Simple, stratified, pseudostratified and transitional epithelium !

Tissue

How the main covering epithelia look under the microscope, and why each organ has the lining it has.

Updated 2026-11-01

See it in 3D: Trachea · Esophagus · Urinary bladder · Skin

What it is

Each covering epithelium is built for the job of its surface. Thin single layers let gases and fluid pass; tall columnar cells absorb and secrete; many layers of flat cells protect against wear; a stretchy urothelium holds urine. On an H&E slide the epithelium is identified by counting its layers, looking at the shape and position of its nuclei, and checking the apical surface for cilia, microvilli or keratin.

Structure

Simple squamous: a single row of flat cells whose nuclei bulge into the lumen like fried eggs seen from the side; endothelium and mesothelium are this type.
Simple cuboidal: one row of cells as tall as they are wide, with round central nuclei, as in kidney tubules and thyroid follicles.
Simple columnar: tall cells with oval nuclei lined up near the base; in the intestine a pink brush border (microvilli) and pale goblet cells sit among them.
Pseudostratified ciliated columnar: nuclei crowded at several heights, a fringe of cilia on top and goblet cells; every cell reaches the basement membrane.
Stratified squamous: a basal layer of dividing cuboidal cells that flatten toward the surface; keratinized skin adds a pink anucleate keratin layer.
Transitional (urothelium): several layers topped by large dome-shaped umbrella cells, sometimes binucleated, that flatten when the bladder is full.

Function

Simple squamous: fast diffusion and filtration.
Simple columnar: absorption with microvilli, mucus secretion by goblet cells.
Pseudostratified ciliated: traps particles in mucus and sweeps them toward the pharynx.
Stratified squamous: protection where friction is high.
Urothelium: distension without leaking; the umbrella cells form a barrier to urine.

Clinical notes

Barrett esophagus: chronic reflux turns the lower esophageal squamous lining into columnar epithelium with goblet cells, a precursor of adenocarcinoma.
Cigarette smoke paralyses cilia and causes squamous metaplasia in the bronchi, so mucus clearance fails.
Most bladder cancers arise from the urothelium (urothelial carcinoma); smoking is the main risk factor.
In asthma the airway epithelium shows more goblet cells and a thickened basement membrane zone.

Test yourself

Think of the answer, then tap the question to see it.

Which cells on the luminal surface identify urothelium on a slide?

Large dome-shaped umbrella cells, sometimes with two nuclei, that flatten when the bladder stretches.

What two apical features distinguish small-intestinal from tracheal epithelium?

The intestine has microvilli (a brush border) on simple columnar cells; the trachea has motile cilia on pseudostratified cells.

What change in epithelium defines Barrett esophagus?

Metaplasia of stratified squamous epithelium into intestinal-type columnar epithelium with goblet cells in the distal esophagus.

Why is stratified squamous epithelium found in the esophagus rather than simple columnar?

Swallowed food causes friction; many layers of cells that are constantly replaced from the basal layer protect against abrasion.

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See it in 3D

The structures of Durgical's 3D anatomy where it is found.

← All of histology

Educational content on normal microscopic structure and its clinical relevance; no substitute for studying slides or for a health professional's advice.

Sources: 4.2 Epithelial Tissue (OpenStax, 2022); Epithelial Tissue (National Cancer Institute, SEER Training Modules, 2024).

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Representative model, for educational purposes only.