• 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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