Skeletal muscles are composed of striated muscle tissue.

Muscles are innervated by the somatic nervous system. Circulatory system transports oxygen and nutrients to the muscles, and from the muscles - carbon dioxide and other metabolic products.

Muscle tissue cell - myocyte- has the appearance of a long and thin fiber, which is why it is called muscle fiber. Each muscle fiber is a multinucleated cell ( simplast), obtained as a result of the fusion of a large number of cells.

Properties of muscle cells: excitability and contractility.

There are two types of muscle fibers:

red muscle fibers	white muscle fibers
slow (tonic)	fast (phasic)
speed of nerve impulse up to 8 m/sec	speed of nerve impulse up to 40 m/sec
	practically do not contain myoglobin (white)
deep muscles of the limbs	superficial muscles of the limbs
weak contraction strength slow contraction and slow relaxation	greater contraction force rapid contraction and rapid fatigue
many mitochondria; energy source (ATP) aerobic respiration	few mitochondria
little glycogen; with a lack of oxygen, glycolysis with the formation of lactic acid	a lot of glycogen; energy source (ATP) anaerobic respiration (glycolysis)
maintaining posture	locomotion

The functional unit of muscle fiber is myofibril. Myofibrils occupy almost the entire cytoplasm of the muscle fiber, pushing the nuclei to the periphery.

myofibril structure

Myofibrils- cylindrical threads 1 - 2 microns thick, running lengthwise from one end of the muscle fiber to the other.

Sarcomere- contractile unit of muscle fiber. The boundaries of the sarcomeres of adjacent muscle fibers coincide, which explains the transverse striation of the myofibrils.

Sarcomeres consist of two types of protein filaments:

• thick - made from the protein myosin
• thin - made of actin protein

On a longitudinal section of the muscle at high magnification, alternating light and dark stripes are visible within each sarcomere.

A-disc: dark fiber stripes;

I-disc: light fiber stripes;

Z-line, or Z-disk: A line in the center of the I band that separates one sarcomere from another.

Thin and thick filaments overlap in the A-disc region.

In the Z-disk region, in the spaces between myofibrils, intermediate filament protein is found - desmin, which is involved in connecting neighboring sarcomeres to each other.

muscle contraction

All skeletal muscles are under the control of the will and contract only when receiving a signal from the corresponding motor neurons.

A nerve impulse passing through a motor neuron stimulates the release of acetylcholine into the neuromuscular synapse, which causes an action potential in the cytoplasmic membrane of the muscle cell. In response to this, the endoplasmic reticulum releases into the cytoplasm a large number of calcium ions. A sharp increase in calcium concentration causes contraction of myofibrils. Since the signal reaches the sarcomere within a few milliseconds, all myofibrils of the muscle cell contract simultaneously.

During muscle contraction, each sarcomere is shortened as a result of the sliding of thick filaments relative to thin ones, and the length of both remains unchanged.

Thick myosin filaments form cross bridges directed towards the actin filaments. The bridges end with protein heads, which cling to actin filaments like hooks. Each myosin head “steps” along the adjacent actin filament. It rests on the actin filament and causes it to move relative to the thick filament. During those periods when a given myosin head is separated from the actin filament, the latter continues to be shifted by the remaining heads that are part of the same thick filament, so that at any given time in a contracting muscle only part of the myosin heads are attached to the actin filaments, while others remain free . Each thick filament contains about 500 myosin heads, and each of them takes about 5 “steps” per second during rapid muscle contraction.

All movements of myosin heads, including their separation from actin, are accompanied by energy costs (ATP hydrolysis).

Breakdown and oxidation occur in the muscle fiber organic matter, mainly carbohydrates.

glycogen - glucose

glucose + oxygen = carbon dioxide + water + chemical energy(ATP)

ATP energy = mechanical energy (muscle work) + thermal energy (maintaining body temperature)

At active work Oxygen deficiency may occur. There is not enough oxygen to oxidize glucose. The product of incomplete oxidation of glucose - lactic acid - accumulates in muscle tissue, causing fatigue and muscle pain.

Muscle work

At the same time, only part of the muscle fibers in the muscle contracts.

A single nerve impulse causes rapid contraction and subsequent relaxation of the muscle.

Smooth, prolonged muscle contraction is ensured by continuous flows of nerve impulses from the brain to motor neurons. Being under the influence of constant nerve impulses, the muscles of our body are in good shape (in a state of prolonged contraction).

During intense muscular work, muscle fatigue may occur.

Muscle fatigue- temporary decrease in their performance.

Causes of fatigue:

1. accumulation of metabolic products (lactic acid) in the muscles;
2. depletion of energy reserves (glycogen, ATP);
3. fatigue of the nerve centers that control muscle function.

After a period of rest, the muscles regain their functionality.

I.M. Sechenov studied the patterns of work of skeletal muscles and the development of fatigue in them.

Results of the work of I. M. Sechenov:

• combination a certain rhythm of muscle contractions with optimal load ensures long-term muscle work without much fatigue;
• muscle work stimulates mental work;
• active recreation is most effective.

Regulation of muscle fiber contraction

1. Motor neurons release neurotransmitter acetylcholine at neuromuscular synapses. Acetylcholine promotes the formation of action potentials on the postsynaptic membrane. Excitation is transmitted to many muscle cells. Within a few milliseconds, the cycle of muscle fiber contraction discussed above is realized.
2. The endoplasmic reticulum of a muscle cell contains a high concentration of Ca2+ ions. The release of Ca2+ ions into the space between the actin and myosin filaments is the trigger for the process of myofibril contraction.
3. Protein complex troponin And tropomyosin occupy a binding site with myosin on the actin molecule. Calcium ions bind to troponin, troponin changes its structure, the protein complex is destroyed and releases a binding site for myosin on the actin molecule. This initiates a cycle of muscle contraction. When the concentration of calcium ions in the cytoplasm decreases, the Ca2+ complex with troponin dissociates, troponin restores its original conformation, the myosin binding site on actin is blocked and the muscle relaxes.

structure of skeletal muscles

Each muscle fiber has its own wrapping of loose fibrous connective tissue - endomysium. The bundles are combined into even denser bundles, separated by layers - perimysium, which contains blood and lymphatic vessels and nerves.

The muscle as a whole is surrounded by connective tissue epimysium (fascia). At the ends of muscle fibers sarcolemma(cell membrane) and endomysium form tendon fibers.

Fascia- connective tissue sheaths for muscles that delimit muscles from each other, create support for the abdomen during contraction, weaken friction of muscles against each other, and prevent compression of blood vessels.

Each muscle has a proximal (closer to the central axis of the body) and a distal (closer to the periphery of the body) end.

The muscle consists of a head, body (abdomen) and tail.

Vessels and nerves enter the muscle from the inside. Arteries, veins and lymphatic vessels entering the muscle branch to capillaries, which form a network along the muscle fiber.

Muscles differ in the number of heads:

• biceps (biceps)
• triceps (triceps)
• quadriceps

Antagonist muscles: oppositely acting (for example, flexors and extensors);

Synergistic muscles: located on one side of the joint axis and act in one direction.

Sphincters- circular muscles (orbicularis oris muscle, sphincters of the digestive canal).

Basic human muscles

Functions of skeletal muscles

• set bone levers in motion;
• maintaining balance;
• movement in space;
• facial expressions;
• participate in the formation of the walls of body cavities;
• are part of the walls of some internal organs(pharynx, upper esophagus, larynx);
• carry out eye movement (oculomotor muscle);
• breathing and swallowing.

A person has approximately 400 muscles (40% of body weight).

Proprioception

Most proprioceptors are located in muscles, tendons and joints. Their stimulation comes from the body itself, and not from the external environment.

A person constantly feels the position of his limbs and the movement of his joints; he precisely determines the resistance to his every movement.

TO proprioception applies:

• position sense: informs at what angle each joint is, and ultimately the position of all limbs;
• sense of movement: awareness of the direction and speed of joint movement. A person perceives both active joint movement during muscle contraction and passive movement caused by external causes;
• sense of strength: the ability to estimate the muscle strength needed to move or hold a joint in a certain position.

