The connective tissue has two components:
- (a) matrix, the ground substance
- (b) cells
Proper Connective Tissue
1. Areolar: Most widely spread connective tissue. The cells forming the tissue are:
- (i) Fibroblasts which form the yellow (elastin) and white (collagen) fibres in the matrix.
- (ii) Macrophages which help in engulfing bacteria and micro-pathogens.
- (iii) Mast cell which secretes heparin, that helps in clotting of blood.
2. Adipose Tissue: It has specialized cells which store fat and provide help in forming paddings.
3. Fibrous: It is mainly made up of fibroblasts. It forms tendons and ligaments.
Supporting Connective Tissue
Matrix is composed of chondrin. The cells lie in the matrix singly or in groups of two or four surrounded by fluid-filled spaces. The cartilage may be elastic whose matrix has yellow fibres as in the pinna of the ear.
The cartilage is a flexible and strong type of connective tissue in most of the vertebrates usually occurring as part of their endoskeleton.
The cartilage can be calcified where calcium salts are deposited in the as in head of long bones.
Matrix is composed of ossein. Matrix also contains salts of calcium, phosphorus and magnesium. Matrix in mammalian long bones (such as the thigh bone) is arranged in concentric rings. The osteocytes (bone cells) lie on the lamellae (concentric rings in the matrix.) Osteocytes give out branched processes which join with those of the adjoining cells. Some bones have a central cavity which contains a tissue that produces blood cells. The substance contained in the bone cavity is called bone marrow.
Bones are of two types: Spongy and Compact. In a spongy bone, the bone cells are irregularly arranged. Such bones are found at the ends of the of long bones. In the compact bones, cells are arranged in circles or lamellae around a central canal- the Haversian canal.
Fluid Connective Tissue
Blood and Lymph are the two forms of fluid connective tissue.
It is a complex of blood cells and plasma. Plasma forms the matrix. The blood cells are
- Red Blood Cells (Erythrocytes) - Transport O2 and CO2
- White blood cells (Leucocytes) - Function in defence against bacteria, viruses and other invaders
- Platelets (Thrombocytes) - help in the clotting of blood
Plasma is the extracellular fluid matrix in the ground substance. It contains a large number of proteins such as Fibrinogen, Albumin, and Globulin to be transported to various parts of the animal body for various purposes.