of the layers of the skin, the appearance and further transformation of numerous appendages and glands.

In all chordates, the skin has a double - ecto- and mesodermal - origin. The epidermis develops from the ectoderm, and the dermis develops from the mesoderm. The non-cranial are characterized by a weak degree of differentiation of both layers of the skin. The epidermis is single-layer cylindrical, containing unicellular mucous glands, the dermis is loose, contains no a large number of connective tissue cells.

In the Vertebrate subtype, the epidermis becomes multi-layered, and in the lower layer the cells constantly multiply, and in the upper layers they differentiate, die and exfoliate. Connective tissue fibers appear in the dermis, giving the integument strength. The skin forms appendages, diverse depending on the lifestyle and level of organization, as well as glands that perform various functions.

In fish, the glands in the epidermis are unicellular. Like the lancelet, they secrete mucus that facilitates movement in the water. The body of fish is covered with scales, which have a different structure depending on their systematic position. The scales of cartilaginous fish are called placoid. It has the shape of a spike and consists of dentine covered with enamel on the outside (Fig. 14.1). Dentin is of mesodermal origin, it is formed due to the functioning of connective tissue cells that protrude from the outside in the form of a papilla. Enamel, which is a non-cellular substance harder than dentin, is formed by the papilla of the epidermis and covers the placoid scale from the outside.

The entire surface of the body of cartilaginous fish, as well as the oral cavity, the mucous membrane of which comes from the ectoderm, are covered with placoid scales. Naturally, the functions of the scales in the oral cavity are associated with the capture and retention of food, therefore they are greatly enlarged and are teeth. Bony fish have scales of a different type. It looks like thin round bone plates covered with a thin layer of the epidermis. The bony scales develop entirely at the expense of the dermis, but are related in origin to the primitive placoid.

The skin of primitive extinct amphibians - stegocephals - corresponded to the integument of fish and was also covered with scales. Modern amphibians have thin, smooth skin without scales, which takes part in gas exchange. This is facilitated by the presence of a large number of multicellular mucous glands, the secret of which constantly moisturizes the integument and has bactericidal properties. Some skin glands of a number of amphibians have differentiated into organs producing toxins that protect them from enemies (see Section 23.1).

Rice. 14.1. Laying of the placoid scale:

1 - enamel-forming cells, 2- epidermis, 3- enamel, 4- scleroblasts - dentine-formers, 5- dentine, 6- dermal papilla

Reptiles that have completely switched to terrestrial existence have dry skin that is not involved in respiration. Upper layer of the epidermis becomes keratinized. Horny scales in some reptiles are thin and elastic, in others they merge together, forming, like in turtles, a powerful horny shell. Most reptiles molt as they grow, periodically shedding their horny cover. Modern reptiles do not have skin glands.

The skin of mammals is built the most complex in connection with the performance of their diverse functions. Various derivatives of the skin are characteristic: hair, claws, horns, hooves, as well as sweat, sebaceous and mammary glands. More primitive mammals - insectivores, rodents and some others - along with the hairline, also retained horny scales on the tail. Their hair grows in the spaces between the scales, in groups of 3-7. In more advanced mammals that have lost scales, the same arrangement of hair is preserved (Fig. 14.2), covering almost the entire body, except for some areas, such as the soles and palms of humans.

Hair many mammals are differentiated into typical, serving for thermoregulation, and large, or vibrissae, the bases of which are associated with sensitive nerve endings. In most mammals, vibrissae are located in the mouth and nose, in primates they are reduced due to the increased tactile function of the forelimbs, in many oviparous and marsupials they are scattered throughout the body. This fact may indicate that the hairline of the ancestors of mammals primarily performed tactile functions, and then, as the number of hairs increased, it began to take part in thermoregulation. In human ontogenesis, it is laid large quantity hair rudiments, but by the end of embryogenesis, reduction of most of them occurs.

sweat glands mammals are homologous to the skin glands of amphibians. Their secret may be mucous, contain proteins and fat. Some sweat glands differentiated in early mammals in mammary glands. In oviparous (platypus, echidna) mammary glands are similar to sweat glands in structure and development. Along the edges of the developing nipple of the mammary gland, successive transitions from typical sweat to mammary glands can be found (Fig. 14.3). The number of mammary glands and nipples correlates with fertility (from 25 to one pair), but in the embryogenesis of all mammals, “milky lines” are laid on the abdominal surface, stretching from armpit to the groin Subsequently, the nipples differentiate on these lines, most of which then undergo reduction and disappear. So, in human embryogenesis, five pairs of nipples are laid first, and subsequently only one remains (Fig. 14.4).

Rice. 14.4. Embryogenesis of the human anterior abdominal wall. A - embryo at the age of 5 weeks (milky lines are visible); B - differentiation of five pairs of nipples; IN - fetus at 7 weeks

Rice. 14.5. Atavistic anomalies of skin development.

A - hypertrichosis; B - polymastia

Sebaceous glands are produced in the skin only in mammals. Their secret, lubricating the hair and the surface of the skin, makes them non-wettable and elastic.

The ontogeny of the integuments and appendages of the skin of mammals and humans reflects their evolution according to the type of archallaxis. Indeed, neither the rudiments of horny scales, characteristic of reptiles, nor the earlier forms of skin appendages recapitulate in their embryogenesis. At the same time, at the stage of secondary organogenesis, the rudiments of hair follicles develop immediately. Violations of the early ontogenesis of human skin can cause the occurrence of some minor atavistic malformations: hypertrichosis (increased hairiness), polythelia (increased number of nipples), polymastia (increased number of mammary glands) (Fig. 14.5). All of them are associated with a violation of the reduction of the excess number of these structures and reflect the evolutionary relationship of man with the closest ancestral forms - mammals. That is why it is impossible for humans and other mammals to give birth to offspring with atavistic signs of the skin, characteristic of more distant ancestors. One of the most well-known signs of prematurity in newborns is increased skin hairiness. Shortly after birth, excess hair usually falls out and their follicles are reduced.

musculoskeletal system

The phylogenesis of motor function underlies the progressive evolution of animals. Therefore, the level of their organization primarily depends on the nature of motor activity, which is determined by the characteristics of the organization. musculoskeletal system, undergone great evolutionary transformations in the Chordata type due to the change of habitats and changes in the forms of locomotion. Indeed, the aquatic environment in animals that do not have an external skeleton suggests uniform movements due to the bends of the whole body, while life on land is more conducive to their movement with the help of limbs.

Consider separately the evolution of the skeleton and the muscular system.

Skeleton

In chordates internal skeleton. According to the structure and functions, it is divided into axial, skeleton of the limbs and head.

