Vergetures, striae, or stretch marks – whatever you want to call them – the fact is, those pesky little (or not so little) lines are a common sight for a wide variety of people, although more predominant in women, than in men.
But what is the process behind their development? Who are “the usual suspects” at risk of acquiring stretch marks? And did you know there are seven clinically distinct types of striae?
Sounds interesting, doesn’t it? If so, let’s get right into it.
First, we must define what is a stretch mark. You see, stretch marks are essentially linear scars, which most often appear as a result of epidermal atrophy due to excessively rapid stretching . They can differ in size, position on the body, even color, but basically have the same “origin story”.
Figure 1. Types of stretch marks by origin .
Speaking of differences, here is a neat classification list to help you become an expert in discerning stretch marks (Figures 1,2):
1. Striae distansae (general name of scarring due to stretching)
2. Striae gravidarum (occur secondary to pregnancy)
3. Striae atrophicans (atrophic lesions with extremely thinned out skin, usually follow medical conditions, in particular, Cushing’s syndrome)
4. Striae rubrae (“fresh” slightly raised pinkish-red to dark red scars)
5. Striae alba (“mature” permanent scarring)
6. Striae nigra (black striae, prevalent in the skin with dark pigment)
7. Striae caerulea (bluish to dark-blue scars)
Figure 2. Types of stretch marks differing in color. Striae rubrae and Striae caerulea are “young stretch marks”, while Striae alba is the “older” permanent stage of the condition.
So, what are the risk groups, or, in other words, who is more prone to acquiring stretch marks?
Short answer – it is a genetic Russian roulette; long answer – it could well depend on your circumstances. So, let’s dive right in!
1. Pregnant and nursing women
Stretch marks occur as a result of rapid weight gain in conjunction with spurts of abdomen growth, especially in the second and third trimesters. Localization of scars is usually the belly, lower back, and breasts .
2. Individuals suffering from obesity as well as those who lost a formidable amount of weight in a short period of time
In these cases, the skin just can’t adjust to the changes in the volume of the body (alterations consider specifically the fatty tissue).
3. Teenagers during puberty
Pubescent boys and girls often experience random growth spurts where bones grow faster than the skin can accommodate resulting in it tearing up (especially prevalent along the spine). In such circumstances stretch marks are usually superficial and are almost invisible with time.
4. Professional bodybuilders and weightlifters
In such cases overstretching of the skin is observed due to rapid growth of muscle tissue under the influence of heavy weights and overwhelming physical strain. The use of anabolic steroids also contributes to the formation of striae in athletes. Stretch marks are often seen in the shoulder-bicep area as well as in the hip region.
5. Persons suffering from various diseases (Cushing’s and Marfan syndromes)
In Cushing’s syndrome body produces too much cortisol which after some time leads to a rapid weight gain and consequently skin fragility. In the case of the Marfan sundrome, a decrease in elasticity in the skin tissue is frequently observed , hence leading to rising in levels of risk for obtaining stretch marks.
By now you must be squirming in your seat in anticipation of knowing how, oh how do these stretch marks develop? Don’t worry, you’re going to get scienced in no time!
Firstly, imagine an elastic ribbon with a piece of paper glued on top of it. If you stretch the ribbon – the paper will crack in several places. The same can happen to the middle layer of the skin (dermis) if your body increases in size in a relatively short period of time. The dermis is not elastic enough and doesn’t stretch at the same rate as the underlying fatty tissue or the surface layer of the skin – epidermis. This results in the formation of skin scars, which is a consequence of healing of the damaged tissue. Like any other scars, stretch marks lack hair follicles, as well as sebaceous and sweat glands, and are less elastic than the surrounding skin.
One of the root causes of stretch mark formation is a decrease in the synthesis of collagen and elastin by fibroblasts while the ability to synthesize metalloproteases (collagenase and elastase) is maintained. In other words, the spectrum of fibroblastic cells, in this case, is dominated by fibroclasts that synthesize enzymes and destroy collagen and elastin proteins that maintain skin strength. As a result – when the skin is overstretched – a rupture occurs, the reticular layer of the dermis is destroyed with maintaining epidermis. Vessels, collagen, and elastin fibers are torn, and a piece of skin is “collapsed” [5-7].
Biopsies show that in such areas there is a decrease in the proliferation and migration of fibroblasts, a decrease in the expression of fibronectin and procollagen genes, a disruption of the elastin fiber network, and the appearance of disordered fibrils rich in tropoelastin .
Hormonal influences are studied relatively poorly, but the data obtained so far suggests that in striae-damaged skin, there is an increased expression of receptors for estrogen, androgens, and glucocorticosteroids .
Now, as we’ve touched on the causes of skin damage, let’s talk histology, or, in other words, what is going on with the cells and tissues.
In the early stages of striae development (striae rubra) the most notable pathogenetic symptoms are inflammatory skin changes, dermal edema, and perivascular lymphocyte infiltration. In the later stages (striae alba) the epidermis flattens, becomes thinner, loses in vascularity, and notably, a gradual leveling of rete ridges can be observed (those are extensions of epithelia that project into the connective tissue that lies underneath). Elastic fibers in the scar area break apart, tighten and twist along the edges of the stretch mark, forming a characteristic pattern on the skin .
Figure 3. Histological comparison between normal skin and striae distensae (ED (epidermis); PD (papillary dermis); RD (reticular dermis)) .
When comparing histological sections of normal and striae-damaged skin (Figure 3), it is well observed that the normal epidermis has a basketweave appearance and well-formed rete pegs. In contrast, striae show loss of the rete peg-specific pattern. Additionally, normal dermis demonstrates parallel collagen bundles to the surface, which are evenly spaced, in opposition to striae dermis .
It is clear that in the process of natural healing, striae-affected skin becomes quite different from so-called “normal” skin, both inside and out. But despite an inherent “pathological’ process underlying the formation of striae, it is leaps and bounds from being a pathology in its broad definition. In fact, in the era of #bodyacceptance stretch marks became one of the symbols of the movement, encouraging people to embrace these scars and even use them as a backdrop for art pieces .
So, whether you have stretch marks or not, whatever is your attitude towards them, I hope this article gave you more than just a “skin-deep” glimpse into the intricacies of our bodies, and who knows, maybe changed your whole perspective?
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