Consists only of coarse guard hairs. Wool fibers and their properties. Life cycle of hair

Hair is characteristic only for representatives of the class of mammals, which in this regard are also called Trichozoa(hairy animals), or Pelifera(bearing hair). The oldest finds of hair-like structures are 200–210 Ma old. Already in the probable ancestors of mammals - theriodonts ( Theriodontia) at the end of the muzzle and along the entire upper lip there was a sensory field and, possibly, "protovibrissae" were present.

There are hypotheses according to which hair originated from the horny tactile hairs of squamous reptiles, or prototrichia ("hair precursors") - tailless amphibians (which really very much resemble embryonic hair), or organs of the lateral line of larvae of aquatic tailed amphibians, which could have correspondingly changed in connection with with land access.

Indeed, in embryos of mammals (including humans), the development of scales and hair is preceded by an increase in the number of squamous cells in the integument, which is sometimes considered a short-term embryonic repetition of the stages of development of the ancestral organ. There is a disease “black hairy tongue”, in which the filiform papillae of the tongue hypertrophy in a person and take on the appearance of real hair - i.e. in principle, such a modification of horn structures is possible.

However, at present, the prevailing opinion is that hair is a new acquisition of mammals and is not evolutionarily associated with any derivatives of the outer coverings of their ancestors. The formation of hair may be associated with the development of skin glands. Keratinization of the epidermis is a secretory process; scales, feathers and hair are glandular structures, the secret of which - keratin - performs a protective function.

Therapsida ( Therapsida- animal-like reptiles) were aquatic and semi-aquatic forms with soft, elastic and, apparently, glandular skin, which, in the process of their evolutionary entry onto land, became keratinized and became waterproof. The glands descended deep into the skin, isolating themselves from keratin structures, and the latter turned into hair and scales.

The immediate ancestors of mammals were probably the small carnivorous reptiles cynodonts ( Cynodontia). In their various families and genera, in one way or another, the signs of both reptiles and mammals were combined. It is assumed that at least the most evolutionarily advanced representatives of cynodonts possessed such features of animals as warm-bloodedness and the production of milk to feed the young. The development of the coat at the same time had a heat-insulating value and was important for the development of homoiothermy. However, there is an opinion that the original function of the hairline in ancient mammals was, on the contrary, protection against overheating, since the inability to intensively give off heat hampered the evolution of the class in the hot and humid climate of the Mesozoic.

Hair probably already existed in the descendants of cynodonts (230 million years ago), and in the branch that gave rise to egg-laying mammals, it was only hair as such, and in the branch that led to the emergence of marsupials and placentals, both hair and vibrissae (sensing hair ). Modern monotremes do not have vibrissae (they have developed skin mechano- and electroreceptors), in marsupials vibrissae are present on the muzzle and limbs, and in placental ones their distribution on the body can be very diverse.

The qualitative and quantitative differences between hair itself and vibrissae are so great that a number of researchers ask themselves: are hair vibrissae? The movement of the vibrissae is provided by striated muscles, the hair is smooth (the only exception, or perhaps one of the parallel branches of development, is the hair of monotremes, which are equipped with striated muscles). The connective tissue capsule of the vibrissa bursa is much more developed than that of the hair follicle. Vibrissae do not have sweat glands, and the accompanying sebaceous glands are poorly developed. The differences between hair and vibrissae also concern the nature of their blood supply and innervation, structure (vibrissae lack a core layer), the nature of molting (vibrissae are replaced one at a time as they are erased, regardless of the total molt), the principle of functioning (vibrissa as a movable lever) and their very functional value (sensitive in vibrissae and heat-insulating in hair).

The structure of the hair (left) and vibrissae (right)

Indirect evidence of the possible separation of the developmental pathways of hair and vibrissae is also provided by the advanced development of the innervation of the not yet formed vibrissae follicle in ontogenesis, the possibility of reverse development of vibrissae into receptors (as occurs in dolphins), the deep occurrence of vibrissae follicles in the subcutaneous tissue and the isolation of their muscles from the subcutaneous striated muscles and, finally, the representation of each vibrissa in the sensory areas of the brain.

Vibrissae can either move at will (“active”), or involuntarily, or not move at all (“passive”). In great apes, sparse (2-3 bundles) facial vibrissae do not have their own muscles and are set in motion by mimic muscles; in horses, bulls and representatives of the pig family, they are motionless.

In rodents, vibrissae are equipped with large muscles and actively move.

With a general reduction in the hairline, vibrissae are preserved and can even be evenly distributed over the body - as in sirenaceae.

On the head of minke whales ( Balaenoptera) there are numerous vibrissae - not the rudimentary organs of the once well-developed hairline, but quite specialized sensory organs. In toothed whales, vibrissae are present only in embryos. In adults, most representatives of the dolphin family ( Delphinidae) “pits” remain in the skin of the muzzle after the degeneration of juvenile vibrissae, and, as already mentioned, their follicles may be involution into specialized tactile organs that respond to changes in water pressure and low-frequency vibrations.