Axial skeleton

In the subtype Cranial there is only axial skeleton in the form of a chord. It is built from highly vacuolated cells, tightly adjacent to each other and covered on the outside with common elastic and fibrous membranes. The elasticity of the chord is given by the turgor pressure of its cells and the strength of the membranes. The notochord is laid in the ontogeny of all chordates and in more highly organized animals performs not so much a support function as a morphogenetic one, being an organ that carries out embryonic induction.

Throughout life in vertebrates, the notochord is preserved only in cyclostomes and some lower fish. In all other animals, it is reduced. In humans, in the postembryonic period, the rudiments of the notochord are preserved in the form of the nucleus pulposus of the intervertebral discs. Preservation of an excess amount of chordal material in case of violation of its reduction is fraught with the possibility of developing tumors in humans - chord, arising from it.

In all vertebrates, the notochord is gradually replaced vertebrae developing from somite sclerotomes, and is functionally replaced spinal column. This is one prominent example of homotopic organ substitution (see § 13.4). The formation of vertebrae in phylogenesis begins with the development of their arches, covering the neural tube and becoming places of muscle attachment. Starting with cartilaginous fish, cartilage of the notochord membrane and growth of the bases of the vertebral arches are found, as a result of which the vertebral bodies are formed. The fusion of the upper vertebral arches above the neural tube forms the spinous processes and the spinal canal, which contains the neural tube (Fig. 14.6).

Rice. 14.6. Vertebral development. A-early stage; B- subsequent stage:

1 -chord, 2- chord shell, 3- upper and lower vertebral arches, 4- spinous process, 5- ossification zones, 6-rudiment of chord, 7 - cartilaginous body of the vertebra

Replacement of the chord with the spinal column - a more powerful support organ with a segmental structure - allows you to increase the overall size of the body and activates the motor function. Further progressive changes in the spinal column are associated with tissue substitution - replacement cartilage tissue on the bone, which is found in bony fish, as well as with its differentiation into sections.

Fish have only two sections of the spine: trunk And tail. This is due to their movement in the water due to the bends of the body.

Amphibians also acquire cervical And sacral departments, each represented by one vertebra. The first provides greater mobility of the head, and the second - support for the hind limbs.

In reptiles, the cervical spine lengthens, the first two vertebrae of which are movably connected to the skull and provide greater head mobility. Appears lumbar department, still weakly delimited from the thoracic, and the sacrum already consists of two vertebrae.

Mammals are characterized by a stable number of vertebrae per cervical region, equal to 7. Due to the large value in the movement of the hind limbs, the sacrum is formed by 5-10 vertebrae. The lumbar and thoracic regions are clearly separated from each other.

In fish, all trunk vertebrae bear ribs that do not fuse with each other and with the sternum. They give the body a stable shape and provide support for the muscles that bend the body in a horizontal plane. This function of the ribs is preserved in all vertebrates that perform serpentine movements - in caudate amphibians and reptiles, therefore, their ribs are also located on all vertebrae, except for the caudal ones.

Reptiles have part of the ribs thoracic grows together with the sternum, forming the chest, and in mammals in the composition chest includes 12-13 pairs of ribs.

Rice. 14.7. Anomalies in the development of the axial skeleton. A - rudimentary cervical ribs (shown by arrows); B - nonunion of the spinous processes of the vertebrae in the thoracic and lumbar regions. Spinal hernias

The ontogenesis of the human axial skeleton recapitulates the main phylogenetic stages of its formation: in the period of neurulation, a notochord is formed, which is subsequently replaced by a cartilaginous and then a bone spine. A pair of ribs develops on the cervical, thoracic and lumbar vertebrae, after which the cervical and lumbar ribs are reduced, and the thoracic ribs fuse in front with each other and with the sternum, forming the chest.

Violation of the ontogenesis of the axial skeleton in humans can be expressed in such atavistic malformations as nonunion of the spinous processes of the vertebrae, resulting in the formation of spinabifida - spinal defect. In this case, the meninges often protrude through the defect and form spinal hernia(Fig. 14.7).

At the age of 1.5-3 months. the human embryo has a caudal spine, consisting of 8-11 vertebrae. Violation of their reduction subsequently explains the possibility of such a well-known anomaly of the axial skeleton as tail persistence.

Violation of the reduction of the cervical and lumbar ribs underlies their preservation in postnatal ontogenesis.

Head skeleton

The continuation of the axial skeleton in front is axial, or cerebral, skull, serving to protect the brain and sensory organs. Next to him develops visceral, or face Skull, forming a support for the anterior part of the digestive tube. Both parts of the skull develop differently and from different rudiments. At the early stages of evolution and ontogenesis, they are not connected with each other, but later this connection arises.

Rice. 14.8. Human skull with methodical suture (indicated by arrow)

In the posterior part of the axial skull, traces of segmentation are found during development; therefore, it is believed that it is the result of the fusion of the anlages of the anterior vertebrae with each other. The structure of the brain skull also includes bookmarks of cartilaginous capsules of mesenchymal origin, surrounding the organs of hearing, smell and vision. In addition, the part of the brain skull (lying anterior to the sella turcica), which does not have segmentation, apparently develops as a neoplasm due to an increase in the size of the forebrain.

Phylogenetically, the brain skull went through three stages of development: membranous, cartilaginous And bone.

In cyclostomes, it is almost entirely membranous and does not have an anterior, non-segmented part.

The skull of cartilaginous fishes is almost completely cartilaginous, and includes both the posterior, primarily segmented part, and the anterior part.

In bony fish and other vertebrates, the axial skull becomes bony due to the processes of ossification of cartilage in the region of its base (basic, sphenoid, ethmoid bones) and due to the appearance of integumentary bones in its upper part (parietal, frontal, nasal bones). The bones of the axial skull in the process of progressive evolution undergo oligomerization. The appearance of a large number of ossification zones and their subsequent fusion together during the formation of such bones as the frontal, temporal, etc., testify to this. Widely known in humans are such anomalies of the brain skull as the presence of interparietal, as well as two frontal bones with a metopic suture between them (Fig. 14.8). They are not accompanied by any pathological phenomena and are therefore usually discovered by accident after death.

The visceral skull also appears for the first time in lower vertebrates. It is formed from mesenchyme of ectodermal origin, which is grouped in the form of thickenings, having the shape of arches, in the intervals between the gill slits of the pharynx. The first two arches are particularly strongly developed and give rise to the jaw and hyoid arches of adult animals. The following arcs, including 4-5 pairs, perform a supporting function for the gills and are called gill.

In cartilaginous fish, in front of the jaw arch, there are usually 1-2 more pairs of premaxillary arches, which are of a rudimentary nature. This indicates that the ancestors of vertebrates had a greater number of visceral arches than 6 or 7, and their differentiation occurred against the background of oligomerization.

