Lanugo (; from Latin lana "wool") is very thin, soft, usually unpigmented, downy hair that is sometimes found on the body of a foetal or new-born human. It is the first hair to be produced by the foetal hair follicles, and it usually appears around sixteen weeks of gestation and is abundant by week twenty. It is normally shed before birth, around seven or eight months of gestation, but is sometimes present at birth. It disappears on its own within a few weeks.
It is replaced by hair covering the same surfaces, which is called vellus hair. This hair is thinner and more difficult to see. The more visible hair that persists into adulthood is called terminal hair. It forms in specific areas and is hormone-dependent.
Video Lanugo
Occurrence
In humans
Foetal development
During human development, the lanugo grows on foetuses as a normal part of gestation, but it is usually shed and replaced by vellus hair at about thirty-three to thirty-six weeks of gestational age. As the lanugo is shed from the skin, it is normal for the hair to be consumed by the developing foetus, since it drinks from the amniotic fluid and urinates into its environment. As a result, lanugo contributes to the new-born baby's meconium. The presence of lanugo on new-borns is not necessarily a sign of premature birth. It is seen on infants born at thirty-nine weeks of gestation, that is, full term.
Lanugo functions as an anchor to hold the vernix caseosa on the skin. Together they protect the delicate foetal skin from being damaged by the amniotic fluid. The vernix caseosa also helps to prepare the foetus for life outside the womb. It provides lubrication for birth and contributes to thermoregulation, prevention of water loss, and innate immunity. Without the lanugo to anchor the vernix caseosa, these functions would be compromised.
Malnutrition
Lanugo can be observed in malnourished patients, including those with eating disorders. When found along with other physical symptoms, for example, lanugo can help a physician make a diagnosis of anorexia nervosa or bulimia nervosa.
Teratoma
It is often found in teratomas (congenital tumours).
In other animals
Lanugo is also common on other animals. For example, seals and elephants are often born with a covering of lanugo.
Foetal whales also have lanugo, and is the only time such species show an example of external hair.
Maps Lanugo
References
External links
- Photo of lanugo in a human infant, The Royal Infirmary of Edinburgh
Source of the article : Wikipedia
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