Question

Explain epithelial tissue, and it's types?

Answer 1

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Answer 2

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Epithelial tissue -:

• Epithelial tissue covers most organs and cavities of body.

• Epithelial tissue cells are tightly packed in a single multilayered sheet.

• They have only a small amount of cementing material between them, and almost no intercellular spaces.

• All types of epithelial tissue rest on an extra cellular basement membrane.

• The epithelial cells possesses the power of division and regeneration.

• Epithelium of alveoli of lungs helps in exchange of oxygen and carbon dioxide between the blood and inhaled air.

• It produces exoskeletal structures, such as feather's, nails, etc.

• The tissue facilitates rapid healing of wounds by its regeneration power.

• Sensory epithelium in the olfactory organs and taste buds recieves sensory stimuli.

• Epithelial cells having cilia help in movement of various materials like dust particles in nasal passage, mucus in respiratory tract, urine in uriniferous tubules, etc.

TYPES OF EPITHELIAL TISSUES-:

• Squamous Epithelium

=> It is composed of thin flat cells.
=> Forms a delicate lining.
=> Cells have centrally placed nucleus.

=> It protects the underlying parts of body from mechanical injuries, and also prevent entry of germs and chemicals into the body.
=> In lung alveoli, it allows diffusion of oxygen into the blood and carbon dioxide from the blood into alveoli.

=> It is in lining of blood cells, lung alveoli, oesophagus, lining of mouth.


• Stratified squamous epithelium

=> Arranged in many layers to prevent wear and tear.
=> As they are arranged in a pattern of layers, hence called as stratified squamous epithelium.

=> Occurence - Skin Epithelial cells.

• Columnar Epithelium

=> Tall Epithelial cells.
=> Facilitate movement across the Epithelial barrier.
=> The basal part of the cells resting on the basement membrane bears oval Nucleus.
=> The free end of the cells has large number of microvilli, it increase absorptive surface.

=> Occurence - Present at places where absorption and secretion occurs like in lining of intestine.

• Ciliated columnar epithelium

=> Tall cells with hair like projections on outer surface of epithelial cells.
=> Cilia moved and it's movement pushes the mucus forward to clean it.

=> Occurence - In respiratory tract

• Cuboidal Epithelium

=> Cube shaped cells.
=> Provides mechanical support

=> Occurence - Lining of kidney tubules, ducts of salivary glands.

• Granular Epithelium

=> Epithelial cells often acquire additional specialisation as gland cells which secrete substances at the Epithelial surface.
=> Epithelium is often infolded to form multicellular glands.

=> Occurence - Sweat glands, oil glands , digestive glands, and endocrine glands.

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