MUSCLES MUSCLES

muscles (musculi), organs of the body of animals and humans, consisting of muscle tissue capable of contracting under the influence of nerve impulses. They move the body in space, shift some of its parts relative to others (dynamic function), actively fix their position relative to each other (static function), change the volume of the body cavity or the lumen of a vessel, move the skin, and other functions. Collectively, muscles form the muscular system. In humans, M. range from 28-32% (women) to 35-45% (men) of body weight. Depending on the structure of muscle cells, smooth muscles forming visceral muscles and striated muscles forming parietal muscles are distinguished. Most M., mainly skeletal, classified as striated. Numerous M. (in humans there are about 600 skeletal M.) have different. form, structure, function and development. M. are distinguished by shape: long, short, wide and round, by internal. organizations - simple (muscle fibers are parallel) and feathery (oblique fibers are attached to the tendon on one or both sides), by position - superficial and deep, external and internal, lateral and medial, by the number of joints involved in movement - one-, two- or multi-joint muscles. The work of simple muscles depends on the number of fibers and the magnitude of their contraction, which can exceed half of the original. fiber length. Cirrus fibers, as a rule, are stronger than simple ones, provide an increase in speed, and, in addition, they have a larger number of fibers that occupy a smaller volume. Transformations dept. M. in the course of evolution are associated with restructuring of their internal. structures. In a typical muscle, there is an actively contracting part - the body (abdomen) and a passive part - a tendon, which, as a rule, is located at both ends of the muscle and attaches it to the bones of the skeleton. Each muscle is abundantly supplied with nerve fibers and capillaries that approach it through connective tissue membranes - perimysium and endomysium. For example, per 1 mm3 M, a person normally has approx. 2000 capillaries; one nerve fiber can innervate from 3-6 muscle fibers (in the lateral rectus muscle of the eye) to 120-160 (in the triceps surae muscle) - All muscles, except for facial muscles, are surrounded by fascia. By the nature of the basic tasks performed. movements and according to the effect on the joint, M-flexors, or flexors, and extensors, or extensors, are distinguished; adductors - adductors and abductors - abductors; rotating - rotators (instep supports rotate the limb outward, pronators rotate the limb inward); lifting - levators, lowering - depressors; compressing - sphincters, or constrictors, dilating - dilators; tensors - tensors and straightening - erectors. There are also facial, chewing and respiratory muscles. Most definitions of functions refer to the work of muscles of the extremities free from support. Sometimes they are introduced into the name. M. All M. are multifunctional and their action cannot be reduced to one function. Thus, for most limbs, their work at the moment of support and repulsion is important. Systematic intensive work of muscles (training) increases their mass, strength and performance; excessive work leads to fatigue, and inactivity leads to atrophy.

.(Source: “Biological Encyclopedic Dictionary.” Editor-in-chief M. S. Gilyarov; Editorial Board: A. A. Babaev, G. G. Vinberg, G. A. Zavarzin and others - 2nd ed., corrected . - M.: Sov. Encyclopedia, 1986.)

muscles

(muscles), organs of the body of animals and humans, consisting of muscle tissue, which has the property of contracting under the influence of nerve impulses. They are divided into smooth, striated and cardiac muscles. Skeletal muscles are formed by striated muscles. The ends of the muscles turn into tendons, which are attached to the bones. There are long, short, broad and circular muscles. Skeletal muscles move one, two, or more joints. Their contraction ensures movement, maintaining body balance, and maintaining posture. Due to the contraction and relaxation of striated muscles, such important functions for the body as chewing, swallowing, voice formation, and movement of the eyeballs are also performed. Muscle contraction occurs under control cerebral cortex brain.
The muscular membranes of the internal hollow organs form smooth muscles, their function is to maintain tone and promote contents (food, blood, lymph, etc.). Smooth muscle contraction is involuntary; excessive - causes spasm, which leads to pain, difficulty swallowing, attacks of suffocation (bronchospasm), headaches (migraine), stomach and intestinal colic, etc.
The heart muscle has increased endurance and automatic contractions (see. Heart).

.(Source: “Biology. Modern illustrated encyclopedia.” Chief editor A. P. Gorkin; M.: Rosman, 2006.)

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"Muscular system"

Introduction

Muscles (musculi) are the active part of the human locomotor system. Bones, ligaments, and fascia form its passive part.

All skeletal muscles of our body: the muscles of the head, torso and limbs, consist of striated muscle tissue. The contraction of such muscles occurs voluntarily.

The contractile part of the muscle, formed by muscle fibers, passes into the tendon at both ends. With the help of tendons, muscles are attached to the bones of the skeleton. In some cases (facial facial muscles), the tendons are woven into the skin. Tendons are built from shaped dense fibrous connective tissue and are very strong. For example, the calcaneal (Achilles) tendon, which belongs to the triceps surae muscle, can withstand a load of 400 kg, and the quadriceps femoris tendon can withstand more than half a ton (600 kg). The broad muscles of the trunk have flat tendon stretches - aponeuroses.

Muscles and muscle groups are surrounded by connective tissue membranes - fascia. Fascia also covers entire areas of the body and limbs and is named after these areas (fascia of the chest, shoulder, forearm, thigh, etc.). Fascial sheaths consist of unformed dense fibrous connective tissue, so they are very strong and perfectly resist mechanical stretching during muscle contraction. The great Russian surgeon and anatomist N.I. Pirogov called the fascia the “soft skeleton of the body.”

The skeletal muscles of an adult make up 40% of his total body weight. In newborns and children, muscles account for no more than 20-25% of body weight, and in old age there is a gradual decrease in muscle mass to 25-30% of body weight. There are about 600 skeletal muscles in the human body.

Muscle shape. The simplest form is the fusiform muscle. It is distinguished by a thickened middle part - the abdomen and two ends, of which the upper one is usually the beginning (the fixed point of the muscle), and the lower one is the attachment (the moving point of the muscle). As a result of contraction, the muscle shortens and its moving point approaches the fixed point.

On the torso, it is customary to take the beginning of the muscle as the part that is closer to the spine. On the limbs, the beginning of the muscle is considered to be the part closest to the body.

There are long, wide and short muscles. Long muscles are located mainly on the limbs, where there is a large range of movements. There are especially many short muscles among the deep muscles of the back. The broad muscles are located in the torso area: on the chest, abdomen and back. Along with simple muscles, there are complex ones: biceps, three- and four-headed, serratus, etc. Due to the peculiarities of the location of muscle bundles relative to the tendon part, one-, two- and multipennate muscles are distinguished.

Throwing over a joint, and sometimes through two or more joints, the muscles produce movements in them. For example, the brachialis muscle extends in front of the elbow joint and, when contracted, causes flexion of the forearm. Thus, this muscle belongs to the flexors. The triceps brachii muscle, located behind and opposite in action (antagonist), straightens the arm. It belongs to the extensors. The muscles that move the limbs away from the body are called abductors (for example, the deltoid muscle, which abducts the arm to the side). The antagonists of the abductor muscles are the muscles that press the arm to the body - the adductors. There are also muscles for rotating one or another part of the body (head, shoulder, forearm) - rotators. Muscles never contract alone, they always act in groups.

Muscles that perform the same movement are called synergists.

The action of each muscle can only occur with the simultaneous relaxation of the antagonist muscle. This coordination is called muscle coordination. Complex movements, such as walking, involve many muscle groups. Coordination of contraction and relaxation of the muscles of both legs and torso is necessary. In this case, contraction and relaxation of muscle groups occur in a certain order and with the required force, thereby achieving smooth movements. It is not surprising, therefore, that learning to walk is a very slow and lengthy process.

The central nervous system plays the main role in coordinating movements. In some diseases, when nervous control is lost, the uniformity and smoothness of movements disappear, they become sharp and jerky.

I. Muscles of the trunk

1. Muscles and fascia of the back

The back muscles are divided into superficial and deep.

Superficial muscles. The trapezius muscle is located in the upper back. It starts from the occipital bone, nuchal ligament and spinous processes of all thoracic vertebrae. Attached to the acromial end of the clavicle, acromion and to the spine of the scapula. Top part the muscles raise the scapula, the lower one lowers it, the middle part brings the scapula closer to the spine. When the muscle contracts as a whole, the scapula is brought to the midline; when the scapula is fixed, the head is extended.

The latissimus dorsi muscle has a wide origin: from the spinous processes of the six lower thoracic and all lumbar vertebrae, from the thoracolumbar fascia and the iliac crest. Covers the inferolateral part of the back and, rising upward, attaches to the crest of the lesser tubercle of the humerus. The muscle pulls the shoulder and arm back while simultaneously rotating it inward.

The rhomboid muscles (major and minor) lie under the trapezius. They start from the spinous processes of the two lower cervical and four upper thoracic vertebrae and are attached to the vertebral edge of the scapula. The muscles lift the scapula, bringing it closer to the midline. The simultaneous contraction of the right and left rhomboid muscles brings the shoulder blades closer together.

The levator scapulae muscle lies above the rhomboids, in the back of the neck, originating from the transverse processes of the four upper cervical vertebrae and attaching to the upper corner of the scapula. Raises the shoulder blade. The superior posterior serratus muscle is located under the rhomboids, starts from the spinous processes of the two lower cervical and two upper thoracic vertebrae, and is directed obliquely downward and outward; attaches to the upper ribs (II-V).

The lower serratus posterior muscle is located under the latissimus dorsi muscle, starts from the spinous processes of the two lower thoracic and two upper lumbar vertebrae, and is directed obliquely upward; attaches to the four lower ribs. The superior serratus posterior muscle raises the ribs, the inferior muscle lowers them. There is an expansion of the intercostal spaces and an increase in the volume of the chest (participation in the act of inhalation).

Deep muscles. The deep back muscles form two tracts - lateral and medial, located on both sides of the spine itself along its entire length from the occipital bone to the sacrum. The lateral tract consists of the more superficial long muscles that form the erector spinae muscle. The muscles of the medial tract (transverse spinous) lie deeper than the others; they are groups of short muscle bundles that spread across the vertebrae (superficial - through 5-6 vertebrae, middle - through 3-4 and deep - through one vertebra). In the back of the neck, on top of both tracts lies the splenius capitis and neck muscle.

Fascia of the back. The superficial fascia covers the trapezius and latissimus dorsi muscles. In addition to it, there is the thoracolumbar fascia, which separates the superficial muscles of the back from the deep ones. The superficial layer of the thoracolumbar fascia fuses from below with the aponeurosis of the latissimus dorsi muscle. Together with the deep layer of this fascia, it forms the sheath for the erector spinae muscle.

