Lanugo is a noun referring to the soft, fine, and downy hair that covers the body of a developing fetus or newborn baby. It is derived from the Latin word "lana," meaning wool.
In human embryonic development, lanugo typically appears during the 20th week of gestation. It forms as a protective layer to keep the fetus warm, regulating body temperature in the womb. Lanugo is distinct from the terminal hair that develops later in life and is characterized by its fine texture, lack of pigmentation, and limited length. It commonly covers the entire body, including the face, limbs, and even the back, but tends to be more prominent on the shoulders and back.
Lanugo typically begins to shed around the 32nd to the 36th week of gestation, gradually replaced by vellus hair (short, fine, and barely noticeable hair) or the terminal hair that grows after birth. By the time the baby is born, lanugo is usually absent, except in premature infants, who may still exhibit traces of it on their bodies.
The presence of lanugo in newborns is considered a normal, temporary occurrence and not a cause for concern. However, its persistence beyond the newborn period or appearance in older children or adults may indicate an underlying medical condition or hormonal imbalance, such as anorexia nervosa or malnutrition.
Overall, lanugo serves as a biological phenomenon in human development, contributing to the protection, insulation, and nourishment of the developing fetus in the womb.