It can be assumed that in the ancestral forms of mammals, vibrissae originated from the embryonic anlages of primitive mechanoreceptors, while hair, later, from scaly epidermal anlages.

The stiff, straight stem of the vibrissae and their lack of hair characteristic of hair indicate that they appeared first - in such ancestral forms in which the thick skin was not firmly attached to the body. Hair arose in later forms, in which, as the subcutaneous structures formed, the skin became thinner, but more firmly connected to the body, and the growing hair acquired a slope due to the stretching, stretching and growth of such fixed skin. This process can also be traced in individual development: first, at the stage of skin layers not yet fully formed and not attached to the subcutaneous muscles, vibrissae are laid, and hair - later, in fully formed, thinner and attached skin. In mature-born forms, vibrissae are laid earlier in the process of individual development, but they develop more slowly and take shape in a later embryonic period than in immature-born ones.

Despite the differences, both vibrissae and all other types of hair and their derivatives (needles, semi-needles, spines, semi-thorns, bristles, covering, guides, guard hairs of different categories, downy, tylotrichia, monotrichia, osmetrichia, etc.) have a common type of microstructure. The hair shaft is a keratinized cylinder of various configurations, covered with a single or multilayered cuticle, filled with dense spindle-shaped cortical cells and a not always present central tender core layer - keratinized remnants of the walls of the core cells of a metabolically active follicle.

The structure of the hair follicle:
1 - external root sheath;
2 – Henley layer;
3 – Huxley layer;
4 - cuticle of the internal root sheath;
5 - core;
6 - bark;
7 - cuticle of the cortex

The hair follicle is a dynamic complex system subject to age-related and seasonal changes under hormonal control, with a sufficiently large functional plasticity that allows you to change the parameters of the hair. It is believed that follicles appear only once in ontogenesis, however, new hair formation during skin regeneration has been experimentally proven.

With the individual development of the hairline, there is heterochrony- the difference in the time of laying and development of different types of hair. First, as already mentioned, the most complex structures are formed - vibrissae, then sensory hair - equipped with capillaries and nerves of tylotrichia, and even later - hair of different types - from complex guard hairs (from primary follicles, equipped with muscles and glands) semi-needles, needles, bristles to simply arranged downy (from independent bookmarks or from secondary follicles). Primary follicles originate from the epidermis, while secondary follicles are the product of budding of the primary follicles.

The process of evolutionary formation of needles in mammals is very interesting. The formation of needles occurred in different groups in parallel and in connection with specific adaptations to lifestyle. The fact that needles are a modification of hair is evidenced by numerous transitional forms (bristles, half-needles). In hedgehog embryos, the quills are laid later than the hair and are formed by the fusion of several follicles, which is quite common in species that have tufts of hair growing from a common follicle. However, the formation of a needle in a hedgehog is not a mechanical union of follicles, but a more complex process. Each needle is formed as a result of a different rate of development of a group of follicles, in which the central, largest, follicle develops faster than others and, growing, “captures” smaller and slower growing ones. As a result, the needle turns out to consist of strands of core cells separated by thick longitudinal septa, among which the central strand is the largest. Representatives of a completely different group - porcupines - have simpler needles: the septa are much thinner, and the core cells are either the same in shape and size, or slightly larger in the central part of the rod. In the furrowed needles and semi-needles of some hamsters and mice (of course, in those representatives of these families that have such formations), the core is preserved only in the lateral parts of the needle and is separated by a thickened cortical layer, which suggests the formation of these needles from one large hair tab without a core and two smaller ones - with a core. Pork and peccary bristles ( Tayassuidae) are very similar to "combined" needles and also consist of strands of core cells separated by thick septa. In the spines (or half-quills) of tenrecs and echidnas, there are no longitudinal septa, the core cells are similar in size and differ in thickened walls and weak development of cavities; these structures are formed from a single bookmark.

Hair reduction in humans is associated with the formation of bipedia - bipedalism, fetalization - a slowdown in the development of individual organs and their parts in the ontogeny, and sexual selection - the preference for hairless sexual partners and a kind of sexual revolution - enjoying love games.

It is possible that heat stress played the role of an important factor: during the formation of an adaptive type of constitution in early tropical hominids, intense sweating became the main mechanism of thermoregulation. The hairline hindered the release of heat and was lost.

Slow development under hormonal control leads to the suppression of a number of signs, in particular the hairline, i.e. from a certain point of view, a person can be considered as an embryo of a primate that has reached puberty (a kind of neoteny).

Like humans, gestated gorilla and chimpanzee fetuses have long hair on the head, but little hair on the muzzle and torso, and their baldness is similar to that of humans.

Embryonic hair ( vellus, lanugo) of a person develop earlier than coarser and larger "terminal" hair. Bookmarks of hair appear at different times on the face and head, then all over the body from top to bottom. It is believed that the hair of the human fetus is a recapitulation (repetition in embryos of signs of adult ancestors) of the hair of great apes, however, their functional significance is also shown: the reaction of these hairs in response to the movement of amniotic fluid (the pile is directed against it, and the hair acts as levers with a long arm ) enhances the activity of skin receptors and maintains muscle tone, providing a certain posture of the fetus.