The jaw arch is made up of two cartilages. Top call palatine-square, he performs the function of the primary upper jaw. lower, or Meckel, cartilage - primary lower jaw. On the ventral side of the pharynx, the Meckel cartilages are connected to each other in such a way that the jaw arch encircles oral cavity. The second visceral arch on each side consists of giomandibular cartilage fused with the base of the brain skull, and hyoid connected to Meckel's cartilage. Thus, in cartilaginous fish, both primary jaws are connected to the axial skull through the second visceral arch, in which the hyomandibular cartilage acts as a suspension to the cerebral skull. This type of connection between the jaws and the axial skull is called hyostyle(Fig. 14.9).

In bony fish, the primary jaws begin to be replaced by secondary ones, consisting of superimposed bones - the jaw and premaxilla from above and the dentary below. The palatine-square and Meckel cartilages decrease in size and shift backwards. The hyomandibular cartilage continues to function as a suspension, so the skull remains hyostyle.

Amphibians in connection with the transition to terrestrial existence have undergone significant changes in the visceral skull. Gill arches are partially reduced, and partially, changing functions, are part of the cartilaginous apparatus of the larynx. The jaw arch, with its upper element - the palatine-square cartilage - fuses completely with the base of the brain skull, and the skull thus becomes autostyle. The hyomandibular cartilage, greatly reduced and freed from the function of a suspension, located in the region of the first branchial fissure inside the auditory capsule, took on the function of the auditory ossicle - column - transmitting sound vibrations from the outer to the inner ear.

The visceral skull of reptiles is also autostyle. The jaw apparatus is characterized by a higher degree of ossification than that of amphibians. Part of the cartilaginous material of the gill arches is part of not only the larynx, but also the trachea.

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

One auditory ossicle column,- characteristic of amphibians and reptiles, decreasing in size, turns into stapes, and the rudiments of the palatine-square and Meckel cartilages, completely leaving the composition of the jaw apparatus, are transformed, respectively, into anvil And hammer. Thus, a single functional chain of three auditory ossicles in the middle ear is created, which is characteristic only for mammals (Fig. 14.9).

Rice. 14.9. Evolution of the first two visceral gill arches of vertebrates.

A- cartilaginous fish; B- amphibian; IN- reptile; G- mammal:

1 - palatine-square cartilage, 2-Meckel cartilage, 3- hyomandibular cartilage, 4-hyoid, 5- column, 6- superimposed bones of the secondary jaws, 7-anvil, 8- stapes, 9- hammer; homologous formations are indicated by the corresponding shading

The recapitulation of the main stages of the phylogenesis of the visceral skull also occurs in human ontogeny. Violation of the differentiation of the elements of the jaw gill arch into the auditory ossicles is a mechanism for the formation of such a malformation of the middle ear as the location in the tympanic cavity of only one auditory ossicle - the column, which corresponds to the structure of the sound-transmitting apparatus of amphibians and reptiles.

limb skeleton

In chordates, unpaired and paired limbs stand out. Unpaired (dorsal, caudal, and anal fins) are the main organs of locomotion in non-cranial, fish, and, to a lesser extent, tailed amphibians. Fish also have paired limbs - pectoral and ventral fins, on the basis of which paired limbs of terrestrial tetrapods subsequently develop.

Let's take a closer look at the origin and evolution of paired limbs.

In fish larvae, as well as in modern non-cranial ones, lateral skin folds stretch along the body on both sides, called metapleural(Fig. 14.10). They have neither a skeleton nor their own muscles, performing a passive role - stabilizing the position of the body and increasing the area of \u200b\u200bthe abdominal surface, facilitating movement in the aquatic environment. It is probable that in the ancestors of fishes, passing to a more active way of life, muscle elements and cartilaginous rays appeared in these folds, connected with somites by origin and, therefore, located metamerically. Such folds, having acquired mobility, can serve as depth rudders, however, for changing the position of the body in space, their anterior and posterior sections are of greater importance, as they are the most distant from the center of gravity. Therefore, evolution followed the path of intensifying the functions of the outermost divisions and weakening the functions of the central parts.

Rice. 14.10. Formation of the fore and hind limbs from metapleural folds: I-III- hypothetical stages of evolution

As a result, pectoral fins developed from the anterior sections of the folds, and ventral fins from the posterior ones (Fig. 14.10). It is possible that the formation of only two pairs of limbs on the lateral sides of the body was preceded by the disintegration of continuous folds into a number of paired fins, of which the anterior and posterior fins were also of greater importance. This is evidenced by the existence of fossil remains of the most ancient low-organized fish with numerous fins (Fig. 14.11). Due to the fusion of the bases of the cartilaginous rays, brachial And pelvic belt. Rest their regions differentiated into free limb skeleton.

Rice. 14.11. An ancient shark-like fish with numerous paired limbs

In most fish, in the skeleton of paired fins, a proximal section is distinguished, consisting of a small number of cartilaginous or bony plates, and a distal section, which includes a large number of radially segmented rays. The fins are inactively connected to the limb girdle. They cannot serve as a support for the body when moving along the bottom or on land. In lobe-finned fish, the skeleton of paired limbs has a different structure. The total number of their bone elements is reduced, and they are larger. The proximal section consists of only one large bone element corresponding to the humerus or femur of the forelimbs or hind limbs. This is followed by two smaller bones, homologous to the ulna and radius or the tibia and tibia. They are supported by 7-12 radially arranged beams. In connection with the limb belts in such a fin, only homologues of the humerus or femur are involved, therefore the fins of lobe-finned fish are actively mobile (Fig. 14.12, A, B) and can be used not only to change the direction of movement in water, but also to move on a solid substrate.

The life of these fish in shallow, drying up reservoirs in the Devonian period contributed to the selection of forms with more developed and mobile limbs. The presence of additional respiratory organs in them (see section 14.3.4) became the second prerequisite for the emergence of land and the emergence of other adaptations to terrestrial existence, which resulted in the origin of amphibians and the entire Tetrapoda group. Their first representatives - stegocephals - had seven- and five-fingered limbs, retaining a resemblance to the fins of lobe-finned fish (Fig. 14.12, B)

Rice. 14.12. Skeleton of the limb of a lobe-finned fish ( A), its base ( B) and the skeleton of the forepaw of a stegocephalus ( IN):I- humerus, 2-ulna, 3- radius

The correct radial arrangement of bone elements in 3-4 rows is preserved in the skeleton of the wrist, 7-5 bones are located in the metacarpus, and then the phalanges of 7-5 fingers also lie radially.

