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FUNCTIONS OF THE SKIN
I only realized the importance of the sense of touch after the doctor told me that I might lose it. Our sense of touch takes on such an important role in our lives. Yet many of us take it for granted and do not see that the skin is actually vital to us.
Here are 10 functions of our skin:
1) Protective layer
- defense from the external environment
2) Sensation:
- sense of touch
3) Heat Regualtion:
- dilation and constriction of blood vessels and shunt vessels.
4) Controls rate of evaporation:
- prevents excessive water loss
5) Storage:
- stores lipids and water
6) Synthesis:
- synthesizes Vitamin D from UV rays
7) Excretion:
- sweat excretes small amounts of urea
8) Absorption:
- In humans, for certain forms of medication administration, such as adhesive patch. E.g. Nicotine patch
- in animals, their skin is their respiratory organ
9) Water resistance:
- a water resistant barrier
10) Aesthetics:
- affects how we look and the image we portray to others
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Structure |
Function |
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The Epidermis is the relatively thin, tough, outer layer of the skin. Most of the cells in the epidermis are keratinocytes. These cells slowly migrate up toward the surface of the epidermis. Once they reach the skin surface, they are gradually shed and are replaced by younger cells pushed up from below. |
EPIDERMIS |
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1 |
Hair
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Grows hair by packaging old cells together. Attached to it is a sebaceous gland and a sebum-producing gland. There are structures called papilla, made up of connective tissue and a capillary loop It is covered with epidermal cells and constantly divide to grow new skin cells. (Other structures include arrector pili muscle.)
It is attached to the hair follicle. When it contracts, it causes our hair to stand in its ends. Skin around the hair will be raised as well, resulting in what we commonly call ‘goose pimples’.
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The dermis is a thick layer of fibrous and elastic tissue that makes the skin flexible and strong. It is the skin's supporting tissue and is particularly rich in nerve endings. |
DERMIS |
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2 |
Sweat Glands
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It is a coiled tube which forms a tight knot, surrounded by many blood capillaries, from the down growth of epidermis.
Secreted sweat from the sweat glands flows through the sweat duct, then the swear pore, which is an opening to the surface of our skin.
Secretes sebum
Consists of water, dissolved salts, and small amounts of urea (excretes small amounts of metabolic waste product) |
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3 |
Sensory Receptor
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Gives the sensation of touch
Modified dendrites of sensory neurons which allows us to sense pain, pressure and temperature changes in our surroundings.
They are mechanoceptors, responding to pressure, or any kind of mechanical stimulus causing a deformation of the corpuscle. |
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4 |
Nerve fibre |
Nervous impulses from the receptors move along the nerve fibre to the central nervous system to bring about a response. |
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5 |
Blood vessels |
They provide nutrients to the skin and help regulate body temperature. Heat makes the blood vessels enlarge (dilate), allowing large amounts of blood to circulate near the skin surface, where the heat can be released. Cold makes the blood vessels narrow (constrict), retaining the body's heat. |
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Below the dermis lies a layer of fat that helps insulate the body from heat and cold, provides protective padding, and serves as an energy storage area. The fat is contained in living cells, called fat cells, held together by fibrous tissue. |
HYPODERMIS |
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6 |
Sub-cutaneous fat |
Insulating layer for heat loss prevention which is made up of adipose cells (tissue) |
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Click here to learn more about receptor endings
Human skin colour can range from almost black to nearly colorless (appearing pinkish white due to the blood in the skin) in different people. Skin color is determined by the amount and type of melanin, the pigment in the skin. On average, males have darker skin tones than females.
In general, people with ancestors from tropical regions (hence greater sunlight exposure) have darker skin than people with ancestors from subtropical regions.
Melanin
Melanin comes in two types: pheomelanin (red) and eumelanin (dark brown to nearly black). Both amount and type are determined by four to six genes which operate under incomplete dominance. One copy of each of those genes is inherited from the father while the mother contributes the other. Each gene comes in several alleles (refers to one member of a pair or series of different forms of a gene), resulting in a great variety of different skin tones.
Health-related effects
Dark skin protects against ultraviolet light. UV rays cause mutations in skin cells, which in turn cause skin cancers. Light-skinned persons have about a tenfold greater risk of getting skin cancer under equal sunlight exposure, with redheads having the greatest risk. Furthermore, dark skin prevents radiation of UV-A rays from destroying the essential folic acid, derived from B vitamins. Folic acid (or folate) is needed for the synthesis of DNA in dividing cells, and folate deficiency in pregnant women are associated with birth defects.
While dark skin preserves vitamin B, it can lead to a vitamin D deficiency. To address this issue, some countries have programs to ensure fortification of milk with vitamin D.
The advantage of light skin is that it does not block sunlight as effectively, leading to increased production of vitamin D, necessary for calcium absorption and bone growth. The lighter skin of women may result from the higher calcium needs of women during pregnancy and lactation (secretion of milk from the mammary glands).
Cultural effects
Skin tone has sometimes been used in an often controversial attempt to define human races. On a cultural level, color terminology for race has evolved, based upon genetic variations in human skin tone and changing customs or traditions of what arbitrary criteria and the amount of categories to use.
Albinism
It is a form of hypopigmentary congenital disorder, characterized by a partial or total lack of melanin pigment in the eyes, skin and hair (or more rarely the eyes alone). Hence, an albino has light-coloured (or even white) skin and hair. However, the iris of albinos are red due to the presence of blood vessels in them. This condition is known to affect mammals (including humans), fish, birds, reptiles, and amphibians. Albinism results from inheritance of recessive (not dominant) alleles. It is hereditary. Hence, it is not an infectious disease and cannot be transmitted through contact, blood transfusions, or other vectors.
Isn't this so fascinating? I never knew that albino humans exist! I thought this only happened to animals like rats. I hope you guys learnt something about skin colour from my entry and found this topic as intersting as I did!
Alyssa Ho (8) -
Designer: US
Base codes: detonatedlove♥
Featuring: The skin