With hormonal deficiency or due to gene mutations, a person may develop pathological conditions, for example, excessive hairiness - hypertrichosis. In this case, the embryo is covered with long, thin, silky and wavy, like a lap dog, hair (“dog people”) that grow and remain for life (hairy man Andrian Evstikhiev).

But a person does not have vibrissae - there are not even their bookmarks. Functionally, they are partially replaced by telotrichia - sensory hairs, evenly distributed throughout the body.

Dry hair is 97% protein (keratin) and 3% water. Hair in good condition can absorb up to 30% of its own weight in water; in poor condition - up to 45%. The optimum water temperature for washing hair is 35-45 °C.

Schematic representation of the main categories of hair:
I - guide hair; II - guard hair; III - downy hair;
1 - root zone; 2 - the base of the hair; 3 - transition zone; 4 - granny; 5 - the tip of the hair

The skin of the head of an adult has 100 - 150 thousand hair follicles. The total number of hairs (on average, of course) on the head of blondes is 140 thousand, for brown-haired women - 110 thousand, for brunettes - 100 thousand, for redheads - 90 thousand. On the crown, there are an average of 300-320 hairs per 1 cm 2, on the back of the head and forehead - about 240. The number of hair follicles on the head is always greater than the number of hairs. Not all follicles are productive. Their activity can be influenced by hormonal factors and age.
The total surface area of ​​the hair of an adult - with a length of 20 cm - 6 m 2.
Hair density - 1.3 g / cm 3. The mass of the hairline increases by 0.2 g per day, by 6 g per month and 72 g per year.
Hair grows by about 0.35 mm per day, by 1 cm per month, by 12 cm per year. Accordingly, in total, 35 m of hair fiber grows on the head of an adult per day, 1.1 km per month, and per year - 13 km.
The age of a hair 12 cm long, respectively, is 1 year. A hair 1 m long should grow for 8 years. Thus, a man who has never been to a hairdresser in his life could theoretically have hair 9.2 m long, and a woman - 10.2 m. But in fact, hair growth stops when a certain length is reached. The world record for hair length is 4.2 m (but one Indian has 7.93 m!).
Hair does not grow continuously, but in cycles. The hair growth period (anagen phase) lasts from 2 to 6 years. Then, in a transitional phase (catagen phase), lasting about 2 weeks, the hair stops growing. In the last (telogen) phase, lasting 3–4 months, the hair follicle becomes cone-shaped, its papilla becomes empty, the bulb loses its nutrition, and becomes spindle-shaped. After that, within 60-90 days, the hair falls out. In its place, a new hair grows from the remaining papilla or from the newly formed papilla and bulb.

1 - growth; 2 - transitional; 3 - final

From one hair follicle, an average of 20 hairs consistently grows during a lifetime. But with painful changes, this process stops and the hair falls out irrevocably.
When everything is in order, approximately 85–90% of the hair on a person’s head is in the growth phase, about 1% is in a transitional state, 9–14% is dying off. The norm is the loss of up to 100 hairs from the head per day.
Maximum hair growth in summer, minimum - in winter. Massage and heat stimulate hair growth, while in the cold this process slows down.
Hair grows well from 15 to 30 years. At 40-50 years of age, hair growth gradually stops.

Baldness is an inherited trait transmitted by a gene, the manifestation of which depends on sex. If the gene is present, baldness will develop if there is enough testosterone, a male sex hormone that stimulates body hair growth and reduces hair growth on the head. As a result, men with a lot of body hair usually tend to lose scalp hair at an earlier age than others. Since testosterone begins to be produced during puberty, a man castrated in childhood does not go bald.
Intensive hair loss in both sexes is observed after 50 years and is increasing every year. But only the loss of 50% of the head hair makes baldness noticeable.
Surveys have shown that by the age of 25, about 25% of men have signs of baldness, and by the age of 50, 50-70% are bald; 25-40% of menopausal women lose their hair. The frequency of hair loss in men is 8 times higher than in women.
Baldness is more common in Caucasians (40% of Europeans become bald by the age of 35) than in Mongoloids or Negroids.
According to some estimates, there are about 300,000 different ways to treat baldness in the world. Although tests have shown that, for example, minoxidil, one of the patented remedies, can only restore hair to 5-8% of bald people, according to press materials, Upjohn has been selling this drug for $ 180 million annually since 1988.

Hair covers 95% of the human skin surface. Only the lips, soles of the feet and palms of the hands are deprived of hair. Each eyebrow has about 700 hairs, on each eyelid - about 80 eyelashes, in the armpit - about 6000 hairs, on the pubis - about 7000.
The growth rate of long hair and the area of ​​their distribution on the pubis, in the beard and in the armpits reaches a maximum by 30-35 years.
For the hair of the eyebrows and ear passages, the growth phase is 4–8 weeks, then they die off within 3 months. On the back of the hand, hair grows in 10 weeks and dies off in 7 weeks. The beard hair cycle lasts about a year. Each eyelash lives on average 100 days.
The hair is strong, like a copper wire of similar thickness. A bunch of 100 hairs can withstand 10 kg, all the hair on the head - 12 tons. The hair can be pulled to 50% of its length before it breaks.

