Connective tissue is made up of a few cells present in the intercellular framework of protein fibres secreted by the cells, known as collagen or elastin. The cells also secrete a thin gel of polysaccharides, which together with fibres make matrix or ground substance. The elasticity, flexibility and strength of the connective tissues are due to fibres. The function and types of connective tissues depend on the nature of the intercellular substance present. Connective tissues contain three types of fibres: collagen, elastic and reticular. Collagen fibres are the most widespread and made up of fibrous protein, collagen. Collagen fibres are flexible and have high tensile strength (comparable to steel). Elastic fibres form a network and can be stretched like a rubber band. They are made up of protein elastin. They retain their original shape and size once the force is removed. Source: https://byjus.com/neet/connective-tissue/