Anatomy and Physiology: The Integumentary System

Comprehensive vocabulary flashcards covering the anatomy, histology, physiological functions, appendages, and clinical pathologies of the integumentary system.

Cutaneous Membrane

An epithelial surface layer (epidermis) resting on underlying connective tissue (dermis) that serves as a vital protective interface between internal physiological systems and external surroundings.

Epidermis

The superficial epithelial region of the skin composed of keratinized stratified squamous epithelium; it is avascular and receives nutrients entirely via diffusion from the underlying dermis.

Dermis

The middle layer forming the structural bulk of the skin ("hide"), composed of strong, flexible, dense irregular connective tissue supplied with blood vessels, lymphatic vessels, and sensory nerve networks.

Hypodermis (Subcutaneous Layer)

A layer located deep to the dermis (not strictly part of the skin) composed primarily of loose connective tissue and adipose tissue; functions in thermal insulation, shock absorption, and anchoring the skin to deep fascia.

Thick Skin

Skin containing five structural strata located in high-abrasion regions (palms of the hands, soles of the feet, and digits); arranged superficial to deep via the mnemonic "Can Lucy Get Some Beer".

Thin Skin

Skin containing four structural strata that covers the majority of the body surface; it lacks the stratum lucidum and is arranged superficial to deep via the mnemonic "Can Get Some Beer".

Stratum Basale (Stratum Germinativum)

The deepest epidermal layer, anchored directly to the dermal basal lamina, consisting of a single layer of active cuboidal stem cells undergoing continuous mitosis.

Stratum Spinosum

An epidermal layer several cells thick where cells exhibit a spiny histological appearance due to cytoplasm shrinkage around desmosomes; keratinocytes synthesize pre-keratin and secrete water-repelling glycolipids.

Stratum Granulosum

An epidermal layer consisting of $3-5$ layers of flattened keratinocytes undergoing structural breakdown, accumulating keratohyaline granules and lipid-rich lamellar granules for waterproofing.

Stratum Lucidum

A thin, clear, translucent band consisting of $2-3$ layers of dead, flattened, fully keratinized keratinocytes located exclusively in thick skin superficial to the stratum granulosum.

Stratum Corneum

The most superficial epidermal layer exposed to the external environment, composed of $15-30$ layers of dead, flattened, anucleated scale-like cells filled with tough fibrous keratin and reinforced with glycolipids.

Keratinocytes

The dominant cell type of the epidermis that synthesizes the tough, durable fibrous protein keratin.

Melanocytes

Cells accounting for $10-25\%$ of cells in the stratum basale that synthesize the protective dark pigment melanin to shield keratinocyte nuclear DNA from UV damage.

Papillary Layer

The superficial layer of the dermis composed of loose areolar connective tissue; features dermal papillae, capillary loops, free nerve endings, and Meissner's corpuscles.

Melanin

A pigment ranging from yellow to reddish-brown to dark black synthesized in melanosomes within melanocytes and transferred into keratinocytes to shield nuclear DNA from ultraviolet radiation.

Vitiligo

An autoimmune condition characterized by the loss of functional melanocytes within specific skin areas, producing distinct unpigmented (white) patches.

Hair Follicle

An epidermal epithelial structure extending deep into the dermis or hypodermis that expands at its base into a hair bulb supplied by a vascularized hair papilla and houses the dividing hair matrix.

Hair Matrix

The actively dividing germinal stem cell layer within the hair bulb responsible for generating new hair tissue.

Arrector Pili Muscle

A bundle of smooth muscle attached to the hair follicle that pulls the hair upright and produces "goosebumps" in response to cold or fear.

Vellus Hair

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

Terminal Hair

Coarse, long, pigmented hair found on the scalp, eyebrows, axillary, and pubic regions, and on the face and neck in mature males.

Nail Body (Plate)

The visible attached portion of the nail resting directly upon the underlying epidermal nail bed.

Nail Matrix

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

Lunula

The crescent-shaped white region at the proximal nail surface overlying the thickened nail matrix.

Eponychium (Cuticle)

The proximal nail fold extending directly onto the surface of the nail body.

Eccrine (Merocrine) Sweat Glands

Abundant, simple coiled tubular glands with ducts extending to skin surface pores that secrete hypotonic sweat for thermoregulation.

Sebaceous (Oil) Glands

Branched alveolar glands present across the entire body except palms and soles that secrete lipid-rich sebum into hair follicles or pores to soften hair and provide bactericidal action.

Free Nerve Endings

Non-encapsulated nerve endings distributed throughout the dermis and epidermis that respond to temperature changes and painful stimuli.

ABCDE Clinical Rule

Diagnostic criteria used for clinical assessment of melanoma: Asymmetry, Border irregularity, Color inconsistency, Diameter larger than $6\,\text{mm}$ ($0.24\,\text{in}$), and Evolving changes in lesion characteristics over time.

Eczema

An allergic inflammatory condition characterized by dry, itchy, red, flaky rash-like patches on skin surfaces.

Acne

A disorder triggered by hyperactive sebaceous glands, resulting in plugged follicles (keratin and sebum accumulation), bacterial proliferation, and localized inflammation (comedones, papules, pustules).

Basement Membrane

A specialized non-cellular layer that anchors the stratum basale of the epidermis to the underlying connective tissue of the dermis.

Dermal Papilla

A peg-like upward projection of the superficial dermis into the epidermis containing capillary loops and sensory receptors.

Sweat Gland Pore

The minute external opening on the epidermal surface through which fluid secretions exit the skin.

Sweat Gland Duct

A coiled tubular pathway that conveys fluid from the deep secretory unit in the dermis to the external surface pore.

Hair Root

The lower portion of the hair structure anchored beneath the skin surface within the follicle, composed of keratinized cells.

Region of Cell Division (Hair)

The active germinal zone located at the base of the bulb where rapid cellular mitosis produces new cells to elongate the hair.

Touch Receptor

A specialized mechanosensory nerve structure situated within upper dermal papillae that detects light tactile stimuli.

Dermal Blood Vessels

A circulatory vascular network within the dermis that delivers nutrients, removes metabolic waste, and facilitates body temperature regulation via vasodilation and vasoconstriction.

Adipose Cells

Lipid-storing cells located within the subcutaneous layer that provide thermal insulation, energy reserves, and mechanical cushioning.

Nerve Cell Process

A fibrous axonal extension distributed through dermal tissue that carries sensory impulses toward the central nervous system.

Hair Shaft

The dead, keratinized filament of hair that projects outwardly beyond the epidermal surface.

Muscle Layer Below Skin

The deep skeletal muscular tissue lying beneath the subcutaneous fascia that provides support and movement under the integument.