Hair color is determined by the pigment melanin. The more melanin granules, the darker the hair. Two types of molecules of this protein are known: eumelanin colors hair in color from chestnut to black, and iron-rich pheomelanin - from gold to red. Hair color depends on the absorption and reflection of light by melanin (mainly the cortical layer) and its scattering by the walls of the air layers of the core. Black hair contains optically dense very dark melanin both in the cortex and in the core, therefore it reflects only a very small part of the light rays. Gray hair is generally devoid of pigment, and its color is determined by the uniform scattering of light.

Hair color and shape are inherited. Moreover, each nation has its own characteristics of hairline, which is well known to anthropologists.
Abundant body hair refers to the features of the Semites and Indo-Germanic peoples.
The hairline is most developed among Europeans, especially among the Portuguese and southern Spaniards.
Poverty or complete absence of body hair is the most typical feature among the North Asian Mongols and the original inhabitants of North America.
The Ainu are considered the most hairy people on the planet - the original inhabitants of Kamchatka and the Kuril Islands (not to be confused with the Japanese).

The hairline of animals, which has spinning qualities or felting properties, is called wool. Various fabrics and cloths, blankets and carpets, hats, felts and felt mats, heat and sound insulating materials used in construction, aviation, etc. are made from it. Woolen fabrics are beautiful, hygienic, lightweight and elastic, retain heat well, and are wear-resistant.

Sheep wool in the mass consists of individual fibers. According to their appearance and technical properties, the following types of woolen fibers are distinguished: down, awn, transitional fiber, dead, dry, covering, protective, tactile hair, pesigu and camp. The fibers differ from each other in appearance, morpho-histological structure and physical and technical properties.

Down is the thinnest and most crimped wool fibers, usually without a core layer. The fineness of down fluctuates from 25 to 14 or less micrometers. The wool of fine-fleeced sheep consists of fluff, and coarse-wooled sheep consists of fluff, transitional hair, awn. Downy fibers consist of cortical and scaly layers, the cross section has a round or oval shape. Compared to other fibers, down has a shorter length, due to which a lower, shorter layer of wool is formed in sheep with heterogeneous wool. An exception among the coarse-wooled is the Romanesque sheep, in the wool coat of which the down is longer than the awn. In terms of technical properties, down is the most valuable fiber.

Awn - less crimped and thicker, having a well-developed heart-shaped layer, wool fibers that are longer than fluff and transitional hair. Awned fiber characterized by wool fineness from 52 to 75 microns, consists of scaly, cortical and core layers, the core layer is continuous. The awn is part of the coat of coarse-wooled and semi-coarse-wooled sheep. The thinner it is, the more valuable wool is in terms of its technological qualities.

The technical properties of the awn are lower than those of down. With a decrease in the fineness of the awn, its technical properties increase.

A variety of awns are dry, dead, covering, protective, tactile hair, dog and camp.

dry hair- coarse awn, characterized by dryness, stiffness and fragility of the outer ends of the fibers. It differs from the usual awn in less brilliance. Technologically, dry hair occupies an intermediate position between the awn and dead hair. It is found in the wool of most coarse-wooled sheep.

Dead hair -- very coarse and brittle outer fiber, with an extremely developed core layer and a wool fineness of more than 75 microns. When bent, it does not form an arc, but breaks. When you try to stretch it, it breaks. It does not have the shine characteristic of wool fibers, it does not stain. It does not hold well in woolen products, quickly collapses and greatly reduces the quality of the fabric. The presence of dead hair in wool, even in small quantities, drastically impairs its technological properties.

Covering hair in structure and fineness close to the awn. It differs from other fibers in a short length (no more than 3-5 cm), stiffness, strong luster, lack of crimp, often has a different color than the bulk of the wool. Has no practical value.

Pesiga- Woolen fibers found in the wool of fine-fleeced and semi-fine-fleeced lambs, which stand out among other fibers with greater length, coarseness and less crimp. During the first year of life, the dog is replaced by the usual fibers typical of the breed. It is noted that lambs with a large number of dogs are stronger.

Protective hair -- awn fiber growing on the eyelids of sheep.

Tactile hair -- awn fiber growing at the tip of the muzzle of a sheep. The tactile hair is connected with the endings of the nerves, it is a kind of biological “radar”, it is important for animals when orienting themselves to the pasture, using feeders, drinking troughs, etc. It is impossible to cut tactile hair.

Kemp -- coarse fibers of the awn type, white, not stained, brittle, found in the wool of fine-wool and semi-fine-wool sheep, are inherited, which must be taken into account in the breeding process.

According to external features, wool fibers are divided into the following types: fluff, awn, transitional hair, dead, dry, covering hair and dog (see Fig. 2).

fluff- the thinnest fibers, the most crimped, forming the lower, shorter tier of the coat (undercoat) in coarse-wool sheep. The fineness of down is from 15 to 30 microns. The wool cover of fine-fleeced sheep consists only of downy fibers.

