Innervation of the skin: nerve endings, Merkel cells, Ruffini, Meissner, Pacinian corpuscles. Review of the innervation of the skin, muscles and organs by region Which nerves innervate the skin

Blood And lymphatic skin systems. The arteries that supply the skin form a wide-loop network under the hypodermis, which is called the fascial network. Small branches extend from this network, dividing and anastomosing among themselves, forming a subdermal arterial network. From the subdermal arterial network, branching and anastomosing vessels go up in straight and oblique directions and at the border between the papillae and the reticular layer of the dermis, a superficial vascular plexus is formed from them. From this plexus arterioles originate, forming terminal arteriolar arcades of a looped structure in the skin papilla. The density of papillary capillaries in the skin corresponds to the density of the papillae and varies in different areas of the body, varying between 16-66 capillaries per 1 mm of skin. Hair follicles, sweat and sebaceous glands are equipped with vessels extending horizontally from the deep choroid plexus. The venous system begins with postcapillary venules, forming four venous plexuses in the papillary layer and subcutaneous fatty tissue, repeating the course of the arterial vessels. A characteristic feature of intradermal vessels is a high degree of anastomosis between vessels of the same type and of different types. Glomus, or arteriovenous glomerular anastomoses, are often found in the skin - short connections of arterioles and venules without capillaries. They participate in the regulation of body temperature and maintain the level of interstitial tension, which is necessary for the functioning of capillaries, muscles and nerve endings.

The lymphatic vessels of the skin are represented by capillaries, forming two networks located above the superficial and deep vascular plexuses. Lymphatic networks anastomose with each other, have a valve system and, having passed through the subcutaneous fatty tissue, at the border with the aponeurosis and muscle fascia they form a wide-loop plexus - plexus lymphaticus cutaneus.

Innervation of the skin. The receptor function of the skin is of particular importance. The skin serves as a barrier between the external and internal environment and perceives all types of irritations. The skin is innervated by the central and autonomic nervous systems and represents a sensitive receptor field. In addition to the usual nerve endings in the form of tree-like branches, glomeruli that innervate the sebaceous and sweat glands, hair follicles and blood vessels, the skin has unique nervous apparatus in the form of so-called encapsulated bodies and nerve endings. The main nerve plexus of the skin is located in the deep sections of the subcutaneous fatty tissue. Rising from it to the surface, the nerve branches approach the appendages of the skin and form a superficial nerve plexus in the lower part of the papillary layer. Branches extend from it into the papillae and epidermis in the form of axial cylinders. In the epidermis they penetrate to the granular layer, lose their myelin sheath and end in a simple point or thickening. In addition to free nerve endings, the skin also contains special nerve formations that perceive various irritations. Encapsulated tactile corpuscles (Meissner's corpuscles) are involved in the implementation of the functions of touch. The feeling of cold is perceived with the help of Krause's flasks, the feeling of heat is perceived with the participation of Ruffini's corpuscles, the position of the body in space, the sensation of pressure is perceived by lamellar corpuscles (Vater-Pacini corpuscles). Sensations of pain, itching and burning are perceived by free nerve endings located in the epidermis. The tactile corpuscles are located in the papillae and consist of a thin connective tissue capsule containing special receptor cells. They are approached through the lower pole of the capsule by a non-myelinated nerve fiber in the form of a non-myelinated axial cylinder, ending with a thickening in the form of a meniscus adjacent to the receptor cells. The Krause end flasks are located under the papillae. Their elongated oval shape is directed with the upper pole towards the papillae. In the upper pole of the connective tissue capsule there is an unmyelinated nerve cylinder ending in a glomerulus. Ruffini corpuscles are located in the deep dermis and upper part of the subcutaneous fat. They are a connective tissue capsule in which the end of the nerve axial cylinder is divided into numerous branches. Lamellar bodies are located in the subcutaneous fatty tissue and have a capsular structure. The skin also contains many autonomic nerve fibers located on the surface of all blood vessels, including capillaries. They regulate the functional activity of the choroid plexus and thereby influence the physiological processes in the epidermis, dermis and subcutaneous fat.

Functions of the skin.

2-interaction between the body and the environment. environment.

Thermoregulating function skin is carried out both due to changes in blood circulation in the blood vessels and due to the evaporation of sweat from the surface of the skin. These processes are regulated by the sympathetic nervous system.

Secretory function skin is carried out by sebaceous and sweat glands. Their activity is regulated not only by the nervous system, but also by hormones of the endocrine glands.

The secretion of the sebaceous and sweat glands maintains the physiological state of the skin and has a bactericidal effect. The glands also secrete various toxic substances, i.e. they perform excretory function. Many fat- and water-soluble chemicals can be absorbed through the skin.

Exchange function The skin consists in its regulating effect on metabolism in the body and the synthesis of certain chemical compounds (melanin, keratin, vitamin D, etc.). The skin contains a large number of enzymes involved in protein, fat and carbohydrate metabolism.

The role of the skin in water and mineral metabolism is significant.

