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
| CHARACTERISTICS | Cells are flat, cuboidal or columnar in shape. |
| LOCATION | Covers the whole body surface. |
| FUNCTION | 1. 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:
| CHARACTERISTICS | Cells are large, extremely thin and flat. |
| LOCATION | Situated in the lining of blood vessels, lung alveoli, oesophagus, the lining of the mouth and the inner lining of the cheek. |
| FUNCTION | Transportation of substances through selectively permeable membrane |
Stratified squamous epithelium:
| CHARACTERISTICS | Cells are arranged in a pattern of layers, resembling a brick wall. |
| LOCATION | Located as the outer protective covering all over the body surface. |
| FUNCTION | Provides protection to underlying tissues which are subjected to continuous wear and tear. |
Columnar epithelium:
| CHARACTERISTICS | Cells are tall, cylindrical and are arranged like pillars. |
| LOCATION | Found where absorption and secretion occur, as in the inner lining of the stomach, intestines and gall bladder. |
| FUNCTION | Secrete digestive enzymes and perform the function of absorption of nutrients from the digested food. |
Ciliated columnar epithelium:
| CHARACTERISTICS | Cells possess fine hair-like cilia which are capable of rapid, rhythmic, wave-like beatings in a certain direction on their free surface. |
| LOCATION | Found in the inner lining of the wind pipe or trachea, lungs, respiratory system and buccal chambers. |
| FUNCTION | In the respiratory tract, the cilia move and their movement pushes the mucus forward to clear it. |
Cuboidal epithelium:
| CHARACTERISTICS | Cells are cube-shaped and are placed on a basement membrane. |
| LOCATION | Found in the lining of the kidney tubules as well as in the ducts of the salivary glands. |
| FUNCTION | Helps in the absorption of useful material from the urine before it is passed out. |
Glandular epithelium:
| CHARACTERISTICS | It is a portion of the epithelial tissue that folds inwards to form a multicellular gland. |
| LOCATION | Present in the secretory organs. such as stomach, intestine, pancreas etc. |
| FUNCTION | Capable of synthesising and secreting certain substances such as enzymes, hormones, milk, mucus, sweat, wax and saliva at the epithelial surface. |
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