Clic Cosmetology: Properties Of The Hair And Scalp (Part 1)

Wet hair with normal elasticity will stretch up to 50 percent of it's original length and return to that same length without breaking. Dry hair stretches about 1/5 (20%) of it's length.

Hair growth does occur in cycles, with each cycle consisting of three phases - anagen, catagen, and telogen. These phases are repeated throughout an individual's life. Therefore, the statement "Hair growth occurs in cycles. Each complete cycle has three phases that are repeated over and over again throughout life" is true.

Sebaceous glands are connected to the hair follicles and are responsible for producing sebum, an oily substance that helps to moisturize and protect the skin and hair. Sebum is released through the hair follicles and helps to keep the skin and hair lubricated. These glands are located in the dermis layer of the skin and are most commonly found on the face, scalp, and upper back.

Polypeptide chains intertwine around each other in a spiral shape called a helix.

Healthy hair with a compact cuticle layer is naturally resistant to penetration. Porous hair has a raised cuticle layer that easily absorbs water. Hair with low porosity is considered resistant hair. Hair with average porosity is considered normal hair. Hair with high porosity is considered overly porous hair and is the result of previous overprocessing. Overly porous hair is damaged, dry, fragile, and brittle.

The hair shaft refers to the portion of the hair that is visible above the skin's surface. It is the part of the hair that we can see and touch. The hair shaft is composed of dead cells that have been pushed up from the hair follicle, which is located beneath the skin. It is responsible for giving hair its length, color, and texture. The hair shaft can vary in thickness and texture depending on factors such as genetics and overall hair health.

Carbon: 51% in normal hair
Oxygen: 21% in normal hair
Hydrogen: 6% in normal hair
Nitrogen: 17% in normal hair
Sulfur: 5% in normal hair

Melanin is the pigment located within the cortex of the hair that gives it its natural color. It is responsible for determining the darkness or lightness of the hair, as well as its shade, such as brown, black, or blonde. Melanin is produced by specialized cells called melanocytes, and its presence or absence in the cortex determines the color of the hair. Therefore, melanin is the correct answer as it accurately describes the tiny grains of pigment that give natural color to the hair.

All natural hair color is the result of the ratio of eumelanin to pheomelanin, along with the total number and size of pigment granules.

Gray hair grows from the hair bulb in exactly the same way that pigmented hair grows and has exactly the same structure, but without the melanin pigment.

Sebum is the oily substance secreted by the sebaceous glands. It acts as a natural lubricant for both the hair and skin. By keeping the hair and skin moisturized, sebum helps to prevent dryness and maintain their health. It also helps to protect the skin from environmental factors, such as bacteria and pollutants. Overall, sebum plays a crucial role in maintaining the overall health and condition of the hair and skin.

Hair density can be classified as low, medium, or high. The average hair density is about 2,200 hairs per square inch. Hair with high density has more hairs per square inch and hair with low density has fewer hairs per inch. The numbers of hairs on the head varies with the color of hair.
Blonde: 140,000
Brown: 110,000
Black: 108,000
Red: 80,000

The hair root refers to the part of the hair that is located below the surface of the scalp. It is responsible for anchoring the hair follicle in the scalp and contains the hair bulb, which is where the hair growth occurs. The hair root is also connected to the blood vessels and nerves in the scalp, providing nourishment and sensation to the hair.

It is commonly found on infants and can be present on children until puberty. On adults, vellus hair is usually found in places that are normally considered hairless (forehead, eyelids, and bald scalp), as well as nearly all other areas of the body, except the palms of the hands and the soles of the feet. Women normally retain 55% more vellus hair than men. Vellus hair helps in the efficient evaporation of perspiration.

Shaving or cutting the hair has no effect on the hair growth. When hair is blunt cut to the same length, it grows back more evenly. Although it may seem to grow back faster, darker, and coarser, shaving or cutting hair has no effect on the hair growth.

It usually has a medulla and is easily distinguished from vellus hair by it's dark color and coarse texture. Normally changes during puberty cause some areas of fine vellus hair to be replaced with thicker terminal hair. All hair follicles are capable of producing either vellus or terminal hair, depending on genetics, age and hormonal changes.

The hair is either shed during the telogen phase or remains in place until the next anagen phase, when the new hair growing in pushes it out. About 10% of scalp hair is in the telogen phase at any one time. The telogen phase lasts for approximately three to six months. As soon as the telogen phase end, the hair returns to the anagen phase and begins the entire cycle again. On average, the entire growth cycle repeats itself once every four to five years.

It consists of a single, overlapping layer of transparent, scale-like cells that overlap like shingles on a roof. Swelling the hair raises the cuticle layer and opens the space between the scales, which allows liquids to penetrate. A healthy cuticle layer protects the hair from penetration and prevents damage to hair fibers.

It is quite common for very fine and naturally blonde hair to entirely lack a medulla. Generally, only thick coarse hair contains a medulla. All male bear hair contains a medulla. As far as cosmetology is concerned, the medulla is an "empty" air space and is not involved in salon services.