Receptor function The skin is carried out due to the rich innervation and the presence of various terminal nerve endings in it. There are three types of skin sensitivity: tactile, temperature and pain. Tactile sensations are perceived by Meissner's corpuscles and lamellar corpuscles of Vater-Pacini, tactile Merkel cells, as well as free nerve endings. To perceive the feeling of cold, Krause's corpuscles (flasks) are used, and Ruffini's corpuscles (flasks) of warmth. Pain sensations are perceived by free, non-encapsulated nerve endings that are found in the epidermis, dermis and around the hair follicles.

The skin of the face includes sweat and sebaceous glands, hair, muscle fibers, nerve endings, blood and lymphatic vessels. Its structure has its own characteristics, knowledge of which is especially important for surgeons. At the same time, it will be interesting for an ordinary person to get acquainted with these features. Facial injuries are possible in everyday life, and they are especially common in car collisions. After car accidents, it is often the face that suffers. Frightening bleeding occurs, which frightens both the patient himself and those close to him.

Nevertheless, it is precisely the structural features of the facial skin, its muscles, innervation and blood supply that allow us to hope for a successful outcome with timely professional surgical care. Next, we will look at methods of providing first aid before the arrival of doctors for facial injuries. A text you read accidentally, maybe even not remembered, will come to mind in a critical situation and will allow you to avoid mistakes in car accidents and other injuries.

Not too few people in our country, in addition to doctors, have primary medical training with first aid skills. These are pharmacists, nurses, orderlies, police officers and employees of the Ministry of Emergency Situations, medical instructors after military service, sorry if we forgot anyone. For acute injuries, there are the main principles of first surgical aid; they allow you to save life and avoid dangerous consequences for the victim. Don't let special medical terms scare you. Even a simple understanding of the basic features of the structure of the body and its physiology helps in difficult times. At the same time, awareness of the threat of complications during exacerbation of surgical dental diseases will help you make the right decision.

The outer layer of the skin forms a multinucleated squamous keratinizing epithelium, which fits tightly to the underlying layer in the skin itself. The latter consists of two not clearly demarcated layers - subepithelial papillary and reticular. The papillary layer consists of loose connective tissue; it contains blood vessels and nerve endings that cause skin sensitivity.

On the face, the papillae are low and even, so the skin on the face is thin and smooth. The scars on her are clearly visible. However, experienced surgeons achieve amazing aesthetic results by connecting the edges of the wound with intradermal sutures and masking the sutures in anatomical folds.

The papillary layer contains collagen, denser, frame fibers and elastic elastic and reticular fibers, as well as cellular elements, then it passes into a denser mesh layer, which is distinguished by a large number of collagen and elastic fibers and a relatively small number of cellular elements.

The presence of elastic and collagen fibers in the connective part of the facial skin determines the skin's ability to stretch during facial expressions and conversation, and a large number of elastic fibers in the reticular layer creates constant physiological tension of the skin, which decreases with age. These lines also define the areas of the face; incisions are made in relation to them and the edges of the wound are drawn together. It is because of the presence of elastic fibers that facial injuries look so frightening - the edges of the wound diverge to the sides. At the same time, after properly bringing the edges together and applying sutures, the face restores its appearance.

The reticular layer passes into mobile connective tissue, which differs from the skin in its significant thickness and loose arrangement of bundles of fibrous tissue, as well as the lesser development of subcutaneous fatty tissue (compared to other parts of the body).

Subcutaneous fatty tissue forms an elastic lining and is a plastic support layer that softens mechanical stress from the outside. In the area of ​​the superciliary arches and eyebrows, the subcutaneous layer is a direct continuation of the tissue of the aponeurosis of the skull, but is devoid of the characteristic cellular structure. When moving to the eyelids and nose, the subcutaneous fat layer takes on the character of delicate connective tissue.

This structure of the subcutaneous layer in some areas of the face contributes to the rapid spread of hemorrhages, swelling, and inflammatory processes along the length. An example of this is boxers during fights. Facial edema and hepatomas reach significant sizes, especially in those who neglect protective mouth guards.

Oral and maxillofacial surgeons and ordinary dentists know the ways of penetration of pus from the primary focus. Such conditions are formidable complications, life-threatening, and yet their root cause may be a complication of caries - an exacerbation of chronic periodontitis or sometimes a festering hematoma.

The buccal part of the face is rich in fatty tissue. The fatty body of the cheek runs along the anterior edge of the masseter muscle, isolated from the surrounding tissue by thin fascia. In the area of ​​the upper and lower lips, the subcutaneous fatty tissue is much less developed; these formations are mainly formed by the orbicularis oris muscle.

The facial skin ends with a large number of striated muscle fibers, which together make up the facial muscles. A feature of the facial muscles is that they are attached at one end to the inert skeleton of the face, and at the other end they are woven into the connective tissue structures of the skin itself, which determines the mobility of the skin under the action of the facial muscles.

In places of greatest accumulation of muscle fibers, elastic fibers are especially developed. In the areas where the elastic network connects with the underlying epithelial layer, depressions form on the skin. Their sequential arrangement leads to the formation of skin grooves and folds, which are the guide lines along which it is recommended to make incisions when cutting out and comparing skin flaps. The scar located along the folds, due to the constant contraction of the facial muscles, quickly stretches in length, becomes thinner and becomes less noticeable.