The roots of down fibers are arranged in bundles in the skin, because the bulbs of these roots lie in nests. In the skin of fine-fleeced sheep, from 5 to 15 or more roots are found in one bundle. As a result, two or more roots merge into a common hair sheath with one outlet. In fluff, the roots lie in the upper part of the skin layer.

According to the internal (histological) structure, the down of sheep's wool consists of scaly and cortical layers. The scaly layer is annular. The core of the down of sheep's wool is absent.

The down of different types of wool differs in fineness, crimp, length and histological structure.

Down is the most common type of fiber, found in all types of wool along with other types of fibers or forming the entire coat (in fine-fleeced sheep).

In technological terms, down fibers are the most valuable.

ost- slightly crimped, sometimes almost straight, thick, coarse fibers. The fineness of the spine in some cases is 30-35 microns, more often from 40 to 80, there are guard fibers up to 120-140 microns. The awn is usually longer than the down, forms the upper tier of the coat. The roots of the awning fibers are located in the skin one by one, without any regularity. The bulbs of the spine lie deeper than those of the down, reaching the border with the subcutaneous tissue.

The spine consists of three layers of cells: squamous, cortical and core. The scaly layer is not annular. The core layer is different, usually the core increases as the outer fibers thicken. There is an awn with a discontinuous core.

The outer fibers in the coat are mixed with down; there is no wool, consisting entirely of one awn. The guard fibers are included in the coat of semi-coarse and coarse-wooled sheep along with other types of fibers.

The awn is a less technologically valuable fiber compared to down. In different types of wool, the awn differs both in technical properties and in its histological structure.

Transitional (intermediate) hair - the fiber, the middle between the awn and down, is thicker than down, but thinner than awn. The fineness of transition fibers ranges from 30 to 50-52 microns. The length of the transitional hair differs little from the long down and the middle awn. Therefore, they are sometimes difficult to distinguish.

According to the histological structure, the transitional hair is closer to the down than to the awn. The core in it is often absent or less developed than in the spine, resembling islets (discontinuous core).

A typical transitional hair forms the coat of semi-fine-fleeced sheep (Tsigai, Kuibyshev, fine-coarse-wool crossbreeds, and other breeds). In most types of coarse wool, transitional hair is usually found in smaller quantities than awn and down. But in the wool of such coarse-wooled sheep as Tushino, Balbas, Saraja, a significant amount of transitional hair is contained. There is especially a lot of transitional hair in the semi-coarse cross-breed wool of fine-wool-coarse-wool sheep.

In terms of technological value, transitional hair is closer to fluff.

dead hair- very coarse, brittle, usually short, almost straight awn fiber with a fineness of up to 160 microns.

According to the histological structure, the dead hair is close to the thick awn. The scaly layer is not annular. Scales of dead hair look like narrow plates, arranged in 6-8 pieces. around the fiber.

Dead hair has a highly developed core. On cross sections of dead hair fibers, a very thin cortical layer is hardly recognizable. Such a strong development of the core is one of the main reasons for its low tensile strength. Due to the porous core layer, dead hair is practically not amenable to dyeing. Dead hair in wool products is poorly retained, quickly destroyed, falls out of yarn and fabric, as a result of which the quality of the product is greatly reduced.

dry hair- this is a coarse awn, characterized by great rigidity and dryness of the outer ends, less shine, fragility in the upper part of the hair. The greater the difference in the braids of wool between the length of the awn and down, the more dry hair there is in such wool. Fiber fineness - from 50 to 140 microns.

According to the histological structure, dry hair occupies an intermediate position between the awn and dead hair.

In the upper part of the dry hair, it resembles a dead one, and in the middle and lower part, located along with the transitional and downy fibers, there is an awn.

Dry hair is found in the wool of most coarse-haired breeds of sheep, being a companion of the dead streak (in fat-tailed sheep), and in some breeds of sheep a large amount of dry hair is not accompanied by dead hair (Voloshsky, Cherkasy).

In technological terms, dry hair approaches the awn.

Covering hair- straight, hard, with a strong splash, short, usually 3-5 cm long. Approaching the awn in structure. The roots of the covering hair are located obliquely, so one hair covers the other. Covering hair is found on the head, limbs and tail of the animal. On the body of the animal, the covering hair, due to its oblique position, makes it impossible to cut it, and therefore it is not included in wool products obtained from sheep.

Pesiga (dog hair)- woolen fibers found in fine-fleeced and some semi-fine-fleeced lambs and distinguished from other fibers by their great length, thickness and less crimp. Some lambs are born with such fibers, and then during the first year of life, the dog is replaced by typical downy wool fibers. Therefore, the dog is found in thin and semi-thin wool (wool from lambs) and in wool from young (one-year-old) fine-fleeced sheep.

The fur skin has a hairline and leather tissue, that is, a structure similar to the skins of animals that are used to make skins, that is, from the epidermis, dermis, subcutaneous adipose tissue.

The epidermis makes up 2-5% of the total thickness of the skin and consists of the stratum corneum and germ layers.

