Hair Anatomy & Physiology

The correct answer refers to the bulk or core of hair specifically, not to be confused with other meanings such as the part of the brain responsible for higher-order brain functions, the outer layer of the Earth's mantle, or a type of tree found in tropical rainforests.

The medulla is the innermost layer of the hair shaft and is made of soft keratin, typically 2-3 layers thick. Hard keratin is found in nails and hooves, melanin gives hair its color, and collagen is a protein found in connective tissues.

The shaft of the hair is the visible part that is composed of keratinized epithelial cells, while the root, follicle, and bulb are also involved in hair growth but do not consist of keratinized cells.

The three layers that create the hair root and shaft are the bulb, root, and shaft. The bulb is the base of the hair follicle, the root is the part of the hair beneath the skin, and the shaft is the visible part of the hair.

The correct answer varies depending on the location on the body, with back or dense areas having up to 150 follicles in one square centimeter of skin.

The hair follicle originates in the dermis where it is rooted in the dermal papilla bulb which is nourished by capillaries carrying blood and oxygen. The epidermis, subcutaneous tissue, and muscle tissue are not the origins of the hair follicle.

Hair turns gray due to a decrease in melanin production with age, not due to lack of care, sunlight exposure, or solely genetic factors.

Hair color inheritance is more complex, with multiple genes playing a role. This can lead to various combinations and expressions of hair color, making it inaccurate to say dark hair is always dominant over light hair.

Red hair is caused by a modified type of melanin that contains iron, which results in the distinctive red color. It is not directly related to sunlight exposure, genetic mutations, or a skin condition.

The papilla on the surface of the tongue contain blood vessels which help in maintaining circulation to the taste buds located on the tongue.

The correct answer describes the location and function of the matrix specifically in relation to hair cells. The incorrect answers provide alternative definitions or locations for the term 'matrix' to create confusion.

Hard keratin is found in the cortex and cuticle layers of the hair, providing strength and protection to the hair strands. The medulla is the innermost layer, the follicle is the structure from which the hair grows, and the sebaceous gland produces oil for the hair and skin. The shaft is the visible part of the hair, while the root is the part embedded in the skin.

The papilla's function is to supply nourishment to the cell through blood vessels, aiding in maintaining the health and functioning of the cell.

The hair bulb is located below the surface of the skin and is where the base of the hair root is found. The bulb contains the matrix and papilla, which provide nutrients for hair growth.

The cortex refers to the bulk core of hair, not the outer layer of the brain, part of a tree trunk, or a type of bone marrow.

When superficial skin is damaged, the undamaged part of the hair follicle that lies deep in the elements serves as a source of new epithelium because it contains stem cells that can differentiate and regenerate new skin cells.

Maximum hair length is not solely determined by one factor such as genetics, hair products, treatments, or hair color. Rather, it is influenced by a combination of individual factors including health, rate of hair growth, and length of the growing phase.

After shaving, hairs may feel coarse and bristly because the blunt ends of the hair are less flexible compared to when they have tapered ends. This creates a rougher texture on the skin.

Eyelashes have a growth phase of approximately 30 days, followed by a resting phase of about 150 days. The incorrect answers provided vary in the length of time for growth and rest periods of eyelashes compared to the correct information.

Scalp hairs grow for about 3 years before entering the resting phase for 1-2 years. The incorrect answers provided do not accurately reflect the typical growth and rest periods for scalp hairs.

Loss of hair usually means that the hair is in the process of being replaced by new hair growth.

The correct stages of hair growth are Anagen (active growth), Catagen (transitional phase), and Telogen (resting phase) where the hair is shed before the cycle starts again.

The anagen stage is known as the active growth phase of hair growth where the hair follicle is actively producing hair. It lasts between 2 to 6 years and contains an abundance of melanin. Approximately 85% of the hair on one's head is in this stage at any given time.

The catagen or Regression phase is a transition phase lasting 1-2 weeks where the hair follicle starts to destroy itself. The hair disconnects from the papilla, with lower parts stopping in terms of growth. Eventually, the follicle is reabsorbed.

The telogen phase is known as the resting phase in the hair growth cycle where the hair follicle rests and prepares for the next growth phase. It typically lasts for 5-6 weeks, during which the hair sheds to make way for new growth in the anagen phase.

The correct answer is estimated 90% of scalp hairs are in the growing stage. The normal cycle of hair growth involves approximately 90% of scalp hairs being in the growing stage at any given time.

The erector pili muscle is responsible for causing the hair to become erect, giving rise to phenomena such as 'goosebumps'. The other muscles listed are not associated with hair erection.

Hair is not found in certain specific areas of the human body due to the absence of hair follicles, which are responsible for producing and growing hair.