{{short description|Waxy white substance found coating the skin of newborn human babies}} alt=Baby held in a gloved hand, with creamy substance smeared all over|thumb|300x300px|Newborn baby immediately after birth, covered in vernix '''Vernix caseosa''', or simply '''vernix''', is the waxy white substance found coating the skin of newborn human babies.<ref name=":0">{{cite journal | vauthors = Nishijima K, Yoneda M, Hirai T, Takakuwa K, Enomoto T | title = Biology of the vernix caseosa: A review | journal = The Journal of Obstetrics and Gynaecology Research | volume = 45 | issue = 11 | pages = 2145–2149 | date = November 2019 | pmid = 31507021 | doi = 10.1111/jog.14103 | doi-access = free }}</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.
==Etymology== 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 development== 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>{{cite book |author5-link=Michael Longaker | vauthors = Moore AL, Marshall CD, Nauta A, Lorenz HP, Longaker MT | chapter = Chapter 5 - Scarless Wound Healing: From Experimental Target to Clinical Reality|date=2019-01-01 | title = Principles of Regenerative Medicine | doi = 10.1016/B978-0-12-809880-6.00005-9 | edition = Third |pages=65–92| veditors = Atala A, Lanza R, Mikos AG, Nerem R |place=Boston|publisher=Academic Press|language=en|isbn=978-0-12-809880-6 | s2cid = 81194374}}</ref> Vernix, in itself, is also believed to aid in the formation of stratum corneum.<ref>{{cite book | vauthors = Hoath SB, Shah KN | chapter = 49 - Physiologic Development of the Skin|date=2017-01-01| doi = 10.1016/B978-0-323-35214-7.00049-4 | title =Fetal and Neonatal Physiology | edition = Fifth |pages=498–514.e4| veditors = Polin RA, Abman SH, Rowitch DH, Benitz WE |publisher=Elsevier |language=en |isbn=978-0-323-35214-7 }}</ref> By early third trimester, the process is complete.<ref>{{cite book | vauthors = Karperien M, Roelen BA, Poelmann RE, Gittenberger-de Groot AC, Hierck BP, DeRuiter MC, Meijer D, Gibbs S | chapter = Chapter 3 - Tissue Formation during Embryogenesis | date = 2015-01-01 | doi = 10.1016/B978-0-12-420145-3.00003-1 | title = Tissue Engineering | edition = Second | pages = 67–109 | veditors = Blitterswijk CA, De Boer J | place = Oxford | publisher = Academic Press | isbn = 978-0-12-420145-3 | url = https://ris.utwente.nl/ws/files/31463929/Karperien2014tissue.pdf | archive-date = 2023-12-14 | access-date = 2023-11-27 | archive-url = https://web.archive.org/web/20231214053608/https://ris.utwente.nl/ws/files/31463929/Karperien2014tissue.pdf | url-status = dead }}</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" />
==Characteristics==
===Composition=== 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>{{cite book | vauthors = Schachner LA, Hansen RC |title=Pediatric dermatology |publisher=Mosby |location=St. Louis |year=2003 |isbn=978-0-323-02611-6 |pages=206–7}}</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>{{cite journal | vauthors = Harazim E, Vrkoslav V, Buděšínský M, Harazim P, Svoboda M, Plavka R, Bosáková Z, Cvačka J | display-authors = 6 | title = O-acylceramides in vernix caseosa | journal = Journal of Lipid Research | volume = 59 | issue = 11 | pages = 2164–2173 | date = November 2018 | pmid = 30254076 | doi = 10.1194/jlr.M088864 | pmc = 6210899 | url = http://www.jlr.org/content/59/11/2164 | doi-access = free }}</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>{{Cite journal |last1=Menzel |first1=Jan Philipp |last2=Young |first2=Reuben S. E. |last3=Benfield |first3=Aurélie H. |last4=Scott |first4=Julia S. |last5=Wongsomboon |first5=Puttandon |last6=Cudlman |first6=Lukáš |last7=Cvačka |first7=Josef |last8=Butler |first8=Lisa M. |last9=Henriques |first9=Sónia T. |last10=Poad |first10=Berwyck L. J. |last11=Blanksby |first11=Stephen J. |date=2023-07-04 |title=Ozone-enabled fatty acid discovery reveals unexpected diversity in the human lipidome |journal=Nature Communications |language=en |volume=14 |issue=1 |page=3940 |doi=10.1038/s41467-023-39617-9 |pmid=37402773 |pmc=10319862 |bibcode=2023NatCo..14.3940M |issn=2041-1723|doi-access=free }}</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" />
===Morphology=== 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>{{cite book | vauthors = Hoath SB, Narendran V, Visscher MO |first3=Marty O.| chapter =Vernix Caseosa and Innate Immunity|date=2011|title =Innate Immune System of Skin and Oral Mucosa|pages=145–169|publisher=John Wiley & Sons, Ltd|language=en|doi=10.1002/9781118025338.ch8|isbn=978-1-118-02533-8 }}</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>{{cite journal | vauthors = Rissmann R, Groenink HW, Weerheim AM, Hoath SB, Ponec M, Bouwstra JA | title = New insights into ultrastructure, lipid composition and organization of vernix caseosa | journal = The Journal of Investigative Dermatology | volume = 126 | issue = 8 | pages = 1823–33 | date = August 2006 | pmid = 16628195 | doi = 10.1038/sj.jid.5700305 | doi-access = free }}</ref>
