AN65.1-2 | Epithelium histology — Glossary

Avascular tissue covering all body surfaces; derived from all three germ layers; rests on a basement membrane; high regenerative capacity

Single layer of flat cells for diffusion and filtration; found in alveoli, Bowman's capsule, endothelium, and mesothelium

All cells touch the basement membrane but nuclei are at different levels creating a false appearance of stratification; ciliated type lines the respiratory tract

Urothelium — specialised epithelium of the urinary tract (bladder, ureter, renal pelvis) that stretches from dome-shaped to flat without breaking

Zonula occludens — most apical junction sealing the intercellular space; formed by claudin and occludin proteins; creates a permeability barrier

Macula adherens — spot weld junction linking keratin intermediate filaments of adjacent cells via desmoglein and desmocollin; provides resistance to shearing forces

Junction anchoring the basal surface of an epithelial cell to the basement membrane via integrins linked to keratin intermediate filaments

Connexon channels between adjacent cells allowing direct passage of ions and small molecules for cell-cell communication

Finger-like apical projections containing actin filaments that increase surface area; form the brush border of the small intestine and proximal tubule

Motile hair-like projections with a 9+2 microtubule arrangement powered by dynein arms; essential for mucociliary clearance in the respiratory tract

Structure between epithelium and connective tissue composed of the basal lamina (type IV collagen, laminin) and reticular lamina (type III collagen)

Reversible replacement of one mature cell type by another in response to chronic irritation; may be a precursor to dysplasia and cancer

Intestinal columnar metaplasia of the lower oesophageal squamous epithelium from chronic GERD; premalignant condition for oesophageal adenocarcinoma

The point where stratified squamous epithelium meets columnar epithelium; at the cervix, this is the transformation zone where cancer arises

Area of the cervix where columnar epithelium has undergone squamous metaplasia; the site where CIN and cervical squamous cell carcinoma develop

Immotile cilia syndrome — defective dynein arms causing situs inversus, bronchiectasis, sinusitis, and male infertility

Autoimmune blistering disease caused by antibodies against desmoglein (desmosomal protein); results in intraepithelial acantholysis and flaccid blisters

Wine-glass shaped mucus-secreting cell found in the intestinal and respiratory epithelium; distended apex filled with mucin granules

Tough fibrous protein produced by keratinocytes; forms the waterproof barrier of the epidermis and the structural component of hair and nails

Key glycoprotein of the basal lamina that anchors epithelial cells to the basement membrane via integrin receptors

Non-fibrillar collagen forming the meshwork of the basal lamina; a key structural component of the basement membrane

Disordered growth with abnormal cell morphology (increased nuclear:cytoplasmic ratio, atypical mitoses); may be precancerous if not reversed