Tissues: Epithelial, Connective, Muscle and Nervous: every key term you need (+ practice quiz)
25 flashcard terms for Anatomy & Physiology I Topic 3, 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.
A group of structurally similar cells and their surrounding matrix that perform a shared function. The four primary types are epithelial, connective, muscle and nervous, and every organ is built from some combination of them.
Epithelial tissue
Sheets of tightly joined cells covering surfaces, lining cavities and forming glands. Epithelia are avascular, rest on a basement membrane, show distinct apical and basal surfaces, and regenerate rapidly.
Apical and basal surfaces
The polarity of an epithelial cell. The apical surface faces the lumen or exterior and may bear cilia or microvilli, while the basal surface adheres to the basement membrane and faces the underlying connective tissue.
Basement membrane
A thin extracellular layer formed by the epithelial basal lamina together with a reticular lamina from the connective tissue. It anchors the epithelium, filters diffusing material and guides repair after injury.
Simple squamous epithelium
A single layer of flat cells suited to rapid diffusion and filtration. It forms alveolar walls, the glomerular capsule lining, and the endothelium and mesothelium of vessels and serous cavities.
Stratified squamous epithelium
Multiple cell layers whose surface cells are flattened, specialized for protection against abrasion. Keratinized versions cover the skin; nonkeratinized versions line the mouth, esophagus and vagina.
Simple columnar epithelium
A single layer of tall cells often bearing microvilli and interspersed goblet cells, specialized for absorption and secretion. It lines the stomach, intestines and much of the uterine tube.
Pseudostratified columnar epithelium
A single layer in which nuclei sit at different heights, creating a false appearance of layering because not every cell reaches the surface. The ciliated form lines much of the respiratory tract.
Transitional epithelium
A stretchable stratified epithelium whose surface cells change from rounded to flattened as the organ distends. It lines the urinary bladder, ureters and part of the urethra.
Tight junction
A belt of fused membrane proteins encircling the apical region of adjacent epithelial cells. It seals the space between them, preventing leakage between compartments and preserving the polarity of membrane proteins.
Desmosome
A rivet-like adhesion junction in which cadherin proteins link neighboring cells and anchor internally to intermediate filaments. Desmosomes resist mechanical shear in skin and cardiac muscle.
Gap junction
A cluster of connexon channels forming direct cytoplasmic pores between adjacent cells. Ions and small molecules pass through, permitting electrical coupling in cardiac and smooth muscle.
Exocrine gland
A gland that releases its product through a duct onto an epithelial surface. Sweat, salivary, sebaceous and pancreatic acinar glands are examples, and they may secrete by merocrine, apocrine or holocrine modes.
Endocrine gland
A ductless gland that releases hormones into the interstitial fluid and bloodstream to act on distant target cells bearing the appropriate receptors. The thyroid and adrenal glands are typical.
Connective tissue
The most diverse tissue class, characterized by relatively few cells scattered in an abundant extracellular matrix of ground substance and fibers. It binds, supports, protects, insulates and transports.
Ground substance
The unstructured gel component of connective tissue matrix, composed of water, proteoglycans, glycosaminoglycans and adhesion proteins. It resists compression and forms the medium through which nutrients diffuse.
Collagen fiber
The thickest and strongest matrix fiber, built from triple-helical protein bundles that resist tension. It dominates tendons, ligaments, dermis and bone, giving those structures great tensile strength.
Elastic fiber
A branching matrix fiber containing elastin that stretches and recoils. It is prominent in the walls of large arteries, in the lung and in the skin, where it restores shape after deformation.
Reticular fiber
A fine collagenous fiber forming delicate branching networks that support soft cellular organs. It builds the stroma of lymph nodes, spleen, bone marrow and liver.
Fibroblast
The principal cell of connective tissue proper, responsible for secreting the fibers and ground substance of the matrix. It becomes highly active during wound repair and scar formation.
Areolar connective tissue
A loose, soft tissue with a jelly-like matrix and all three fiber types, holding organs in place and serving as the reservoir of tissue fluid. It is the tissue that swells visibly in inflammatory edema.
Dense regular connective tissue
Tightly packed parallel collagen bundles with rows of fibroblasts between them, built to resist tension along one axis. It forms tendons, aponeuroses and most ligaments.
Skeletal muscle tissue
Long multinucleate striated fibers under voluntary somatic control that attach to bone and move the skeleton. Striations reflect the regular register of contractile filaments within each fiber.
Nervous tissue
Excitable tissue composed of neurons that generate and conduct electrical signals and neuroglia that support, insulate and protect them. It coordinates rapid communication throughout the body.
Tissue repair
The response to injury, proceeding through inflammation, organization with new capillary ingrowth, and either regeneration by native cells or replacement by fibrous scar when regenerative capacity is limited.