Most women get them. Some men get them. Few people welcome them. Stretch marks, or stria distensae as they are known medically, are scars that appear when the skin is stretched beyond its elastic limit.
Physicists define the elastic limit as the maximum force that can be applied to solid material before the onset of permanent deformation. In dermatology, when stresses up to the elastic limit are removed, the skin resumes its original size and shape. When forces beyond the elastic limit are removed, the skin remains permanently stretch marked.
The younger you are, the firmer your skin. The firmer your skin, the lower your elastic limit and the more likely you are to develop stretch marks. Stretch marks occur most frequently during adolescent or pregnancy growth.
The primary cause is mechanical stretching of the skin due to underlying tissue expansion. Parallel inflammatory streaks appear and align perpendicular to the direction of skin tension. Microscopically, the skin is initially swollen, inflamed and elastin bundles in the inner layer of skin (the dermis) are disrupted.
Over time, the inflammation eventually fades and is replaced by scar tissue. This produces a thinned outer layer of skin (the epidermis), loss of dermal elastin, and a replacement of the dermis by abnormally dense collagen fibres.
Click here to read more in the article published on 27 Apr 2017 by Professor Rodney Sinclair.