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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
Left: Cold water with ice, Middle: Water at room temperature, Right: Hot water
I blindfolded Kay
She put her left hand in the cold water and her right hand in the hot water
Then, she put both her hands into the middle bowl (which had water at room tempture)
Conclusion: The hand in the cold water feels hotter while the hand in the hot water feels particularly cold.
WHY IS THAT SO?
Firstly, what allows us to feel the temperature of the water?
Sensory receptors (in the skin) receive information about changes in the environment and then nerve impulses would be sent to the brain. Our sense of touch is made up of:
1. pain
2. heat
3. cold
4. pressure
5. touch
Interesting fact 1:
Receptors vary in terms of structure
Pressure receptors consist of nerve endings encapsulated by specialized connective tissues while touch receptors form neuronal fiber nets around the base of hairs.
Interesting fact 2:
Receptors vary in terms of abundance.
There are more pain receptors than cold receptors in the body.
Interesting fact 3:
Receptors vary in terms of distribution over the surface of the body
Your fingertips have more touch receptors than the skin on your belly.
EXPLANING THE EXPERIMENT...
When Kay puts her hand in the bowl of cold water, sensory receptors send impulses to the brain to notify it of the temperature change. Hence, she feels cold. Similarly, when she puts her hand in the bowl of hot water, nerve impulses are sent to her brain and she knows that it is hot. As she puts both her hands in the bowl of water at room temperature, the temperature of her skin is changed rapidly. The sensation evoked depends on the change in temperature, otherwise known as the acclimation temperature.
Initially, when she puts her hands into the left and right bowls of water, her skin temperature has to be raised so that she can feel warmth or lowered so she can feel coldness. However, after putting her hand in the water at room temperature, her skin only needs to be warmed by a little bit to feel warmth but must be cooled by a lot more to feel coldness.
Hence, her left hand feels hotter while the right seems colder.
That being said, the sense of touch is very important to us as:
1. It allows us to sense temperature which will remind us to wear more clothes during winter and to cool off after exercising.
2. It allows us to feel pain which will warn us to quickly pull our hand away from a hot stove or to not grab the wrong end of a knife.
3. It allows us to differentiate different textures (smooth from rough, soft from hard)
AMAZING BUT TRUE!
We do not only have skin and sense of touch on the external of the body. Internally, we can feel pain when we have a sore throat or we can even feel food in our stomach after a meal.
Eve Tan Jia Ee (6)
References:
http://www.unmc.edu/Physiology/Mann/mann5.html
http://qldscienceteachers.tripod.com/junior/expt/biology_nervous.html
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