Epithelial Tissue – Vocabulary Review

A comprehensive set of vocabulary flashcards covering characteristics, structures, classifications, functions and glandular aspects of epithelial tissue.

Epithelial Tissue

Tissue composed of tightly packed cells with minimal extracellular substance that covers surfaces, lines cavities and forms glands.

High Cellularity

Characteristic of epithelium in which cells are densely packed with little intercellular space.

Avascular

Lacking blood vessels; epithelial cells receive nutrients by diffusion from underlying tissue.

Polarity (epithelial)

Presence of distinct apical, lateral and basal domains with different structures and functions.

Ectoderm

Epithelium covering external body surfaces such as skin, cornea, mouth and anus.

Endoderm

Epithelium lining digestive tract (except mouth and anus), liver, gallbladder, pancreas, respiratory tract, urinary bladder and urethra.

Mesoderm

Epithelium lining heart, blood and lymph vessels, serous cavities, kidneys and reproductive organs.

Basement Membrane

Specialized extracellular matrix anchoring epithelium to connective tissue; composed of basal lamina and reticular lamina.

Basal Lamina

Upper part of basement membrane consisting of lamina rara externa, lamina densa and lamina rara interna.

Lamina Rara Externa (Lamina Lucida)

Outer electron-lucent layer of the basal lamina adjacent to epithelial cells.

Lamina Densa

Electron-dense middle layer of basal lamina rich in type IV collagen and laminin.

Lamina Rara Interna

Inner electron-lucent layer of basal lamina next to reticular lamina.

Reticular Lamina

Deeper layer of basement membrane composed of collagen fibrils from connective tissue.

Squamous Cell

Flat, thin epithelial cell broader than tall.

Cuboidal Cell

Epithelial cell approximately as tall as it is wide with a round central nucleus.

Columnar Cell

Tall epithelial cell higher than wide with an oval, basally placed nucleus.

Microvillus

Short fingerlike apical projection that increases surface area; forms brush border in small intestine.

Stereocilium

Very long microvillus found in ductus epididymis and inner ear hair cells.

Cilium

Motile apical projection longer than microvilli that moves fluid or mucus over epithelial surfaces.

Flagellum

Extremely long motile projection present only on spermatozoa.

Tight Junction (Zonula Occludens)

Lateral junction that seals adjacent cells, preventing paracellular passage of molecules.

Adherens Junction (Zonula Adherens)

Lateral junction near apex linking actin filaments of neighboring cells to provide tissue stability.

Desmosome

Spotlike lateral junction using intermediate filaments for strong adhesion, abundant in stratified squamous epithelium.

Gap Junction

Communicating junction allowing ions and small molecules to pass between adjacent cells.

Hemidesmosome

Basal specialization anchoring epithelial cells to the basal lamina via intermediate filaments.

Basal Infolding

Invaginations of the basal plasma membrane that increase surface area for ion and fluid transport.

Surface Lining Epithelium

Epithelium that covers external surfaces and lines internal cavities and organs.

Glandular Epithelium

Epithelial tissue specialized for secretion, forming endocrine and exocrine glands.

Protection (epithelial function)

Role of epithelium in shielding underlying tissues from abrasion, injury and pathogens.

Transcellular Transport

Movement of molecules through epithelial cells from one side of the layer to the other.

Secretion (epithelial)

Release of substances such as mucus, enzymes or hormones by epithelial cells or glands.

Absorption (epithelial)

Uptake of materials from a lumen into epithelial cells and underlying tissues.

Selective Permeability

Control of material movement between compartments via intercellular junctions.

Sensory Epithelium

Specialized epithelial cells that detect stimuli, e.g., taste buds, retina, inner ear hair cells.

Myoepithelial Cell

Contractile epithelial cell surrounding glandular acini that helps expel secretions.

Excretory Epithelium

Epithelial cells, particularly in kidneys, involved in waste elimination.

Germinal Epithelium

Epithelial tissue that gives rise to gametes in the testes and ovaries.

Simple Epithelium

Epithelium composed of a single layer of cells.

Stratified Epithelium

Epithelium composed of two or more cell layers.

Pseudostratified Epithelium

Single layer of cells with nuclei at different levels giving a stratified appearance; all cells contact basal lamina.

Simple Squamous Epithelium

Single layer of flat cells lining alveoli and Bowman's capsule; called endothelium in vessels and mesothelium in serous membranes.

Simple Cuboidal Epithelium

One layer of cuboidal cells lining small ducts, kidney collecting tubules and thyroid follicles.

Simple Columnar Epithelium

One layer of tall cells; non-ciliated type lines stomach and intestines, ciliated type lines uterus, oviducts and bronchi.

Stratified Squamous Epithelium

Multiple layers with flat superficial cells; keratinized in skin, non-keratinized in oral cavity, esophagus and vagina.

Stratified Cuboidal Epithelium

Two or three layers of cuboidal cells lining larger ducts of glands such as major salivary glands.

Stratified Columnar Epithelium

At least two layers of columnar (or upper columnar, lower cuboidal) cells lining some exocrine ducts.

Transitional Epithelium (Urothelium)

Stratified epithelium that stretches; dome-shaped superficial cells when relaxed, thin squamous profile when distended; lines urinary tract.

Endocrine Gland

Ductless gland releasing hormones directly into blood or lymph.

Exocrine Gland

Gland delivering its secretion onto an epithelial surface, usually through ducts.

Goblet Cell

Unicellular mucous exocrine gland scattered within some epithelia.

Secretory Epithelial Sheet

Surface epithelium in which most cells are secretory, e.g., stomach lining.

Intraepithelial Gland

Small cluster of secretory cells forming a shallow invagination around a tiny duct opening within a surface epithelium.

Simple Gland

Exocrine gland whose duct is unbranched.

Compound Gland

Exocrine gland with a branched duct system.

Tubular Gland

Exocrine gland whose secretory unit is an elongated tube.

Alveolar (Acinar) Gland

Exocrine gland whose secretory unit is globular or flask-shaped.

Tubuloalveolar Gland

Gland containing both tubular and acinar secretory units.

Mucous Secretion

Viscous secretion rich in mucin glycoproteins.

Serous Secretion

Watery, enzyme-rich secretion.

Mixed Secretion

Combination of mucous and serous secretions in the same gland.

Merocrine Secretion

Release of product by exocytosis with no loss of cell material.

Holocrine Secretion

Release of product accompanied by destruction and shedding of the entire secretory cell, as in sebaceous glands.

Apocrine Secretion

Release of product together with the apical portion of cell cytoplasm and membrane.