Category : UPSC
It is a tissue that is made up of tightly packed cells. Without much materials with in these cells. The reasons for the tightly packed cells are to act a barrier against mechanical injury, invading micro-organisms and fluid loss. We can define epithetical tissue by considering two points in mind one is the number of cells layers and two the shape of the cells.
(i) On the basis of cell layers
(a) When an epithelium has a single layer of cells it is called a simple epithelium.
(b) Where as a multiple tier of cells are known as stratified epithelium.
(ii) On the basis of simple shape of cells:
A. Areolar tissue: It fills spaces inside organs found around muscles, blood vessels and nerves. Its main function is to join skin to muscles, support internal organs, help in the repair of tissues. Whereas tendon’s main function is to connect muscles to bones and ligament is connects bones to each other.
B. Adipose tissue: its occurrence is below skin, between internal organs and in the yellow bone Marrow. Its main function is to storage of fat and to conserve heat.
C. Skeletal tissue: Bone & Curtilage cartilage occurrences is in nose pic, epiglottis and in intervertebral disc of mammals. Its main function is to provide support and flexibility to body part. Whereas bone protects internal delicate organs provides attachments for muscles, bone marrow makes blood cells.
D. Fluid tissue: Blood & Lymph blood transport nutrients, hormones to tissues and organs. Where as leucocytes fight diseases and platelets help in clothing blood.
Lymph transport nutrients into the heart and it also forms the defense system of the body.
It is specialized for an ability to contract muscle cells. These are elongated and referred to as muscles fibers. When a stimulates is received at one end of a muscle cell, a wave of excitation is conducted through the entire cell so that all parts contract in harmony. There were three types of muscles cells: skeletal, cardiac, and smooth muscles.
A. Skeletal muscle: It attached primarily to bones. Its main function is to provide the force for locomotion and all other voluntary movements of the body.
B. Cardiac muscle: It occurs only in the heart. The contraction and relaxation of the heart muscles help to pump the blood and distribute it to the various parts of the body.
C. Smooth muscles: It can be found in stomach, intestines, and blood vessels these muscles cause slow and prolonged contractions which are involuntary.
D. Nervous tissue: This tissue is specialized with a capability to conduct electrical impulses and convey information from one area of the body to another. Most of the nervous tissue (98%) is located in the central nervous system. The brain and spinal cord. There are two types of nervous tissue neurons and neuroglia.
Neurons: It actually transmit the impulses, receptor nerve ending of neurons react to various kind of stimuli and can transmit waves of excitation from the farthest point in the body to the central nervous system. You will read all the details in Chapter Four.
Important facts regarding animal tissue:-
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