ch .5

Hair

Dead keratinized cells.

Hard keratin

More durable than soft keratin, does not flake off.

Function of hair

Protects from physical trauma, heat loss, and sunlight.

Hair color production

Produces hair pigments.

Types of hair pigments

Yellow, rust, brown, black.

Pheomelanin

The pigment responsible for yellow and red hair colors.

Condition for gray/white hair

Decrease in melanin production.

Why hair turns gray

Air bubbles replace melanin in the hair shaft.

Hair type shaft shapes

Flat for kinky, oval for wavy, perfectly round for straight.

Vellus hair

Pale, fine hair on the body of children and adult females.

Coarse hair

Long hair found on the scalp, eyebrows, and eyelashes.

Influence on coarse hair

Stimulated by androgens (testosterone) during puberty.

Nutrition and hormones

Affect hair growth.

Active phase of hair growth

Phase where the hair matrix divides.

Resting phase duration

Duration reduces in time, a few months for eyebrows, 1 month for eyelashes.

Alopecia

Thinning of hair in both sexes, common in ages 60-65.

Male pattern baldness

Genetically determined and sex linked baldness.

Myoepithelial cells

Contract in response to the sympathetic nervous system to force sweat.

Sebaceous glands

Glands that secrete sebum to lubricate and soften the skin.

Sudoriferous glands

Sweat glands found on all skin surfaces.

Eccrine glands

Abundant sweat glands on palms, soles, and forehead.

Apocrine sweat glands

Glands found in axillary and anogenital regions, odorless until bacteria breakdown.

Ceruminous glands

Modified apocrine glands that secrete ear wax.

Mammary glands

Glads that secrete milk.

Insensible perspiration

Unnoticeable sweat.

Sensible perspiration

Sweat that is noticeable due to temperature rises.

Cutaneous sensation

Includes pain, pressure, touch, and temperature stimuli.

Dendritic cells

Epidermal phagocytes that present foreign antigens.

Skin cancer incidence

1 in 5 individuals will develop skin cancer.

Basal cell carcinoma

Least deadly skin cancer, 99% curable if detected early.

Squamous cell carcinoma

Rapidly growing cancer from keratinocytes; can metastasize.

Melanoma

Most dangerous skin cancer developing from melanocytes.

ABCDE rule for skin cancer

A = asymmetry, B = border irregularity, C = color, D = diameter, E = evolving.

First degree burns

Partial thickness burn affecting the epidermis, heals in 2-4 days.

Second degree burns

Burn affecting epidermis and upper dermis, may blister.

Third degree burns

Full thickness burn that destroys nerve endings.

Rule of nines in burns

Used to assess the percentage of the body burned.

Critical burn condition

25% 2nd degree burns or 10% 3rd degree burns.

Immediate threat of serious burns

Risks of fluid loss, dehydration, and electrolyte imbalance.

Role of skin in vitamin D synthesis

Converts 7-dehydrocholesterol to cholecalciferol upon UV exposure.

Thermoregulation

Function of sweat glands regulated by the sympathetic nervous system.

Bactericidal action of sweat

Inhibits bacterial growth via dermcidin.

Hair follicle receptors

Sensitive to light touch and bending of hair.

Meissner's corpuscles

Detect light touch and discriminative touch.

Bulbous corpuscles

Detect deep, continuous pressure in the dermis.

Laminar corpuscle

Detect deep pressure and vibration.

Epithelial tactile complex

Responds to light touch.

Hirsutism

Excessive body hair in females caused by androgens.