As a result of constant contraction of facial muscles, the elastic frame of the skin wears out, breaks in the elastic fibers form, characteristic facial wrinkles appear, and the contractility of the skin decreases. The contractility of the skin of the face is lower than the contractility of the skin of other parts of the body. This ability of the structure of the facial skin is of great importance in skin grafting. When it is necessary to decide which area of ​​the body’s skin is most suitable in its structure for the full replacement of soft tissue defects, the surgeon must take these directions into account.

Facial muscles determine the individual characteristics and expressiveness of the face, the emotions characteristic of a person, and also carry out the movement of the lips, eyelids, and nostrils.

Blood supply to the soft tissues of the face Arteries and veins of the head

Anatomy and topography of the temporal and facial regions

The passage of blood vessels in the soft tissues of the face has its own characteristics. It is carried out by a powerful highway - the system of the external carotid artery, as well as through the ophthalmic artery, some branches of the internal carotid artery, and then splits into the facial, superficial temporal and other arteries. An extensive network of blood vessels and powerful blood flow allow an always open face to withstand the harshest factors of the external environment. In case of injuries and damage to one vessel, the blood supply is duplicated through the flow of blood from another line. All arteries are paired.

The main arterial trunk of the anterior part of the face is arteria facialis facial artery.

It anastomoses (connects) with the frontal artery and on its way gives many branches to the surrounding tissues, the largest of which are the mental, superior and inferior labial arteries.

Scheme of cranial topography

The largest diameter of the arteries is at the attachment points of the facial muscles of the skin. Smaller arteries are distributed in the skin evenly over the entire surface. In places where the skin is most mobile, arteries and veins are more tortuous. In most cases, arteries and veins run parallel.

It is the presence of a large number of vascular anastomoses that makes it possible to widely use soft facial tissues when replacing defects. Taking into account the direction of the main arterial trunks as well as their combinations with venous lymphatic vessels makes it possible, for various defects of the soft tissues of the face, to use skin flaps taken in certain directions, without, if possible, interfering with their blood circulation.

The venous system is well developed in the soft tissues of the face. The veins of the face widely anastomose, connecting with each other, as well as with the veins of the orbit. The veins of the middle ear and nose connect with the veins of the base of the skull and the superior sagittal sinus, through the veins of the orbit with the dura mater. The veins of the face are located in two layers with the exception of the veins of the forehead. The venous network is expressed in the area of ​​the wings of the nose and lips. In the event of purulent inflammatory processes on the face, increased vascularization and anastomosis can act as an aggravating factor in the course of the disease. Breakthrough of infection into the vessels of the face or along these vessels leads to damage to the orbit and brain, which is practically a death sentence. This is why dentistry is such a developed field of medicine.. Complications of caries - periodontitis, periostitis, abscess and phlegmon sometimes lead to the immediate death of the patient. In critical situations, a hand with a phlegmonous lesion can be amputated, but the person will remain alive. But an infected cavernous sinus does not give us this opportunity.

Lymphatic system of the face Vessels of the lymphatic system

An extensive lymphatic network and a barrier of lymph nodes determines the lymph circulation of facial tissues and largely distinguishes the maxillofacial area from other areas. Almost every area of ​​the face has its own group of regional lymph nodes - powerful analytical laboratories and producers of local immunity factors. Also, each section of the mucous membrane of the nasopharynx and oral cavity has its own accumulation of lymphoid tissue.

The lymphatic system forms two networks in the facial skin - superficial and deep.

Connection between the superficial and deep veins and the meninges

The superficial lymphatic network is finely looped and located under the papillary layer of the skin itself. A deep looped network lies in the reticular layer of the corium.

Due to the characteristic attachment of the facial skin facial muscles and the absence of fascia on the face, the draining lymphatic vessels of the facial skin have their own characteristics.

Arising from a deep capillary network, they form a plexus in the superficial layers of subcutaneous fatty tissue. Larger draining lymphatic vessels are directed to regional lymph nodes located on top of the facial muscles, or to the deep layers of subcutaneous fat, passing under several facial muscles.

The main lymphatic collectors in the form of large lymphatic vessels, penetrating under the muscles or their fascia, as a rule, join along the main arterial and venous trunks and follow them to the regional lymph nodes, which are divided into three sections.

Innervation of soft tissues of the face Nerve trunks of the face

Innervation of the face is carried out by the facial nerve and

The facial nerve leaves the corresponding bone canal and enters the tissue of the parotid gland, splitting into numerous branches that form the nerve plexus plexus parotideus. Fan-shaped diverging branches of the facial nerve go to all facial muscles and ensure their contraction. There is some individual variability in the structure of the facial nerve, but in general there are two types of structure. But in any case, the main branches of the facial nerve are present.

1. Marginal branch of the mandible
2. Buccal branch
3. Zygomatic branch
4. Temporal branch

These branches are directed in a fan-like fashion from the tragus of the ear (where the nerve begins on the face) to the corner of the mouth, along the lower edge of the lower jaw, to the tip of the nose and to the outer corner of the eye.