2. Muscles and fascia of the chest

The chest muscles are divided into chest muscles related to the shoulder girdle and upper limb (major and minor pectoral muscles, subclavian and serratus anterior muscles), and the intrinsic muscles of the chest (external and internal intercostal muscles).

The pectoralis major muscle lies superficially and is triangular. It starts from the outer part of the clavicle, sternum and from the cartilage of the II-VII ribs. Attaches to the crest of the greater tubercle of the humerus. The muscle brings the arm to the body, rotating it inward. The clavicular part of the muscle lifts the arm forward. When the upper limb is fixed, it raises the ribs, participating in the act of inhalation.

The pectoralis minor muscle is located deeper than the major muscle, begins with teeth from the II-V ribs and is attached to the coracoid process of the scapula. Pulls the shoulder blade forward and slightly downward. With a fixed shoulder blade, it raises the ribs, making it easier to inhale.

The subclavian muscle is very small in size, located between the first rib and the collarbone. Pulls the collarbone down and medially.

The serratus anterior muscle occupies lateral surface chest. It begins with teeth from the nine upper ribs and is attached to the lower angle and medial edge of the scapula. Pulls the scapula anteriorly, while simultaneously turning its lower angle outward. This ensures that the arm is abducted above the horizontal level. Together with the rhomboid muscle, it presses the scapula to the body.

All of the listed muscles, when fixing the shoulder and upper limb, can participate in the act of inhalation, which explains the forced posture of patients who have difficulty exhaling (for example, patients bronchial asthma). They usually sit holding tightly to the headboard of a bed or chair. In this position, contraction of the chest muscles enhances exhalation and makes breathing easier.

The external and internal intercostal muscles fill the intercostal spaces. The first raise the ribs (inhale), the second lower them (exhale).

Fascia of the chest. The pectoral and intrathoracic fascia are distinguished. The pectoral fascia has two layers - superficial and deep. The superficial layer covers the outside of the pectoralis major and serratus anterior muscles. The deep layer is called the clavipectoral fascia; it forms fascial sheaths for the pectoralis minor and subclavian muscles. The inside of the chest is lined by the intrathoracic fascia, which extends to the diaphragm.

The diaphragm, the abdominal obstruction, is a thin flat muscle curved in the form of a dome with its convexity upward. The muscle bundles of the diaphragm begin from the sternum, ribs and lumbar vertebrae (along the entire circumference of the lower opening of the chest). According to their origin in the diaphragm, the sternum, costal and lumbar parts are distinguished. The muscle bundles, heading towards the middle of the diaphragm, pass into tendon stretching and form the tendon center. The lumbar part is the strongest and consists of two legs - right and left. The medial parts of the crura limit two large openings through which the esophagus and aorta pass. In the tendon center there is an opening for the inferior vena cava. The diaphragm is the main breathing muscle. When it contracts, it flattens and lowers, while the volume of the chest increases, and inhalation occurs. When the diaphragm relaxes, it rises again in the form of a dome, the lungs collapse and exhalation occurs.

3. Muscles and fascia of the abdomen

The abdominal muscles are represented by the external and internal obliques, transverse and rectus abdominis, as well as the quadratus lumborum muscle.

The external oblique muscle of the abdomen runs in a wide layer from the outside to the inside and from top to bottom. It begins with teeth from the eight lower ribs. Its posterior bundles are attached to the iliac crest. Anteriorly and downward, the muscle passes into a wide flat tendon - aponeurosis. In front, it takes part in the formation of the anterior wall of the rectus sheath and the white line of the abdomen. The lower edge of the aponeurosis is tucked in, forming the inguinal (Pupart's) ligament. It extends between the anterior superior iliac spine and the pubic tubercle.

The internal oblique muscle of the abdomen is located under the external oblique muscle. Its fibers are directed fan-shaped from bottom to top. The muscle originates from the thoracolumbar fascia, the iliac crest and the inguinal ligament. The posterior bundles are attached to the three lower ribs, and the anterior ones pass into the aponeurosis.

The transverse abdominis muscle is located under the previous two. It starts from the inner surface of the six lower ribs, the thoracolumbar fascia, the iliac crest and the inguinal ligament. Its muscle bundles are directed transversely and anteriorly pass into the aponeurosis.

The rectus abdominis muscle lies outward from the midline and is formed by muscle bundles running longitudinally from top to bottom. It starts from the xiphoid process of the sternum and the cartilages of the 5th and 6th ribs, and attaches to the pubic bone. Along its length it is interrupted by transverse bridges (3-4). The rectus muscle is enclosed in a strong sheath formed by the aponeuroses of the external and internal oblique muscles and the transverse abdominis muscle.

The quadratus lumborum muscle starts from the iliac crest and attaches to the XII rib and the transverse processes of the lumbar vertebrae (I to IV). Takes part in the formation of the posterior abdominal wall.

The rectus abdominis muscles are involved in bending the torso forward (with bilateral contraction). The oblique muscles of the abdomen ensure that the spine tilts to the sides and rotates it together with the chest to the right and left. The abdominal muscles not only participate in the movements of the torso and chest. No less important is their participation in the formation of the anterior and lateral walls of the abdominal cavity. By contracting, they increase intra-abdominal pressure, forming the so-called abdominal press. The abdominal muscles help keep the insides in their normal position. They facilitate bowel movements (defecation), urination, and in women, expulsion of the fetus during childbirth. In addition, due to their attachment to the ribs, the abdominal muscles are involved in breathing.

Fascia of the abdomen. On the outside, the abdominal wall is covered with the abdominal fascia, which is a continuation of the external fascia of the chest. The inside of the abdominal wall is lined with peritoneum (serous membrane) and transverse fascia, which covers the muscle of the same name on the abdominal side.

The white line of the abdomen (lineaalbaabdominis) is a dense light strip of tendons that stretches along the midline of the anterior abdominal wall from the xiphoid process of the sternum to the pubic symphysis. It is formed as a result of the interweaving of fibers of the aponeuroses of both oblique and transverse abdominal muscles of the right and left sides.

The spaces between the fibers of the linea alba may become wider than normal (pregnancy, postoperative period, a disease associated with long stays in bed). They are “weak spots” of the anterior abdominal wall, through which the insides can protrude under the skin, forming hernias (hernias of the white line).

Approximately in the middle of the white line of the abdomen is the navel (umbilicus) - a hole bordered by the umbilical ring and filled with scar tissue and fat. In the embryonic period, the umbilical cord passes through the umbilical ring. At certain conditions the umbilical ring can also become the site of formation umbilical hernias.

The inguinal canal (canalisinguinalis) is located above the inguinal ligament, behind the aponeurosis of the external oblique muscle of the abdomen and looks like a slit through which the spermatic cord passes in men, and the round ligament of the uterus in women. The length of the canal is about 5 cm. It is directed obliquely from top to bottom, from back to front and from outside to inside. Its anterior opening, or superficial (subcutaneous) inguinal ring, is limited by the divergence of the fibers of the inguinal ligament in the area of ​​its attachment to the pubic bone. The posterior, or internal, opening - the deep inguinal ring - is located on back surface abdominal wall, 2 cm above the middle of the inguinal ligament. It is limited by thickening of the intra-abdominal transverse fascia. The anterior wall of the inguinal canal is the aponeurosis of the external oblique abdominal muscle, the lower wall is the groove formed by the bend of the inguinal ligament, the upper wall is the lower free edges of the internal oblique and transverse abdominal muscles, and the posterior wall is the transverse fascia and peritoneum.

II. Muscles and fascia of the head

All head muscles are divided into two groups: 1) facial muscles and 2) masticatory muscles.

Facial muscles (facial muscles) are thin muscle bundles devoid of fascia. They differ from other muscles of the human body in that, starting from the bones of the skull, they are woven into the skin. Their contraction causes displacement of the skin, the formation of folds and wrinkles. This determines facial expressions. The manifestation of complex sensations (emotions): joy, shame, contempt, grief, pain, etc. is determined by numerous combinations of contractions of facial muscles, subject to impulses coming to them from the cerebral cortex along the facial nerve.

Located in groups around the natural openings of the face (eye sockets, mouth, ears, nostrils), facial muscles are involved in closing or expanding these openings. They also provide mobility of the cheeks, lips, and nostrils.

Below is a description of only the most important facial muscles.

The supracranial muscle consists of an extensive supracranial aponeurosis (tendinous helmet). It fuses firmly with the skin and loosely with the periosteum of the skull. Parts of the occipitofrontal muscle are woven into it: in front - the frontal belly, in the back - the occipital belly. Contraction of the occipital abdomen tightens the tendon helmet and the skin of the scalp. When the frontal abdomen contracts, the eyebrows rise and the skin of the forehead gathers into transverse folds, which is why it is called the surprise muscle.

The corrugator muscle lies under the frontalis muscle, originating from the nasal part of the frontal bone and woven into the skin just above the middle of the eyebrow. With bilateral contraction, it brings the eyebrows together, forming vertical folds between them. It is called the muscle of pain and suffering.

The orbicularis oculi muscle consists of circular muscle bundles that surround the eye socket and are woven into the skin of the eyelids. When contracting, the palpebral fissure closes.

The orbicularis oris muscle lies in the form of circular muscle bundles under the skin of the lips and around them. When contracting, it closes its mouth.

