Chapter-3
The Tissues
Syllabus: Elementary tissues: Elementary tissues of the body, i.e. epithelial tissue, muscular tissue, connective
tissue and nervous tissue.
A group of cells having the same origin, similar shape and specific or common generalised function is known as a tissue.
CLASSIFICATION OF TISSUES:
Tissues are classified into four major groups. They are :
1. Epithelial tissue
2. Connective tissue
3. Muscular tissue
4. Nervous tissue
These four groups of tissues are called elementary tissues.
EPITHELIAL TISSUE
● This type of tissue cover the body and lines the cavities, hollow oranges and lines. It is also found in glands.
● The cells of epithelial are very closely packed in a form of continuous sheet, so intracellular substance, the matrix is minimal.
Epithelial tissues form the covering or lining to the free surfaces of the body. They perform vital functions like protection, excretion, glandular secretion and absorption.
Epithelium is further classified as:
1) Simple epithelium (single layer of Cell)
2) Stratified epithelium (multiple layer of Cell)
Simple epithelium: It consists of a single layer of cells. It is further divided into :
1) Squamous
2) Cuboidal
3) Columnar
4) Ciliated
5) Glandular.
1. Squamous (or pavement) epithelium: It consists of flat cells arrangement edge to edge as in a mosaic. This type of epithelium covers the alveoli of lungs, peritonial cavities.
2. Cuboidal epithelium: Here, the cells are cubical. They are arranged over a basement membrane. It is found in the distal convoluted tubules of the kidney.
3. Columnar epithelium: It consists of tall, pillar like cells arranged on a basement membrane. It is found in lungs and ducts of glands.
4. Ciliated epithelium: The cells may be cuboid or columnar. But they contain hair like structures called cilia present in the free border, e.g. cells lining the trachea.
5. Glandular epithelium: It consists of cylindrical or columnar cells. It is present in secretory glands like salivary gland,and breast.
CONNECTIVE TISSUE
Connective tissues serve to connect or bind together different organs or different parts of an organ. They contain an intercellular substance called matrix. It helps in binding and supporting the cells.
Connective tissues are classified as:
1. Areolar tissue (loose connective tissue): It is the most widely distributed tissue in the body. It is a loose irregular connective tissue. It connects the skin to the underlying structures. Also it fills un- occupied spaces between organs. It is found between muscles, blood vessels and nerves.
2. Dense fibrous tissue: This tissue has compactly arranged fibres with greatly reduced interspace. The cells are less in number than areolar tissue. This type of tissue is present in dermis of skin.
3. Elastic tissue: This tissue is yellow in colour and contains more number of elastic fibres. It is present in tissues where strength is required with elasticity e.g. trachea and bronchi.
4. Adipose tissue (Fatty tissue): It contains large, rounded cells and cytoplasm is loaded with fat. The nucleus of the cells is pushed towards the periphery e.g. subcutaneous tissue of skin.
5. Cartilage: It has a tough, gelatinous and elastic matrix formed of chondrin. The cells are more or less round and lie in groups of four embedded in the matrix. Cartilage is of three types:
a) Hyaline cartilage : Here, the. matrix is free from fibres and is transparent. Also, the cells are arranged in small groups. e.g. trachea and tip of nose.
b) Fibro cartilage : Here, the ground substance contains thick bundles of collagen fibres. It is found in the inter-vertebral discs.
c) Elastic cartilage : It is almost similar to hyaline cartilage. But it contains a net work of branching and rejoining collagenous fibres (which give a yellow colour to the matrix) e.g. epiglottis and laryngeal cartilage.
6. Bone : It is the hardest connective tissue. Bones contain a high concentration of salts like calcium phosphate and calcium carbonate.
MUSCULAR TISSUE
Muscle is a tissue which has the power of contraction. Contraction of muscles produces movements. All muscles contain bundles of fibres which run in the same direction. Muscles are classified into three types. They are :
1) Voluntary muscle
2) Involuntary muscle
3) Cardiac muscle
NERVOUS TISSUE
Nervous tissue is composed of three kinds of matter.
1. Gray matter which forms the nerve cells.
2. White matter which forms the nerve fibres.
3. Neuroglia which is a supporting tissue. It holds together and supports nerve cells and fibres.
Short Question and Answer
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