(a) White fibres are formed of collagen protein while yellow fibres are formed of elastin protein.
(b) Different types of cells of areolar tissue are :
(i) Fibroblasts and fibrocytes. Fibroblasts secrete matrix and the material of which fibres are formed. Inactive fibroblasts are called fibrocytes. They are small and change into fibroblasts to secrete fibres during wound healing.
(ii) Macrophages or Histocytes. These engulf the microbes, foreign bodies and damaged cells.
(iii) Mast cells. They secrete heparin and histamine.
