Histology Key Terms: Epithelial Tissue and Germ Layers

A set of vocabulary-style flashcards covering key terms related to nervous, muscular, and especially epithelial tissue, including germ layers, tissue organization, cell shapes, layers, and specific epithelium types discussed in the lecture notes.

Excitable tissues

Tissues capable of responding to stimuli by generating and transmitting electrical signals; examples include nervous tissue and muscular tissue.

Ectoderm

The outer embryonic germ layer that gives rise to the epidermis and nervous system.

Mesoderm

The middle embryonic germ layer that gives rise to mesenchyme and most connective tissues, muscle, and related structures.

Endoderm

The inner embryonic germ layer that forms the lining of the digestive and respiratory tracts.

Mesenchyme

Embryonic connective tissue derived from the mesoderm; precursor to connective tissues.

Epithelial tissue

Sheets of tightly packed cells with little extracellular matrix; covers body surfaces, lines cavities, and forms glands; avascular and nourished by underlying connective tissue; basally anchored to connective tissue via the basement membrane; functions include protection, secretion, excretion, absorption, filtration, and sensation; highly mitotic.

Extracellular matrix (ECM)

Non-cellular material between cells; epithelial tissue has little ECM, while connective tissue has abundant ECM.

Basal surface

Bottom surface of epithelial cells that faces the basement membrane.

Apical surface

Top or free surface of epithelial cells exposed to the environment or a hollow organ.

Lateral surface

Sides of epithelial cells that contact neighboring cells.

Basement membrane

A protein- and carbohydrate-rich layer that anchors epithelium to the underlying connective tissue and delineates the boundary between epithelial and connective tissues.

Simple epithelium

Epithelium that is one cell layer thick.

Stratified epithelium

Epithelium that has two or more cell layers.

Squamous

Flat, tile-like epithelial cells.

Cuboidal

Cube-shaped epithelial cells; nucleus typically round.

Columnar

Tall, column-like epithelial cells; nucleus oval or elongated and located near the base.

Pseudostratified epithelium

One cell layer thick, but appears layered because not all cells reach the surface; all cells contact the basement membrane; often has cilia and goblet cells; exists as pseudostratified columnar.

Goblet cell

Mucus-secreting cell commonly found in simple columnar and pseudostratified columnar epithelia.

Keratinized stratified squamous epithelium

Stratified squamous epithelium with dead surface cells filled with keratin; waterproofs skin and reduces water loss; found in the epidermis, especially palms and soles.

Nonkeratinized stratified squamous epithelium

Stratified squamous epithelium with living cells at the surface; found in the mouth, esophagus, vagina; resists abrasion and pathogen entry.

Urothelium (transitional epithelium)

Multilayered epithelium of the urinary tract that stretches as urine volume changes; found in ureters and urinary bladder.

Endothelium

Simple squamous epithelium lining blood vessels and the heart.

Simple squamous epithelium

Single layer of thin, flat cells; rapid diffusion/filtration; found in alveoli of the lungs, glomeruli of the kidneys, and lining of blood vessels and heart (endothelium).

Simple cuboidal epithelium

Single layer of cube-shaped cells; function: absorption and secretion (and mucus production); locations include liver, thyroid, mammary and salivary glands, bronchioles, kidney tubules.

Simple columnar epithelium

Single layer of tall, columnar cells; function: absorption and secretion (often mucus via goblet cells); found in stomach and intestines.

Goblet cell location

Goblet cells are commonly found in simple columnar and pseudostratified columnar epithelia and secrete mucus.

Alveolar epithelium

Simple squamous epithelium lining the alveoli in the lungs, facilitating gas exchange.