Skin & Body Membranes - VOCABULARY Flashcards

A set of vocabulary flashcards covering key terms and concepts from the lecture notes on skin, membranes, epidermal layers, skin appendages, and related pathologies.

Tight Junctions

Weblike strands of transmembrane proteins that fuse adjacent cell surfaces to seal passageways and retard paracellular transport; common in epithelia lining stomach, intestines, and bladder.

Adherens Junctions

Cadherin-containing junctions with a plaque that attaches to membrane proteins and to microfilaments; form adhesion belts in epithelia to resist separation during contraction.

Desmosomes

Cadherin-based junctions whose plaques attach to intermediate filaments (keratin) rather than microfilaments; provide spot-weld-like cell cohesion in skin and heart.

Hemidesmosomes

Anchor epithelial cells to the basement membrane via integrins; connect intracellular keratin to laminin in the basement membrane.

Gap Junctions

Connexin-forming connexons create tunnels that let ions and small molecules diffuse between neighboring cells, enabling rapid intercellular communication.

Epithelial Membrane

Membranes composed of an epithelial layer plus a supporting connective tissue layer; includes mucous, serous, and cutaneous membranes (synovial lacks epithelium).

Basement Membrane

Thin extracellular layer with basal lamina (epithelial secretions) and reticular lamina (connective tissue secretions) that anchors and supports epithelium.

Stratum Basale (Basal Layer)

Deepest epidermal layer; single row of keratinocytes capable of mitotic division; contains stem cells and Merkel cells.

Stratum Spinosum

8–10 cell layers with spine-like borders due to desmosomes; contains keratin filaments; Langerhans cells and melanocyte processes may be present.

Stratum Granulosum

Middle epidermal layer with keratohyalin granules; 2–5 flattened cells undergoing apoptosis; site of keratinization and lipid secretion (lamellar granules) forming part of the barrier.

Stratum Lucidum

Thin, clear layer of 3–5 dead keratinocytes with high keratin content; present only in thick skin (fingertips, palms, soles).

Stratum Corneum

Outermost epidermal layer of 25–30 layers of dead, flattened keratinocytes; cornified envelope; major waterproof barrier and protective layer.

Keratinocytes

Primary cell type of the epidermis; originate in the basal layer and migrate upward to form the epidermal layers; produce keratin.

Melanocytes

Pigment-producing neural crest-derived cells in the basal layer that synthesize melanin; depletion in vitiligo. Lines between epidermal cells.

Merkel Cells

Slowly adapting mechanoreceptors in the basal epidermis; involved in tactile sensation, especially in hairy and glabrous skin.

Langerhans Cells

Antigen-presenting dendritic cells in the epidermis; contain Birbeck granules; reduced by UV exposure.}

Dermis

Layer beneath the epidermis with vascular, lymphatic, and nerve networks; provides strength, elasticity, and nourishment to the epidermis; contains fibroblasts.

Papillary Dermis

Upper, thin dermal layer with nipplelike projections; contains tactile receptors; accounts for ~1/5 of dermal thickness.

Reticular Dermis

Deeper, dense irregular connective tissue region with elastic fibers; forms most of the dermis and attaches to the hypodermis.

Hypodermis (Subcutaneous Layer)

Not part of the skin proper; an insulating layer of adipose tissue and loose connective tissue containing larger vessels and nerves.

Dermal-Epidermal Junction (DEJ)

Basement membrane zone that anchors the dermis to the epidermis and provides resistance to shear forces; semipermeable barrier.

Mucous Membrane

Membranes lining body cavities that open to the exterior; epithelium plus connective tissue; lines digestive, respiratory, reproductive, and urinary tracts and secretes mucus.

Serous Membrane

Membranes lining closed body cavities; parietal layer lines cavity walls, visceral layer covers organs; secretes serous fluid; mesothelium.

Cutaneous Membrane

The skin; consists of epidermis (keratinized stratified squamous epithelium) and dermis (connective tissue).

Synovial Membrane

Lining of joints lacking epithelium; composed of connective tissue and synoviocytes; secretes synovial fluid to lubricate joints.

Hair

Keratinized epidermal structure composed of shaft (visible above skin) and root (below skin); shaft/root have medulla, cortex, and cuticle.

Hair Follicle

Structure surrounding the hair root; has external and internal root sheaths; dermal root sheath; bulb at base with papilla and hair matrix.

Hair Shaft

Superficial portion of hair above the skin; composed of medulla, cortex, and cuticle.

Hair Root

Portion of hair within the follicle; extends into the dermis; connected to the hair shaft.

Hair Matrix

Germinal layer at the base of the hair bulb; site of cell division that produces hair growth.

Sebaceous Glands

Oil glands connected to hair follicles; secrete sebum; absent on palms/soles; enlarge at puberty and implicated in acne.

Eccrine Sweat Glands

Merocrine, simple coiled tubular glands distributed widely; secrete watery sweat to regulate temperature.

Apocrine Sweat Glands

Simple coiled tubular glands in axillae, groin, areolae, and bearded regions; ducts open to hair follicles; secretions are viscous and begin at puberty.

Nails

Keratinized plate on distal digits; consists of nail body, root, and free edge; lunula, hyponychium, eponychium; nail matrix for growth.

Acne Vulgaris

Inflammation of sebaceous glands and follicles during puberty; treated with topical/oral antibiotics and other agents; not caused by chocolate or fried foods.

Burns (First–Fourth Degree)

Injuries to skin: first-degree epidermis only; second-degree epidermis and part of dermis; third-degree destroyed epidermis and dermis; fourth-degree extends to muscles/b bones; loss of sensation in deep burns.

Basal Cell Carcinoma

Most common invasive skin cancer; slow-growing; sun-exposed areas; pearly papules and telangiectasias.

Squamous Cell Carcinoma

Second most common skin cancer in sun-exposed areas; UV-induced DNA damage; invades basement membrane of the DEJ.

Meissner's Corpuscles

Superficial mechanoreceptors for light touch; dense in hairless skin areas.

Pacinian Corpuscles

Lamellated mechanoreceptors for vibration and deep pressure; onion-skin appearance; rapidly adapting.

Epidermal Layers Order

From deep to surface: Stratum Basale, Stratum Spinosum, Stratum Granulosum, Stratum Lucidum (only in thick skin), Stratum Corneum.

Skin Appendages

Structures derived from the epidermis including hair follicles, sebaceous glands, nails, and sweat glands.