The Integumentary System: every key term you need (+ practice quiz)
25 flashcard terms for Anatomy & Physiology I Topic 4, written to match the course framework. Study them here, then drill them as interactive flashcards, or test yourself with the 15-question quiz — free, no account needed.
The skin together with hair, nails, and cutaneous glands. It forms the boundary organ of the body, serving in protection, thermoregulation, sensation, excretion and the first step of vitamin D synthesis.
Epidermis
The outer avascular layer of skin, a keratinized stratified squamous epithelium renewed continuously from its deepest layer. Its cells migrate upward, accumulate keratin, die and are shed from the surface.
Dermis
The strong vascular connective tissue layer beneath the epidermis, built of collagen and elastic fibers. It carries blood vessels, nerve endings, hair follicles and glands, and it supplies the skin with tensile strength.
Hypodermis
The subcutaneous layer of areolar and adipose tissue beneath the dermis. Not strictly part of the skin, it anchors skin to underlying structures, stores energy and provides insulation and shock absorption.
Keratinocyte
The dominant epidermal cell type, produced by mitosis in the deepest stratum and specialized to manufacture keratin. Its accumulated protein and lipid products create the tough waterproof surface barrier.
Melanocyte
A branched pigment cell of the deepest epidermal layer that synthesizes melanin and transfers it in vesicles to surrounding keratinocytes, where the pigment shields nuclear DNA from ultraviolet damage.
Melanin
The brown to black or reddish pigment that determines much of skin and hair color and absorbs ultraviolet radiation. Racial differences in skin tone reflect pigment production and breakdown, not melanocyte number.
Tactile epithelial cell
A sensory epidermal cell of the deepest layer that associates with a disc-shaped nerve ending to detect light touch. It is one of the receptors giving the fingertips fine discriminative sensitivity.
Dendritic cell of the epidermis
A star-shaped immune cell that arises in bone marrow, migrates into the epidermis, and captures invading microbes for presentation to lymphocytes, making the skin an active immune surveillance organ.
Stratum basale
The single deepest epidermal layer resting on the basement membrane, where mitosis renews the epidermis. It also contains melanocytes and tactile epithelial cells among its dividing keratinocytes.
Stratum spinosum
The several-cell-thick layer above the basal layer whose cells appear spiny in prepared sections because tissue shrinkage exposes their numerous desmosomes. It provides much of the epidermis mechanical strength.
Stratum granulosum
The layer in which keratinocytes accumulate keratohyalin and lipid-filled granules, release waterproofing lipid into the intercellular space, and begin to die as they move away from the dermal blood supply.
Stratum lucidum
A thin translucent band of flattened dead cells present only in thick skin of the palms and soles. It lies between the granular and cornified layers and adds to abrasion resistance.
Stratum corneum
The outermost layer of many flattened dead keratinized cells surrounded by lipid. It is the main barrier against abrasion, microbial invasion and water loss, and it is shed and replaced continually.
Papillary layer
The thin superficial dermal layer of areolar tissue projecting upward as dermal papillae. It carries capillary loops and touch receptors and produces the friction ridges that create fingerprints.
Reticular layer
The thick deep dermal layer of dense irregular connective tissue whose interwoven collagen bundles provide strength in all directions. Tears in its collagen produce the visible marks called striae.
Eccrine sweat gland
A widely distributed coiled gland that releases a watery secretion of water, salts and traces of waste onto the skin surface. Evaporation of this fluid is the principal route of heat loss during exertion.
Apocrine sweat gland
A larger gland confined mainly to the axillary and genital regions that empties a protein-rich and lipid-rich secretion into a hair follicle. Bacterial breakdown of that secretion produces body odor.
Sebaceous gland
A holocrine gland usually opening into a hair follicle that secretes sebum, an oily mixture of lipids and cell debris. Sebum softens hair and skin and inhibits some surface bacteria.
Hair follicle
A downgrowth of epidermis into the dermis that surrounds and produces a hair. Mitosis in the matrix of its bulb pushes older cells upward, where they keratinize and die to form the shaft.
Arrector pili
A small band of smooth muscle running from the dermal papillary layer to a hair follicle. Sympathetic contraction pulls the hair upright and dimples the skin, producing goose bumps.
Nail
A scale-like plate of hard keratin covering the dorsal tip of a finger or toe. It grows from the nail matrix beneath the proximal end and provides a firm backing for delicate touch.
Cutaneous vasomotor response
Sympathetic adjustment of dermal blood flow for thermoregulation. Vasodilation shunts warm blood toward the surface to lose heat, while vasoconstriction diverts it inward to conserve core temperature.
Vitamin D synthesis in skin
The ultraviolet-driven conversion of a cholesterol derivative in epidermal cells into a precursor that liver and kidney then modify into the active hormone required for calcium absorption from the intestine.
Rule of nines
A rapid clinical estimate of the body surface area burned, assigning multiples of nine percent to the head, each limb segment and the trunk surfaces. It guides fluid replacement in serious burns.