Injuries to the branches of the facial nerve lead to paralysis of the facial muscles. To avoid damage to the branches of the facial nerve, deep incisions on the face are made only relative to the lines connecting the ear to the outer canthus, the tip of the nose, the corner of the mouth and parallel to the edge of the lower jaw, moving one and a half to two cm higher from it. Surgeons know these lines by heart; a non-specialist may have no use for this information. But you never know what kind of knowledge you will need in life. Let’s say that in addition to acute injuries, there are also chronic ones. The facial nerve, before it begins to innervate the face, passes through the temporomandibular joint and the parotid gland. In both regions, problems and inflammatory processes are possible, mainly related to teeth. As luck would have it, the facial nerve is mixed, responsible for both facial muscles and sensitivity in the oral cavity and areas of the face. Moreover, it also communicates with other nerves through nerve ganglia.

People perceive problems with teeth as something ordinary and everyday, as an annoying hindrance. But problems with facial expressions and taste disturbances cannot but worry, or rather, cause panic.

And this is where the problems begin. It is very, very difficult even for a qualified and experienced dentist or surgeon to identify the source of the problem. The innervation of the head is too complex, involving many nerves and plexuses.

But that's not even sad. With disturbances in sensitivity and facial expressions, people often turn to a neurologist. He prescribes treatment based on his knowledge and his pharmacological arsenal, most often these are severe, highly specialized drugs with psychotropic side effects. People have been undergoing treatment for years without success. Meanwhile, the root cause of the disease, bad teeth, may not be eliminated, and therefore treatment will be ineffective.

This problem does exist. For those interested, here is the background information.

"Emergency care in neurostomatology."

Anyone who can get hold of this publication about syndromes of damage to the cranial nerve systems, especially the autonomic sections, write to the site’s corporate email.

Deep facial area

The sensory innervation of the face is complex. Sensitive trunks and everyone take part in it three branches of the trigeminal nerve, as well as branches of the cervical plexus. The rich innervation and blood supply of the face makes it possible to duplicate the innervation and blood circulation of each part of the head multiple times, promotes tissue stability in case of injury, and accelerates the healing of injuries on the face. Even extensive head injuries heal well in most cases. At the same time, if the disease does occur, this creates certain difficulties in diagnosis and treatment. Over the past 20 years, the problem of innervation has again become relevant, which is associated with the massive use of implants for dental prosthetics. No matter how the examination is carried out before implantation surgery, but statistically, injuries or compression of nerve trunks occur when implants are installed, which suggests that anatomy as a science must continue to develop, identifying cases of anatomical variability and atypia.

When it comes to facial injuries, it’s amazing what situations happen in life. Wanting only the best, people sometimes make serious mistakes when providing first aid. At the same time, the correct decisions have long been described; you just need to know them and implement them. But more on that in our next article.

The skin is innervated by both branches of the cerebrospinal nerves and nerves of the autonomic system. The cerebrospinal nervous system includes numerous sensory nerves, forming a huge number of sensory nerve plexuses in the skin. The nerves of the autonomic nervous system innervate blood vessels, smooth myocytes and sweat glands in the skin.

The nerves in the subcutaneous tissue form the main nerve plexus of the skin, from which numerous trunks extend, giving rise to new plexuses located around the roots of the hair, sweat glands, fat lobules and in the papillary layer of the dermis. The dense nerve plexus of the papillary layer sends myelinated and unmyelinated nerve fibers into the connective tissue and into the epidermis, where they form a large number of sensory nerve endings. Nerve endings are distributed unevenly in the skin. They are especially numerous around the hair roots and in sensitive areas of the skin, such as the palms and soles, face, and genital area. These include free and non-free nerve endings: lamellar nerve corpuscles (Vater-Pacini corpuscles), terminal flasks, tactile corpuscles and tactile Merkel cells. It is believed that the feeling of pain is transmitted by free nerve endings located in the epidermis, where they presumably reach the granular layer, as well as by nerve endings lying in the papillary layer of the dermis.

It is likely that the free endings are also thermoreceptors. The sense of touch (touch) is perceived by the tactile corpuscles and Merkel cells, as well as by the nerve plexuses around the hair roots. Tactile corpuscles are located in the papillary layer of the dermis, tactile Merkel cells are located in the germinal layer of the epidermis.

The feeling of pressure is associated with the presence of lamellar nerve corpuscles of Vater-Pacini, lying deep in the skin. Mechanoreceptors also include terminal flasks, located, in particular, in the skin of the external genitalia.

Skin glands

Human skin contains sweat and sebaceous glands (the mammary glands are a type of sweat glands). The surface of the glandular epithelium is approximately 600 times greater than the surface of the epidermis itself. The skin glands provide thermoregulation (about 20% of the heat is given off by the body through the evaporation of sweat), protect the skin from damage (fatty lubricant protects the skin from drying out, as well as from maceration by water and humid air), and ensure the removal of metabolic products from the body (urea, uric acid , ammonia, etc.).

