Lanugo

Fine, soft hair covering the body of a fetus or newborn

Lanugo is a type of fine, soft, and usually unpigmented hair that covers the body of a fetus or newborn. It is the first type of hair to be produced by the fetal hair follicles and plays a crucial role in the development and protection of the fetus.

Development

Lanugo begins to develop on the fetus around the fourth or fifth month of gestation. It is typically shed before birth, around the seventh or eighth month of pregnancy, although some infants are born with lanugo still present. This hair is replaced by vellus hair, which is finer and less noticeable.

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Lanugo covering the skin of a newborn.

Function

The primary function of lanugo is to protect the delicate skin of the fetus. It helps to hold the vernix caseosa, a waxy substance that covers the skin of the fetus, in place. The vernix caseosa acts as a barrier, protecting the skin from the amniotic fluid and preventing it from becoming waterlogged.

Lanugo also plays a role in regulating the temperature of the fetus. By trapping heat close to the skin, it helps to maintain a stable body temperature in the womb.

Postnatal Presence

In some cases, lanugo is still present at birth, especially in premature infants. It usually disappears within a few weeks after birth as the infant's body hair matures into vellus hair. In rare cases, lanugo can persist longer, but it is generally not a cause for concern.

Lanugo in Adults

While lanugo is primarily associated with fetal development, it can also appear in adults under certain conditions. For example, individuals with anorexia nervosa may develop lanugo as a physiological response to severe weight loss and malnutrition. The growth of lanugo in these cases is thought to be a mechanism to conserve body heat.

Related pages

• Vellus hair
• Terminal hair
• Vernix caseosa
• Anorexia nervosa