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

Further progressive transformation of the limbs is expressed in an increase in the degree of mobility of bone joints, in a decrease in the number of bones in the wrist, first to three rows in amphibians and then to two in reptiles and mammals. In parallel, the number of phalanges of the fingers also decreases. Also characteristic is the lengthening of the proximal limbs and the shortening of the distal ones.

The location of the limbs also changes during evolution. If in fish the pectoral fins are at the level of the first vertebra and are turned to the sides, then in terrestrial vertebrates, as a result of the complication of orientation in space, a neck appears and head mobility occurs, and in reptiles and especially in mammals, in connection with the elevation of the body above the ground, the forelimbs move backwards and are oriented vertically rather than horizontally. The same applies to the hind limbs.

The variety of habitat conditions provided by the terrestrial lifestyle provides a variety of forms of movement: jumping, running, crawling, flying, digging, climbing rocks and trees, and when returning to aquatic environment- and swimming. Therefore, in terrestrial vertebrates, one can find both an almost unlimited variety of limbs and their complete secondary reduction, and many similar adaptations of limbs in various environments repeatedly arose convergently (Fig. 14.13). However, in the process of ontogenesis, most terrestrial vertebrates show common features in the development of limbs: the laying of their rudiments in the form of poorly differentiated folds, the formation of six or seven rudiments of fingers in the hand and foot, the outermost of which are soon reduced and only five develop later (Fig. 14.14 ).

Rice. 14.13. Skeleton of the forelimb of terrestrial vertebrates. A-frog- B-salamander; IN-crocodile; G-bat; D-Human: 1 - humerus, 2-radius bone, 3 - wrist bones 4 -pasti, 5 -phalanges of fingers 6 -elbow bone

Rice. 14.14. The structure of the developing limb of a vertebrate: pp - prepollex, pin - postminimus - additional rudimentary fingers I and VII

Interestingly, in the embryogenesis of higher vertebrates, not only the structure of the limbs of the ancestors recapitulates, but also the process of their heterotopy. So, in a person, the upper limbs are laid at the level of the 3-4th cervical vertebrae, and the lower ones - at the level of the lumbar vertebrae. At the same time, the limbs receive innervation from the corresponding parts of the spinal cord. Heterotopia of the limbs is accompanied by the formation of the cervical, lumbar and sacral nerve plexuses, the nerves of which are connected, on the one hand, with those segments of the spinal cord from which they grew at the time of the formation of the limbs, and on the other hand, with the limbs that have moved to a new place (Fig. 14.15; see also section 14.2.2.2).

In human ontogenesis, numerous disorders are possible, leading to the formation of congenital malformations of the atavistic limbs. So, polydactyly, or an increase in the number of fingers, inherited as an autosomal dominant trait, is the result of the development of bookmarks of additional fingers, which are normal for distant ancestral forms. The phenomenon of polyphalangy is known, characterized by an increase in the number of phalanges usually of the thumb. At the heart of its occurrence is the development of three phalanges in the first finger, as is normally observed in reptiles and amphibians with undifferentiated toes. Bilateral polyphalangy is inherited in an autosomal dominant manner.

A serious malformation is a violation of the heterotopia of the belt of the upper extremities from the cervical region to the level of the 1st-2nd thoracic vertebrae. This anomaly is called Sprengel's disease or congenital high standing of the scapula (Fig. 14.16). It is expressed in the fact that the shoulder girdle on one or both sides is several centimeters higher than the normal position. Due to the fact that such a violation is often accompanied by anomalies of the ribs, thoracic spine and deformation of the shoulder blades, it should be thought that the mechanisms of its occurrence are not only a violation of the movement of organs, but also a violation of morphogenetic correlations caused by this (see § 13.4).

A comparative anatomical review of the evolution of the chordate skeleton indicates that the human skeleton is completely homologous to the supporting apparatus of ancestral and related forms. Therefore, many malformations of its development in humans can be explained by the relationship of mammals with reptiles, amphibians and fish. However, in the process of anthropogenesis, such features of the skeleton appeared that are characteristic only of man and are associated with his upright posture and labor activity. These include: 1) changes in the foot that has ceased to perform a grasping function, expressed in the loss of the ability to oppose the thumb and the appearance of its arches, which serve to cushion when walking; 2) changes in the spinal column - its S-shaped bend, providing plasticity of movements in a vertical position; 3) changes in the skull - a sharp decrease in its facial part and an increase in the brain, displacement of the large occipital foramen anteriorly, an increase in the mastoid process and smoothing of the occipital relief, to which the muscles of the neck and the nuchal ligament are attached; 4) specialization of the upper (front) limbs as an organ of labor; 5) the appearance of a chin protrusion in connection with the development of articulate speech.

Rice. 14.15. Formation of the forelimbs, their heterotopy and innervation in human ontogenesis. A- ingrowth of cervical myotomes into the developing forelimb of the embryo; B-development of skin innervation of the hand; IN- location of the cervical and brachial plexuses involved in the innervation of the hand:

1 - cervical myotomes, 2- thoracic myotomes, 3 - lumbar myotomas; the letters C, T, L denote the cervical, thoracic and lumbar segments

Rice. 14.16. Sprengel's disease (see text for explanation)

Despite the fact that the formation of the anatomical and morphological features of the human skeleton, apparently, has been completed, adaptations to upright posture in him, like all adaptations in general, are relative. So, with a big physical activity possible displacement of the vertebrae or intervertebral discs. Man, having switched to upright posture, has lost the ability to run fast and moves much more slowly than most four-legged animals.

Naturally, in the course of intrauterine development, the skeletal features that characterize a person as a unique biological species are formed at its final stages or even, such as, for example, an S-shaped spine, in the early postnatal period of development. They are actually anabolics that arose during the phylogenesis of primates. That's why atavistic anomalies skeleton, associated with developmental delays of signs characteristic only for humans, are most common. They practically do not reduce vitality, but children with them need orthopedic correction, gymnastics and massage. Such anomalies include mild forms of congenital flat feet, clubfoot, narrow chest, absence of a chin protrusion, and some others.

Muscular system

In representatives of the Chordata type, the muscles are subdivided according to the nature of development and innervation into somatic and visceral.

Somatic musculature develops from myotomes and is innervated by nerves, the fibers of which exit the spinal cord as part of the abdominal roots of the spinal nerves. Visceral musculature develops from other parts of the mesoderm and is innervated by the nerves of the autonomic nervous system. All somatic muscles are striated, and visceral muscles can be either striated or smooth (Fig. 14.17).

