Animal Tissue

Tissue is the group of cells having similar structure & function. Animals contain 4 basic types of
tissues which are :- epithelial tissue, connective tissue, muscular tissue and nervous tissue. Epithelial
tissue can be derived from any of the three germinal layers. Epithelial tissues are of different types such
as : Squamous, cuboidal, columnar, ciliated, pseudo-stratified, stratified, and transitional.
Functions of epithelial tissue : Protection, secretion & absroption. There are 3 types of connective
tissues which are differentiated on the basis of extracellular material. Secreted by cells themselves. (a)
Connective tissue proper- (soft jelly like matrix with fibres) – are of five types : areolar, adipose, white
fibrous, tendon and legament.
(b) Skeletal tissue (Supportive connective tissue) includes cartilage and bones which form the
endoskeleton of the vertebrate body. The Cartilages are classified in to four group : Hyaline, white
fibrous, yellow elastic fibro cartilage and calicified cartilage.
(c) Blood (fluid connective tissue) is a fibre-free fluid extra cellular matrix.
It is a mobile connective tissue (Vascular/Fluid tissue). It is composed of plasma, blood cells and
blood platlets. It is a opaque trubid fluid.
Blood cells are erythrocytes and Leucocytes. There are five types of leucocytes : neutrophils,
eosinophils, basophils, monocytes and lymphocytes.
WBCs are colourless, nucleated found in blood (and lymph). Which are devoid of haemoglobin.
They are capable of coming out of blood capillaries through the process of diapendesis. (i. e. Greek
Word – diapendesis – leaping through)
(d) Mascular tissue (mostly mesodermal origin) is made up of elongated and contractive cells :
called muscles cells or myocytes.
There are three types of Muscular tissue : Skeletal muscle (striated), non striated and cardiac,
. Myoglobin – Muscle haemoglobin
. Myoblasts – Muscle forming cells.
. Myology : study of all aspects of muscles & accessory structures .
(e) The nervous tissue it is composed of two types of cells – (a) neurons : (Nerve cells) are
structural & functional unit, they transmit nerve impulses, (b) neuroglia. Neuron has one or more processes
extending from it . (i) Axon – carries impulses away from the cell body.
(ii) dendrites (G.K. dendron tree) take nerve impulse to the cell body.
On the basis of number of processes, neurons are : unipolar, bipolar & multipolar.
The nerve fibres may be surrounded by two concentric sheath. The inner is known as medullary
or myelin sheath.
Myelin is secreted by schwann cells in peripheral nerve fibes and oligodendrocytes in central
Nervons system.Schwann cells form the outer sheath called neurilema (GK. neuron- nerve, lemna-skin).
There is a physical gap between the nerve ending of axon and dendrites called synapse.

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