Lanugo: Characteristics And Functions Of This Type Of Body Hair
Lanugo is a term that refers to a type of very fine body hair, which grows as a skin insulator in response to the absence of fat. It occurs in humans during fetal development, but is also present in other mammals.
Although it is a typical structure of the human gestational period, these villi can also appear as symptoms of eating disorders such as anorexia nervosa.
If you want to know more about this type of hair so closely linked to the first stages of human life, we encourage you to continue reading.
Before delving fully into the functionality of these very specific structures, it is necessary to clarify what hair is in general and what types human beings present throughout their lives.
Hair, an ancestral trait
Hair, in itself, is a continuation of the scalp formed by a keratin fiber, fibrous structural protein rich in sulfur. This structure, so common in basically all mammals, is divided into root and stem. The lanugo, despite being very different from the hairs present on the head, shares this basal structure to some extent. Even so, we will describe hair as a functional unit taking as reference the “terminal hair”, that is, the hair that we all have on our heads.
High metabolic and mitotic activity occurs in the root. This ends in a bulb, which houses the dermal papilla responsible for feeding the hair. The shaft, for its part, is the main section of the hair and is divided into three different areas: cuticle, cortex and medulla, in order of depth.
The cortex, the intermediate zone, occupies 70% of the hair and gives it its characteristic mechanical properties. The cuticle, on the other hand, represents 9% of the hair shaft and is responsible for protecting it from environmental influences. Finally, the medulla, the innermost area, occupies 21% of the hair surface and is made up of rounded corneas.
Human beings have three types of hair throughout their lives:
As we can see, the world of villi holds more secrets than one might initially think. If you want to know more about lanugo, we encourage you to continue with the following lines.
Location and function
As we have said previously, lanugo is a type of fine hair that is present in fetuses, newborns and people with certain nutritional disorders.
This type of structure plays an essential role in the attachment of the caseous vernix (fatty material that protects the skin of the fetus against chafing and cracking) to the skin of the developing infant This is very important, because without vernix caseosa, the baby’s skin would wrinkle excessively due to constant exposure to amniotic fluid.
In addition to this integral function, lanugo protects the fetus from harmful substances present in the maternal environment, such as urea and electrolytes. It also prevents water loss, promotes the innate immunity of the fetus and plays an essential role in thermoregulation. Who would have thought that such an apparently basic structure would play such an important role in the development of human beings in their early stages?
This special hair appears approximately in the 13th week of gestation, and as we have already said before, it is the first type of hair that appears in human beings. Its appearance and development is directly linked to the expression of certain hormones Its growth begins around the eyebrows, nose and forehead, and later spreads throughout the body. By week 20, lanugo covers the entire body surface of the fetus.
During weeks 33-36 it begins to disappear to integrate into the amniotic fluid This is digested by the fetus, so it will later end up forming part of meconium, a viscous substance composed of dead cells and stomach secretions that line the intestine of the newborn. Speaking clearly, meconium is the first stool of the newborn, as it is expelled by the baby during the first 48 hours of life after birth.
As strange as it may seem, yes, the first hairs that appear on the surface of the newborn end up being excreted in their first bowel movement. If this meconium is not excreted by the infant after the first 48 hours after birth (which happens in 99% of cases), it is necessary to go to the pediatrician urgently, as it is likely that something is wrong. It is possible that the newborn presents anatomical or neuromuscular pathologies.
Lanugo is still present in 30% of newborns This is a normal occurrence that certainly does not have to alert parents. In any case, if it is present at the birth of the baby, it falls out on its own after the first weeks of delivery, leaving room for body hair and the terminal hairs that we have already described previously.
Lanugo and diseases
As we have already said in previous lines, the presence of lanugo in an adult individual is a symptom of a serious pathology. Among the diseases that cause the emergence of these villi we find anorexia nervosa, bulimia nervosa, various nutritional disorders or the presence of a teratoma. Below, we briefly explain these pathologies.
Anorexia and bulimia nervosa
Anorexia and bulimia manifest themselves in various ways on the patient’s skin, since These disorders generate malnutrition, psychiatric disorders and atypical muscular efforts due to the continued induction of vomiting.
Although the reason for the appearance of these villi in patients with anorexia and bulimia is not clear, it could respond to a protective function of the skin due to the absence of fat.
Of course, the appearance of these villi is not the most serious consequence of these eating disorders. Other effects may be hypertension, the appearance of edema or abnormal water retention, and anemia due to lack of iron and protein intake. Emotional symptoms such as depression, sleep disorders and abandonment of normal activities also appear. For all these reasons, both medical and psychological approaches become essential in the treatment of this pathology.
Teratomas are encapsulated tumors with tissue or organ components that resemble the “normal” structures of the three germ layers that make them up Lanugo usually appears in these congenital tumors.
Other specific cases have been detected in which lanugo can appear without apparent correlation with other pathologies. There are cases, for example, in which this type of villi have appeared in patients who have later been diagnosed with cancerous processes. Although the causal mechanisms are not completely known, hypertrichosis (or excessive appearance of villi) seems to be correlated with the appearance of carcinomas.
Conclusions
As we have seen in the previous lines, lanugo is a type of very fine body hair that grows as an insulator for the skin due to the absence of fat. This is present in fetuses during the development of pregnancy, but also can occur in pathological processes such as the appearance of teratomas or nutritional disorders such as anorexia or bulimia nervosa.
Despite being characteristic of human beings, this type of hairiness It is also present in other mammals, such as seals, elephants or deer during their fetal development. Despite its anecdotal nature and the lack of knowledge of these structures by the general population, we can affirm that the lanugo is an essential structure for the correct development of the newborn.
