Skin Accessory Structures Overview

Overview

This lecture reviews the accessory structures of the skin, their functions, conditions affecting them, and the processes of wound healing and burns.

Hair follicles are highly keratinized squamous cells derived from the epidermis but located in the dermis.
The hair bulb contains dividing cells and DNA; the root is under the skin, the shaft is above and dead.
Hair growth cycles include rest and replacement; baldness can occur when hair is not replaced.
Androgenic alopecia (male pattern baldness) is genetic and linked to male hormones; alopecia areata is autoimmune.
Sebaceous glands secrete oil (sebum) to keep skin and hair pliable and waterproof; they are holocrine glands.
Excess sebum can cause acne or seborrhea (body acne); sebaceous glands are absent on palms and soles.
Nails are protective, highly keratinized structures; the lunula is where mitosis occurs.
Damaging the lunula may cause permanent nail loss; nails aid in manipulation and protection.

Sweat glands (sudoriferous glands) are widespread; two types: eccrine and apocrine.
Eccrine glands respond to heat/stress and secrete watery sweat directly onto the skin.
Apocrine glands are in armpits and groin, activate at puberty, and produce sweat mixed with oil, causing body odor.
Apocrine secretions are involved in pheromone production and emotional responses.
Modified sweat glands include ceruminous glands (produce earwax) and mammary glands (produce milk).

Melanin gives brown color; carotene provides yellow-orange tint, especially in fat and stratum corneum.
Hemoglobin, although not a pigment, influences skin redness and warmth due to blood flow.

Skin condition affects aesthetics and communication; good skin is socially valued.
Most skincare products remain on the surface due to the barrier of the stratum corneum.
Nutrients like vitamins A (retinol), C, and E support skin structure and protection.

Inflammation is a normal healing response, bringing blood and immune cells to injury.
Shallow cuts heal by increased epithelial mitosis; deep cuts require blood clots and collagen (fibroblasts) formation.
Scars form when connective tissue replaces epithelial tissue following deep wounds.
Granulation tissue is moist, bumpy tissue seen during healing.

First-degree burns affect epidermis only, heal without scarring.
Second-degree burns reach dermis, cause blisters, and may scar if severe.
Third-degree burns destroy epidermis, dermis, and hypodermis, require grafts, and result in scarring.
Burn severity is measured using the "rule of nines" to estimate total body area affected.

Keratinization — process where cells fill with keratin and die, making structures like hair and nails tough.
Sebum — oily secretion from sebaceous glands.
Alopecia — loss of hair; can be hormonal or autoimmune.
Eccrine gland — sweat gland that produces watery, odorless sweat.
Apocrine gland — sweat gland that produces thicker, odorous sweat.
Lunula — white, crescent area at nail base where growth occurs.
Granulation tissue — new connective tissue and tiny blood vessels formed during healing.
Autograft — transplant of skin from another area of a patient’s own body.
Rule of Nines — method to estimate body surface area affected by burns.