Vernix caseosa

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Traces of vernix caseosa on a full term newborn.

Vernix caseosa, also known as vernix, is the waxy or cheese-like white substance found coating the skin of human babies.

Contents

[edit] 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.[1] 12% of the dry weight of vernix is branched-chain fatty acid-containing lipids,[2] cholesterol and ceramide. Vernix of term infants has more squalene and a higher wax ester to sterol ester ratio than preterm infants.[1]

[edit] Function

Vernix is theorized to serve several purposes, including moisturizing the infant's skin, and facilitating passage through the birth canal. Vernix is also thought to have an antibacterial effect;[3] though there is little to support a chemical role of vernix in protecting the infant from infection, it may form a physical barrier to the passage of bacteria.[1]

[edit] Secretion

The sebum in vernix is produced in utero by the sebaceous glands around the 20th week of gestation. Vernix appears primarily in full term infants, while premature and postmature births generally lack any.[1]

[edit] Etymology

In Latin vernix means varnish and caseosa means cheesy.

[edit] Relation to the aquatic ape hypothesis

The vernix is sometimes offered as supporting evidence for the aquatic ape hypothesis (AAH) that human evolution involved a period of adaptation to a semi-aquatic environment No other land mammal, including other apes, produces vernix-coated pre-term infants. In contrast, some sea mammals, including the harbour seal, do.[4] It has been pointed out that this comparison is interesting, but not necessarily proof of the validity of the theory.[5] The AAH is not considered a serious hypothesis within paleoanthropology[6]

[edit] References

  1. ^ a b c d Schachner, LA; Hansen RC (2003). Pediatric dermatology. Gulf Professional Publishing. pp. 206-7. ISBN 0323026117. 
  2. ^ Ran-Ressler, RR; Devapatla S; Lawrence P; Brenna JT (2008). "Branched chain fatty acids are constituents of the normal healthy newborn gastrointestinal tract". Pediatric Research 64 (6): 605-9. PMID 18614964. 
  3. ^ Hoath, SB; Maibach HI (2003). Neonatal skin: structure and function. Informa Health Care. pp. 71-3. ISBN 0824708873. 
  4. ^ Attenborough, D (2005-04-19). "Sir David Attenborough looks at the 'aquatic ape hypothesis'". BBC. http://www.bbc.co.uk/radio4/science/scarsofevolution.shtml. Retrieved 2009-09-25. 
  5. ^ Moore, J (2005-04-25). "Notes on the second half hour of David Attenborough's "Scars of Evolution" radio show on BBC Radio 4, broadcast Tuesday, 19 April 2005". aquaticape.org. http://www.aquaticape.org/bbc4_notes.html. Retrieved 2009-09-25. 
  6. ^ Meier, R (2003). The complete idiot's guide to human prehistory. Alpha Books. pp. 57-59. ISBN 0028644212. 
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