Vernix caseosa
Vernix caseosa, also known as vernix, is the waxy white substance found coating the skin of newborn human babies.<ref name=":0">Template:Cite journal</ref> It is produced by dedicated cells and is thought to have some protective roles during fetal development and for a few hours after birth.
EtymologyEdit
In Latin, vernix means varnish and caseosa means cheesy. The term was first published in 1846 in the Dunglison Dictionary of Medical Sciences.<ref name=":0" />
In-utero developmentEdit
Vernix is produced during a distinct phase of the epidermal development.<ref name=":1" /> 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.<ref name=":0" /><ref name=":1" /><ref>Template:Cite book</ref> Vernix, in itself, is also believed to aid in the formation of stratum corneum.<ref>Template:Cite book</ref> By early third trimester, the process is complete.<ref>Template:Cite book</ref>
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.<ref name=":1" />
CharacteristicsEdit
CompositionEdit
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.<ref name = Schachner2003>Template:Cite book</ref> Chemically, it is water (80%), lipids (10%) and proteins (10%).<ref name=":0" /> The lipids include ceramides, cholesterol, fatty acids, triglycerides, waxes and sterol esters, squalene, and phospholipids;<ref name=":0" /> multiple detailed analyses of the polar components have been done.<ref>Template:Cite journal</ref> 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.<ref>Template:Cite journal</ref>
The protein composition is relatively understudied.<ref name=":0" /> Vernix of term infants has more squalene and a higher wax ester to sterol ester ratio than preterm infants.<ref name="Schachner2003" />
MorphologyEdit
Vernix is composed of mobile corneocytes embedded in an amorphous lipid matrix.<ref name=":0" /> Precise biological mechanisms leading to its formation are poorly understood.<ref>Template:Cite book</ref>
The cells are polygonal or ovoid in shape, malleable, and lack nuclei; typical thickness is 1-2 μm.<ref name=":0" /> Nuclear ghosts are frequently observed and Acid Phosphatase Activity is nonuniform.<ref name=":0" /> Keratin filaments build a scaffold like structure which form a water-storage area.<ref name=":0" /> As opposed to stratum corneum, the vernix corneocytes lack desmosomal attachment and the lipid layer is more disordered.<ref>Template:Cite journal</ref>
Physical propertiesEdit
Vernix is a white viscous cream-like substance in appearance.<ref name=":0" />
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.<ref name=":0" /><ref name="nskin">Template:Cite book</ref><ref>Template:Cite journal</ref>
FunctionsEdit
Vernix appears in all full term infants but with widely varying body-coverage, while premature and post-mature births generally do not display any.<ref name="Schachner2003" /><ref name=":1" /><ref>Template:Citation</ref>
It is theorized (and observed) to serve several purposes:<ref name=":0" /><ref name=":1">Template:Cite journal</ref><ref name="nskin" />
- 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.
- Moisturizing the stratum corneum whilst in gestation (and controlled drying in post-partum phase).
- Thermoregulation in post-partum phase — evidence is mixed.
- Quick healing of epidermal wounds.
- Development of gut, after intra-uterine consumption.
Electrical isolation of the fetus is also thought to occur due to vernix caseosa (this could affect accurate fECG measurement of fetal heartbeat).<ref>Template:Cite journal</ref>
Medical usesEdit
Vernix is used as a reliable site-of-record for measuring cocaine exposure in pregnant women.<ref name=":1" /><ref>Template:Cite journal</ref> Using vernix for diagnosing uterine rupture and amniotic fluid embolism has been proposed.<ref name=":1" />
DisordersEdit
Granuloma and peritonitis of vernix have been observed in Caesarean sections.<ref name=":1" /> High volumes of vernix cause Neonatal Aspiration Syndrome.<ref name=":1" />
Other speciesEdit
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.<ref>Template:Cite journal</ref>
Additional imagesEdit
- Vernix feet.jpg
Vernix on a newborn's legs and feet.
- Newborn minutes after delivery.jpg
Traces of vernix on a full term newborn.
- Postpartum baby3.jpg
Closeup of baby's face right after birth, skin covered in vernix and some blood.