Epithelial Tissue

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Histology:

Epithelial Tissue:

General Characteristics

Very close packed cells

Usually form a barrier

Have a free surface that is exposed to the body's exterior. Or the cavity of an internal Organ

The basement membrane anchors base surface of epithelium to underlying connective tissues

Do Not have blood vessels (in underlying loose connective tissue)

Held together by special contacts; tight junction and desmosomes

Genereal Functions

Protect underlying Structors

Barrier to stop movement of substances through epithelial layer

Allow some movement through epithelial layer such as oxygen and carbon Dioxide

Simple Epithelium - Single Layer

Simple squamous epithelium:

Tissue composed of a single layer of flatted cells

nucleus resembles flattened ovals.

Cells are very thin and nucleus is often thicker than the rest

Forms the walls of capillaries in the cardiovascular system and alveoli in the lungs.

Simple cubical epithelium:

Composed of a single layer of cells that have roughly the same height as width.

Large round nuclei that are typically near the center of the cell.

Often form ducts or tubes.

Round nuclei are linded up in a single row.

Longitudinal section resemble a string of beads.

Tubules of the kidneys

forming exocrine glands and their ducts

forming choroid plexus of the brain and ovaries

Simple columnar epithelium: