Study Notes on Epithelium

Epithelium Overview

• Function: Covers surfaces and forms glands.

• Polarity: Has apical (top) and basal (bottom) ends; basal lamina resembles a basement.

Characteristics

• Cell Arrangement: Cells are closely packed; differs from connective tissue.

• Support: Supported by connective tissue beneath basal lamina, called reticular lamina.

• Avascular and Innervated: No blood supply (vascular); nerve receptors present (innervated).

• Regeneration: High regeneration rate, especially in stratified squamous epithelium (e.g., oral cavity).

Classification

• Cell Layers: Can be simple (one layer) or stratified (multiple layers).

• Cell Shape: Squamous, cuboidal, or columnar.

  • Common types include:

    • Simple squamous epithelium

    • Simple cuboidal epithelium

    • Simple columnar epithelium

    • Stratified squamous epithelium

Simple Squamous Epithelium

• Description: Single layer of flattened cells with central nucleus.

• Function: Facilitates diffusion and filtration; secretes lubricating substances.

• Location: Kidney glomeruli, air sacs (alveoli) of lungs, lining of heart, blood vessels, lymphatic vessels,
  and serous membranes (visceral and parietal pericardium).

Simple Cuboidal Epithelium

• Description: Single layer of cube-shaped cells; spherical central nucleus that occupies much of the cell.

• Function: Secretion and absorption, akin to a sponge absorbing and secreting.

• Location: Kidney tubules, ducts and secretory portions of small glands, ovary surface.