The dense dermis of the skins includes two layers: papillary and reticular.

Collagen bundles of the papillary layer are thinner and randomly intertwined. Between them are the sebaceous and sweat glands, hair roots. The lower border of the papillary layer conditionally passes at the depth of the hair follicles. In different types of fur skins, the depth of occurrence and the angle of inclination of the hair bags are not the same. During the year, the depth of the hair follicles varies: the follicles of growing hair during the molting period of fur-bearing animals are located in the lower layers of the dermis, and the follicles of grown hair are in the superficial ones. The reticular layer is located under the papillary and is characterized by a more uniform weave of powerful collagen fibers. Subcutaneous adipose tissue is located directly under the dermis. This loose connective tissue connects the skin tissue with the carcass of the animal, in which three layers are distinguished: fatty, muscular and subcutaneous tissue. In the process of dressing fur and furs, subcutaneous adipose tissue is removed.

Hairline - a set of various hairs that cover the body of an animal and perform a number of physiological functions: it is a thermoregulatory layer and protects the body from excessive loss of heat and moisture, as well as mechanical influences.

Keratin is the main protein that forms the hair and the main layer of the epidermis.

Hair structure. The hair consists of 2 parts: the root, which lies in the skin, and the rod, which goes to the surface of the skin. A thickening at the end of the root forms a hair follicle. The root and bulb are surrounded by several shells. The outer shells formed from the connective tissue of the dermis are called the hair bag, and the inner shells of epidermal origin are called the root sheath. Growing hair at the bottom of the bulbs have a depression where the connective tissue with blood vessels enters, forming the hair papilla.

A narrow bundle of smooth muscle fibers adjoins the lower part of the hair follicle, one end of which is attached to the hair follicle, and the other is lost in the adjacent dermal fibers. By contracting, this muscle can change the angle of inclination of the hair bag, while changing the heat-insulating layer of air in the hairline.

The hair shaft consists of three layers: the cuticle (outer scaly layer), the cortical layer and the core.

The cuticle is a very thin, 0.5-3 micron thick, outer shell of the hair, consisting of keratinized lamellar cells containing amorphous keratin. The scales are stacked one on top of the other like fish scales so that their free ends are directed towards the top of the hair shaft. The cuticle protects the hair from external influences, and also determines its shine, feltability, resistance to abrasion.

The cortical layer is a concentric layer of the hair, located under the cuticle and formed by spindle-shaped keratinized cells located along the axis of the hair. Cells are connected to each other by intercellular substance and are stacked tightly to each other. The cortical layer determines the mechanical properties of the hair: tensile strength, elasticity, extensibility. Hair color depends on the presence of black or yellow pigment (melanin) in the cells of the cortical layer. All variations in the color of the hairline depend on the combination and degree of development of these pigments. In the absence of pigment, the hairline has a white color.

The core of the hair is a loose, porous tissue, consisting of many-sided cells with a keratinized membrane and protoplasm.

Inside the cells there are air bubbles and pigment grains, air is also in the intercellular spaces.

Hair in shape can be of three types: spindle-shaped, cylindrical and conical.

The most common spindle-shaped hair, which consists of 4 parts: tip, granny (the widest part), neck and base. In cross-section, granna hair has a different shape: round (mole, hamster), oval (arctic fox, sable, marten), flat (otter, nutria), bean-shaped (marmot), dumbbell-shaped (rabbit).

Cylindrical hairs have almost the same diameter throughout, sharply tapering at the tip and base, forming a thin stem.

Tapered hair gradually expands from the tip to the base.

According to the nature and degree of crimp, the hair of fur-bearing animals can be of various shapes: straight, curved at an angle, curved in length, wavy, corkscrew-shaped, spiral.

The hairline of fur raw materials includes several categories of hair: tactile (vibrissae), covering (guides and guard), thermoregulatory (downy).

Vibrissae play the role of an organ of touch, because. perceive the slightest mechanical influences of the environment and are located on the head, upper lip (moustache), lower lip, above the eyes, on the cheeks, limbs of the animal.

Covering hairs consist of guides (straight, thick and long, protruding above the hairline, forming a "veil"; for many animals their number is from 5 to 20 per 1 cm 2) and guard hairs (shorter and thinner guides, 50-200 hairs per 1 cm 2) hair.

Downy hairs are thin and short, the most numerous (from 0.5 to 50 thousand hairs per 1 cm 2), which are almost always crimped and protected by guiding and guard hairs.

The topography of fur raw materials also differs from the topography of the skin intended for the manufacture of leather, and consists of a tail, a rump, a ridge, a scruff, a muzzle, a duck, sides, a casing, and paws.

Biological bases for sorting fur raw materials and semi-finished products. Under the sorting of fur raw materials and semi-finished products is understood the division of skins into various quality groups: ridges, varieties, color categories, sizes, categories of defects.

Fur raw material is a raw material of natural origin, its quality and properties depend mainly on the natural, biological characteristics of the skin.

