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Question
Explain simple epithelium and its types.
Long Answer
Solution
Simple Epithelium:
- It is formed of a single layer of cells. It forms a lining for the body cavities and ducts.
- Simple epithelium is further divided into the following types.
- Squamous epithelium
- Cuboidal epithelium
- Columnar epithelium
- Ciliated epithelium
- Glandular epithelium
a. Squamous epithelium:
- It is made up of thin, flat cells with prominent nuclei. These cells have irregular boundaries and bind with neighboring cells.
- The squamous epithelium is also known as pavement membrane, which forms the delicate lining of the buccal cavity, alveoli of lungs, proximal tubule of kidneys, blood vessels etc.
- It protects the body from mechanical injury, drying and invasion of germs.
b. Cuboidal epithelium:
- It is composed of single layer of cubical cells.
- The nucleus is round and lies in the center.
- This tissue is present in the thyroid vesicles, salivary glands, sweat glands, exocrine pancreas.
- It is also found in the intestine and tubular part of the nephron (kidney tubules) as microvilli that increase the absorptive surface area.
- Their main function is secretion and absorption.
c. Columnar epithelium:
- It is composed of a single layer of slender, elongated, and pillar-like cells.
- Their nuclei are located at the base.
- It is found lining the stomach, gall bladder, bile duct, small intestine, colon, oviducts and forms a mucous membrane.
- They are mainly involved in secretion and absorption.
d. Ciliated epithelium:
- Certain columnar cells bear numerous delicate hair like out growths called ilia and are called ciliated epithelium.
- Their function is to move particles or mucus in a specific direction over the epithelium.
- It is seen in the trachea of the wind-pipe, bronchioles of respiratory tract, kidney tubules and fallopian tubes of oviducts.
e. Glandular epithelium:
- Epithelial cells are often modified to form specialized gland cells which secrete chemical substances at the epithelial surface.
- This lines the gastric glands, pancreatic tubules, and intestinal glands.
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