Rice. 14.17. Somatic and visceral muscles of vertebrates:

1 - somatic muscles that develop from myotomes, 2- visceral musculature of gill region

Visceral musculature

The visceral muscles associated with the visceral arches of the anterior part of the digestive tube underwent the most significant changes. In lower vertebrates, most of this musculature is represented by a common constrictor of the visceral apparatus - m. constrictor superficialis, covering the entire area of the gill arches from all sides. In the region of the jaw arch, this muscle is innervated trigeminal nerve(V), in the region of the hyoid arch - facial(VII), in the region of the first gill arch - glossopharyngeal(IX), finally, its part, lying more caudal, - wandering nerve (X). In this regard, all derivatives of the corresponding visceral arches and the muscles associated with them are subsequently innervated in all vertebrates by the listed nerves.

In front of the decompressor, a large muscular mass is separated, serving the jaw apparatus. Behind the visceral apparatus, the trapezius muscle m. trapezius, attached in separate bundles to the last gill slits and the anterior edge of the dorsal section of the shoulder girdle. Part of the superficial constrictor in the region of the hyoid arch in reptiles grows, covers the neck from below and from the sides and forms the neck constrictor m. sphincter colli. In mammals, this muscle is divided into two layers: deep and superficial. The deep retains its former name, and the superficial is called platysma myoides and is located subcutaneously. These two muscles grow over the entire region of the head and give rise to a complex system of facial subcutaneous muscles, which in primates and humans is called mimic. Therefore, all mimic

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

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

Motivation: - - - the possibilities of the movement being made, the volume of movement; active or passive movements are triggered by one or another muscle group; acting on the muscular apparatus, we change the general state; muscle relief is a guide for the topography of blood vessels and nerves; muscle transplantation, that is, the muscle can be "retrained".

The development of muscles of cranial origin - from the head myotomes (sclerotomes) and the mesenchyme of the gill arches. Innervated by branches of the cranial nerves Spinal origin - from the myotomes of the trunk of the embryo: from the ventral myotomes are innervated by the anterior branches of the SMN; - from the dorsal myotomes are innervated by the posterior branches of the SMN - Autochthonous muscles - muscles that remain in the place of their primary laying. Truncofugal muscles are muscles that have moved from the trunk to the limbs. Truncopetal muscles - muscles that have moved from the limbs to the trunk.

Striated Smooth 1. The unit of organization is the myocyte. The length is about 50 µm. Width from 6 µm. 2. Involuntary contraction Control by the autonomic nervous system The movement is undulating, it works slowly, since the nerve fiber does NOT fit to each cell Slowly enter into action, but persist for a long time Does not have an accurate spatial orientation of cells 3. 4. 5. 6. 1 2. 3. 4. 5. 6. Cardiac The unit of organization is the muscle fiber - a multitude of myoblasts floating in the common cytoplasm (sarcoplasm). They share a common sarcolemma. Length about 40 -100 mm. Width from 7 mm. Voluntary contraction Controlled by the somatic nervous system Rapid contraction, rapid reaction, as each muscle fiber has a neuromuscular junction Quickly engaged but short-lived Clear orientation of muscle fibers

Between the muscle fibers are thin layers of loose fibrous connective tissue - endomysium. The collagen fibers of the outer sheet of the basement membrane are woven into it, which contributes to the unification of efforts during the contraction of 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.

In the muscle as an organ there is a connective tissue Endomysium - 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. Vessels and nerves approach the muscle fiber through endomysium and perimysium. Form the stroma of the organ; 2. Muscle fibers are formed into bundles, bundles into muscle; 3. Since the endomysium is fused with the sarcolemma of the muscle fiber, therefore, the contracting muscle fiber can only stretch up to a certain limit

Myofibrils in the fiber are surrounded by a shell - the sarcolemma, and immersed in a special environment - the sarcoplasm. Depending on the content of pigment and oxygen, the fibers are divided into white and red. White fibers are anaerobes, contain more myofibrils, less sarcoplasm. They start quickly, but they 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 less myofibrils. Slow start, but work for a long time. Example: back muscles, diaphragm.

Each muscle has a network of blood vessels. Muscle contraction promotes 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.

Muscle structure Each muscle connects at one end to one bone (the beginning of the muscle), and at the other to the other (muscle attachment). In the muscle, they distinguish: head, abdomen, 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 surrounded by a network of hemocapillaries, forming a complex called myon. A group of muscle fibers innervated by one motor neuron is called a motor unit. Characteristically, the muscle fibers belonging to one motor unit do not lie side by side, but are located mosaically among the fibers belonging to other units.

A tendon is a dense fibrous connective tissue cord with which a muscle begins 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 bone tissue, forming ridges, tubercles, tuberosities, depressions, depressions on the bones.

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

1. 2. 3. 4. 5. Fascia separate the muscles from the skin and eliminate the displacement of the skin during the movements of contracting muscles. Fascia conserve muscle contraction force by eliminating friction between muscles during contraction. Fascia stretch large veins under tension, as a result of which blood from the periphery is "sucked" into these veins. Fascia are important as barriers to the spread of infection and tumors. During operations, fasciae help determine the location of muscles, blood vessels, and viscera.

Classification of muscles Skeletal muscles are diverse in shape, structure, position relative to the axes of the joints, etc., therefore they are classified in different ways.

III. By functional features Static (strong) - a short abdomen and a long tendon. Muscles work with more force, but with a smaller range of motion. Dynamic (dexterous) - long muscle bundles, short tendons. Muscles work with less force but produce larger movements

Auxiliary apparatus of muscles Skeletal muscles have an auxiliary apparatus that facilitates their functioning. n n n Fascia; Bone-fascial sheaths; Synovial bags; Synovial tendon sheaths; muscle blocks; Sesamoid bones.

Anomalies in muscle development They 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.

Malformations Underdevelopment of the sternocleidomastoid muscle - Torticollis Underdevelopment of the diaphragm. Cause of diaphragmatic hernia. Underdevelopment of the deltoid and trapezius muscles - Deformity of the shoulder girdle and shoulder

I. Shape: Fusiform; ribbon-like; Flat wide; jagged; Long; n n n Square; triangular; round; deltoid; soleus, etc.

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

IV. By function: Leading; outlet; flexors; extensor; Pronators; n n Arch supports; Straining; Muscles are synergists; Muscles are antagonists.

V. In relation to the joint: Single-joint; biarticular; Polyarticular.

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Introduction

Myology (Myologia) is a branch of the anatomy of domestic animals 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 are carried out. internal organs including the work of the heart.

Muscle tissue has special contractile organelles - myofibrils. Myofibrils, consisting of thin protein filaments (myofilaments), may be unstriated or striated (striated). Accordingly, unstriated and striated muscle tissue is distinguished.