Depressor anguli oris muscle triangular shape, begins with a wide base on the lower jaw, and the apex is woven into the skin of the corner of the mouth. Straightens the nasolabial fold, pulls the corner of the mouth down, giving the face an expression of sadness and dissatisfaction.

The levator anguli oris muscle is a quadratus muscle, originating from the upper jaw and attached to the skin of the angle of the mouth and upper lip. Pulls the corner of the mouth upward, raises the upper lip.

The buccal muscle forms the lateral wall of the oral cavity. Starting from the back of the jaws, it goes in a transverse direction and is woven into the skin of the cheeks and lips. When contracting, it presses the cheek to the teeth, facilitating the movement of the bolus of food, and participates in the act of sucking.

On top of it there is an accumulation of fatty tissue, which determines the convex contour of the cheeks (better expressed in children and women).

The group of facial muscles also includes other muscles, for example, the zygomatic major and minor muscles, the laughter muscles, the “proud muscles,” the muscles that raise and lower the lips, the mental muscle, etc.

The masticatory muscles are represented by four pairs of strong muscles, two of which are superficial (masseter proper and temporal muscles), two are deep (lateral and medial pterygoid muscles). What the chewing muscles have in common is that, starting on the bones of the skull, they are attached to various parts of the lower jaw and activate the temporomandibular joint.

The masticatory muscle starts from the zygomatic arch and is attached to the outer surface of the angle of the lower jaw. Raises the lower jaw, pressing the molars of both jaws against each other. The dense fascia covering it passes onto the adjacent parotid salivary gland and is therefore called the parotid-masticatory fascia.

The temporal muscle starts in a fan-shaped manner from the parietal and temporal bones and performs the entire temporal fossa; attaches to the coronoid process of the mandible. The muscle is covered with a strong tendinous shiny temporal fascia. Raises the lower jaw. The posteriormost fibers of the temporalis muscle pull the lower jaw back.

The lateral pterygoid muscle is triangular and lies in the infratemporal fossa. It starts from the pterygoid process of the sphenoid bone and attaches to the condylar process of the mandible. With bilateral muscle contraction, the lower jaw moves forward. Unilateral contraction moves the lower jaw to the opposite side.

The medial pterygoid muscle starts from the fossa of the pterygoid process and is attached to the roughness of the same name on the inner surface of the angle of the mandible. Together with the masticatory muscle, it forms a physiological muscle loop, which ensures the tightest pressing of the lower jaw to the upper jaw. During the act of chewing, the movements of the lower jaw in humans are characterized by great diversity, which is not found in other representatives of mammals.

This diversity stems from the structural features of the temporomandibular joint and the position of the masticatory muscles. Thus, in predators only closing and opening of the jaws (up and down) is possible, in ruminants only lateral movements (right - left), and in rodents sliding movements of the jaws (forward - backward). In humans, all these movements are combined. Their combination helps to carry out the main function - grinding and chewing food. In this case, the lower jaw, together with the teeth, makes an almost complete circle. Therefore, the human chewing mechanism is universal, and not specialized, like in animals.

III. Muscles and fascia of the neck

The neck muscles are divided into superficial and deep. IN separate group The muscles attached to the hyoid bone are distinguished - the suprahyoid and subhyoid muscles.

The superficial muscles of the neck include the subcutaneous neck muscle and the sternocleidomastoid muscle.

The subcutaneous muscle (platysma) is a thin muscle plate located under the skin. Starts from the fascia of the chest below the collarbone, covers the lateral and partially anterior surfaces of the neck; attaches to the lower part of the face. Pulls down the corner of the mouth and tightens the skin of the neck.

The sternocleidomastoid muscle is the strongest and largest of all the neck muscles. It starts with two legs from the clavicle and from the sternum and is attached to the mastoid process of the temporal bone. With unilateral contraction, it produces a tilt of the neck in the same direction with a simultaneous rotation of the head in the opposite direction. With bilateral contraction, it supports the head in an upright position, and with maximum contraction, it throws it back.

In the group of muscles attached to the hyoid bone, a distinction is made between the muscles located above this bone (above the hyoid bone) and the muscles lying below it (under the hyoid bone). There are four suprahyoid muscles. The digastric muscle has an anterior belly, starting from the lower jaw and passing into the intermediate tendon, secured by a fibrous loop at the hyoid bone. The posterior belly begins from the tendon, which is attached to the notch of the mastoid process of the temporal bone.

The stylohyoid muscle runs from the styloid process of the temporal bone to the hyoid bone. The mylohyoid muscle stretches from the jaw arch to the hyoid bone, forming the floor of the mouth, its diaphragm. The geniohyoid muscle runs from the mental spine of the mandible to the hyoid bone. All of these muscles lift the hyoid bone upward, and with it the larynx, participating in swallowing and articulate speech. When the hyoid bone is fixed, three of them (with the exception of the stylohyoid muscle) lower the lower jaw.

There are also four sublingual muscles. The sternohyoid muscle starts from the sternum and attaches to the hyoid bone, pulling it down. The scapulohyoid muscle goes from the scapula to the hyoid bone, has two bellies (upper and lower), connected by an intermediate tendon, and lowers the hyoid bone. The sternothyroid muscle runs from the sternum to the outer surface of the thyroid cartilage, lowers the thyroid cartilage, and with it the larynx and hyoid bone.

The thyrohyoid muscle is a continuation of the previous one, stretches from the thyroid cartilage to the hyoid bone; with a fixed hyoid bone, it raises the larynx. The subhyoid muscles are of great importance in fixing the hyoid bone and are involved in lowering the lower jaw.

The deep muscles of the neck include the scalene muscles (anterior, middle and posterior) and the prevertebral muscles (longus capitis and cervical muscles, anterior and lateral rectus capitis muscles). The scalene muscles begin from the transverse processes of the cervical vertebrae and are attached to the ribs: the anterior and middle muscles to the first rib, and the posterior muscles to the second rib. In front of the anterior scalene muscle there is a prescalene space, between the anterior and middle muscles there is an interscalene space in which blood vessels and nerves pass.

Fascia of the neck. All fascia of the neck are united into one cervical fascia, in which there are three leaves, or three plates: superficial, pretracheal and prevertebral. The superficial plate is located under the platysma and forms the sheath for the sternocleidomastoid and trapezius muscles. The pretracheal plate is stretched between both omohyoid muscles, covers the salivary glands and forms sheaths for the supra- and subhyoid muscles, as well as for other structures of the neck located in front of the trachea. The prevertebral plate covers the prevertebral and scalene muscles, forming sheaths for them.

IV. Muscles and fascia of the upper limb

The muscles of the upper limb are divided into the muscles of the upper limb girdle and the muscles of the free upper limb.

1. Muscles of the upper limb girdle

The muscles of the upper limb girdle surround the shoulder joint, providing numerous movements in it. All six muscles of this group begin on the bones of the shoulder girdle and attach to the humerus.

The deltoid muscle, starting in three parts from the scapular spine, acromion and clavicle, is attached to the tuberosity of the humerus. The anterior (clavicular) part of the muscle flexes the shoulder, the middle part abducts the shoulder to a horizontal level, and the posterior part extends the shoulder.

The supraspinatus muscle starts from the same-named fossa of the scapula and, passing under the coracoacromial ligament, is attached to the greater tubercle of the humerus. Abducts the shoulder, being a synergist of the middle bundles of the deltoid muscle.

The infraspinatus muscle starts from the fossa of the same name in the scapula and is attached to the greater tubercle of the humerus; rotates the shoulder outward.

The teres minor muscle starts from the outer edge of the scapula and attaches to the greater tubercle of the humerus; rotates the shoulder outward. The teres major muscle runs from the outer edge of the scapula to the crest of the lesser tubercle of the humerus. Pulls the shoulder downwards and backwards, while simultaneously rotating it medially.

The subscapularis muscle occupies the entire fossa of the same name and is attached to the lesser tubercle of the humerus. Rotates the shoulder medially, pulls the bag shoulder joint, preventing it from being pinched during movements.

2. Muscles of the free upper limb

The muscles of the free upper limb include the muscles of the shoulder, forearm and hand.

The shoulder muscles are divided into anterior muscle groups (flexors) and posterior muscle groups (extensors). The anterior group consists of three muscles. The biceps brachii muscle (biceps) begins with two heads: a long one - from the upper edge of the glenoid cavity of the scapula and a short one - from the coracoid process of the scapula; attached by a common tendon to the tuberosity of the radius. Some of the tendon fibers form a narrow aponeurosis that passes into the fascia of the forearm. The muscle flexes the shoulder and forearm at the elbow joint, turns the forearm outward, and supinates it. The coracobrachialis muscle comes from the coracoid process of the scapula along with the short head of the previous muscle, and is attached to the humerus below the crest of the lesser tubercle; flexes and adducts the shoulder. The brachialis muscle is located under the biceps brachii muscle, starts from the humerus, attaches to the tuberosity of the ulna; flexes the forearm at the elbow joint.

The posterior muscle group of the shoulder consists of the triceps brachii and the anconeus muscle. The triceps brachii muscle begins with three heads: long - from the lower edge of the glenoid cavity of the scapula, external and internal - from the corresponding surfaces of the humerus. The common tendon attaches to the olecranon process of the ulna. Extends the forearm. The anconeus muscle is small, triangular, originating from the outer condyle of the humerus and attaches to the ulna. Participates in extension of the forearm.

