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) -

Audrey Wong (19) 4H

http://www.azmedassn.org/publications/topics/sun_safety.pdf

http://www.cetaphil.com.au/fascinating-skin-facts.asp

www.cetaphil.com.au/fascinating-skin-facts.asp

http://www.bad.org.uk/public/skin/facts/

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

Hello everyone!

We were learning about different kinds of diseases in class today, and my teacher told us about skin cancer. I found it very frightening, as effects of it include crabs and ulcers in the skin, and discoloration of our skin. Our skin is such an important organ of our body. Not only does it protect the insides of our body from external damage, it also has many other functions, which I have listed in another part of my blog. I am going to tell you more about skin cancer, like the symptoms, so you can look out for signs of it on your body before it's too late! But the good thing is, skin cancer generally develops in the epidermis (the outermost layer of skin), so a tumor is usually clearly visible. This makes most skin cancers detectable in the early stages, and can usually be cured before the condition worsens.

Types of skin cancer
Skin cancer is a malignant growth on the skin which can have many causes. There are three common types of skin cancer, each of which is named after the type of skin cell from which it arises:

1) Basal cell carcinoma (BCC)
It is the most common form of skin cancer. It usually looks like a raised, smooth, pearly bump on the sun-exposed skin of the head, neck or shoulders and sometimes, small blood vessels can be seen within the tumor. Crusting and bleeding in the center of the tumor also frequently develops. Very often, it is mistaken for a sore that does not heal. The risk of metastasis (spreading of cancer to other parts of the body) is larger than with basal cell carcinoma.

2) Squamous cell carcinoma (SCC)
It is the second most common type of skin cancer (after basal cell carcinoma but more common than maglinant melanoma). It commonly develops as a red, scaling, thickened patch on sun-exposed skin. Ulceration and bleeding may also occur. When SCC is not treated, it may develop into a large mass. Sunlight exposure and immunosuppression are risk factors for SCC of the skin.

3) Malignant melanoma
It is one of the rarer types of skin cancer but it causes the majority of skin cancer related deaths. Most melanomas are brown to black looking lesions. Change in size, shape, color or elevation of a mole are signs that might indicate a malignant melanoma. Hence, it is advised that the appearance of a new mole during adulthood, or new pain, itching, ulceration or bleeding of an existing mole should be checked.

The BCC and the SCC often carry a UV-signature mutation indicating that these cancers are caused by UV-B radiation via the direct DNA damage when the DNA directly absorbs the UV-B-photon. However, the malignant melanoma is predominantly caused by UV-A radiation via the indirect DNA damage. The indirect DNA damage is caused by free radicals and reactive oxygen species. It has been shown that exposure of skin to sunbeds and the absorption of sunscreen into the skin leads to an increase of free radicals in the skin. Thus, sunscreen increases the risk of developing skin cancer too!

Risk & Risk reduction
Risk of developing skin cancer is higher when you are overexposed to UV-radiation either via the direct or via the indirect DNA damage mechanism. UV-A and UV-B have both been implicated in causing DNA damage resulting in cancer. Natural sunlight (sun exposure between 10AM and 4PM is most intense and therefore most harmful) and artificial UV exposure (tanning salons) are both associated with skin cancer.

Although it is impossible to completely eliminate the possibility of skin cancer, the risk of developing such a cancer can be reduced significantly when exposure to ultraviolet (UV) radiation is reduced, especially in early years. We should also try to avoid sunburns, not with sunscreens (as while it prevents sunburns, it may cause melanoma), but with sunblocks of about SPF 50 . Sunblocks should be reapplied every two hours. Avoiding sun exposure and UV rays by wearing protective clothing (long sleeves and hats) when outdoors during the day (usually from 10AM to 4PM when the sun is most intense) will also help to reduce the risk of developing skin cancer.

Treatment
Most skin cancers can be treated by excision, the removal of the lesion or tumor, making sure that the edges (margins) are free of the tumor cells. Excisions provide the best cure for both early and high-risk disease.
For low-risk disease, radiation therapy and cryotherapy (freezing the cancer off) can provide adequate control of the disease. However, both have lower overall cure rates than surgery.
Moh's Microsurgery is a technique used to remove the cancer with the least amount of surrounding tissue, with the edges are checked immediately to see if any tumor is found. This provides the opportunity to remove the least amount of tissue and the best cosmetically favorable results. This is especially important for areas where excess skin is limited, such as the face, and its cure rates are equivalent to excision.
However, in the case that the disease has metastasized , further surgical or chemotherapy may be required.

Skin cancer is an increasingly common condition. This is in part attributed to increased exposure to ultraviolet radiation, which in turn is thought to be caused by the increased popularity of sun tanning (sun bathing). Lighter-skinned individuals (eg. caucasians) are also more prone to getting skin cancer due to the lack of melanin in their skin. In the United States, about one out of every three new cancers arises from the skin, with most deaths is caused by melanoma. According to the WHO Report, about 48,000 melanoma related deaths occur worldwide per annum.

