|
:''"Striae" is also a general term referring to thin, narrow grooves or channels, or a thin line or band especially if several of them are parallel or close together.'' Stretch marks or striae (singular stria) or striae distensae, as they are called in dermatology, are a form of scarring on the skin with an off-color hue. They are caused by tearing of the dermis, which over time may diminish, but will not disappear completely. Stretch marks are often the result of the rapid stretching of the skin associated with rapid growth or rapid weight changes. Stretch marks in most cases may also be influenced by hormonal changes associated with puberty, pregnancy, bodybuilding, hormone replacement therapy, etc.〔Bernstein, Eric. (What Causes Stretch Marks? ). 15 December 2008. The Patient's Guide to Stretch Marks. 10 Feb 2009〕 Medical terminology for these kinds of markings includes striae atrophicae, vergetures, stria distensae, striae cutis distensae, lineae atrophicae, linea albicante, or simply striae. Stretch marks formed during pregnancy, usually during the last trimester, and usually on the belly, but also commonly occurring on the breasts, thighs, hips, lower back and buttocks, are known as striae gravidarum.〔(【引用サイトリンク】title=Are Pregnancy Stretch Marks Different? )〕 == Signs and symptoms == Striae, or "stretch marks", begin as reddish or purple lesions, which can appear anywhere on the body, but are most likely to appear in places where larger amounts of fat are stored; the most common places are the abdomen (especially near the navel), breasts, upper arms, underarms, back, thighs (both inner and outer), hips, and buttocks. Over time, they tend to atrophy and lose pigmentation. The affected areas appear empty, and are soft to the touch.〔(【引用サイトリンク】title=Stretch Mark )〕 Stretch marks occur in the dermis, the resilient middle tissue layer that helps the skin retain its shape. No stretch marks will form as long as there is support within the dermis; stretching plays a role in where the marks occur and in what direction they run, however, there are a number of contributing factors (see: "Causes", below) to their formation. They can (but do not always) cause a burning and itching sensation, as well as emotional distress. They pose no health risk in and of themselves, and do not compromise the body's ability to function normally and repair itself,〔(【引用サイトリンク】title=How to prevent and treat stretch marks )〕 however, they are often considered a cosmetic nuisance.〔 Young women are generally affected the most and often seek treatment for them from a dermatologist and following pregnancy. == Causes == The Mayo Clinic states that "()tretch marks seem to be caused, literally, by a stretching of the skin," and adds: "Stretch marks are more extreme when coupled with an increase in cortisone, a hormone produced by the adrenal glands. Cortisone weakens elastic fibers in the skin."〔http://www.mayoclinic.org/diseases-conditions/stretch-marks/basics/causes/con-20032624〕 In other words, an increase in cortisone levels can increase the probability or severity of stretch marks by reducing the skin's pliability; more specifically, it affects the dermis by preventing the fibroblasts from forming collagen and elastin fibers, necessary to keep rapidly growing skin taut. This can create a lack of supportive material as the skin is stretched, and lead to dermal and epidermal tearing, which in turn can produce scarring in the form of stretch marks. This is particularly the case when there is new tissue growth (which can interfere with the underlying physical support of the dermis or epidermis, by displacing the supportive tissue). Examples of cases where stretch marks are common, also given by the Mayo Clinic, include weight gain (in the form of fat and/or muscle), pregnancy, and adolescent growth spurts, though it is also noted that some medications, as well as other medical conditions and diseases, may increase the likelihood of stretch marks appearing. In the case of medication, the Clinic points to "Corticosteroid creams, lotions and pills and chronic use of oral or systemic steroids" as a common contributing factor; in the case of medical conditions that can contribute to stretch marks, examples given include Ehlers-Danlos syndrome, Cushing's syndrome, Marfan syndrome, and "adrenal gland diseases". A number of additional factors appear to promote the appearance of stretchmarks: one study of 324 women, done just after they had given birth, demonstrated that low maternal age, high body mass index, weight gain over 15 kg (33 pounds) and higher neonatal birth weight were independently correlated with the occurrence of striae. Teenagers were found to be at the highest risk of developing severe striae. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「stretch marks」の詳細全文を読む スポンサード リンク
|