Cue Column | Notes Column

Simple vs. Compound? | Simple = 1 layer (secretion/absorption/diffusion); Compound = multiple layers (protection only).

5 simple epithelium types? | (1) Squamous: flat, blood vessels + alveoli, diffusion. (2) Cuboidal: cube-shaped, kidney tubules, secretion/absorption. (3) Columnar: tall, stomach + intestine, secretion/absorption. (4) Ciliated: cilia, trachea + oviducts, movement. (5) Glandular: secretory, goblet cells + salivary glands.

Where is compound found? | Skin, pharynx, buccal cavity. Primary function: PROTECTION. Limited secretion/absorption.

What is the basement membrane? | Non-cellular layer beneath all epithelium. Anchors cells to underlying connective tissue. Breach = cancer invasion.

Why avascular? | No blood supply within epithelium. All nutrients diffuse from connective tissue below through basement membrane.

Summary

Epithelial tissue is classified by cell layer number $\frac{simple}{compound}$ and cell shape (squamous/cuboidal/columnar). Simple epithelium is optimized for efficient exchange; compound for protection. The basement membrane is the structural anchor and a cancer invasion checkpoint. Avascularization means all nutrient delivery is via diffusion from underlying connective tissue.