End of work -

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Postcapillaries (or postcapillary venules) are formed as a result of the fusion of several capillaries; in their structure they resemble the venous section of a capillary, but in the wall of these venules

Arteriolo-venular anastomoses
Arteriovenous anastomoses (ABA) are connections between vessels that carry arterial blood into veins, bypassing the capillary bed. They are found in almost all organs. Volume of blood flow in anastomoses in m

Endocardium
The inner lining of the heart, the endocardium, lines the inside of the heart chambers, papillary muscles, tendon filaments, and heart valves. The thickness of the endocardium varies in different areas.

Myocardium
The middle, muscular layer of the heart (myocardium) consists of striated muscle cells - cardiomyocytes. Cardiomyocytes are closely interconnected and form functional fibers, layers

Development
During the embryonic period, three paired excretory organs are formed sequentially: the anterior kidney (pronephros); primary kidney (mesonephros);

Structure
The kidney is covered with a connective tissue capsule and, in addition, in front - with a serous membrane. The substance of the kidney is divided into cortex and medulla. The cortex (cortex renis) forms

Filtration
Filtration (the main process of urine formation) occurs due to high blood pressure in the capillaries of the glomeruli (50-60 mmHg). Many plasma components enter the filtrate (i.e. primary urine)

Renal corpuscle
The renal corpuscle consists of two structural components - the glomerulus and the capsule. The diameter of the renal corpuscle is on average 200 microns. The vascular glomerulus (glomerulus) consists of 40-50 pe

Mesangium
In the vascular glomeruli of the renal corpuscles, in those places where the cytopodia of podocytes cannot penetrate between the capillaries (i.e., about 20% of the surface area), there is mesangium - a complex of cells (mesangium

Proximal convoluted tubule
In the proximal convoluted tubules, active (i.e., due to specially consumed energy) reabsorption of a significant part of water and ions, almost all glucose and all proteins occurs. This reabs

Nephron loop
The loop of Henle consists of a thin tubule and a straight distal tubule. In short and intermediate nephrons, the thin tubule has only a descending part, and in juxtamedullary nephrons it is also long.

Distal convoluted tubule
Two processes occur here, regulated by hormones and therefore called facultative: 1) active reabsorption of remaining electrolytes and 2) passive reabsorption of water.

Collecting ducts
The collecting ducts in the upper (cortical) part are lined with single-layer cuboidal epithelium, and in the lower (brain) part - with single-layer low columnar epithelium. In the epithelium there are light

Renin-angiotensin apparatus
It is also the juxtaglomerular apparatus (JGA), periglomerular. The JGA includes 3 components: the macula densa, the JG cells and the SE cells of Gurmagtig. 1. Dense spot (macula densa) - t

Prostaglandin apparatus
In its action on the kidneys, the prostaglandin apparatus is an antagonist of the renin-angiotensin-aldosterone apparatus. The kidneys can produce (from polyunsaturated fatty acids) prostaglandin hormones

Age changes
Age-related features of the kidney structure indicate that the human excretory system in the postembryonic period continues its development for a long time. Thus, the thickness of the cortical layer in novo

Urinary tract
The urinary tract includes the renal calyces (small and large), pelvis, ureters, bladder and urethra, which in men simultaneously performs the function of excreting the organ

Development
The development of the male and female gonads begins in the same way (the so-called indifferent stage) and is closely related to the development of the excretory system. There are three components of developing sex

Structure
Outside, most of the testis is covered with a serous membrane - the peritoneum, under which there is a dense connective tissue tunica albuginea (tunica albuginea). On the posterior edge of the testicles

Generative function. Spermatogenesis
The formation of male germ cells (spermatogenesis) occurs in the convoluted seminiferous tubules and includes 4 successive stages or phases: reproduction, growth, maturation and formation. Began

Vas deferens
The vas deferens constitute a system of tubules of the testicle and its appendages, through which sperm (sperm and fluid) move into the urethra. The outflow tracts begin straight

Seminal vesicles
The seminal vesicles develop as protrusions of the wall of the vas deferens in its distal (upper) part. These are paired glandular organs that produce a liquid mucous secretion, slightly alkaline

Prostate
Prostate gland [Greek. prostates, standing, located in front], or prostate, (or the male second heart) - a muscular-glandular organ covering part of the urethra (urethra

Penis
The penis is a copulatory organ. Its main mass is formed by three cavernous (cavernous) bodies, which, when filled with blood, become rigid and provide an erection. Outside

Ovaries
The ovaries perform two main functions: a generative function (formation of female germ cells) and an endocrine function (production of sex hormones). Development of female organs

Ovary of an adult woman
On the surface, the organ is surrounded by a tunica albuginea (tunica albuginea), formed by dense fibrous connective tissue covered with peritoneal mesothelium. The free surface of the mesothelium is equipped with micro

Generative function of the ovaries. Oogenesis
Oogenesis differs from spermatogenesis in a number of features and occurs in three stages: · reproduction; · growth; · maturation. The first stage is the period of ra

Endocrine functions of the ovaries
While the male gonads continuously produce the sex hormone (testosterone) throughout their active activity, the ovary is characterized by cyclic (alternate

The fallopian tubes
The fallopian tubes (oviducts, Fallopian tubes) are paired organs through which the egg passes from the ovaries to the uterus. Development. Fallopian tubes develop from the upper part of the paramesonephus

