Untitled Quiz

Epithelial Tissue

• Epithelial tissue covers surfaces or lines cavities throughout the body.

• Develops from ectoderm, mesoderm, or endoderm.

• Rests on a basement membrane (B.M.).

• Avascular, meaning it does not contain blood vessels.

• Receives nutrition through diffusion from the underlying connective tissue.

• Consists of numerous crowded cells with minimal intercellular substance forming continuous sheets.

• Can be modified to produce secretions (glandular epithelium), receive sensation (neuroepithelium), or acquire contractile function (myoepithelium)

• Can regenerate quickly.

• Classified into:

  • Surface epithelium
  • Glandular epithelium
  • Neuroepithelium
  • Myoepithelium

Surface Epithelium

• Classified based on the number of layers:
  • Simple epithelium: one layer of cells.
  • Stratified epithelium: multiple layers of cells.
• Further classified by cell shape within the layer:

  • Simple Squamous Epithelium:

    • Flat, thin cells with a flat nucleus.
    • Functions for easy movement, gas and fluid exchange due to its thin surface.
    • Found: mesothelium (pleura, pericardium, peritoneum), endothelium (heart and blood vessels), lung alveoli, Bowman's capsule of kidney.

  • Simple Cubical Epithelium:

    • Cube-like cells with a central, rounded nucleus.
    • Functions for secretion and reabsorption.
    • Found: thyroid follicle, small ducts of salivary glands, renal convoluted tubules.

  • Simple Columnar Epithelium

    • Tall cells with an oval, basal nucleus.
    • Functions for secretion and absorption (microvilli, e.g. intestine).
    • Found: stomach, intestine, goblet cells (secrete mucus), uterus, fallopian tubes

  • Simple Columnar Ciliated Epithelium

    • Tall cells with cilia, basal, oval nucleus.
    • Functions for movement of particles or fluids over the surface.
    • Found: lung bronchioles, uterus, fallopian tubes.

  • Pseudostratified Columnar Epithelium:

    • Single layer of cells, but nuclei appear at different levels, giving a stratified appearance.
    • Can be ciliated or non-ciliated, with or without goblet cells.
    • Found: male genital system (non-ciliated), respiratory epithelium (ciliated), epididymis (ciliated).