Body of a multicellular animal is formed of many cells. Group of cells similar in structure , function and origin form a "Tissue". Branch of Biology that deals with the study of tissues is known as 'Histology'.
Animal cells have narrow space around them which contains fluid called as Extra cellular fluid/ Intercellular fluid.
ORIGIN OF TISSUES: All tissues originate from the cells of any of the three germ layers - ectoderm, mesoderm and endoderm.
TYPES OF TISSUES: 4 major types of tissues are there- Epithelial tissues, Connective tissues, Muscular Tissue and Nervous Tissue.
1.1. Epithelial Tissues : ( Gr. Epi - Upon thele - nipple)
Epithelial tissues are the tissues composed of one or more layers of cells covering the external surface of the body and internal organs or lining the cavities in the body and viscera
There are no blood vessels supplying nourishment to these tissues but they receive nutrients from underlying connective tissues.
Structure: These tissues consist of variously shaped cells arranged closely in one /more layers. There is little intercellular material between the cells and cells are held together by intercellular junctions. Epithelia rests on a thin basement membrane which is made up of Glycoproteins and collagen fibres.
Types: On the basis of arrangement and shape of cells, the epithelia are classified into two groups:-
Covering & Glandular Epithelia
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