السبت، 22 نوفمبر 2014

Simple Epithelial Tissue

The epithelial tissue has the following characteristics:
1)It covers surfaces or lines cavities.
2)Rapid turn-over (time of renewal).
3)It’s formed sheets of closely packed cells.
4)The cells are polar.
5)The epithelium rests upon a sheet of extracellular matrix called the Basal Lamina. Also, most epithelia have connective tissue under them.

6)Epithelial tissues lack blood supply.

Basement Membrane

Ø Basement membrane is formed of the basal lamina and the reticular lamina. The reticular layer is the upper part of the connective tissue that’s usually located under the epithelium.















Simple Squamous epithelium
oFormed of a single layer of flattened cells.
§
oIt’s found in:
      - Capillaries à Endothelium
      - Lining of body cavities à Mesothelium
      - Lining alveoli à Pneumocytes
oFunction: Their thin cytoplasm allows various substances to pass easily across them (endothelium and pneumocytes). Mesothelial cells, also, produce a lubricating fluid.








Simple Cuboidal epithelium
§Formed of a single layer of cubical cells.
§
§It’s found in:
      - Renal collecting tubules
      - Covering the ovary
§
§Function: Covering of organs. Involved in active transport.










Simple Columnar epithelium
§Formed of a single layer of tall cells that could be ciliated or not.
§
§It’s found in:
      - Ciliated: Uterine tubes.
      - Non-ciliated: most of the GIT.
§
§Function: Secretion as in the stomach. Absorption as in the small intestine.














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