The muscles of the forearm are divided into anterior and posterior groups according to their position. The muscles of the anterior group mainly originate from the inner condyle of the humerus and are located in two layers - superficial and deep. By function they are divided into flexors of the hand and fingers and pronators. Most of the muscles of the posterior group begin from the outer condyle of the humerus. They also make up two layers - superficial and deep. By function they are divided into extensors of the hand and fingers and supinators.

The anterior muscle group of the forearm includes the following muscles. The superficial layer is formed by: pronator teres (attached to the upper third of the radius), flexor carpi radialis (attached to the base of the P metacarpal bone), palmaris longus (woven into the palmar aponeurosis), flexor digitorum superficialis (attached to the middle phalanges of the II-V fingers), flexor carpi ulnaris (attaches to the pisiform bone). The deep layer is formed by: flexor longus thumb brushes (goes to the nail phalanx of the thumb), deep flexor digitorum (attaches to the nail phalanges of the II-V fingers) and pronator quadratus (connects the lower parts of the radius and ulna bones). The posterior group includes the following muscles of the forearm. The superficial layer consists of: the brachioradialis muscle (goes from the outer edge of the lower third of the humerus to the styloid process of the radius, flexes the forearm and rotates the radius), long and short extensor carpi radialis (attached to the bases of the II and III metacarpal bones), extensor digitorum (attached to to the phalanges of the II-V fingers) and the extensor carpi ulnaris (attached to the base of the fifth metacarpal bone). The deep layer is formed by: the supinator of the forearm (attached to the radius, rotates the forearm outward), the abductor pollicis longus muscle (attached to the base of the first metacarpal bone), the short and long extensor pollicis (attached to the base of the first and second phalanges of the thumb, respectively) ), extensor of the index finger (attached to the nail phalanx along with the tendon of the common extensor digitorum).

The muscles of the anterior group flex the hand and fingers, rotate the forearm medially (pronate it), and also bend the forearm at the elbow joint along with the shoulder muscles. The muscles of the posterior group extend the hand and fingers, rotate the forearm outward (supinate it), and together with the muscles of the shoulder participate in the extension of the forearm.

The muscles of the hand are located only on its palmar surface. They are divided into three groups: the thumb eminence group, the palmar cavity muscle group, or middle group, and the little finger eminence group. The muscle group of the thumb consists of four short muscles: the flexor pollicis brevis; abductor pollicis brevis; the muscle that drives the thumb and the muscle that opposes the thumb. The eminence group of the little finger is formed by three short muscles: the abductor little finger muscle; the opponensis muscle and the flexor digiti brevis muscle. Middle group formed by four lumbrical muscles (flex the main phalanges) and interosseous muscles. The latter fill the intermetacarpal spaces and are divided into palmar and dorsal. There are three palmar interosseous muscles; they bring the fingers together, bringing them to the midline. The dorsal interosseous muscles, there are four of them, spread the fingers.

Thus, thanks to the presence of their own muscular system, the fingers of the hand, especially the thumb, acquire greater mobility and are capable of a variety of movements, which is extremely important when working. The hand reached perfection in the process of long evolution under the influence of labor activity. “The hand... is not only an organ of labor, she is also a product of it" .

The fascia of the shoulder girdle, shoulder, forearm and hand essentially merge into one another.

The fascia of the shoulder is a thin but dense layer covering the muscles of the shoulder. Two intermuscular septa extend deep from it, separating the anterior muscle group from the posterior one.

The fascia of the forearm covers the muscles of the forearm and forms intermuscular septa. At the top it is more dense due to the tendon fibers woven into it superficial muscles. At the border with the hand, the fascia thickens and forms the dorsal ligament - the extensor retinaculum. This ligament fuses with the periosteum of the bones of the forearm, forming six osteofibrous canals in which the extensor tendons pass to the hand, surrounded by synovial sheaths. The synovial fluid found in these sheaths facilitates the gliding of tendons during movement. On the palmar surface, a smaller thickening of the fascia of the forearm forms the superficial transverse metacarpal ligament, and the fascia itself passes into the dense palmar aponeurosis, which is a tendinous stretch of the palmaris longus muscle. Under the aponeurosis there is a strong ligament - the flexor retinaculum, which closes the carpal tunnel. In the latter lie two synovial sheaths surrounding the flexor tendons. On both sides of the aponeurosis, the fascia of the hand thins and covers the muscles of the hand, forming sheaths for the muscles of all three groups. On the back of the hand, the fascia is less pronounced and covers the dorsal interosseous muscles.

On the fingers, the aponeurotic plates fuse with the periosteum of the phalanges and form osteo-fibrous canals of the fingers on the palmar side, in which the flexor tendons of the fingers pass, surrounded by synovial sheaths. Fingers II-IV have isolated synovial sheaths extending to the wrist area. In this case, the synovial sheath of the fifth finger communicates with the common synovial sheath of the flexor tendons of the fingers. This is why, when taking blood for analysis, you should never inject your little finger: if an infection occurs, it can spread to the entire palm. For the same reason, suppuration in the area of ​​the little finger is especially dangerous.

When the arm is abducted, the axillary (under the pterygoid) fossa is clearly visible, and the ulnar fossa is located on the border between the shoulder and forearm. Knowledge of these formations is important for practice.

Under the skin of the axillary fossa is the axillary cavity, bounded by the anterior (pectoralis major and minor), posterior (latissimus dorsi, teres major and subscapularis), medial (serratus anterior) and lateral (coracobrachialis and short head of the biceps brachii muscle) ) walls. The cavity is filled with fatty tissue, in which numerous lymph nodes lie, vessels and nerves pass through. On the posterior wall of the axillary cavity there are two openings - three-sided and four-sided, through which vessels and nerves pass.

Cubital fossa located in the elbow bend, it is limited medially by the pronator teres, laterally by the brachioradialis muscle, and its bottom is formed by the brachialis muscle. Under the skin of this fossa there are superficial veins, most often used for intravenous infusions of drugs and blood transfusions. Arteries and nerves run deeper.

V. Muscles and fascia lower limb

The muscles of the lower limb are divided into the muscles of the pelvis and the muscles of the free lower limb.

1. Pelvic muscles

The pelvic muscles, which act on the hip joint, originate from the pelvic bones and insert on the femur.

The iliopsoas muscle consists of two separate muscles - the psoas major (starts from the lumbar vertebrae) and the iliacus (starts from the fossa of the same name) pelvic bone). The iliopsoas muscle passes under the inguinal ligament and exits onto the anterior surface of the thigh through the muscle lacuna, attaching to the lesser trochanter of the femur; flexes the hip while simultaneously rotating it outward. With a fixed limb, the spine bends in the lumbar region. The piriformis muscle begins in the pelvic cavity from the anterior surface of the sacrum, exits the pelvic cavity through the greater sciatic foramen, dividing it into two slits - above the piriformis and below the piriformis. Attaches to the greater trochanter of the femur. Rotates the hip outward.

The obturator internus muscle originates from the inner surface of the pelvis in the region of the obturator foramen and from the obturator membrane. It exits the pelvic cavity through the lesser sciatic foramen and attaches to the fossa of the greater trochanter. Rotates the hip outward.

The gluteus maximus muscle starts from the outer surface of the ilium, from the sacrum and coccyx, from the thoracolumbar fascia, and is attached to the tuberosity of the same name as the muscle on the femur. Rotates the hip outward while simultaneously extending it. When standing, it prevents the body from tilting forward and provides the so-called military posture. Medium and small gluteal muscles lie one under the other. They start from the outer surface of the ilium and attach to the greater trochanter; abduct the thigh. The obturator externus muscle originates from the outer surface of the pelvis in the region of the obturator foramen and from the obturator membrane. Attached to the greater trochanter, it rotates the femur outward. The quadratus femoris muscle runs from the ischial tuberosity to the greater trochanter, externally rotating the thigh. The tensor fascia lata extends from the anterior superior iliac spine and is woven into the thickened part of the fascia lata; strains the fascia.

2. Muscles of the free lower limb

There are muscles of the thigh, leg and foot. The thigh muscles are divided into three groups: anterior, posterior and medial. The anterior group includes two muscles: the quadriceps muscle and the sartorius muscle. The quadriceps femoris muscle consists of four heads, occupying the entire anterolateral surface of the thigh. The straight head (rectus femoris muscle) starts from the anterior inferior iliac spine, and the other three muscles: the lateral, medial and vastus intermedius muscles - from the anterior surface of the femur. The common powerful tendon covers the patella and passes into the patellar ligament, which is attached to the tuberosity tibia. Extends the lower leg at the knee joint. The rectus muscle, spreading over the hip joint, bends it. The sartorius muscle stretches obliquely from top to bottom and medially from the anterior superior iliac spine to the tibial tuberosity. Flexes the lower leg, helps flex the hip.

The posterior group consists of three muscles: semitendinosus, semimembranosus and biceps. The semitendinosus and semimembranosus muscles are located medially, starting from the ischial tuberosity and attaching to the tibia. Bend the shin at the knee joint, with the knee bent, rotate the shin inward; participate in extension of the hip joint. The biceps femoris muscle with its long head starts from the ischial tuberosity, and its short head starts from the outer lip of the roughness of the femur. Located on the back of the thigh, at the outer edge. Attaches to the head of the fibula. The function is similar to that of the previous muscles; When the knee is bent, it rotates the lower leg outward.