By the time the hair shaft emerges from the scalp, the cells of the hair are completely keratinized and are no longer living. Hair is approximately 91% protein. The protein is made up of long chains of amino acids, which, in turn, are made up of elements.

All natural hair color is the result of the ratio of eumelanin to pheomelanin, along with the total number and size of pigment granules.

The average growth of healthy scalp hair is about 1/2 inch per month. Scalp hair grows faster on women than on men. Scalp hair grows rapidly between the ages of 15 and 30, but slows down sharply after the age of 50. About 90% of scalp hair is growing in the anagen phase at any one time. For each specific hair, the anagen phase generally lasts from three to five years, but it some cases, it can last as long as ten years.

Although it is true that cross-sections of straight hair tend to be round and curlier hair tends to be more oval, modern microscopes have shown that a cross-section of hair can be almost any shape, including triangular, and that the shape of the cross-section does not always relate to the amount of curl.

Extremely curly hair grows in long twisted spirals. Some extremely curly hair has a natural tendency to form a coil like a telephone cord or the spring in an ink pen. Coiled hair usually has a fine texture, with many individual strands winding together to form the coiled locks that characterize this type of hair. Coiled hair usually has low elasticity, breaks, easily, and has a tendency to knot, especially on the ends.

Fear or cold causes it to contract, which makes the hair stand up straight, resulting in "goose bumps."

About 90% of the total weight of hair comes from the cortex. The elasticity of the hair and it's nature color are the result of the unique protein structures located within the cortex. The changes involved in oxidation haircoloring, wet setting, thermal styling, permanent waving, and chemical hair relaxing all take place within the cortex.

Permanent waves and chemical hair relaxers change the shape of hair by chemically changing the hair's disulfide bonds. Thio permanent waves break disulfide bonds, which are re-formed by thio neutralizers. Hydroxide chemical hair relaxers break disulfide bonds, which are converted to lanthionine bonds when the relaxer is rinsed from the hair. The disulfide bonds that are broken by hydroxide relaxers are broken permanently and can never be re-formed.

Two streams flowing in opposite directions form a natural part in the hair.

During the catagen phase, the follicle canal shrinks and detaches from the dermal papilla. The hair bulb disappears and the shrunken root end forms a rounded club. Less than 1% of scalp hair is in the catagen phase at any one time. The catagen phase is very short and lasts from one to two weeks.

These side bonds hold the hair fibers in place and account for the incredible strength and elasticity of human hair. These side bonds are essential to wet sets, thermal styling, permanent waving, and chemical hair relaxing.

Although individual hydrogen bonds are very weak, there are so many of them that they account for about one-third of the hair's overall strength.

A whorl normally forms in the crown with all the hair from that point growing down.

Wave pattern is the result of genetics and racial background. Although there are exceptions, as a general rule, Asians tend to have extremely straight hair, Caucasians tend to have straight to wavy hair, and African Americans tend to have extremely curly hair. But straight, curly, and extremely curly hair occurs in all races.

The dermal papilla contains the blood and nerve supply that provides the nutrients needed for hair growth.

The lower part of the hair bulb fits over and covers the dermal papilla.

Straight hair has a fairly regular and uniform diameter along a single strand, and its cross sections are usually round. This means that each strand of straight hair has a consistent thickness throughout its length, and the shape of the hair shaft is circular. In contrast, wavy and extremely curly hair often have irregular diameters and non-round cross sections, resulting in a more textured and varied appearance.

A peptide bond is the correct answer because it is the chemical bond that joins amino acids together in a polypeptide chain. This bond forms between the carboxyl group of one amino acid and the amino group of another amino acid, resulting in the formation of a peptide bond. It is a covalent bond and is essential for the formation of proteins in living organisms.

Wavy hair is characterized by cross-sections that are usually oval and have a fairly regular and uniform diameter along a single strand. This means that the hair strands have a slight wave pattern, with a consistent width throughout. Unlike extremely curly hair, which has irregular and varied cross-sections, and straight hair, which has circular cross-sections, wavy hair falls in between, showcasing oval-shaped cross-sections.

Hair follicles are distributed all over the body, with the exception of the palms of the hands and the soles of the feet.

Salt bonds are easily broken by strong alkaline or acidic solutions and account for about one-third of the hair's overall strength.

Hair texture can be classified as coarse, medium, or fine. Coarse hair has the largest diameter. Medium hair texture is the most common and is the standard to which other hair is compared. Medium hair is considered normal and does not pose any special problems or concerns. Fine hair has the smallest diameter and is more fragile, easier to process, and more susceptible to damage from chemical services.

Hair analysis is performed by observation using the sense of sight, touch, hearing, and smell. The four most important factors to consider in hair analysis are texture, porosity, elasticity, and density. Other factors you should also be aware of are growth pattern as well as dryness and oiliness.

Amino acids are the units of structure in proteins that are linked together end to end like pop beads. Peptide bonds are the chemical bonds that connect amino acids in a protein chain, forming a polypeptide chain. Therefore, the correct answer is amino acids.

Cowlicks are usually more noticeable at the front hairline, but they may be located anywhere.