Collagen is a protein made up of amino-acids. Collagen makes up approximately 30% of the proteins within the body. These are tough and strong structures found all over the body: in bones, tendons and ligaments.
Collagen helps to give strength to various structures of the body and also protects structures like the skin by preventing absorption and spreading of pathogenic substances, environmental toxins, micro – organisms and cancerous cells. Collagen protein is the cement that holds everything together.
Collagen is also present in all the smooth muscle tissues, blood vessels digestive tract, heart, gallbladder, kidneys and bladder holding the cells and tissues together. Collagen is even the major component of the hair and nails
With age, collagen production slows and the cells structures weaken. The skin gets thinner and is easier to damage, hair gets lifeless, skin sags and wrinkles, tendons and ligaments become less elastic, joints get stiff etc
Source : https://www.news-medical.net/health/What-is-Collagen.aspx