Skin & Membranes – Human Anatomy and Physiology, Chapter 7

Vocabulary flashcards covering major structures, cell types, layers, pigments, glands, functions, pathological conditions, and terminology from the Skin & Membranes lecture notes.

Integumentary System

The organ system consisting of skin, hair, nails, sweat glands, and sebaceous (oil) glands.

Epidermis

Superficial, avascular layer of skin composed of keratinized stratified squamous epithelium.

Dermis

Deep, vascular layer of skin made of fibrous connective tissue; supports the epidermis.

Hypodermis (Superficial Fascia)

Subcutaneous layer of adipose tissue beneath skin that anchors skin to underlying muscles, absorbs shock, and insulates; not part of the skin proper.

Keratinocytes

Major epidermal cells that produce fibrous protein keratin, providing protective properties.

Melanocytes

Spider-shaped epidermal cells that produce melanin pigment to protect nuclei from UV damage.

Dendritic (Langerhans) Cells

Star-shaped macrophages in epidermis that ingest foreign substances and activate immune response.

Tactile (Merkel) Cells

Epidermal cells associated with sensory nerve endings; function as touch receptors.

Stratum Basale (Stratum Germinativum)

Deepest epidermal layer; single row of mitotic stem cells where keratinocyte production begins; contains melanocytes.

Stratum Spinosum

Several layers of “prickle” cells with prekeratin filaments; contains abundant dendritic cells.

Stratum Granulosum

1–5 cell layers where keratinization starts; cells flatten, organelles disintegrate, and lamellar granules add water-resistant glycolipid.

Stratum Lucidum

Thin, clear layer of flat dead keratinocytes present only in thick skin (palms, soles).

Stratum Corneum

Outermost 20–30 layers of dead, anucleate keratinized cells providing abrasion resistance and water barrier.

Papillary Layer

Superficial dermal layer of areolar connective tissue with dermal papillae projecting into epidermis.

Dermal Papillae

Fingerlike projections of the papillary dermis that create epidermal ridges and house capillaries or tactile receptors.

Reticular Layer

Deep dermal layer (~80%) of dense irregular connective tissue with collagen and elastic fibers; provides strength and recoil.

Striae (Stretch Marks)

Dermal scars produced by extreme stretching that tears collagen in reticular layer.

Cutaneous Plexus

Network of blood vessels between reticular dermis and hypodermis.

Melanin

Only skin-made pigment; ranges reddish-yellow to brown-black; shields DNA from UV radiation.

Carotene

Yellow-orange pigment accumulated in stratum corneum and hypodermis; can convert to vitamin A.

Hemoglobin

Oxygen-binding pigment in red blood cells that imparts pinkish hue to fair skin.

Hair (Pilus)

Flexible strand of dead, hard-keratinized cells produced by hair follicles.

Hair Shaft

Part of hair projecting above skin surface where keratinization is complete.

Hair Root

Hair portion within the skin where keratinization is ongoing.

Medulla (Hair)

Central core of large cells and air spaces within the hair shaft.

Cortex (Hair)

Several layers of flattened cells surrounding the medulla.

Cuticle (Hair)

Outer single-cell layer of overlapping shingle-like cells protecting the hair shaft.

Hair Follicle

Tubular invagination of epidermis extending into dermis that produces hair.

Hair Bulb

Expanded deep end of the hair follicle housing the hair matrix and papilla.

Root Hair Plexus

Sensory nerve endings wrapping the hair bulb; acts as a touch receptor.

Hair Papilla

Dermal tissue containing capillaries that supply nutrients to growing hair.

Hair Matrix

Mitotically active region of the hair bulb producing hair cells.

Arrector Pili

Small band of smooth muscle attached to hair follicle causing “goose bumps.”

Vellus Hair

Fine, pale body hair of children and adult females.

Terminal Hair

Coarse, long hair of scalp, eyebrows, and, post-puberty, axillary, pubic, and male facial regions.

Alopecia

Hair thinning after age 40 due to follicle cycle limitations; terminal hair replaced by vellus hair.

Nail

Hard keratin plate covering distal digits; composed of free edge, nail plate, and root.

Nail Bed

Epidermis beneath the translucent keratinized nail plate.

Nail Matrix

Thickened proximal nail bed responsible for nail growth.

Eponychium (Cuticle)

Skin fold projecting onto nail body at proximal edge.

Hyponychium

Area under free nail edge that accumulates dirt.