The medial group of thigh muscles includes five muscles: pectineus, gracilis and adductors (large, long and short). They all start from the pubic and ischium bones and are attached to the femur (the exception is the gracilis muscle, which is attached to the tibia). The femur is adducted with a slight outward rotation. The thin muscle flexes the lower leg at the knee joint, turning it inward.

The lower leg muscles form three groups: anterior, posterior and lateral. All of them are attached to the foot. The anterior group is represented by three muscles: tibialis anterior, extensor digitorum longus and extensor pollicis longus. The tibialis anterior muscle attaches to the base of the first metatarsal bone and to the medial cuneiform bone, extends the foot (dorsiflexion) and raises its medial edge (supination). Two other muscles, attaching to the phalanges of the fingers, produce dorsiflexion of the foot and extension of the fingers. The posterior group consists of four muscles: triceps surae, tibialis posterior, flexor digitorum longus and flexor hallucis longus. The triceps surae muscle is located superficially, it is formed by three heads, of which two (superficial) are calf muscle, and one (deep) is the soleus muscle. Both muscles end in the calcaneal (Achilles) tendon, which attaches to the calcaneal tubercle. The triceps surae muscle produces plantar flexion at the ankle joint.

The tendons lying deeper than the tibialis posterior muscle, flexor digitorum longus and flexor hallucis longus, going around the medial malleolus of the tibia, pass to the foot, where the tibialis posterior muscle attaches to the tarsal bones and the bases of the II-IV metatarsal bones, and the flexor digitorum to the phalanges of these bones. All three of these muscles produce plantar flexion of the foot and toes.

The lateral group consists and £ two muscles - the long and short peroneus. When moving to the foot, their tendons bend around the lateral malleolus of the fibula. Both muscles, in addition to participating in plantar flexion of the foot, produce pronation of the foot (lowering its medial edge and raising its lateral edge). The peroneus longus muscle is also involved in strengthening the transverse arch of the foot, forming a physiological loop together with the tibialis anterior muscle.

The dorsal and plantar muscles are distinguished on the foot. There is only one dorsal muscle. This is the short extensor of the digitorum. Starting on the superolateral surface of the tarsal bones, it is divided into tendons going to the fingers. Extends the toes.

The plantar muscles are divided into three groups: 1) the muscles of the big toe, 2) the muscles of the little toe and 3) the middle group of muscles lying in the recess of the sole. There are three muscles of the first group: the abductor muscle, the adductor muscle and the short flexor of the big toe. The second group also contains three muscles: the abductor of the little toe, the short flexor of the little toe and the abductor of the little toe. The middle group is formed by the flexor digitorum brevis, the quadratus plantae muscle, the four lumbrical muscles (all of the listed muscles in this group are involved in flexing the fingers), as well as the interosseous muscles (the three plantar interosseous muscles bring the fingers together, and the four dorsal interosseous muscles spread them apart).

Fascia. Internal muscles The pelvis is covered with the iliac fascia, which is part of the common intra-abdominal fascia. Moving to the thigh, the fascia iliacus continues into the fascia lata of the thigh. The fascia lata is the densest fascia of the human body. It covers all the muscles of the thigh and gives rise to three intermuscular septa, which, attached to the periosteum of the femur, form strong fascial sheaths for muscle groups. The fascia lata becomes especially thick on the outer surface of the thigh, where it forms the iliotibial tract in the form of a wide strip along the entire length of the thigh. On the contrary, in the anterosuperior region of the thigh (under the inguinal ligament) the lata fascia is thinned, here it is pierced by a significant number of vessels and nerves, which is why it is called a perforated plate, the crescent-shaped edge of which limits the subcutaneous gap.

The fascia of the leg, being a continuation of the fascia lata of the thigh, covers the muscles of the leg, separates muscle groups, forming vaginas for them. In the area of ​​the ankle joint and above it there are a number of thickenings of the fascia of the leg, which serve as retainers for the muscle tendons. There are superior and inferior retinaculum of the extensor tendons, retinaculum of the flexor tendons and peroneal tendons. Under the retinaculum ligaments, the muscle tendons are surrounded by synovial sheaths. In front of the ankle joint there are three synovial sheaths for the extensor tendons, behind the medial malleolus there are also three synovial sheaths for the flexor tendons, and behind the lateral malleolus there are first two and then one common synovial sheath for the peroneus brevis and longus muscles.

The fascia of the dorsum of the foot is thin and transparent, and on the sole it is significantly compacted and forms a strong plantar aponeurosis.

For practical reasons, the femoral triangle is considered on the anteromedial surface of the thigh, within which the most important blood vessels and nerves are located - the femoral arteries, vein and nerve. The boundaries of the triangle are: the upper - inguinal ligament, the outer - the sartorius muscle, the inner - the long adductor muscle of the thigh.

It is equally important to know about the femoral canal and popliteal fossa.

The femoral canal does not normally exist; it occurs only in the case of femoral hernias.

The space under the inguinal ligament is divided into two slits - lacunae - by a process of the deep layer of the femoral fascia. One of them is located lateral, through which the iliopsoas muscle exits the pelvic cavity, which is why it is called the muscle lacuna. Blood vessels pass through the medial lacuna - the femoral arteries and vein, which is why it is called the vascular lacuna. It is through the internal angle of the vascular lacuna that when hernias form, the internal organs protrude from the pelvic cavity or from the abdominal cavity under the lata fascia of the thigh. In these cases, a small femoral canal (2 cm long) arises between the superficial and deep layers of the fascia lata in front and behind; the femoral vein serves as the lateral wall of this canal. The internal angle of the vascular lacuna becomes the internal opening of the canal. Its boundaries are on top - the inguinal ligament, laterally - the femoral vein, medially - a special ligament that rounds the corner of the lacuna, and behind - the pubic bone with the ligament covering it. The external opening of the femoral canal will be a subcutaneous ring, covered by a perforated plate of the fascia lata of the thigh. It will turn out to be the “weak spot” through which the hernial sac, after passing through the canal, will emerge under the skin of the thigh.

The popliteal fossa has the shape of a diamond and is covered by fascia. Under the fascia there are lymph nodes, popliteal arteries and veins located in the fatty tissue, as well as nerves that pass into the ankle-popliteal canal. The popliteal fossa is bounded above and outside by the biceps femoris muscle, and above and inside by the semimembranosus muscle; from below it is limited by the medial and lateral heads of the gastrocnemius muscle.

VI. Physiology

Muscle tissue has three physiological properties: excitability - the ability to respond to stimulation with excitement, conductivity - the ability to conduct excitation and contractility - the ability to contract. When a muscle contracts, it shortens or develops tension.

Skeletal, striated (striated) muscles consist of individual multinucleated fibers with transverse striations. Along each muscle fiber there are an average of 2,500 myofibrils, consisting of two types of filaments called myofilaments (protofibrils). Thick filaments are made of myosin protein molecules, and thin filaments are made of actin. Actin filaments are attached to the Z strip, their ends extend into the spaces between the myosin filaments. The transverse striation of muscles is explained by different light refraction of actin (I) and myosin (A) disks. Dark myosin disks are birefringent.

When a muscle contracts, the myofilaments do not shorten. Actin filaments move between the myosin filaments, as if sliding along them, disk I is shortened, and A remains unchanged. This idea of ​​the mechanism of muscle contraction is called the gear theory. Causes a “slip” action potential, which activates the muscle fiber calcium pumps and the Ca2+ concentration in the sarcoplasm increases. Calcium triggers the mechanism of “sliding” of myofilaments, i.e. muscle contraction. As soon as the contraction ends, the calcium pump lowers the Ca + concentration and the myofibrils relax. The source of energy required for muscle contraction is the breakdown of adenosine triphosphate (ATP). It is called a universal cellular fuel.

Motor units. In the body, skeletal muscles are excited by impulses coming to them along the motor nerves from the motor neurons of the central nervous system. The axon, approaching the muscle, branches into many branches ending in terminal motor plaques on the muscle fibers. Each motor neuron innervates from several tens to several thousand muscle fibers. A motor neuron and the group of muscle fibers it innervates is called a motor unit. The motor unit works as a single unit, with all its muscle fibers contracting simultaneously. The more subtle, precise movements a muscle can make, the smaller the motor unit. Consequently, motor units are very large in the leg muscles and small in the arm muscles, especially in the muscles that control the movements of the fingers.

Method of graphic recording of muscle contractions. In an experiment, muscle contraction can be caused either by irritating it electric shock(direct irritation), or irritating the nerve innervating it (indirect irritation). To record and analyze muscle contraction, the muscle is strengthened in a special device - a myograph. It consists of a clamp in which one end of the muscle is fixed, and a lever to which the second end is attached using a hook. It is more convenient to use an isolated frog calf muscle.

For irritation, electric current from a stimulator or induction coil is usually used. The muscle responds to a single irritation with a single contraction, while it pulls the lever behind it. At the end of the lever there is a scribe filled with ink. If it touches the paper stretched on the moving drum of the kymograph, then a muscle contraction curve is recorded. Types of muscle contractions. If a muscle, when contracting, can shorten and lift a load, then such a contraction is called isotonic. With this type of contraction, the tone, or tension of the muscle, does not change, but its length does. If both ends of the muscle are fixed motionless and irritated, tension will arise in it, but the length will remain unchanged. This contraction is called isometric.