1) Non-striated muscle tissue consists of cells (smooth myocytes) of a fusiform shape. These cells form muscle layers in the walls of blood and lymph 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), the diameter is from 2 to 20 µm. In functional terms, unstriated muscle tissue has a number of features: it has great strength (for example, significant masses of food constantly move in the intestines), has low fatigue, slow contraction and rhythm of movements (in the intestinal wall, unstriated 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, has 2 varieties.

A) Striated cardiac muscle tissue consists of elongated cells (cardiomyocytes) of a 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, the functional muscle "fibers" form the muscular membrane of the heart (myocardium), the 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 multinuclear muscle formations (myosymplasts) of a cylindrical shape. The length of myosymplasts varies from a few millimeters to 13-15 cm, the diameter is 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.). In functional terms, skeletal muscle tissue is easily excitable and contracts faster than non-striated muscle (for example, under normal conditions, skeletal muscle contracts within 0.1 s, and non-striated muscle within a few seconds). But, unlike the smooth (non-striated) muscles of the internal organs, skeletal muscles tire faster.

The muscular system, depending on the structural features, the nature of the motor function and innervation, is divided into somatic and visceral.

The 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, vigorously, but they tire for a short time and quickly. This type of contraction is called tetanic and is characteristic of somatic muscles. It includes:

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

2) skeletal muscles, which are fixed on 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.

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

1. Phylo-ontogeny of the muscular system

In the phylogeny of chordates, the muscular system successively passes through a series of stages.

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

With an increase in mobility, isolation of the head, and development of a limb (in the form of fins), in fish, the longitudinal muscle is divided by a horizontal septum into dorsal and ventral muscles.

Isolation of the muscles of the heads, torso, 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 strands: lateral (transverse costal muscle) and medial (transverse spinous m.). In addition, in reptiles, subcutaneous muscles appear for the first time from the lateral cord, which are attached to the skin.

In more highly organized animals (birds and mammals), further differentiation of the muscular system occurs: the lateral and medial strands, each of them, are divided into two layers (superficial and deep). In addition, the 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 (trapezoid, 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, differentiate into superficial and deep layers, the latter give rise to certain muscle groups. For example, the iliocostal muscles develop from the surface layer of the lateral layer, and the longest muscles of the back, neck, and head develop from the deep layer of the lateral layer.

2. Subcutaneous muscles -musclescutanei

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 strongly developed in dogs). It goes along the neck, closer to its ventral surface and passes to the front 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 scapula and partially the shoulder. Well expressed in horses and cattle.

3) Subcutaneous muscle of the body - m. Cutaneus trunci. It is located on the sides of the chest and abdominal walls and caudally gives the bundles to the knee crease.

4) In females, in the area of \u200b\u200bthe 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 to remove milk. Strongly developed in carnivores.

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

3. Skeletalmusculature

Skeletal muscles are the active part of the musculoskeletal system. It consists of skeletal muscles and their accessories, which include fascia, synovial bags, synovial tendon sheaths, blocks, sesame bones.

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

The muscles in the animal's body are not arranged randomly, but naturally, depending on the action 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, syndesmoses.

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

The main functions of skeletal muscles:

1) The main function of the 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 done, the result of which is movement.

2) Another function of the muscles 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 up (horse).

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

4) At the same time, during their work, skeletal muscles help the work of the heart, 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."

4. Structuremusclesfrom a biochemist's point of view

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

The chemical composition of skeletal muscle

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

5. Structuremusclesfrom an anatomist's point of view

Skeletal muscle (Musculus skeleti) is an active organ of the apparatus of movement, the shape and structural features of which are determined by the function performed and location on the skeleton. In the muscle, an actively contracting part is distinguished - the muscle belly and a passive part, with which it is attached to the bones, - the tendon.

1) The muscular abdomen (venter) consists of parenchyma and stroma. The parenchyma is represented by striated muscle tissue, structural unit which is the myosymplast. Myosymplasts are united by loose connective tissue called endomysium into bundles of the 1st order. The bundles of the 1st order are combined into bundles of the 1st,2,3rd order and connective tissue septa (perimysium) are formed between them, through which vessels and nerves penetrate into the muscle. Outside, the muscular abdomen is covered with a connective tissue sheath (epimysium). Endo-, peri- and epimysium form the stroma of the muscular abdomen and protect the muscle from excessive thickening or stretching. The connective tissue elements present between the muscle fibers, at the ends of the muscle belly, pass into the tendons.

2) The tendon (tendo) is built on the same principle as the muscle belly, with the only difference being that instead of muscle fibers, its bundles contain collagen fibers. Layers of connective tissue inside are called endo- and peritenonium, and outside, dense connective tissue forms a shell (epithenonium), which is a continuation of the epimysium. The tendon has a brilliant light golden color, which differs sharply from the red-brown color of the muscle abdomen. In most cases, the tendon is located at both ends of the muscle and is attached to the bones. Although the tendon is much thinner than the muscle belly, its strength is great, it is able to withstand a large load and is practically inextensible. Studies have shown that to tear the Achilles tendon in an animal, a force of 900 kg per cubic cm is required.

3) Vessels and nerves enter the muscle from its inner side.

Arteries branch to capillaries, which form a dense network in bundles of muscle fibers. Each muscle fiber has at least one blood capillary. Blood enters each muscle through the arteries, and flows out through the veins and lymphatic vessels.

The nerves, branching in the muscle, form a neuromuscular complex - mion, which consists of 1 nerve fiber and several muscle fibers. So, for example, in the triceps muscle of the lower leg, the mion consists of 1 nerve fiber and 227 muscle fibers, and in the lateral muscle of the eye, it consists of 1 nerve fiber and 19 muscle fibers.

Muscle growth in length occurs in the so-called "growth zones", which are located at the transition points of the muscle belly into the tendon and contain a large number of nuclei, and the increase in muscle thickness occurs due to the functional load that this muscle performs.

6. Classificationmuscles

Each muscle is an independent organ and has a certain shape, size, structure, function, origin and position in the body. Depending on this, all skeletal muscles are divided into the following groups.

I. According to the shape, the muscles are long, short, flat, etc.

1) The long muscles correspond to the long levers of motion and are therefore found mainly on the limbs. They have a spindle shape, the middle part is called the abdomen, the end corresponding to the beginning of the muscle is the head, the opposite end is the tail. The tendon of the long muscles has the shape of a ribbon. Some long muscles begin with several heads (multi-headed) on different bones, which enhances their support. There are biceps muscles (two-headed m. of the shoulder), three-headed (three-headed m. of the lower leg) and quadriceps (four-headed m of the thigh).

2) Short muscles are located in those parts of the body where the range of motion is small (between individual vertebrae (multipartite m.), between vertebrae and ribs (rib lifters), etc.).

