Stratified squamous epithelium
Epithelium stratificatum squamosum
Also known as: keratinised stratified squamous epithelium, non-keratinised stratified squamous epithelium
A multilayered epithelium in which basal cuboidal cells divide and move upward, flattening toward the surface; it protects against abrasion and, when keratinised (epidermis), against water loss.
Overview
The basal layer of cuboidal-to-columnar stem cells rests on the basement membrane and divides continuously; daughter cells move up through polyhedral intermediate layers, becoming progressively flatter toward the surface, where they are shed. Because only the surface cells define the name, the deeper layers are not squamous. Numerous desmosomes and keratin filaments make it mechanically strong.
Keratinised stratified squamous epithelium forms the epidermis of the skin: superficial cells lose their nuclei and organelles and become dead, flattened, keratin-filled corneocytes surrounded by lipids — a tough, waterproof layer (stratum corneum). Non-keratinised stratified squamous epithelium lines moist surfaces subject to abrasion: oral cavity, oropharynx, laryngopharynx, oesophagus, vocal folds, vagina, ectocervix, the anal canal below the pectinate line and the anterior surface of the cornea; its surface cells retain their nuclei and are kept moist by glandular secretions. The gingiva and hard palate are parakeratinised (superficial cells keep pyknotic nuclei).
- Location
Epidermis (keratinised); mouth, oesophagus, vagina, ectocervix, lower anal canal, cornea, vocal folds (non-keratinised).
Anatomy
- Histology
Many layers; basal cells cuboidal and basophilic, surface cells flat; anucleate eosinophilic keratin layer in skin; nucleated flat surface cells in non-keratinised epithelium (often glycogen-rich in vagina and oesophagus).
Function
- Protection against abrasion and pathogens.
- Prevents water loss (keratinised).
- Continuous renewal of the surface.
Clinical significance
Squamous cell carcinoma
Arises in skin (sun exposure), oral cavity, oesophagus, anal canal and cervix (high-risk HPV; screened by cervical cytology/HPV testing at the squamocolumnar junction). Well-differentiated tumours form keratin pearls and intercellular bridges.
Leukoplakia
White plaques of hyperkeratosis on oral mucosa (smoking, alcohol) that may harbour dysplasia.
Compiled from standard anatomy and physiology references — see the Cells & Tissues sources. For education only; not medical advice.