What dictates the sizes, lengths, directions, and orientation of stretch marks?
In: Biology
Stretch marks are a type of scar. When the skin goes through rapid stretching (from events such as puberty, weight gain, or pregnancy) and it does not produce collagen and elastin well enough, the skin tissue breaks up and this causes marks on the skin. Specifically the middle skin layer. However, those that have lost weight can also get stretch marks, so it’s not just directed towards a certain group.
If you think about the way humans grow, we grow up and out. The marks form perpendicular to the direction of the skin tension. For example, in the case of weight gain or pregnancy. The stomach stretches out and sideways, so the stretch marks are generally going to go up and down. In the case of growth due to puberty, the stretch marks would generally be side ways because the skin in stretched up.
The length/size is determined by how fast the skin is stretching, and how fast the collagen and elastin are produced to accommodate the skin changes.
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