Covers and protects surfaces, both outside and inside the body

1. Mostly composed of cells. 2. Covers body surfaces. 3. Distinct cell surfaces (Apical, Lateral, Basal). 4. Cell and matrix connections. 5. Nonvascular. 6. Capable of regeneration.

Distinct cell surfaces

• Disk-shaped structures with especially adhesive glycoproteins that bind cells to one another.  • Intermediate filaments that extend into the cytoplasm of the cells.

Attach epithelial cells to the basement membrane.

Hold cells together and form a permeability barrier.

Glycoproteins is found just below the tight junction.

A small, specialized contact region between cells containing protein channels that aid intercellular communication by allowing ions and small molecules to pass from one cell to another.

1. Protecting underlying structures. 2. Acting as a barrier. 3. Permitting the passage of substances. 4. Secreting substances. 5. Absorbing substances.

Classification of Epithelial Tissue

Glandular Epithelia, According to MANNER OF SECRETION:

• Glands without ducts.  • Release their products of secretion into the blood or lymph for transport to target cells in other parts of the body.  • I.E. Pituitary Gland, Adrenal Gland, Thyroid Gland

• Glands with ducts.  • Release their products of secretion into the systems of ducts opening into the external and internal surface. • I.E. Gastric Glands, Salivary Glands and Liver

Grandular Epithelia, According to the NUMBER OF CELLS:

• EXOCRINE GLANDS are composed of a single cell.  • I.E. Goblet Cell (Secretes Mucous)

• Most EXOCRINE GLANDS are composed of many cells.  • Can be classified according to the structure of their ducts (Simple Glands & Compound Glands) and secretory regions (Tubular Gland & Acinar or Alveolar Gland).

Grandular Epithelia, According to the MORPHOLOGY OF THE STRUCTURE:

Glands that have a single duct.

Glands with ducts that branch.

Glands with secretory regions shaped as tubules (small tubes).

Glands that are shaped in saclike structures.

Glandular Epithelia According to the TYPES OF SECRETION:

• Secretes proteins (Enzymes).  • I.E. Gastirc Chief Cell and Paneth Cell

• Secretes mucus.  • I.E. Brunner’s Gland, Esophangeal Gland, Pyloric Gland

• Secrete both protein and mucus.  • I.E. Salivary Gland

• Secrete sebum (a lipid based product).  • I.E. Oil Gland

• Secretion produce cell.  • I.E. Testis, Ovaries

Approximately 13 or 14 days after fertilization, the embryonic stem cells that give ruse to a new individual form a slightly elongated disk consisting of two layers, the:

Epiblast