Vernix caseosa, also known as vernix, is the waxy white substance found coating the

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different ...

of newborn human babies. 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

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

, ''vernix'' means ''varnish'' and ''caseosa'' means ''cheesy''. The term was first published in 1846 in the ''Dunglison Dictionary of Medical Sciences''.

In-utero development

Vernix is produced during a distinct phase of the epidermal development. Around the 21st week of

gestation Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregn ...

, 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. Vernix, in itself, is also believed to aid in the formation of stratum corneum. By early third trimester, the process is complete. 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.

Characteristics

Composition

Vernix has a highly variable makeup but is primarily composed of

sebum A sebaceous gland or oil gland is a microscopic exocrine gland in the skin that opens into a hair follicle to secrete an oily or waxy matter, called sebum, which lubricates the hair and skin of mammals. In humans, sebaceous glands occur ...

, cells that have sloughed off the fetus's skin and shed lanugo hair. Chemically, it is water (80%),

lipid Lipids are a broad group of organic compounds which include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include storing ...

s (10%) and

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

s (10%). The lipids include

ceramide Ceramides are a family of waxy lipid molecules. A ceramide is composed of sphingosine and a fatty acid joined by an amide bond. Ceramides are found in high concentrations within the cell membrane of Eukaryote, eukaryotic cells, since they are co ...

cholesterol Cholesterol is the principal sterol of all higher animals, distributed in body Tissue (biology), tissues, especially the brain and spinal cord, and in Animal fat, animal fats and oils. Cholesterol is biosynthesis, biosynthesized by all anima ...

fatty acid In chemistry, in particular in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated and unsaturated compounds#Organic chemistry, saturated or unsaturated. Most naturally occurring fatty acids have an ...

triglyceride A triglyceride (from '' tri-'' and '' glyceride''; also TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids. Triglycerides are the main constituents of body fat in humans and other vertebrates ...

s, waxes and sterol esters,

squalene Squalene is an organic compound. It is a triterpene with the formula C30H50. It is a colourless oil, although impure samples appear yellow. It was originally obtained from shark liver oil (hence its name, as '' Squalus'' is a genus of sharks). ...

, and

phospholipid Phospholipids are a class of lipids whose molecule has a hydrophilic "head" containing a phosphate group and two hydrophobic "tails" derived from fatty acids, joined by an alcohol residue (usually a glycerol molecule). Marine phospholipids typ ...

s; multiple detailed analyses of the polar components have been done. 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. The protein composition is relatively understudied. Vernix of term infants has more

and a higher wax ester to sterol ester ratio than preterm infants.

Morphology

Vernix is composed of mobile corneocytes embedded in an amorphous lipid matrix. Precise biological mechanisms leading to its formation are poorly understood. The cells are polygonal or ovoid in shape, malleable, and lack nuclei; typical thickness is 1-2 μm. Nuclear ghosts are frequently observed and Acid Phosphatase Activity is nonuniform. Keratin filaments build a scaffold like structure which form a water-storage area. As opposed to stratum corneum, the vernix corneocytes lack desmosomal attachment and the lipid layer is more disordered.

Physical properties

Vernix is a white viscous cream-like substance in appearance. 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.

Functions

Vernix appears in all full term infants but with widely varying body-coverage, while premature and post-mature births generally do not display any. It is theorized (and observed) to serve several purposes: * 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 Lysozyme (, muramidase, ''N''-acetylmuramide glycanhydrolase; systematic name peptidoglycan ''N''-acetylmuramoylhydrolase) is an antimicrobial enzyme produced by animals that forms part of the innate immune system. It is a glycoside hydrolase ...

lactoferrin Lactoferrin (LF), also known as lactotransferrin (LTF), is a multifunctional protein of the transferrin family. Lactoferrin is a globular proteins, globular glycoprotein with a molecular mass of about 80 Atomic mass unit, kDa that is widely repre ...

and antimicrobial components in peptide layer. *Moisturizing the stratum corneum whilst in gestation (and controlled drying in post-partum phase). *

Thermoregulation Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature ...

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).

Medical uses

Vernix is used as a reliable site-of-record for measuring cocaine exposure in pregnant women. Using vernix for diagnosing uterine rupture and amniotic fluid embolism has been proposed.

Disorders

Granuloma and peritonitis of vernix have been observed in Caesarean sections. High volumes of vernix cause Neonatal Aspiration Syndrome.

Other species

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 The California sea lion (''Zalophus californianus'') is a coastal eared seal native to western North America. It is one of six species of sea lions. Its natural habitat ranges from southeast Alaska to central Mexico, including the Gulf of Califo ...

Additional images

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.

References

External links

{{commons category Immune system Neonatology Skin