3) Flat (broad) muscles are located mainly on the trunk and limb belts. They have an enlarged tendon called an aponeurosis. Flat muscles have not only a motor function, but also a supporting and protective one (for example, the muscles of the abdominal wall protect and help hold internal organs).

4) There are also other forms of muscles: square, circular, deltoid, dentate, trapezoid, fusiform, etc.

II. According to the anatomical structure, the muscles are divided depending on the number of intramuscular tendon layers and the direction of the muscle layers:

1) One-pinnate. They are characterized by the absence of tendon layers and muscle fibers are attached to the tendon of one side (external oblique abdominal m.).

2) Bipennate. They are characterized by the presence of one tendon layer and the muscle fibers are attached to the tendon on both sides (trapezoid m.).

3) Multipinnate. They are characterized by the presence of two or more tendon layers, as a result of which the muscle bundles are difficult to intertwine and approach the tendon from several sides (chewing m., deltoid muscle).

III. According to the histostructure, all muscles are divided into 3 types, depending on the ratio of striated muscle tissue to connective tissue:

1) Dynamic type. Dynamic muscles that provide active and versatile work are characterized by a significant predominance of striated muscle tissue over connective tissue (quadriceps femoris).

2) Static type. Unlike dynamic muscles, static muscles do not have muscle fibers at all. They perform a lot of static work when standing and resting the limb on the ground during movement, fixing the joints in a certain position (the third interosseous m. cow and horse)

3) Statodynamic type. This type is characterized by a decrease in the ratio of striated muscle tissue to connective tissue elements (biceps of the horse's shoulder). Statodynamic muscles, as a rule, have a feathery structure.

IV. According to the action on the joints, the muscles are divided into one-, two- and multi-articular.

1) Single-joint act on only one joint (prespinal m., infraspinatus m. act on the shoulder joint).

2) Biarticular, act on two joints (tensor of the wide fascia of the thigh acts on the hip and knee joints).

3) Multi-joint (two-headed m. of the thigh, semitendinous m., semimembranosus m. act on 3 joints (hip, knee, hock).

In addition, it must be emphasized that the muscles act separately or as a group. Muscles that act in the same way are called synergists, and those that act in the opposite way are called antagonists.

V. By function, the muscles are divided into:

1. Flexors, or flexors, which, when contracted, bring the ends of the bones together 2. Extensors, or extensors, which pass through the top of the joint angle and open it when contracted.

3. Abductors, or abductors, lie on the lateral side of the joint and take it away from the sagittal plane to the side.

4. Adductors, or adductor muscles, lie on the medial surface of the joint and, when reduced, bring it to the sagittal plane.

5. Rotators, or rotators, providing rotation of the limb outward (arch supports) or inward (pronators).

6. Sphincters, or lockers, which are located around natural openings and close them when contracted. They, as a rule, are characterized by a circular direction of muscle fibers (for example, the circular muscle of the mouth).

7. Constrictors, or constrictors, which also belong to the type of round muscles, but have a different shape (for example, constrictors of the pharynx, larynx).

8. Dilators, or dilators, open natural openings when contracted.

9. Levators, or lifters, during contraction, raise, for example, ribs.

10. Depressors, or lowerers.

11. Tensors, or tensioners, with their work strain the fasciae, preventing them from gathering in folds.

12. Retainers, strengthen the joint on the side of the location of the corresponding muscles.

VI. By origin, all skeletal muscles are divided into somatic and visceral.

1) Somatic muscles develop from somites of the mesoderm (masticatory m., temporal m., m. of the spinal column).

2) Visceral are derivatives of the muscles of the gill apparatus. The visceral muscles include the muscles of the head (facial, chewing) and some muscles of the neck.

muscular system human animal

7. Muscle accessories

Muscles contracting, perform their function with the participation and with the help of anatomical formations, which should be considered as auxiliary devices of the muscles. They improve muscle performance. These include fascia, bursae, tendon sheaths, blocks, and sesame bones.

Fascia (Latin fascia - wrapper)

Fascia are thin, strong, connective tissue membranes that form peculiar cases around the muscles. They mainly perform supporting and cushioning functions. Fascia delimit the muscles from each other, create support for the muscle belly during its contraction and eliminate the friction of the muscles from each other. Fascia is also called a soft skeleton (it is considered a remnant of the membranous skeleton of vertebrate ancestors). They are rich in nerve endings (receptors) and blood vessels and therefore play an essential role in recovery (regeneration) processes. So, for example, if, when removing the affected meniscus in the knee joint, a fascia flap is engrafted in its place, which has not lost its connection with the vessels and nerves, then with a certain training, after a while, an “organ” like a meniscus will form in its place and the work of the joint as a whole is restored. Therefore, fasciae are widely used in reconstructive surgery for autoplasty of cartilage and bone tissues. Fascia are superficial, deep and special fascia.

Superficial, or subcutaneous, fasciae separate the skin from the skeletal muscles and form a kind of cases for all areas of the animal's body. Subcutaneous muscles are attached to them.

1) Superficial f of the head (f. superficialis capitis), it contains the muscles of the head.

2) Neck f. (f.cervicalis) lies ventrally in the neck and covers the trachea.

3) The thoracolumbar f. (f.thoracolubalis) lies dorsally on the body and is fixed on the spinous processes of the thoracic and lumbar vertebrae and maklok.

4) Pectoral f. (f.thoracoabdominalis) lies laterally on the sides of the chest and abdominal cavity and is fixed ventrally along the white line of the abdomen (linea alba).

5) Surface f. thoracic limb (f.superficialis membri thoracici) is a continuation of the abdominal fascia. It is significantly thickened at the wrist and forms fibrous sheaths for the tendons of the muscles that run here.

6) Surface f. pelvic limb (f.superficialis membri pelvini) is a continuation of the thoracolumbar and is significantly thickened in the tarsal region.

Deep, or own, fasciae are attached to the bones and hold the muscles in a certain position, preventing them from moving. They form cases for individual muscles, muscle groups (synergists) and organs.

1) In the head area, the superficial fascia is divided into the following deep ones: frontal (covers the back of the nose), temporal, parotid-chewing, buccal, submandibular, buccal-pharyngeal.

2) Intrathoracic (f.endothoracica) lines the inner surface of the chest cavity.

3) Transverse abdominal (f.transversalis) lines the inner surface of the abdominal cavity.

4) Pelvis (f.pelvis) lines the inner surface of the pelvic cavity.

5) In the region of the thoracic limb, the superficial fascia is divided into the following deep ones: fascia of the scapula, shoulder, forearm, hand, fingers.