The hairline of animals under the influence of various environmental factors is subject to strong variability, which is associated with living conditions, conditions of keeping and feeding, geographical area (geographical variability), season (seasonal variability), sex (sexual variability), age (age variability) and individual deviations (individual variability).

The living conditions of fur-bearing animals have a great influence on the structure and properties of the hairline.

In fur-bearing animals that lead a terrestrial lifestyle (squirrel, sable, marten, fox), there is a pronounced difference in the pubescence of individual parts of the body: the ridge is always covered with a denser hairline than the belly. The color of the hairline of the ridge is darker. The skin on the ridge is thicker than on the belly.

Animals leading an underground lifestyle, i.e. spending most of the time in burrows (mole, mole rat), covered with uniform hair. Their guiding and guard hairs are slightly longer than down hairs, the quality of the fur in different parts of the body is almost the same. The skin on the belly is much thicker than on the ridge. The color of the entire skin is the same.

In amphibious fur-bearing animals (otter, mink, muskrat, nutria, river beaver), the bellies are covered with a denser hairy coat than the ridge.

The color and thickness of the skin of the ridge and the belly are the same in most species of amphibians.

In animals that spend most of their lives in water, the disappearance of the hairline is observed. In adult seals, the hairline consists of coarse, sparse, mostly guard hairs. From the cold, the body of animals is protected not by a fur cover, but by a layer of subcutaneous fat.

One of the factors that dramatically affect the quality of hair and skin is the climatic features of the area in which the animal lives. Depending on the climate, the following signs of skins change: size, density, length of hair, softness and color of the hairline, and thickness of the skin tissue. Northern fur-bearing animals are covered with thicker and longer hair than southern animals of the same species.

Usually the skins of northern animals are covered with softer hair than the skins of animals from the southern regions. As the density increases, the hair becomes thinner and appears softer. The humidity of the air also affects the softness of the hair. Animals living in more humid climates have coarser fur. The color of the hairline in individuals of the northern regions is lighter or completely white (protective), the forest strip is intensely saturated, the steppe and desert regions are dull, sandy-gray.

The thickness of the skin is also different in different habitats of fur-bearing animals. The more developed the hairline, the thinner the skin is. In animals living in the north, covered with thick high hair, the skin is thinner than that of animals in the southern regions.

Thus, due to the sharp differences in the properties of the skins obtained in different geographical areas, the furs are divided into ridges.

A ridge is a set of certain commercial properties characteristic of fur skins of a given species, mined in a certain geographical area. The ridge, as a rule, is given the name of the geographical area where the skins come from: Amur, Yakut, Altai squirrels.

The quality of fur skins depends on the time of their extraction. Seasonal variability of the skin and hair is the result of the adaptability of the animal organism to changes in environmental conditions, primarily temperature.

The winter and summer hairline of fur-bearing animals of most species differs in color, height, density, different ratio of the amount of outer and down hair, shape and structure of the hair. These differences are most pronounced in fur-bearing animals living in a sharply continental climate.

The change in the hairline of fur-bearing animals is called molting.

During the formation and growth of a new hair in the hair bag, along with the shaft, a hair pigment is formed, which is clearly visible from the side of the mezra in the form of blue spots that exactly correspond to the topography of the molt. As the hair grows, the blue disappears. It is easy to determine the grade of the skin by the blue pattern of the skin.

The quality of the fur of males and females does not have sharp differences. The difference lies in the size of the skins, the length and thickness of the hair, the thickness of the skin tissue. The skins of females, as a rule, are smaller than those of males, and the hairline is softer, less frequent and lower.

The fur of an animal undergoes great changes with age. Baby fur animals in most cases will be born without hair, with a slightly visible embryonic fluff. Then the development of the children's primary hairline begins, which differs from the fur of an adult animal in that it is very soft, low, easily felted, the guard hair almost does not differ from down. The skin is thin and fragile. Such skins are called "puffy". After a certain time for each type of animal, the primary cover is replaced by a secondary one, which is closer in quality to the fur of an adult animal. With the age of the animal, the quality of fur skins deteriorates. The hairline becomes sparse, coarse and dry. The age difference in the quality of the fur cover of the skins of domestic animals is more pronounced. The skins of young domestic animals provide the most valuable fur product (lark kulcha, astrakhan fur, etc.). The skins of adult domestic animals (cattle) are unsuitable for dressing fur.

Differences in the quality of the fur cover, which do not depend on sex, age, season and habitat, are called individual variability, which is due to heredity, differences in living conditions and manifests itself in different density, height, splendor, softness and especially the color of the hairline. In some species of fur-bearing animals, it is weakly expressed (otter), in others (sable) it is so strong that it affects the value of the skin. Sometimes there is a sharp demorphism in color (in white and blue foxes). There are skins with different color deviations from the normal color. This manifests itself in the form of albinism, melanism and chromism. Albinism is the absence of pigment in the fur. It happens full, partial and zone. Complete albinism - the absence of pigment in the entire hairline. Partial albinism - the presence of white hair only in some places of the skin, while the rest of the coat is pigmented normally.

With zonal albinism, the hairline is devoid of pigment only at a certain time of hair growth, so the fur consists of hairs in which the tips are pigmented, but the base is not. Observed in squirrels, moles, etc.

