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| Epithelial Tissue |
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| Nature, Occurrence and Function: |
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| Depending upon the shape and function, Epithelial tissues are classified as: |
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| Side view of simple squamous epithelium |
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| Here the cells are compact, plate-like with no inter-cellular spaces. It forms the outer layer of the skin, and lines cavities and ducts. Its function is to protect underlying parts from germs and injury. |
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| Bone |
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| This is a connective tissue in which the ground substance or matrix is composed of elastin, which is impregnated with salts of calcium and magnesium. Skeletal tissue is of two kinds, bone and cartilage. Cartilage is softer than bone and does not contain the organic salts. Instead they have special cells, which gives strength to the tissue. Cartilage is found in joints and in the discs between vertebrae. |
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| This tissue gives support and flexibility to body part. |
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| Blood cells |
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| Blood |
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| This consists of a fluid called plasma, which has red blood corpuscles (RBC), white blood corpuscles (WBC) and blood platelets. Blood circulates throughout the body in blood vessels. The blood transports oxygen, nutrients, hormones to tissues and organs. |
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| Lymph |
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| This is a straw coloured fluid similar to blood but does not have RBCs. Lymph flows in special vessels called lymph vessels. Its function is to form a defence system for the body. |
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| These consist of cube-like cells, which are square in section but the free surface appears hexagonal. Found in kidney tubules and in glands. These tissues provide mechanical strength to the part where they occur and produce secretions. |
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| Epithelium |
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| These consist of cells that are tall and pillar-like. They form the lining of the stomach and intestine. They are also present in the salivary glands, sweat glands and tear glands. These cells give mechanical strength and some that line the intestine adsorb digested food material. |
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| These are cuboidal or columnar cells, the free surface, of which bear cilia capable of beating rhythmically. These cells are found lining the trachea or wind-pipe of vertebrates. The beating cilia help to keep unwanted particles from entering the lungs. |
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| Glandular epithelium |
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| This is actually a modification of the columnar epithelium in which the cells have become specialized for the manufacture and secretion of chemical substances. These cells are found lining the intestine and various glands. They secrete mucus and other secretions. |
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| Connective Tissue |
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| Nature, Occurrence and Function: |
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| Tissues and organs in a body must be supported and held in position. This function is performed by connective tissue, which binds organs and tissues together. They are of four types. |
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| Areolar tissues |
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| This consists of tendons and ligaments. Tendons are strong inelastic and connect muscles to bones. Ligaments are elastic and connect bones to each other. This tissue has a matrix in which are scattered special cells, which can engulf bacteria and prevent infection, and fibres which may be yellow or white. |
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| Adipose tissues |
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| These are fat cells. They are oval or rounded cells filled with fat droplets. This tissue is found below the skin and in the bone marrow. The function of this tissue is to store fat and conserve body heat. |
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