Features of blood supply and innervation
Vascularization. The uterine blood supply system is well developed. The arteries that carry blood to the myometrium and endometrium spirally twist in the circular layer of the myometrium, which contributes to their automatic

Sexual cycle
The ovarian-menstrual cycle is sequential changes in the function and structure of the organs of the female reproductive system, regularly repeating in the same order. In women and

Age-related changes in the organs of the female reproductive system
The morphofunctional state of the organs of the female reproductive system depends on age and activity of the neuroendocrine system. Uterus. In a newborn girl, the length of the uterus does not exceed

Hormonal regulation of the female reproductive system
As mentioned, follicles begin to grow in the ovaries of the embryo. The primary growth of follicles (the so-called “small growth”) in the ovaries of the embryo does not depend on pituitary hormones and leads to

External genitalia
The vestibule of the vagina is lined with stratified squamous epithelium. In the vestibule of the vagina, two glands of the vestibule open (Bartholin's glands). These glands are alveolar-tubular in shape.

Development

Structure

Structure
The epidermis is represented by multilayered squamous keratinizing epithelium, in which cell renewal and specific differentiation - keratinization - constantly occur. That

Papillary layer
The papillary layer of the dermis (stratum papillare) is located directly under the epidermis and consists of loose fibrous connective tissue that performs a trophic function for the epidermis

Mesh layer
The reticular layer of the dermis (stratum reticulare) provides strength to the skin. It is formed by dense, unformed connective tissue with powerful bundles of collagen fibers and an elastic network

Vascularization of the skin
Blood vessels form several plexuses in the skin, from which branches arise that feed its various parts. The choroid plexuses lie in the skin at different levels. There are deep

sweaty skin
Sweat glands (gll.sudoriferae) are found in almost all areas of the skin. Their number reaches more than 2.5 million. The skin of the forehead, face, palms and soles, and underarms is richest in sweat glands

Sebaceous glands
The sebaceous glands (gll. sebaceae) reach their greatest development during puberty. Unlike sweat glands, sebaceous glands are almost always associated with hair. Only where there is no hair, they

Development
The mammary glands are formed in the embryo at 6-7 weeks in the form of two epidermal seals (the so-called “milk lines”), stretching along the body. From these thickenings the so-called “milk” are formed.

Structure
In a sexually mature woman, each mammary gland consists of 15-20 individual glands, separated by layers of loose connective and adipose tissue. These glands are complex in their structure

Regulation of breast function
In ontogenesis, the rudiments of the mammary glands begin to develop intensively after the onset of puberty, when, as a result of a significant increase in the formation of estrogen, menstruation is established

Hair structure
Hair is an epithelial appendage of the skin. Hair has two parts: the shaft and the root. The hair shaft is located above the surface of the skin. The hair root is hidden in the thickness of the skin and reaches the subcutaneous

Hair change - hair follicle cycle
Hair follicles go through repeating cycles during their life. Each of them includes a period of death of old hair and periods of formation and growth of new hair, which ensures

Thyroid
This is the largest of the endocrine glands and belongs to the follicular type glands. It produces thyroid hormones, which regulate the activity (speed) of metabolic reactions

Parathyroid glands
The parathyroid glands (usually four) are located on the posterior surface of the thyroid gland and are separated from it by a capsule. Functional significance of the parathyroid

Adrenal glands
The adrenal glands are endocrine glands that consist of two parts - the cortex and medulla, which have different origins, structure and function.

The skin has a rich neuroreceptor apparatus. Nerve fibers are represented by branches of the cerebrospinal and autonomic nerves. Cerebrospinal nerve fibers belong to the central nervous system (CNS). They are responsible for various types of sensitivity. Vegetative fibers belong to the autonomic nervous system (sympathetic and parasympathetic) and regulate the functioning of glands, blood vessels and muscles of the skin.

Nerve fibers run parallel to the blood and lymphatic vessels and enter the hypodermis, where they form large plexuses. Thinner branches extend from the plexuses, branching and forming deep dermal plexuses. Small branches from them rise to the epidermis and form superficial plexuses located in the papillary layer of the dermis and in the epidermis.

Receptor endings divided by free And not free. Free ones have the form of naked axial cylinders (devoid of supporting glial cells) and end in the epidermis, hair follicles and glands. Responsible for pain and temperature sensitivity.

Non-free nerve endings are divided into unencapsulated And encapsulated, most often called corpuscles.

Non-encapsulated nerve endings include the terminal sections of neurons in the form of discs that form synapses with Merkel cells, performing the function of touch. Localized in the epidermis.

The encapsulated nerve endings are diverse and are different types of mechanoreceptors (slow and fast adapting receptors):

Meissner's corpuscles located inside the papillae of the dermis, there are many of them in the skin of the palmar-lateral surfaces of the fingers, lips, and genitals;

Krause flasks localized in the dermis, there are especially many of them in the places where the skin passes into the mucous membranes in the area of ​​the lips, eyelids, and external genitalia;

Localized in the lower dermis and upper hypodermis Ruffini bodies;

In the deep layers of the dermis and hypodermis, mainly in the area of ​​​​the palms, soles, nipples of the mammary glands, genitals, there are Vater-Pacini bodies;

Genital Dogel bodies found in the skin of the genital organs, providing increased sensitivity of these areas.

