Integumentary System Part 2: Skin Pigments and Accessory Structures

Comprehensive vocabulary flashcards covering the pigments of skin color and the anatomy and function of accessory structures of the integumentary system: hair, hair follicles, nails, sudoriferous glands, and sebaceous glands.

Melanin

The only pigment made directly in the skin by melanocytes; it is packaged into melanosomes to shield keratinocyte DNA from damaging UV sunlight.

Melanosomes

Intracellular transport vesicles produced by melanocytes that carry melanin pigment to keratinocytes to form a protective shield over their DNA.

Carotene

A yellow to orange pigment that accumulates in the stratum corneum and subcutaneous tissue, most evident in the palms and soles, which can be converted to vitamin A.

Hemoglobin

An oxygen-carrying pigment whose crimson color shows through fair skin to produce a pinkish hue due to lower melanin levels and greater epidermal transparency.

Hard Keratin

A tough, durable form of keratin found in hair and nails whose cells do not flake off, unlike the soft keratin present in the epidermal skin.

Hair Root

The structural portion of the hair embedded within the scalp where active keratinization is still in progress.

Hair Shaft

The visible portion of hair that projects above the scalp surface where keratinization is complete.

Medulla (Hair)

The central core of the hair shaft composed of large cells and air spaces.

Cortex (Hair)

The intermediate layer of the hair shaft surrounding the medulla, consisting of several layers of flattened cells.

Cuticle (Hair)

The outermost layer of the hair shaft composed of a single layer of overlapping cells.

Hair Bulb

The deep, expanded base of the hair follicle that encloses the hair matrix and hair papilla.

Hair Follicle Receptor (Root Hair Plexus)

A network of sensory nerve endings that wraps around the hair bulb, acting as a sensitive touch receptor when the hair is displaced.

Hair Papilla

Dermal tissue containing a knot of capillaries at the base of the hair bulb that supplies nutrients to the growing hair; its destruction stops hair production permanently.

Hair Matrix

The actively dividing germinal region of the hair bulb that generates new hair cells, pushing older cells upward.

Arrector Pili

A tiny bundle of smooth muscle cells attached to a hair follicle whose contraction pulls the hair upright, causing "goose bumps."

Vellus Hair

Pale, fine body hair characteristic of children and adult females.

Terminal Hair

Coarse, longer pigmented hair found on the scalp and eyebrows.

Male Pattern Baldness

A genetically determined, androgen-influenced condition in which hair follicles respond to male sex hormones with progressively shorter growth cycles.

Nail Plate (Nail Body)

The visible, attached portion of the nail made of hard keratin that provides a protective cover for the dorsal tip of a finger or toe.

Nail Bed

The deeper layers of living epidermis directly beneath the keratinized nail plate.

Nail Matrix

The thickened proximal portion of the nail bed responsible for continuous nail growth.

Eponychium (Cuticle)

The fold of skin along the proximal border of the nail plate that extends onto the surface of the nail body.

Hyponychium

The thickened epidermal area beneath the free edge of the nail plate where dirt tends to accumulate.

Lunule

The white, crescent-shaped region at the proximal base of the nail plate, appearing white because of the thickened underlying nail matrix.

Sudoriferous Glands

Cutaneous sweat glands that assist in thermoregulation, categorized into eccrine and apocrine types.

Eccrine (Merocrine) Sweat Glands

The most numerous sweat glands, located abundantly on the palms, soles, and forehead, whose ducts release a watery secretion ($99\%$ water with a pH between $4\text{ to }6$) onto skin pores for thermoregulation.

Dermcidin

A microbe-killing peptide found within eccrine sweat secretions that provides chemical protection against microorganisms.

Apocrine Sweat Glands

Merocrine sweat glands primarily confined to axillary and anogenital areas that produce a viscous, yellowish fluid rich in lipids and proteins, which produces body odor when broken down by bacteria.

Ceruminous Glands

Modified apocrine glands located in the external auditory canal that secrete cerumen, or earwax.

Mammary Glands

Specialized, modified sweat glands of the integumentary system that secrete milk.

Sebaceous Glands

Holocrine oil glands widely distributed throughout the body (except thick skin of palms and soles) that secrete sebum, usually directly into hair follicles.

Sebum

An oily holocrine secretion possessing bactericidal properties that lubricates, waterproofs, and softens hair and skin.