===Physical properties=== 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">{{cite book|last=Hoath|first=Steven|url=https://archive.org/details/neonatalskin00hoat|title=Neonatal skin: structure and function|publisher=Dekker|year=2003|isbn=0-8247-0887-3|edition=2. ed., rev. and expanded.|location=New York [u.a.]|pages=[https://archive.org/details/neonatalskin00hoat/page/n205 193]–208|url-access=limited}}</ref><ref>{{cite journal | vauthors = Visscher M, Narendran V | title = The Ontogeny of Skin | journal = Advances in Wound Care | volume = 3 | issue = 4 | pages = 291–303 | date = April 2014 | pmid = 24761361 | pmc = 3985523 | doi = 10.1089/wound.2013.0467 | url = }}</ref>
==Functions== Vernix appears in all full-term infants, with widely varying body coverage. Premature and post-mature births generally do not display any.<ref name="Schachner2003"/><ref name=":1"/><ref>{{Citation|last=Sidbury|first=Robert|title=Newborn Skin Development|date=2018|url=https://www.sciencedirect.com/science/article/pii/B9780323401395001030|work=Avery's Diseases of the Newborn|pages=1468–1474.e1|publisher=Elsevier|language=en|doi=10.1016/B978-0-323-40139-5.00103-0|isbn=978-0-323-40139-5|access-date=2021-01-04|url-access=subscription}}</ref>
It is theorized (and observed) to serve several purposes:<ref name=":0"/><ref name=":1">{{cite journal |vauthors=Singh G, Archana G |title=Unraveling the mystery of vernix caseosa |journal=Indian Journal of Dermatology |volume=53 |issue=2 |pages=54–60 |date=2008 |pmid=19881987 |pmc=2763724 |doi=10.4103/0019-5154.41645 |doi-access=free}}</ref><ref name="nskin"/>
* Waterproofing the skin while 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 the peptide layer * Moisturizing the stratum corneum while in gestation (and controlling drying in the postpartum period) * Thermoregulation in the postpartum phase (Evidence is mixed.) * Quick healing of epidermal wounds * Development of the gut after intra-uterine consumption
Vernix caseosa is thought to cause electrical isolation of the fetus, which could affect accurate fECG measurement of the fetal heartbeat.<ref>{{cite journal |vauthors=Chiera M, Cerritelli F, Casini A, Barsotti N, Boschiero D, Cavigioli F, Corti CG, Manzotti A |display-authors=6 |title=Heart Rate Variability in the Perinatal Period: A Critical and Conceptual Review |language=English |journal=Frontiers in Neuroscience |volume=14 |article-number=561186 |date=2020 |pmid=33071738 |pmc=7544983 |doi=10.3389/fnins.2020.561186 |doi-access=free}}</ref>
== Medical uses == Vernix is used as a reliable site-of-record for measuring cocaine exposure in pregnant women.<ref name=":1" /><ref>{{Cite journal |last1=Moore |first1=C. |last2=Dempsey |first2=D. |last3=Deitermann |first3=D. |last4=Lewis |first4=D. |last5=Leikin |first5=J. |date=October 1996 |title=Fetal cocaine exposure: analysis of vernix caseosa |journal=Journal of Analytical Toxicology |volume=20 |issue=6 |pages=509–511 |doi=10.1093/jat/20.6.509 |issn=0146-4760 |pmid=8889690|doi-access=free }}</ref> Using vernix for diagnosing uterine rupture and amniotic fluid embolism has been proposed.<ref name=":1" />
=== Disorders === 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 species == Vernix was thought to be unique to human fetal development. In 2018, vernix-like material was reportedly obtained from pups of the California sea lion.<ref>{{cite journal | vauthors = Wang DH, Ran-Ressler R, St Leger J, Nilson E, Palmer L, Collins R, Brenna JT | title = Sea Lions Develop Human-like Vernix Caseosa Delivering Branched Fats and Squalene to the GI Tract | journal = Scientific Reports | volume = 8 | issue = 1 | page = 7478 | date = May 2018 | pmid = 29748625 | pmc = 5945841 | doi = 10.1038/s41598-018-25871-1 | bibcode = 2018NatSR...8.7478W }}</ref> Mass spectrometry of the material showed it to be fundamentally the same as human vernix, in both BCFA (branch-chain fatty acids) and squalene content. The presence of vernix throughout the infant gastro-intestinal tract, as well as in the meconium (first excretion), in both human and sea lion neonates, argues that the function of vernix may not be as an external skin protection, as often described in the literature, but as a preparation of the newborn GI tract against water-borne bacteria. As such, vernix caseosa, not present in any terrestrial mammal, including other primates, is one of several arguments for a possible semi-aquatic past of our ancestors.<ref>{{cite journal |last1=Vaneechoutte |first1=M. |title=Was Man More Aquatic in the Past? |journal=Bentham Publishers |url=https://benthambooks.com/book/9781608052448/ }}</ref>
==Additional images== <gallery> 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. </gallery>
== References == {{Reflist|2}}
==External links== {{commons category}}
Category:Immune system Category:Neonatology Category:Skin