A) Sensitive units. Any nerve fiber, branching, gives rise to nerve endings of one type. The stem nerve fiber and its nerve endings, which perform the same physiological functions, represent a sensitive unit. Together with the original unipolar neuron, the sensory unit is similar to the motor unit described in a separate article on the site.

The area whose stimulation leads to excitation of the sensory unit is called the receptor field. The larger the size of the receptive field, the less acute the sensory sensitivity this area has: for example, in the upper part of the hand the receptive fields occupy an area of ​​2 cm 2, in the wrist area - 1 cm 2, on the fingertips - 5 mm 2.

Sensitive units are intertwined, making it possible for one area of ​​skin to simultaneously perceive different types of sensitivity.

Innervation of hairy skin.
(A) Three morphological types of sensory nerve endings in the skin covered with .
(B) Free nerve endings in the basal layer of the epidermis.
(B) Merkel cell complex with nerve terminal.
(D) Palisade and circular nerve endings on the surface of the outer root sheath of the hair.

b) Nerve endings:

1. Free nerve endings. As they approach the surface of the skin, many sensory nerve fibers lose their perineural and then myelin sheath (if present). Subsequently, the nerve fibers branch and form the subepidermal nerve plexus. The axon is freed from the sheaths formed by Schwann cells, which allows it, branching between the collagen bundles of the dermis, to form dermal nerve endings, and within the epidermis - epidermal nerve endings.

Functions. Some sensory units with free nerve endings are thermoreceptors that innervate “heat spots” or “cold spots” located on the surface of the skin. In addition, in the skin there are two main types of nociceptors (pain receptors), which also have free nerve endings: a-delta mechanonociceptors and polymodal C-nociceptors. A-delta mechanonociceptors are innervated by thin myelinated Aδ-type fibers and perceive significant mechanical deformation of the skin (occurring, for example, when pinched with tweezers). Polymodal C-nociceptors respond to pain stimuli of various types - mechanical deformation, strong heating or cooling (this is typical only for some receptors), exposure to chemical irritants. It is these receptors that are responsible for the implementation of the axon reflex.

2. Follicular nerve endings. The nerve endings of the hair follicle are represented by palisade nerve fibers formed by exposed terminals of myelinated nerve fibers located on the surface of the outer root sheath of the hair follicle below the level of the sebaceous glands, as well as circular nerve endings. Each follicular unit innervates several hair follicles and forms multiple decussations. Follicular units are quickly adapting: they are excited when the position of the hair changes, but when this position is maintained, no stimulation occurs. A person, when dressing, feels the pressure of clothing, but then, due to rapid adaptation, soon ceases to feel its touch. The innervation of hair in other mammals is more complex. The innervation of hair follicles is carried out by three types of mechanoreceptors, each of which transmits information to certain brain structures, which indicates the importance of the sensitive function they perform.

3. . The nerve terminal, expanding in the area of ​​the basal layer of epidermal ridges and grooves, forms a complex with an oval-shaped tactile body - the Merkel cell. Merkel cell complexes with nerve terminals are slow adapters. In response to prolonged pressure (such as holding a pen or wearing glasses), these complexes continuously generate nerve impulses. Merkel cell complexes with nerve terminals are particularly good at recognizing the edges of objects held in the hand.

4. Encapsulated nerve endings. The capsules of the free nerve endings described below consist of three layers: the outer layer is represented by connective tissue, the middle layer by perineural epithelium, and the inner layer by modified Schwann cells (teloglia). Encapsulated nerve endings are mechanoreceptors that convert mechanical action into a nerve impulse.

Meissner's corpuscles found in large quantities in the fingertips and located near the grooves of the epidermis. The corpuscles are oval-shaped cells, inside of which the axons are located in a zigzag pattern between the flattened teglial cells. Meissner's corpuscles are rapidly adapting corpuscles, together with slowly adapting Merkel cell complexes with nerve terminals, they provide accurate perception of textures (for example, the texture of clothing fabric or the surface of wood), as well as relief surfaces (for example, Braille). Such skin receptors are capable of perceiving changes in surface topography even to a height of 5 nm.

Taurus Ruffini present on both smooth, hairless skin and skin with hair. They perceive smooth sliding touches and are slow to adapt. The internal structure of the bodies is similar to the structure of the Golgi tendon organs: axons form branches in the central part of the bodies, represented by collagen fibers.

Pacinian corpuscles in size correspond to the size of a grain of rice. There are about 300 corpuscles in the hand area, which are mainly concentrated on the lateral areas of the fingers and palm. Pacinian corpuscles are located subcutaneously, close to the periosteum. Several layers of perineural epithelium inside the connective tissue capsule are oval and shaped like an onion in cross-section. In the central part of the Pacinian corpuscle, several teglial plates surround a single axon, which, upon entering the corpuscle, loses its myelin sheath. Pacinian corpuscles are rapidly adapting receptors of predominantly vibration sensitivity. These structures are especially susceptible to vibration of bone tissue: a large number of bodies are located in the periosteum of long tubular bones.

