Connective Tissue:

Origin of Connective Tissue:

Connective tissues are formed by the mesoderm of the embryo. Connective tissue is the most abundant and widely distributed tissue of the body. It connects different tissues or organs and provides support to various structures of animal body.

Basic Components of Connective Tissues:

Three components are present in the connective tissues. These are matrix, cells and fibres.

(i) Matrix (ground substance):

It is mainly a mixture of carbohydrates and proteins. These have been identified as various forms of mucopolysaccharides. The most common mucopolysaccharide ground substance is hyaluronic acid.

(ii) Connective Tissue cells:

The cells are of different types:

(a) Fibroblasts produce fibres and matrix,

(b) Adipose cells (= Adipocytes or Lipocytes) store fat.

(c) Plasma cells (= Plasmatocytes) synthesize antibodies. Plasma cells are also called ‘Cart Wheel Cells’ because thin chromatin in the nucleus forms four or five clumps giving the nucleus a resemblance to a cart wheel,

(d) Mast cells (= Mastocytes) produce histamine, heparin andserotonin. Mast cells are related to basophils of the blood. Histamine dilates the walls of blood vessels in inflammatory and allergic reactions while heparin checks clotting of blood (anticoagulant) inside the blood vessels. Serotonin acts as a vasoconstrictor to arrest bleeding and to increase blood pressure,

(e) Macrophages (= Histocytes or Clasmatocytes) ingest cell debris, bacteria and foreign matter. Macrophages are derived from monocytes,

(f) Lymphocytes ingest cell debris, bacteria and foreign matter,

(g) Mesenchyme cells give rise to various types of connective tissue cells,

(h) Chromatophores (Pigment cells) are found in the dermis of the skin where they impart colour to the animal,

(i) Reticular cells. They form reticular tissue and are phagocytic in nature.

(iii) Connective Tissue Fibres:

These are of three types:

(a) Collagenous or collagen fibres (white fibres) are made up of collagen protein. When boiled in water collagen changes into gelatin. These fibres occur in bundles and are un-branched and inelastic,

(b) Elastic fibres (yellow fibres) are formed of a protein called elastin. These fibres are branched and elastic,

(c) Reticular fibres. These fibres are delicate, branched and inelastic. They are made up of reticulin protein. They always form a net work.

Features of Connective Tissues:

The connective tissue consists of living cells and extra-cellular matrix. The extra cellular matrix has nearly amorphous ground substance which is made of glycoproteins with associated mucopolysaccharides. Ground substance of extra cellular may be liquid, gel or solid. Connective tissues connect and provide support to various structures. They develop from embryonic mesoderm.

Functions of Connective Tissues:

These are:

(1) Attachment,

(2) Storage,

(3) Support,

(4) Transport,

(5) Defence and Scavenging,

(6) Shock-proof Cushions,

(7) Formation of Blood Corpuscles,

(8) Packing Material, and

(9) Repair.