Biologie de la peau

vernix caseosa

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During the development of the skin in utero, the skin of the fetus is often covered by a creamy, white, greasy biofilm called vernix caseosa which constitutes a unique barrier between the amniotic fluid and the skin of the fetus. It is present during the last trimester of gestation and dries spontaneously on the skin after delivery. Vernix caseosa is composed of detached, hydrated corneocytes embedded in a lipid matrix. The vernix caseosa corneocytes are polygonal or ovoid in shape, have diameters of 10–40 mm, and are very similar to those of the stratum corneum  . Vernix caseosa consists of 80% water, 10% proteins, and 10% lipids in its natural environment. The lipid fraction is mainly composed of sebaceous-derived, nonpolar lipid classes comprising squalene, sterol esters, wax esters, and triglycerides. The composition of the barrier lipids (cholesterol, free fatty acids, and ceramides ) and of the lipids bound to the corneocytes are similar to that of stratum corneum but their level is much lower. Vernix caseosa contains polypeptides with antibiotic and immunologic properties.

At birth, the vernix caseosa undergoes a substantial change and is transferred from an aqueous, warm and sterile environment to a gaseous, colder, and xenobiotic-containing environment in the post-natal situation. It is supposed to play an important role in barrier formation, SC hydration and pH-regulation in the neonatal skin adaptation process : the vernix caseosa increases the stratum corneum hydration and in addition, it seems to enhance the acid mantle development after birth. It has been proposed to act as a skin cleanser, moisturizer, anti-infective, and antioxidant.

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