Topic 2: Integumentary System

Comprehensive vocabulary flashcards covering the structures, accessory organs, homeostatic temperature regulation mechanisms, and pathologies of the integumentary system.

Integumentary System

The largest organ system of the body, accounting for approximately $16\%$ of body weight and $1.5$ to $2\,\text{m}^2$ in surface area, composed of the cutaneous membrane (skin) and accessory structures.

Epidermis

The outermost and most superficial layer of the skin that provides a waterproof barrier, protects against UV radiation and microorganisms, and contains melanocytes.

Dermis

The middle layer of the skin located between the epidermis and subcutaneous layer; contains collagen and elastin for strength and elasticity, houses blood vessels, sweat glands, hair follicles, and sensory nerve endings.

Hypodermis (Subcutaneous Layer)

The layer below the dermis composed of adipose and loose connective tissue that stabilizes the skin against underlying organs, cushions against impact, stores energy, and insulates the body.

Melanocytes

Specialized cells in the epidermis that produce melanin to determine skin and hair color and disperse harmful UV radiation.

Albinism

A condition in which melanocytes completely fail to secrete melanin, causing the hair, skin, and irises to appear white.

Vitiligo

A condition characterized by a loss of pigment in localized areas of the skin, resulting in white patches due to the disappearance of melanocytes and interruption of melanin production.

Malignant Melanoma

A cancerous change in a mole that can metastasize rapidly, is difficult to treat, and is strongly associated with sunlight exposure.

Stretch Marks

Thickened skin tissue resulting from excessive stretching due to pregnancy or rapid weight gain and obesity.

Arrector Pili

An involuntary smooth muscle attached to a hair follicle that contracts to make hairs stand upright.

Alopecia

The clinical term for hair loss, occurring when hair shedding significantly exceeds the normal rate of approximately $50$ hairs per day (greater than $100$ hairs per day).

Sebaceous Glands

Exocrine oil glands located in the dermis associated with hair follicles that secrete sebum to lubricate and moisten the skin and hair.

Sebum

An oily secretion produced by sebaceous glands that keeps the hair and skin lubricated and prevents moisture loss.

Eccrine Glands

Sweat glands distributed across most of the body surface (especially palms and soles) that secrete a watery fluid consisting of $99\%$ $\text{H}_2\text{O}$, $\text{NaCl}$, and organic wastes to cool the skin and flush out toxins.

Apocrine Glands

Large sweat glands located in the armpits, groin, and around the nipples that produce a sticky, cloudy, and odorous secretion.

Vasodilation

The widening of arterioles in the skin during heat exposure, allowing more blood to flow to surface capillaries to release heat.

Vasoconstriction

The narrowing of skin arterioles in response to cold temperatures, reducing blood flow to the skin surface to preserve core body heat.

Pilorelaxation

A thermoregulatory cooling mechanism in which hair follicles relax, causing body hairs to lie flat against the skin surface.

Piloerection

A thermoregulatory response to cold conditions where arrector pili muscles contract, causing skin hairs to stand up to trap warm air.

Shivering

Rapid, involuntary contraction and relaxation of skeletal muscles that generates internal heat via cellular respiration when core temperature falls.

Nail Matrix

The active growth region of the nail located beneath the skin that continuously generates hard keratin to form the nail plate.