A single muscle contraction consists of three phases: a latent period of excitation, a period of shortening and a period of relaxation.

The latent period of excitation, or latent period, is understood as the time from the moment the stimulus is applied to the beginning of the response to it. In the frog muscle it is 0.01 s. At this time, an action potential is registered in the muscle, but there is no contraction yet. The ascending part of the curve is called the shortening period, it lasts 0.05 s. The downward leg of the curve, corresponding to muscle relaxation, also lasts 0.05 s. Thus, the duration of a single contraction of the frog muscle, together with the latent period, is 0.11 s. A single contraction of the muscles of humans and warm-blooded animals in general proceeds faster and the latent period is shorter.

In a muscle, a wave of excitation precedes a wave of contraction. These are different physiological processes, but they spread throughout the muscle at the same speed - about 10 m/s.

The strength of muscle contraction depends on the strength of irritation. To stimulation of threshold strength, i.e., to the weakest stimulus capable of causing excitation, the muscle will respond by contracting the minimum force. If the force of stimulation is gradually increased, then the force of contraction will also gradually increase until it reaches a certain maximum, at which a further increase in the force of stimulation will no longer increase the force of contraction.

The dependence of the force of contraction on the force of stimulation is explained by the fact that the muscle consists of fibers of varying excitability. Motor units with the greatest excitability respond to weak stimuli. As the strength of stimulation increases, more and more new motor units are excited until the maximum stimulus brings all of them into an active state.

Individual muscle fibers contract according to the “all or nothing” law, i.e. they respond to threshold stimulation with a contraction of maximum force, and if the stimulation is below the threshold, they do not respond at all. An entire muscle, consisting of many motor units, increases contraction with increasing strength of stimulation.

Tetanus. If a muscle is irritated by a series of single electric shocks, i.e., rhythmic stimulation is applied, then a long-term shortening of the muscle occurs, which is called tetanus. The size and shape of tetanus depend on the strength and frequency of stimulation. When exposed to irritations of low frequency, when each subsequent irritation falls into the phase of muscle relaxation, serrated tetanus is observed. If the frequency of irritation is high, when each subsequent irritation occurs during muscle shortening, smooth tetanus develops, a long-lasting maximum non-oscillating muscle shortening.

The frequency of stimulation at which serrated and smooth tetanus occurs varies for different muscles and different muscle fibers. It depends on the duration of the contraction period: the shorter it is, the greater the frequency must be for smooth tetanus to occur.

Functional differences in motor units. There are two types of motor units: fast and slow, consisting of fast and slow muscle fibers, respectively. Some muscles, such as the muscles of the eyeball, consist predominantly of fast fibers with a contraction duration of 10-30 ms. In other muscles, slow fibers predominate (for example, soleus) with a contraction period of 100 ms. Most muscles are mixed.

Slow motor units develop a small force of contraction, but can operate for a long time without fatigue. Fast motor units fatigue quickly but produce greater contractile force.

Muscle tone. Human muscles are never completely relaxed; they are always in a state of some tension, called muscle tone. At the same time, slow motor units contract with a low frequency and maintain a certain position of the body in space - a posture necessary for the implementation of physical short-term movements. Muscle tone causes great difficulties for surgeons. After a hip fracture, it is necessary to ensure that the leg is stretched so that the bones grow together end to end. Without traction, under the influence of muscle tone, the bones will heal incorrectly, which will lead to shortening of the leg.

Muscle strength. When a muscle contracts, it is capable of lifting a large load, the mass of which is many times greater than the mass of the muscle itself.

The strength of a muscle is measured by the maximum load it can lift. The strength of a muscle depends on the number of muscle fibers that make up a given muscle and the thickness of these fibers; it is directly proportional to the physiological cross-section, i.e., the sum of the cross-sections of all the fibers included in it. In muscles with longitudinally located fibers, the physiological cross-section coincides with the anatomical one - the area of ​​the cross-section of the muscle drawn perpendicular to its length. In the pennate and oblique muscles, the physiological cross-section is larger and, accordingly, the muscle strength is greater.

The strength of a muscle per 1 cm2 of its physiological cross-section is called absolute muscle strength. For human muscles it is 5-10 kg. The frog's muscles are much weaker, their absolute strength is only 2-3 kg.

During physical training, muscle fibers thicken and their energy resources increase. In this regard, muscle strength increases.

Muscle work. If a muscle lifts a load during its contraction, then it produces external work, the value of which is determined by the product of the mass of the load and the lifting height and is expressed in kilogram meters (kgm). For example, a person lifts a barbell weighing 100 kg to a height of 2 m, while the work done by him is equal to 200 kgm.

The muscle produces the most work at some average loads. This phenomenon is called the law of average load.

It turned out that this law is true not only in relation to an individual muscle, but also to the whole organism. A person does the most work lifting or carrying weights if the load is neither too heavy nor too light. Great importance has a rhythm of work: both too fast and too slow, monotonous work quickly leads to fatigue, and in the end the amount of work completed is small. Correct dosage load and rhythm of work is the basis for the rationalization of heavy physical labor.

Undefined (smooth) muscles. In their physiological properties they differ from striated muscles. The excitability of smooth muscles is much lower. To excite them, a stronger and longer-lasting stimulus is required. They excite very slowly. For example, in humans, in the muscular lining of the small intestine it spreads at a speed of 1 cm/s. In organs that have long, non-striated muscle cells, for example in the ureters of a rabbit, excitation spreads somewhat faster - 18 cm/s. Unstriated muscles contract very slowly. The contraction period of such muscles is 60-80 s, while the shortening period is 20 s, and relaxation is 60 s, i.e. 3 times longer than the shortening period. In addition, unstriated muscles, unlike striated ones, are characterized by automatism, that is, they are able to contract under the influence of excitation impulses generated in them.

Non-striated muscles have great extensibility. In response to slow stretching, the muscle lengthens, but its tension does not increase. Due to this, when the internal organ is filled, the pressure in its cavity does not increase, as happens, for example, when a rubber chamber is stretched, in which the pressure increases as it inflates. So, the pressure in the stomach will be 7 cm of water. Art. when it contains both 200 ml and 500 ml of liquid. The ability to maintain the length given by stretching without changing the stress is called plastic tone. He is important physiological feature unstriated muscles.

Non-striated muscles are characterized by slow movements and prolonged tonic contractions. An example of slow movements is the peristaltic waves of the digestive tract. Tonic contraction of the walls of blood vessels maintains a constant certain level of blood pressure. Constant state tonic contraction characteristic of the sphincters of hollow organs: stomach, gall and bladder, rectum. The tonic form of contractions requires little energy and, unlike tetanus, is not accompanied by fatigue.

The main irritant for a non-striated muscle is rapid and strong stretching. This property of smooth muscles to respond to stretching by contracting plays an important role in the activity of the digestive tract, ureters, hollow organs, and sphincters. Non-striated muscle tissue is highly sensitive to certain chemical irritants: acetylcholine, adrenaline, norepinephrine, serotonin, etc.

Smooth muscles are innervated by sympathetic and parasympathetic nerves, which have a regulatory effect on it, and not a trigger one, as on skeletal muscles.

Transfer of excitation from nerve to muscle. The motor nerve fiber, entering the muscle, loses its myelin sheath and branches. The terminal branches form nerve endings in the form of rings or horseshoes, which are immersed in depressions on the surface of the muscle fibers. Nerve endings are covered by a membrane called presynaptic. Their axoplasm contains a large number (about 3 million) of vesicles containing acetylcholine.

The portion of the muscle membrane with which the nerve ending is in contact is called the postsynaptic membrane. The latter forms numerous folds, due to which its surface increases. The postsynaptic membrane contains cholinergic receptors and the enzyme cholinesterase, which can destroy acetylcholine. Between the membranes of the nerve and muscle fibers there is a gap of 20-50 nm in size - the synaptic gap. The structural formation that ensures the transmission of excitation from nerve to muscle is called myoneural synapse. It consists of a presynaptic membrane, a synaptic cleft and a postsynaptic membrane. Nerve impulses arriving along the motor fibers produce depolarization of the membrane of the nerve ending, which causes the destruction of the membrane of the vesicles and the entry of acetylcholine into the synaptic cleft. Acetylcholine molecules diffuse to the postsynaptic membrane of the muscle fiber and bind here to the cholinergic receptors of the membrane. This leads to an increase in the permeability of the postsynaptic membrane for Na+ and K+. Positively charged ions rush through the membrane into the muscle fiber and an electronegative postsynaptic potential appears on the membrane. The resulting potential difference between the postsynaptic membrane and the muscle fiber membrane surrounding it creates a local current that excites the muscle membrane: an action potential arises in it, propagating along the muscle fiber. The released acetylcholine is destroyed by the enzyme cholinesterase, and the postsynaptic membrane again acquires its original charge - it becomes polarized.

It has long been known that the transmission of excitation in the neuromuscular synapse stops when an animal is poisoned with the plant poison curare. The Indians used arrows poisoned with curare when hunting. An animal struck by such an arrow lost the ability to move and died after paralysis of the respiratory muscles from respiratory arrest.

Currently, the mechanism of action of this substance has been studied and many others have been discovered that have the same effect: ostubocurarine, flaxidol, listenone, etc. All of them are firmly attached to cholinergic receptors, block access to acetylcholine and stop the transmission of excitation from nerve to muscle. They have found wide application in surgical practice.

