More on subcutaneous fat

sebum
http://en.wikipedia.org/wiki/Vernix_caseosa

The oily layer on our skin is a complex mixture of "skin fat"  (sebum), lipids (from epidermal cells), sweat and intrusions from the environment.

It is produced by the sebaceous glands. These are dispersed all over the body, lesser on hands and feet and lacking on palms of hands and feet. On back, forehead and chin they are bigger and more productive, ( 400-900 sebaceous glands per square centimetre). The same counts for the acoustic ducts and genital parts.

Sebaceous glands are small pockets connected by little tubes to hair follicles. Some are directly opening on the skin surface. Sebum is formed, when sebaceous glands die. The process of formation takes about a week. It is a complex mixture of lipids:

* Glycerides
* Free fatty acids
* Wax esters
* Squaleen
* Cholesterol esters
* Cholesterol

Functions:

* Preventing dehydration of the top layer of the skin.
* Protecting against infectious bacteria and moulds.
* Carrying body odours and pheromones.
* Colonized by the bacterium Proprionibacterium acnes, that participates in balancing the immunity system, Staphylococcus epidermidis and the mould Malassezia furfur.

Hormonal regulation

Its production is influenced by sexual hormones (androgens). The most important are 5-testosterone (DHT) and 5-androstene-317diol. Androgens are activated by enzymes in the skin and do play an important role as inter relational pheromones.

It changes with age

* The foetus produces a thick layer, vernix caseosa, a waxy protective coating.
* Sebum on a 3-6 months old baby resembles that of adults.
* In male puberty, the production increases strongly (stimulated by the outburst of testosterone production).
* Males are producing are in general producing more sebum compared to women.
* It decreases with age, especially after female menopause (due to decreasing testosterone levels)



Hair with sebum gland ©GNU free

Sebum as UV protector? Sebus as water repellent?

Skin care is a billion dollar business. Keeping it spotless and young is one of the more important activities of women.
Isn't that peculiar given the fact that we do possess a natural protective layer that keeps our skin healthy in a natural way.

If we do not use detergents to remove this natural biofilm from our skin, we can observe the water repellent effect ourselves.
Looking at beach combing stone age groups of people on the Andaman Islands. Exploited as a tourist attraction these days, the Andamanese possibly
will soon be using all soaps, body care stuff and the like of the visitors.

You can observe it on your own skin if you shower and swim for several days, not using any detergent. Water will run of your body like from a freshly waxed automobile.

Your proof:

Swimming, bathing, taking a shower or washing only? In all cases your research is this:

Start
Take a close up picture of your skin just rinsed with water of your right and left arm and leg.

Then
Do not use any soap or sopelike substance to wash your left arm and leg for fourteen days.
Do use these substances just for your right arm and leg thoroughly.

After 14 days
Take again a close up picture of your skin just rinsed with water of your right and left arm and leg

End
Do compare the views of the droplets on your tested skinparts and what are your conclusions?

Film fragment of Andamanese

Courtesy of George H.J. Weber
The Andaman Association
Waldstrasse 6
CH-4410 Liestal
Switzerland
andaman@bluewin.ch

What about it?

Is it possible that the water proofing sebum bio film on human skin does give some protection against UV radiation damage?
The idea is, that it should fit in an adaptation of nakedness under the tropical sun, an extra protection apart from the strong pigmentation in the original Homo litoreus.
and Homo sapiens itself.



The sebum layer is a biofilm; find out what makes a layer a real "biofilm" (definition, short description of general properties).

The mentioned possibility has been researched, as a fact by scientists in the cosmetics industry. Abstracts of their publications are on the internet. Look up one ore more of these abstracts

The also naked, amphibian animal, the hippopotamus, also has a well developed sebum film on its skin.
The function of it is also studied. Find out what outcomes are mentioned in the literature.

If you succeeded in finding the information on the hippo, look again into the central question in this assignment and what do you think..