Waxy white substance found coating the skin of newborn human babies
Newborn baby immediately after birth, covered in vernix
Vernix caseosa, also known as vernix, is the waxy white substance found coating the skinofnewborn human babies.[1] It is produced by dedicated cells and is thought to have some protective roles during fetal development and for a few hours after birth.
Vernix is produced during a distinct phase of the epidermal development.[2] Around the 21st week of gestation, periderm cells are being shed and replaced with stratum corneum; these shedding mix with secretions of sebum by the sebaceous glands to form vernix, which gradually covers the body in an anteroposterior and dorsoventral pattern.[1][2][3] Vernix, in itself, is also believed to aid in the formation of stratum corneum.[4] By early third trimester, the process is complete.[5]
Soon enough, part of the vernix is emulsified by increasing concentrations of pulmonary surfactants and desiccates, only to be consumed by the fetus; a corresponding increase in amniotic fluid turbidity is noticed.[2]
Vernix has a highly variable makeup but is primarily composed of sebum, cells that have sloughed off the fetus's skin and shed lanugo hair.[6] Chemically, it is water (80%), lipids (10%) and proteins (10%).[1] The lipids include ceramides, cholesterol, fatty acids, triglycerides, waxes and sterol esters, squalene, and phospholipids;[1] multiple detailed analyses of the polar components have been done.[7] The total fatty acid profile in vernix (either as part of lipids or as fatty acids) contains a variety of less common fatty acids, such as omega-7 polyunsaturated fatty acids or non-methylene-interrupted omega-3 fatty acids.[8]
The protein composition is relatively understudied.[1] Vernix of term infants has more squalene and a higher wax estertosterol ester ratio than preterm infants.[6]
Vernix is composed of mobile corneocytes embedded in an amorphous lipid matrix.[1] Precise biological mechanisms leading to its formation are poorly understood.[9]
The cells are polygonal or ovoid in shape, malleable, and lack nuclei; typical thickness is 1-2 μm.[1] Nuclear ghosts are frequently observed and Acid Phosphatase Activity is nonuniform.[1] Keratin filaments build a scaffold like structure which form a water-storage area.[1] As opposed to stratum corneum, the vernix corneocytes lack desmosomal attachment and the lipid layer is more disordered.[10]
Vernix is a white viscous cream-like substance in appearance.[1]
The water is not uniformly distributed throughout, but rather exclusively present in the sponge-like corneocytes; despite its high water content, vernix is non-polar (due to lipids) and more vapor-permeable than stratum corneum.[1][11][12]
Vernix appears in all full term infants but with widely varying body-coverage, while premature and post-mature births generally do not display any.[6][2][13]
It is theorized (and observed) to serve several purposes:[1][2][11]
Waterproofing the skin, whilst in gestation.
Lubricating the infant's skin, and facilitating easy passage through the birth canal.
Preventing infections — primarily as a mechanical barrier and secondarily via the presence of lysozyme, lactoferrin and antimicrobial components in peptide layer.
Vernix is used as a reliable site-of-record for measuring cocaine exposure in pregnant women.[2][15] Using vernix for diagnosing uterine rupture and amniotic fluid embolism has been proposed.[2]
Vernix is thought to be unique to human fetal development; in 2018, vernix-like material was reportedly obtained from pups of the California sea lion.[16]
^Moore AL, Marshall CD, Nauta A, Lorenz HP, Longaker MT (2019-01-01). "Chapter 5 - Scarless Wound Healing: From Experimental Target to Clinical Reality". In Atala A, Lanza R, Mikos AG, Nerem R (eds.). Principles of Regenerative Medicine (Third ed.). Boston: Academic Press. pp. 65–92. doi:10.1016/B978-0-12-809880-6.00005-9. ISBN978-0-12-809880-6. S2CID81194374.
^Hoath SB, Shah KN (2017-01-01). "49 - Physiologic Development of the Skin". In Polin RA, Abman SH, Rowitch DH, Benitz WE (eds.). Fetal and Neonatal Physiology (Fifth ed.). Elsevier. pp. 498–514.e4. doi:10.1016/B978-0-323-35214-7.00049-4. ISBN978-0-323-35214-7.
^Karperien M, Roelen BA, Poelmann RE, Gittenberger-de Groot AC, Hierck BP, DeRuiter MC, Meijer D, Gibbs S (2015-01-01). "Chapter 3 - Tissue Formation during Embryogenesis". In Blitterswijk CA, De Boer J (eds.). Tissue Engineering(PDF) (Second ed.). Oxford: Academic Press. pp. 67–109. doi:10.1016/B978-0-12-420145-3.00003-1. ISBN978-0-12-420145-3.
^ abcSchachner LA, Hansen RC (2003). Pediatric dermatology. St. Louis: Mosby. pp. 206–7. ISBN978-0-323-02611-6.
^Hoath SB, Narendran V, Visscher MO (2011). "Vernix Caseosa and Innate Immunity". Innate Immune System of Skin and Oral Mucosa. John Wiley & Sons, Ltd. pp. 145–169. doi:10.1002/9781118025338.ch8. ISBN978-1-118-02533-8.