Muscles provide:

human movement,

The work of individual parts of his body and many internal organs (heart, lungs, stomach, etc.).

Muscles are made up of muscle tissue.

Distinguish between muscles Smooth AndSkeletal :

1.Smooth muscles form the walls of blood vessels, respiratory tract, stomach, and intestines.

Smooth muscles contract slowly and can remain in this state for a long time.

They take part in the work of internal organs and regardless of our will controlled by the autonomic nervous system and humorally.

Smooth muscles provide motility of internal organs.

2.Skeletal muscles- This striated muscles head, torso and limbs.

Skeletal muscles contract quickly.

Their work ensures voluntary movements.

Skeletal muscles provide human movement in space.

Structure of Skeletal Muscle:

Consists of striated muscle fibers, collected in bunches;

Outside, each of the muscle bundles and the entire muscle as a whole are covered with connective tissue shells;

Muscles are attached to bones either directly or through tendons. One end of the muscle head, is attached to one bone, the second, tail, through a joint or joints - to another bone so that when it contracts, the bones move;

Each muscle has blood vessels and nerves.

A muscle can only contract when a signal from the central nervous system comes to it. If the nerve is damaged, the muscle will not contract.

For normal muscle function, nutrients and oxygen supplied by the blood are necessary, since the energy of muscle contraction is bound with biological oxidation of organic substances muscle fiber. The breakdown products formed during muscle work are carried away by the blood. This is why deterioration in blood supply disrupts muscle activity and often causes pain.

Feel.

Structure of the Double and TricephalicShoulder Muscles:

1 - heads of the biceps muscle;

2 - belly of the biceps muscle;

3 - tail of the biceps muscle;

4 - tail of the triceps muscle;

5 - belly of the triceps muscle;

6 - heads of the triceps muscle

The main property of muscle tissue is contractility. The work of muscles is based on this property. IN in an excited state, the muscle shortens and thickens-is shrinking, then, at rest, it relaxes and returns to its previous size.

When contracting, muscles perform work to move the body, limbs or hold a load.

Major Skeletal Muscle Groups

I.MusclesHeads - This 1.Chewable and 2. Facial muscles:

1.Masticatory muscles They move the lower jaw, ensure chewing of food and participate in the formation of speech sounds.

Touch your temples and try chewing movements. You will feel how the temporal muscles move under your hand; they belong to the masticatory muscles. Other masticatory muscles can be easily detected if you move your hand a few centimeters forward from the angle of the lower jaw (towards the chin).

2. Facial muscles change facial expression. With the help of these muscles, a person’s face can express feelings of joy and grief, kindness and anger, friendliness and dissatisfaction. The muscles of the mouth are involved in the formation of speech sounds.

The facial muscles are attached to the bones at one end and to the skin at the other.

Of the facial muscles, it is easy to find the orbicularis of the eyes and the orbicularis of the mouth. The latter, together with other muscles, not only changes facial expression, but is also necessary for a person to be able to speak and eat.

Muscles of the Head:

1 - lowering the corner of the mouth;

2 - circular mouth;

3 - circular eyes;

4 - temporal;

5 - sternocleidomastoid;

Line UMK V.I. Sivoglazova. Biology (5-9)

Line UMK V.I. Sivoglazova. Biology (10-11)

Biology

Human muscles

Raise a hand. Now make a fist. Take a step. Isn't it easy? A person performs habitual actions almost without thinking. About 700 muscles (from 639 to 850, according to in various ways counting) allow a person to conquer Everest, descend to depths of the sea, draw, build houses, sing and watch the clouds.

But skeletal muscles are not all the muscles of the human body. Thanks to the work of the smooth muscles of the internal organs, a peristaltic wave travels through the intestines, contracting, ensuring life, the most important muscle of the human body - the heart.

Muscle Definition

Muscle(lat. muscle) - an organ of the human and animal body formed by muscle tissue. Muscle tissue has complex structure: myocyte cells and the membrane covering them - endomysium form separate muscle bundles, which, when connected together, form the muscle itself, dressed for protection in a cloak of connective tissue or fascia.

Muscles of the human body can be divided into:

• skeletal,
• smooth,
• cardiac.

As the name suggests, the skeletal type of muscle is attached to the bones of the skeleton. Second name - striated ( due to transverse striations), which is visible under microscopy. This group includes the muscles of the head, limbs and torso. Their movements are voluntary, i.e. a person can control them. This human muscle group provides movement in space; it is these that can be developed or “pumped up” with the help of training.

Smooth muscle is part of the internal organs - the intestines, Bladder, walls of blood vessels, heart. Thanks to its contraction, blood pressure increases during stress or the food bolus moves through the gastrointestinal tract.

Cardiac - characteristic only of the heart, ensures continuous blood circulation in the body.

It is interesting to know that the first muscle contraction occurs already in the fourth week of the embryo’s life - this is the first heartbeat. From this moment until the death of a person, the heart does not stop for a minute. The only cause of cardiac arrest during life is heart surgery. open heart, but then the AIK (heart-lung machine) works for this important organ.

The navigator textbook is the main module of the innovative educational and methodological set “Navigator”. A simple and convenient navigation system connects the text of the textbook with the information field of the accompanying multimedia manual (disc): all terms and concepts found in the textbook are divided into main and additional material using a color indication. The methodological apparatus of the textbook consists of questions for self-testing, questions of an increased level of complexity (including those establishing interdisciplinary connections), as well as a system of tasks using other components of the educational complex - both printed and electronic, which contributes to the effective assimilation of educational material.

The structure of human muscles

The unit of structure of muscle tissue is the muscle fiber. Even a single muscle fiber can contract, indicating that a muscle fiber is not only a single cell, but also a functioning physiological unit capable of performing a specific action.

An individual muscle cell is covered sarcolemma– a strong elastic membrane provided by proteins collagen And elastin. The elasticity of the sarcolemma allows the muscle fiber to stretch, and some people show miracles of flexibility - doing the splits and performing other tricks.

In the sarcolemma, like twigs in a broom, threads are tightly packed myofibrils, composed of individual sarcomeres. Thick filaments of myosin and thin filaments of actin form a multinucleated cell, and the diameter of the muscle fiber is not a strictly fixed value and can vary over a fairly wide range from 10 to 100 microns. Actin, which is part of the myocyte, is component cytoskeletal structure and has the ability to contract. Actin consists of 375 amino acid residues, which makes up about 15% of the myocyte. The remaining 65% of muscle protein is myosin. Two polypeptide chains of 2000 amino acids form the myosin molecule. When actin and myosin interact, a protein complex is formed - actomyosin.

Description of human muscles difficult, and for a visual representation you can refer to the textbook, where

Name of human muscles

When anatomists in the Middle Ages began to dig up corpses on dark nights to study the structure of the human body, the question arose about the names of the muscles. After all, it was necessary to explain to the onlookers who had gathered in the anatomical theater what a scientist this moment cuts with a sharply sharpened knife.

Scientists decided to name them either by the bones to which they are attached (for example, the sternocleidomastoid muscle), or by appearance(for example, the latissimus dorsi or trapezius), or by the function they perform (extensor digitorum longus). Some muscles have historical names. For example, tailoring so named because it drove the sewing machine pedal. By the way, this muscle is the longest in the human body.

Muscle classification

There is no single classification, and muscles are classified according to various criteria.

By location:

• heads; in turn are divided into:
• – facial expressions
• – chewable
• torso
• belly
• limbs

By fiber direction:

• straight
• transverse
• circular
• oblique
• unipinnate
• bipinnate
• multipinnate
• semitendinosus
• semimembranous

Muscles are attached to bones, extending over joints to produce movement.
Depending on the number of joints through which the muscle is thrown:

• single-joint
• two-joint
• multi-joint

By type of movement performed:

• flexion-extension
• abduction, adduction
• supination, pronation ( supination– outward rotation, pronation– inward rotation)
• compression, relaxation
• raising, lowering
• straightening

To ensure body movement and movement from place to place, muscles work harmoniously and in groups. Moreover, according to their work they are divided into:

• agonists - take on the main load when performing a certain action (for example, biceps when bending the arm at the elbow)
• antagonists - work in different directions (the triceps muscle, which is involved in extending the limb at the elbow joint, will be an antagonist to the triceps); agonists and antagonists, depending on the action we want to perform, can change places
• synergists - assistants in performing actions, or stabilizers

musculoskeletal system.

Smooth muscle is part of the walls of various hollow organs - the bladder, the walls of blood vessels and the heart, which contracts under the influence of the autonomic nervous system, i.e. does not depend on the desire and will of a person. Although they say that some yogis can slow down the heart rate to almost zero with the power of thought. But these are yogis, and an ordinary person cannot control the work of smooth muscles either by willpower or by the power of thought. However, it can indirectly influence through hormones.

Surely, you have all noticed that during an intense and long run, your heart begins to beat faster. And some, even well-prepared students, get sick before a difficult exam and constantly run to the toilet. All this is due to hormonal surges that affect the functioning of the body.

The main functions of skeletal muscles include:

• motor
• supporting or static - maintaining body position in space

Sometimes these two functions are combined into one stato-kinetic function.

The muscular system is also involved in respiration, digestion, urination and thermogenesis.
More details about the function of each group of skeletal muscles are written in the textbook edited by V.I. Sivoglazov.