Hair is a structure that grows from the skin of mammals and contains keratin. It has a high tensile strength and can stretch far before breaking. It also has a variety of proteins.
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Keratin is a protein that forms hair, nails and the outer layer of skin. It is also found in glands and organs. It is a tough and flexible substance. Hair grows from follicles in the skin, primarily on the scalp in humans. It serves a variety of functions, including protection from sunlight, heat and cold, regulation of body temperature, and social identity. Hair has two parts, the shaft and the root. The root is alive and lies beneath the skin, while the shaft sticks out of the skin’s surface. The keratin in the shaft is made of a coiled-coil protein phase, which assembles into intermediate filaments and forms a fiber. It is then enveloped by a cuticle, which is made of dead cells.
There are four basic keratins, K71-K80 and K81-K86, which vary in their specificity for soft or hard keratinization (Coulombe & Omary, 2002; Schweizer et al., 2006). They have a similar amino acid sequence and can form heterodimers with each other. Keratin K71, with a MW of 57 kDa, is specific for the soft-keratinizing cells of the inner root sheath of hair follicles in human, mouse and the marsupial Pototrous tridactylus.
Another basic keratin, K83, has a MW of about 65 kDa and is specific for the hair-specific cells of the companion layer of the inner root sheath of hairs in human, mouse and sheep. This protein has a characteristically high glycine content in its head domain and is cross-linked to the desmosomal proteins of the stratified epithelia by epidermal transglutaminase, which is involved in cornification. It can also form heterodimers with the hair-specific keratins K81 and K86. A fourth basic keratin, K84, has a MW of about 60 kDa and is specific for the companion layer of the hair sheath of human papillomavirus-induced lesions in the sex wall of the male genitalia.
It has a high tensile strength
Hair is one of the toughest natural materials and has high tensile strength. It consists of keratin, which is considered a bio elastomer because of its elasticity. In fact, a single strand of human hair has half the strength of steel, but it is not very stiff. The elasticity of hair is due to its affinity for water. This affinity causes the keratin to stretch, which increases its tensile strength.
Researchers studied the tensile strength of various hairs, including those of humans, bears, boars, horses, capybaras, javelinas and giraffes. They found that the tensile strength decreased as the diameter of the hair increased. In addition, a large proportion of the tensile strength is lost when hairs break apart. This phenomenon is known as shearing, and it occurs when the a-helix of the keratin is unwound during stretching.
The tensile strength of hair is also related to its elasticity. The elasticity of hair depends on the morphology of the keratin microfibrils and their relative arrangement in the fiber. It also depends on the environment and the chemical composition of the hair. A low elasticity is associated with a loss of the a-helix and a transition to a b-sheet structure during stretching.
In a recent study, a team of scientists measured the breaking point and elasticity of human hair using Zwick/Roell equipment. They recruited 120 female volunteers with hair that was at least 15 cm long. They excluded those with proven hair shaft or scalp pathology, nutritional disorders and major systemic illness. The volunteers were divided into four groups to test the tensile strength and elasticity of their hair. Results showed that the tensile strength of children’s hair was higher than that of adults.
It is made up of proteins
Hair is a filamentous biomaterial primarily composed of proteins, in particular keratin. It is one of the most defining characteristics of mammals, and it is believed to have evolved in the common ancestor of mammals around 300 million years ago. Its structure consists of a medulla, a loosely packed region near the centre, and a cortex that contains the major part of its fibre mass consisting of keratin proteins and structural lipids. The cortex is surrounded by a cuticle, a layer of dead cells that form a protective sheath around the hair.
Proteins are essential for maintaining healthy, strong and shiny hair. However, constant straightening and dyeing can cause a significant loss of proteins, which leads to weak, dull and dry hair. Hair treatment products that contain high concentrations of proteins can replenish this lost protein and strengthen the hair. This can also help reduce the frequency of hair fall and breakage.
It grows out of follicles
Hair grows out of follicles (FOL-uh-cles), which are sac-like pits in the skin where new hairs develop. These hairs are made up of a hard outer layer called the cuticle, which protects two softer inner layers called the cortex and medulla. The color of the hair is determined by the number, distribution and type of melanin granules within each of these layers. The follicles produce hair in cycles. Each cycle consists of a growth phase, a transitional phase and a resting phase. At the end of each cycle, the hair falls out and a new one starts growing in its place. Hair typically grows about a half inch each month during the anagen phase, which lasts for 2 to 6 years. Eyebrow and eyelash hairs have a shorter growth phase, which can be as short as a few months.
The first step in the process of making a hair is for living cells to proliferate in the hair matrix, or the area in which hairs form. These cells then push upward, dehydrate and compact into a thick, hard mass known as the hair shaft. The hair shaft contains non-living proteins, and is covered by a thin covering called the epidermis.
During the growth phase, which lasts for about a year, the cells in the hair matrix multiply and expand. They eventually move up through the skin and out of the follicle, where they are surrounded by tiny blood vessels. Once the hairs reach the surface of the skin, they stop growing and become dead, which is why they aren’t felt when someone cuts them.
During the transitional phase, which lasts about two weeks, the hair follicle prepares for a rest. At this point, the lower portions of the follicle collapse and the grip of the follicle on the hair becomes loose. As the follicle moves into the resting stage, it stops producing the proteins that make a hair grow and the hair shaft sheds.
It is made up of sebaceous glands
A sebaceous gland, also known as an oil gland, is a tiny structure that opens into the skin’s hair follicle and secretes an oily substance called “sebum.” Sebum naturally lubricates hair and skin, protecting them from dehydration. It also helps prevent a dry, brittle appearance and gives hair its natural shine. Sebum is also found in the eyes, where it enhances the lubrication of tears. It is found throughout the body, but it is particularly abundant in the face and scalp.
The sebaceous glands are located beneath the surface of the skin and can be seen with a magnifying glass. They have a foamy appearance under the microscope, due to the presence of lipids. They can be stained with a lipophilic stain, such as Nile red. The cells of the sebaceous gland are relatively undifferentiated and lipid-poor, and they gradually become more differentiated and filled with lipids toward the center of the gland. In the center of the gland, mature sebocytes undergo apoptosis and degrade, producing lipid products that combine to form the sebum that is released through the hair follicle.
Each strand of hair grows from a small sac of cells in the skin called the follicle. The follicle gets its nutrients from a blood vessel that runs underneath it. As the follicle grows, the cells that make up the hair shaft divide and harden. This process is called keratinization (kair-tih-NIZ-ay-zen). Then, the follicle pushes the hardened cells up through the hair follicle and through the skin’s surface as a hair.
Each hair follicle has its own sebaceous gland, which produces oily sebum to lubricate and waterproof the strands of hair. This lubrication reduces friction when the hair is brushed or styled and allows it to retain its moisture. The follicle also contains stem cells that keep dividing and growing, which is what causes hair to grow. Lastly, the follicle has a tiny muscle called the arrector pili that contracts when the follicle is stimulated by hormones.