Tabitha is seven months pregnant with her first child. She can't believe how big her "belly" has gotten, but is disturbed by the white streaks appearing on her abdomen. What region of the skin and what structures are responsible for the stretching to accommodate the pregnancy? What is causing the white streaks

The skin consists of three key layers. Stretch marks form in the dermis, or middle layer, when the connective tissue is stretched beyond the limits of its elasticity. This is normally due to rapid expansion or contraction of the skin.

Explanation:

Pregnancy stretch marks are striations or streaky indentations in the skin that are pink, red, purple or brown. The medical term is 'striae gravidarum', which is Latin for stripes of pregnancy. They are very common, and typically appear on the abdomen, breasts, thighs, buttocks, and even upper arms.

Genetics plays a role in whether you get stretch marks, and how visible they are. If you have fair skin they may be more visible. You are more likely to get them if you are a young mum, if you put on a lot of weight quickly during the pregnancy, or if you are expecting twins or multiples, but they become more visible post pregnancy as you lose weight. Other indicators of susceptibility include if you’ve had these marks before being pregnant, or if other members of your family have them. Changes in hormone levels during pregnancy can also make skin a little thinner, making some women more susceptible.

This type of scarring happens when the skin cannot resume normal form after a period of intense growth, often due to pregnancy, weight gain, weight loss.

Stretch marks are scars or disfiguring lesions. They are also called striae, striae distensae (SD), striae atrophicans, and striae gravidarum.

The skin consists of three key layers. Stretch marks form in the dermis, or middle layer, when the connective tissue is stretched beyond the limits of its elasticity. This is normally due to rapid expansion or contraction of the skin.

As the body grows, the connecting fibers in the dermis slowly stretch to accommodate slow growth. However, rapid growth leads to sudden stretching. This causes the dermis to tear, allowing deeper layers of skin to show through.

This can form stretch marks and contributes to the way they look.

Stretch marks eventually fade to a silvery, white, or glossy appearance, due to the pale fat beneath the skin becoming visible instead of the usual blood vessels.

They are more likely to develop and become more severe where there are high levels of circulating cortisone, or when cortisone is applied to the skin. Cortisol, the stress hormone produced by the adrenal glands, is converted into cortisone. This weakens elastic fibers in the skin.