Lunule

Whitish, half-moon region of thickened nail matrix.

Sweat (Sudoriferous) Glands

Exocrine glands producing sweat; include eccrine and apocrine types.

Eccrine Sweat Glands

Most numerous merocrine glands secreting watery sweat for thermoregulation; abundant on palms, soles, forehead.

Thermoregulation

Homeostatic process of maintaining body temperature, aided by eccrine sweating.

Apocrine Sweat Glands

Larger merocrine glands in axillary and anogenital areas; secrete viscous, protein-rich sweat onto hair follicles.

Ceruminous Glands

Modified apocrine glands of external ear canal producing cerumen (earwax).

Mammary Glands

Modified apocrine glands specialized to secrete milk.

Sebaceous (Oil) Glands

Holocrine glands secreting sebum into hair follicles; absent on palms and soles.

Sebum

Oily secretion that lubricates skin and hair, slows water loss, and is bactericidal.

Dermcidin

Antimicrobial peptide present in eccrine sweat.

Lamellar Granules

Granules in stratum granulosum that release water-resistant glycolipids.

Skin Functions

Six roles: protection, body temperature regulation, cutaneous sensation, metabolic functions, blood reservoir, excretion.

Acid Mantle

Slightly acidic film on skin surface inhibiting bacterial growth.

Defensins

Natural antimicrobial peptides secreted by the skin.

Cathelicidins

Antimicrobial peptides released from injured skin aiding defense.

Insensible Perspiration

Unnoticeable sweat (~500 mL/day) produced under resting conditions.

Sensible Perspiration

Visible sweat produced during heat or exercise to cool the body.

Exteroceptors

Cutaneous sensory receptors responding to external stimuli such as touch and temperature.

Vitamin D Synthesis

Skin-mediated conversion of cholesterol derivative to vitamin D precursor for calcium absorption.

Collagenase

Enzyme produced by skin to assist collagen turnover and reduce wrinkle formation.

Skin Lesion

Any measurable variation from normal skin structure.

Papule

Small, firm, raised skin lesion.

Plaque

Large, raised, flat-topped skin lesion.

Vesicle

Small fluid-filled blister.

Pustule

Pus-filled skin lesion.

Crust

Dried exudate forming a scab on skin surface.

Wheal (Hive)

Raised, firm lesion with a pale center, characteristic of urticaria.

Macule

Flat, discolored skin area without elevation or depression.

Excoriation

Scratch-induced loss of epidermis producing a depressed lesion.

Ulcer

Crater-like lesion resulting from tissue destruction.

Fissure

Deep crack or break through epidermis into dermis.

First-Degree Burn

Partial-thickness burn damaging only epidermis; redness and pain.

Second-Degree Burn

Partial-thickness burn involving epidermis and upper dermis; blisters form.

Third-Degree Burn

Full-thickness burn destroying epidermis and dermis; skin appears gray-white or charred, initially painless.

Fourth-Degree Burn

Full-thickness burn extending into muscle or bone.

Rule of Nines

Method dividing adult body into 11 areas of 9% each to estimate burn surface area.

Impetigo

Highly contagious bacterial (staph or strep) skin infection producing pustules and crusts.

Tinea

Fungal (mycotic) skin infection such as ringworm or athlete’s foot.

Wart

Benign skin growth caused by papillomavirus infection.

Boil (Furuncle)

Staphylococcal infection of a hair follicle producing a painful pus-filled nodule.

Scabies

Parasitic mite infestation causing intense itching and burrows in skin.

Decubitus Ulcer (Bedsore)

Skin necrosis due to prolonged pressure reducing blood flow.

Urticaria (Hives)

Red, itchy wheals caused by fluid leakage from blood vessels.

Scleroderma

Autoimmune disorder causing hardening and thickening of skin; localized or systemic forms.

Psoriasis

Chronic inflammatory skin disease with scaly silver plaques.

Eczema

Inflammatory condition with papules, vesicles, and crusts; symptom of underlying issue.

Squamous Cell Carcinoma

Common skin cancer producing hard, raised tumors from keratinocytes of stratum spinosum.

Basal Cell Carcinoma

Most common, least malignant skin cancer forming pearly papules with central crater.

Malignant Melanoma

Cancer of melanocytes within a nevus; most serious skin cancer.

Kaposi Sarcoma

Vascular cancer with purple lesions associated with AIDS and immune deficiencies.