Epithelial tissue

A cell is the basic structural and functional unit of a living organism. A tissue is a group of cells having a common origin, similar structure and function and held together by a cementing substance. Example: Epithelial tissue

Animal Tissues

Animal tissues are different and are broadly classified into four types :

  • Epithelial Tissue
  • Connective Tissue
  • Muscular Tissue and
  • Neural Nervous Tissue

In this article we are going to discuss about Epithelial Tissue only.

Epithelial Tissue

CHARACTERISTICSCells are flat, cuboidal or columnar in shape.
LOCATIONCovers the whole body surface.
FUNCTION1. Protection
2. Absorption
3. Secretion
4. Sensory perception

Types of Epithelial Tissue

  • Simple squamous epithelium
  • Stratified squamous epithelium
  • Columnar epithelium
  • Ciliated columnar epithelium
  • Ciliated columnar epithelium
  • Glandular epithelium

Simple squamous epithelium:

CHARACTERISTICSCells are large, extremely thin and flat.
LOCATIONSituated in the lining of blood vessels, lung
alveoli, oesophagus,
the lining of the mouth and the inner lining of the cheek.
FUNCTIONTransportation of
substances through
selectively permeable

Stratified squamous epithelium:

CHARACTERISTICSCells are arranged
in a pattern of layers, resembling a brick wall.
LOCATIONLocated as the outer
protective covering all
over the body surface.
FUNCTIONProvides protection
to underlying tissues which are subjected to continuous wear
and tear.

Columnar epithelium:

CHARACTERISTICSCells are tall, cylindrical and are
arranged like pillars.
LOCATIONFound where
absorption and secretion occur, as in the inner lining of the stomach, intestines and gall bladder.
FUNCTIONSecrete digestive
enzymes and perform the function of absorption of nutrients from the
digested food.

Ciliated columnar epithelium:

CHARACTERISTICSCells possess fine
hair-like cilia which
are capable of rapid, rhythmic, wave-like beatings in a certain
direction on their
free surface.
LOCATIONFound in the inner lining of the wind pipe or trachea, lungs,
respiratory system and buccal chambers.
FUNCTIONIn the respiratory
tract, the cilia move
and their movement
pushes the mucus
forward to clear it.

Cuboidal epithelium:

CHARACTERISTICSCells are cube-shaped and are placed on a
basement membrane.
LOCATIONFound in the lining of the kidney tubules
as well as in the ducts of the salivary glands.
FUNCTIONHelps in the absorption of useful
material from the urine before it is
passed out.

Glandular epithelium:

CHARACTERISTICSIt is a portion of the
epithelial tissue that
folds inwards to form a multicellular gland.
LOCATIONPresent in the secretory organs. such as stomach,
intestine, pancreas etc.
FUNCTIONCapable of
synthesising and
secreting certain
substances such as
enzymes, hormones, milk, mucus, sweat, wax and saliva at the
epithelial surface.

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