Melanism is the extreme development of black pigment with incomplete or complete disappearance of yellow. It happens complete and partial. Chromism is the development of only yellow pigment.

Before discussing hair removal methods, it is necessary to agree on terminology and understand what generally affects hair growth and what their structure is.

So, hair grows from the most extensive human organ - the skin, and is part of the body's defense system: it retains heat (where it grows densely: for example, on the head), absorbs shocks (on the head), prevents sweat from entering the eyes (eyebrows and eyelashes ), dust - into the lungs (in the nose), etc. Our hair is no different from the hair of the same chimpanzee, and even the number of follicles we have is the same.

Human genetics determines the number of hair follicles, the hair growth program and their sensitivity to hormones. The task of epilation is to exhaust the supply of follicles in a given area. This action, regardless of hormonal characteristics, will lead to the cessation of hair growth.

By type, hair is divided into three types:

• Lanugo(embryonic hair) - fluffy long hair covering the body of the fetus before it is born. Some of this hair falls out in the womb, some - a few months after birth.
• Cannon hair - soft, thin (0.1 mm) and short (up to 20 mm) hair covering almost the entire body. They have shallow roots, often devoid of pigment. When stimulated, such hair can transform into terminal hair.
• Terminal hair - hard, thick (up to 0.6 mm), long (over 20 mm) and pigmented hair that develops from roots in the deep layers of the skin. Such hair includes hair on the head, pubis and armpits.
• Eyelash or bristly hair- coarse, pigmented, but very short hair growing on the eyelids, on the eyebrows, in the nose and ears. They perform a barrier function.

Hair in different nations and in different areas can have a different structure - be straight or curled - and grow at different angles. The position of the hair follicle in the dermis is affected by a history of hair removal and skin diseases. Waxing, sugaring, folliculitis (or pseudofolliculitis due to ingrown hairs) can deform the follicles, which then produce hair that is difficult for long-term types of hair removal.

Rod structure

The structure of the hair on the surface of the skin is formed from 2-3 layers of keratinized cells. Hair color is determined by the melanin pigment produced by melanocytes located in the basal layer of the epidermis. Therefore, vellus hair growing at the very surface of the skin is often devoid of pigment.

The hair consists of a scaly cuticle, a cortex (cortex) and a porous core (medulla or medulla). Cuticle consists of keratinized keratinosites - fats, proteins and wax-like substances that provide elasticity and strength to the hair. Cortext It is built from epidermal stem cells and contains melanin and keratin. Core not contained in all hair, but only in long and thick (on the head, pubis, etc.); its purpose is not entirely clear: according to one version, voids in the core protect the scalp from temperature changes.

Since the rod is a keratinized tissue, no impact on it can affect the further growth of the hair. Shaving and cutting, just like nourishing masks are not able to qualitatively affect already regrown (and damaged) hair shafts, their task is to temporarily glue the scales together.

hair follicle

Each hair develops from hair follicle- This is a special bag in which the hair root is located. Together with its associated systems, it forms hair follicle. These systems include the sebaceous and sweat glands, the levator pilus muscle, blood vessels, and nerve endings.

Each hair is connected to muscle, capable of lifting it, forming "goosebumps" - this involuntary movement helps to retain heat. The hair follicle forms hair follicle, to which nutrients and oxygen enter with the blood, and waste products of cellular metabolism are excreted through the lymph. The division of epidermal cells and melanocytes in the hair follicle, followed by their keratinization, ensures the growth of the hair shaft.

A hair is alive as long as it is made up of blood vessels and nourishes the hair. hair papilla. All types of hair removal are aimed at destroying the hair papilla due to thermal (electroepilation, laser hair removal) or chemical burns (electroepilation, enzymatic hair removal, etc.). There are versions that the hair papilla is able to recover due to stem cells, the reservoir of which is the "niche" of the follicle, located just below the sebaceous gland.

Hair growth and vital activity is controlled by means of hormones produced by the endocrine glands. The necessary hormones come with the blood to the hair follicle, where they interact with special target cells, the task of which is to recognize the instructions sent to them. Thus, hair target cells are sensitive to the action of dihydrotestosterone, the most powerful androgen, formed from free testosterone under the influence of the 5α-reductase enzyme in the skin. The higher the level of free testosterone and the more active the 5α-reductase enzyme, the thicker and darker the hair on the body grows and the more hair falls out on the head. In women, an increase in the concentration of unbound testosterone leads to hirsutism: the degeneration of fine vellus hair into terminal hair in those areas where hair normally grows only in men. This is partly due to the fact that androgens lengthen the phase of active hair growth. The rapid growth of the hormone progesterone also lengthens the growth phase and accelerates the division of hair follicle cells; thanks to this, hair grows better, falls out less everywhere - both on the head and on the body.

Life cycle of hair

Sources:(Mostly) Morris, D. Encyclopedia of hair removal: everything about hair removal for professionals and beauty salons / D. Morris, D. Brown. - M.: RIPOL classic, 2008. - 400, illus.