Tissues, Organs and Organ Systems in Plants and Animals — BIOLOGY STD 7 — Question

Epithelial tissue forms the continuous sheet of cells that v covers the external surface of the body as well as the linings of the internal organs. There is no intercellular space between the cells of epithelial tissue, as they are placed very close to each other. On the basis of the shape of cells : Epithelial tissue is classified in to three types :
(a) Squamous Epithelium : The cells are hexagonal or irregular in shape. The cells are very thin that the surface below which the nuclei are present becomes raised. This tissue is found in the lining of body cavity, blood vessels,
cheeks etc.
(b) Cuboidal Epithelium : The cells are cube like or isodiametric. The nucleus is centrally located. This tissue is found in the nephrons of kidneys, salivary glands, sweat glands etc.
(c) C’ulumnar Epithelium : The cells of this tissue are pillar or column like. The cells are placed side by side like columns. The nucleus is towards the base of the cells. This tissue is found in the lining of the alimentary canal, the sensory organs etc.
(d) Functions of epithelial tissues CO They form the protective internal lining of organs and cover the external body surface.
(ii) In salivary and gastric (stomach) glands, the epithelial tissue is specialized to secrete enzymes and hormones.
(iii) They absorb nutrients from the digested food from the lining of the small intestine.
(iv) The excrete waste products from the body from sweat glands and kidneys.