Pacinian corpuscles generate one or two nerve impulses upon compression and the same number upon cessation of exposure. In the skin of the palms, Pacinian corpuscles function according to a group principle: more than 120 corpuscles are activated simultaneously when a person picks up an object (for example, an orange) and when he releases it. In this regard, Pacinian corpuscles are considered “event detectors” during the manipulation of objects.

Innervation of smooth, hairless skin.
(A) There are two types of nerve endings located on the fingertips.
(B) The diagram of the structure of the skin area from image (A) shows four types of sensory nerve endings.
(B) Meissner's corpuscles.
(D) Ruffini corpuscles.
(D) Pacinian corpuscles.

Experts in the physiology of sensitivity identify the following types of receptors localized in the skin of the fingers.

Merkel cell complexes with nerve terminals- slowly adapting type I receptors (MAP I).

Meissner's corpuscles- rapidly adapting receptors type I (RAR I).

Taurus Ruffini- slowly adapting type II receptors (MAP II).

Pacinian corpuscles- rapidly adapting receptors type II (RAR II).

The perception of sensations of manipulation with a three-dimensional object outside the human visual field is mainly provided by muscle (directed mainly from muscle spindles) and articular (directed from joint capsules) afferent nerve fibers. Cutaneous, muscle and joint afferents independently transmit information to the contralateral somatosensory area of ​​the cerebral cortex. Three different types of information are integrated at the cellular level in the posterior part of the contralateral parietal lobe, which is responsible for tactile and visual spatial sensitivity. Tactile spatial sensitivity is called stereognosis. In clinical practice, to determine stereognosis, the patient is asked to identify what object he is holding in his hands (for example, a key), without looking at it. Skin sensations associated with peripheral neuropathies are described in a separate article on the website.

V) Neurogenic inflammation - axon reflex. When sensitive skin is irritated by a sharp object, the contact line almost instantly turns red, which is caused by the expansion of capillaries in response to skin damage. After a few minutes, the dilation of the arterioles leads to an increase in the zone of hyperemia, and the exudation of plasma from the lumens of the capillaries causes the formation of a pale edematous ridge. This phenomenon represents the skin's "triple reaction" to irritation. The formation of zones of hyperemia and edematous ridge is caused by the axon reflex of the sensory cutaneous nerves. The ongoing processes are described in accordance with the numbering in the figure below.

1. Polymodal nociceptors convert the action of a painful stimulus into nerve impulses.

2. Axons send nerve impulses to the central nervous system not only in the usual orthodromic direction, but also in the opposite antidromic direction from the bifurcation sites to the adjacent areas of the skin. The response of nociceptive nerve endings to antidromic stimulation is manifested in the release of peptide substances, among which substance P is represented in large quantities.

3. Substance P binds to receptors on the walls of arterioles and causes their expansion, which leads to hyperemia.

4. In addition, substance P binds to receptors on the surface of mast cells, which leads to the release of histamine from them. Histamine increases the permeability of capillaries, due to which local accumulation of tissue fluid occurs, causing the appearance of a pale edematous ridge.

G) Leprosy. The causative agent of leprosy is a mycobacterium that enters the human body through the smallest lesions of the skin and, spreading proximally along the perineurium of the cutaneous nerves, causes the death of Schwann cells. The loss of the myelin sheath in certain areas of large nerve fibers (“segmental demyelination”) leads to disruption of the conduction of nerve impulses. As a result of the inflammatory response to the introduction of the pathogen, compression of all axons occurs, which leads to Wallerian degeneration of the nerves and a significant proliferation of their connective tissue membranes. As a result, areas devoid of sensitivity form on the skin of the fingers of the upper and lower extremities, as well as on the nose and ears. Since the protective function of skin sensitivity is impaired, these areas become more susceptible to trauma, which leads to tissue damage. As the disease progresses, motor paralysis occurs due to damage to the trunks of mixed nerves located proximal to the points of origin of their cutaneous branches.

d) Summary. The nerves heading to the skin branch and form the dermal nerve plexus. The sensory nerve fibers of the dermal plexus branch and overlap each other. Each stem nerve fiber and its receptors form a sensory unit. The area innervated by the brainstem nerve fiber is called its receptive field.

Sensory units with free nerve endings include receptors for temperature sensitivity, as well as mechanical and temperature receptors for pain sensitivity. Hair follicle receptors are rapidly adapting tactile mechanoreceptors that are activated only by hair movement. Complexes of Merkel cells with nerve terminals provide the perception of the edge of objects; they are classified as slowly adapting.

The encapsulated nerve endings are mechanoreceptors. Meissner's corpuscles are located in the spaces between the ridges of the epidermis of smooth skin; they are classified as rapidly adapting. Ruffini corpuscles - skin stretch receptors - are located near the nails and hair follicles, they are classified as slow adapters. Pacinian corpuscles are subcutaneous rapidly adapting nerve endings that have vibration sensitivity and are “event detectors.” At the level of the posterior part of the parietal lobe of the cerebral cortex, coded information received from the skin, muscles and joints is combined, which contributes to tactile perception and stereognostic sensitivity.