6) In the region of the pelvic limb, the superficial fascia is divided into the following deep ones: gluteal (covers the croup area), fascia of the thigh, lower leg, foot, fingers

Special ones cover individual muscles. For example, the deep parotid-masticatory fascia is divided into two special ones: the parotid covers salivary gland, and chewing - chewing muscle.

Bursa(bursa - bag)

In places of attachment and the greatest mobility of tendons and muscles, there are bursae. They have the form of a flat connective tissue sac, inside of which there is a liquid. Bursae reduce friction and soften the contact of muscles with other organs (bone, skin). They vary in size from a few millimeters to several centimeters. Depending on what the bursae are filled with, synovial and mucous bursae are distinguished.

1) Synovial bursae (bursa synovialis) are formed by the joint capsule and are filled with synovium, so the bursa cavity communicates with the joint cavity. Such bursae are located mainly in the area of the elbow and knee joint. Inflammation of these burs due to injury can lead to arthritis (inflammation of the joint) of the elbow or knee joints, and this must be remembered in veterinary practice.

2) Mucous bursae (bursa mucosa) are formed in vulnerable places under the ligaments (subglottic), under the muscles (axillary), under the tendons (subtendon) and under the skin (subcutaneous). Their cavity is filled with mucus and they can be permanent or temporary (corns).

Synovial vagina tendons (vagina synovialis tendinis)

The synovial tendon sheath differs from the synovial sac in that it is much larger (length, width) and has a double wall. It completely covers the muscle tendon moving in it, which is enclosed, as it were, in a tube filled with synovia. As a result, the synovial sheath not only performs the function of a bursa, but also strengthens the position of the tendon of the muscle over a significant length of it. They are found in the carpal, tarsal and digital joints.

The synovial sheath is limited by sheets. The visceral (inner) layer surrounds the tendon on all sides and fuses with it. Parietal (external) lines the walls of the fibrous sheath. Both sheets pass into each other at the ends of the vagina and along its tendon. The double sheet of the vagina connecting the inner and outer sheets is called the mesentery of the tendon or mesotendinium.

Block (trochlea)

Blocks are sections of the epiphyses of a certain shape tubular bones through which muscles pass. It is a bony protrusion and a groove in it, where the tendon of the muscles passes. Due to this, the tendons do not move to the side and the leverage for applying force is increased. What bones have blocks? Shoulder, hip.

sesame bones (ossa sesamoidea)

Sesamoid bones are formed in the area of very strong muscle tension and are found in the thickness of the tendons. They change the angle of attachment of the muscles and thereby improve the conditions for their work, reducing friction. Sometimes they are called "ossified areas of the tendons", but it must be remembered that they go through only two stages of development (connective tissue and bone).

The largest sesame-shaped bone in the body is the patella.

Bibliography

1. Agadzhanyan N.A., Vlasova I.G., Ermakova N.V., Troshin V.I. Fundamentals of human physiology: Textbook - M., 2009.

2. Antonova V.A. Age anatomy and physiology. - M.: Higher education. - 192 p. 2006.

3. Vorob'eva E.A. Anatomy and physiology. - M.: Medicine, 2007.

4. Lipchenko V.Ya. Atlas of normal human anatomy. - M.: Medicine. 2009.

5. Obreumova N.I., Petrukhin A.S. Fundamentals of anatomy, physiology and hygiene of children and adolescents. Tutorial for students of the defectological faculty of higher education. ped. textbook establishments. - M.: Publishing Center "Academy", 2008.

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2 Ontogeny of the muscular system: sources and timing of development.

Myotome derivatives: back muscles develop from the dorsal region

from the ventral - the muscles of the chest and abdomen

Mesenchyme - limb muscles

I visceral arch (VD) - masticatory muscles

II VD - mimic muscles

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

V VD - sternocleidomastoid and trapezius muscles

From the occipital myotomes - the muscles of the tongue

From the anterior myotomes - the muscles of the eyeball

Muscles develop from mesoderm. On the trunk, they arise from the primary segmented mesoderm - somites: 3-5 occipital, 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 4-5 coccygeal.

Each somite is subdivided into sclerotome, dermatome and myotome- from it the muscles of the body develop. Somites appear early, when the length of the embryo is 10-15 mm.

From dorsal parts of myotomes arise deep, own(autochthonous) muscles of the back, from ventral- deep muscles of the chest and abdomen. They are laid, develop and remain within the body - therefore they are called autochthonous (local, native). Very early myotomes communicate with the nervous system and each muscle segment corresponds to a nerve segment. Each nerve follows the developing muscle, grows into it, and, until it is differentiated, subordinates to its influence.

In the process of development, part of the skeletal muscles moves from the trunk and neck to the limbs - trunk-fugal muscles: trapezius, sternocleidomastoid, rhomboid, levator scapula, etc. Part of the muscles, on the contrary, is directed from the limbs to the trunk - truncal muscles: latissimus dorsi, pectoralis major and minor, psoas major.

Muscles of the head facial and chewing, supra- and hyoid muscles of the neck develop from non-segmented ventral mesoderm, which is part of the visceral (gill) arches. They are called visceral and, for example, chewing muscles develop on the basis of the first visceral arc, and mimic - the second. However, the muscles of the eyeball and tongue develop from the occipital myotomes of the segmented mesoderm. The deep anterior and posterior muscles of the neck also arise from the occipital cervical myotomes, and the superficial and middle muscle groups in the anterior region of the neck develop on the basis of the unsegmented mesoderm of the visceral arches.

3 Muscle: definition, structure.

Muscle(muscle) - an organ built from muscle fibers (cells), each of them has a connective tissue sheath - endomysium. Another fibrous sheath unites muscle fibers into bundles - perimysium, and the entire muscle is enclosed in a common fibrous sheath formed by fascia - epimysium. Between the bundles are vessels and nerves that supply the muscle fibers.

At the macro level, skeletal muscle has:

abdomen(venter) - the fleshy part of the body, which occupies its middle;

tendon(tendo) related to the distal end, it can be in the form of an aponeurosis, tendon bridges, long bundles of longitudinal fibrous fibers;

head, constituting the proximal part;

tendon and head are attached at opposite ends of the bones.

The proximal tendon or head of the muscle - the beginning of the muscle on the bone is closer to the median axis of the body - this is a fixed point (punctum fixum) (usually coincides with the beginning of the muscle). The distal tendon, "tail" - the end of the muscle lies distally on the bone and, being the point of attachment, is called a mobile point (punctom mobile). When the muscle contracts, the points approach each other, and when the position of the body changes, they can change places.

The tendons are different in shape: thin long tendons have limb muscles; the muscles involved in the formation of the walls of the abdominal cavity have a wide flat tendon located between the two bellies - a tendon stretch or aponeurosis.