That's all I have to say for skin cancer! I hope you have managed to pick up some useful tips about learning how to protect yourself from getting skin cancer, and how to recognise its symptoms. It is important for you to detect skin cancer early, so that chances of complete recovery is higher.

It's getting late. I should go get some sleep. Goodnight! (=


Alyssa Ho (08)-

I’m sure many of you have experienced before this temporary feeling of “pins and needles” on our skin after sitting cross-legged, of fallen asleep with you arm crooked under your head for too long. We call it “numb”/”pins and needles”. But do you actually know what causes this weird effect? At first I intended to only do some light reading on it but found it really interesting. So I guess I shall share with you guys what I have gathered from various websites about “Pins and needles”.

Scientific Term: Paresthesia
What is it? It is the condition commonly known as "pins and needles," where part of the body - typically a foot or hand - begins to tingle and becomes numb, or "falls asleep." In most cases, paresthesia is a short-term condition caused by putting pressure on a nerve, and the tingling sensation will diminish within several minutes.

(Click to enlarge)

And its causes:
- Pressure on nerves
- Reduced blood supply
- Nerve injury
- Hyperventilation or breathing excessively
- The effect of toxic substances on the nerves, such as alcohol or lead
- Certain medications
- Diabetes
- Hypothyroidism (underactive thyroid gland)
- Stroke

_________________________________________________________________

Well, I hope you guys have gained something out of this entry! At least you all now understand what actually happens when we feel such tingling sensations. It’s always good to learn and understand our own bodies and how they function!

I will be back to share more interesting information about the skin with ya’ll!
Good bye for now.

P.S. Note that the numbness that we feel sometimes, is temporary paresthesia. Chronic paresthesia is much more complicated and should be dealt with by a neurologist.

(Lim Fang Ting)

- "You shrink like in the washing machine"

- "Because the water in the tub soaks the water out of your skin"

Recently, I began to wonder it if was really true. I posted this question on several science forums, went to the library to read up on it, and I got the answers.

Actually, the above answers (by moms and dads) were common misconceptions about the shriveling of our skin after a bath/swim! It is in fact the exact opposite! Most people have the impression that they have such fingers because the lose bodily fluids. But it is because there is increased absorption! So let me explain this to you in greater details.

Prune Fingers

The wrinkles that occur in skin after prolonged exposure to water are sometime referred to as prune fingers or water aging. This is a temporary skin condition where the skin on the palms of hand or feet becomes wrinkly. Why is this so?

The epidermis is made up of four layers - the stratum corneum, granular layer, squamous cell layer and basal cell layer. In the stratum corneum, there are dead keratin cells. Keratin is a protein found in hair, nails, and the outermost layer of our skin. When our skin is immersed in water for too long, the dead keratin cells absorb the water. This increases the surface area of our outermost layer of the skin. By right, when the surface area increases, our skin would detach from the other layers! However, the outer layer is tightly attached to the living tissue. Therefore, it wrinkles up to accommodate the increase in surface area.

This happens to our hands and feet and not to other parts of the body. This is because those are the parts of our body with the thickest later of the dead keratin cells. Also, the top layer of skin on fingers and toes is more porous as compared to the layers of skin underneath, and thus they are better at absorbing water. On the other hand, the dermis will not absorb as much water as the epidermis. This is why not our entire finger swells.

If this inflation were the same everywhere, the finger would be just swelling and become fatter. But the skin is not uniform. It is tensed in the direction of the length of the finger. Therefore, the epidermis swells following that direction. And if you look closely, our toes wrinkle as well!

Think time! So do you know why the skin on our hands and feet are much thicker than the rest of our body?

Answer: It is because our body is subjected to a lot of wear and tear so the thick skin is actually a form of protection! Imagine playing basketball with skin on your hands as thin as those on your back! Wouldn’t be so much fun, would it?

Once we step out of the tub, the water from our skin evaporates into the atmosphere and our skin is restored to its original form.

Of course, there is the other form of wrinkling which is due to old age. But since “prune fingers” is what we normally experience, I posted the explanations. Now you guys know what happens about your fingers and toes whenever you immerse in water for too long!

(Lim Fang Ting)

http://en.wikipedia.org/wiki/Wrinkle

http://www.madsci.org/posts/archives/2004-07/1090270850.An.r.html

Our body is really a remarkable miracle! For us to be able to feel such a simple sensation of pain, it involves a whole complete system of organs and nerves. Let me bring you through the whole process, from the moment the drop of oil lands on my hand, until my brain tells me that it hurts. This entire process may occur in a split second, but it is actually a rather complicated process, and involves various organs and nerves all over the body.

Firstly, the nerve fibres, also known as nociceptors, beneath our skin will detect the sudden increase in temperature of the burnt area of skin. They respond to touch, pressure, vibrations and temperature by sending nervous impulses. The nervous impulses transmit messages by sending electrical impulses along a peripheral nerve to the spinal cord and brain.

Then, in the spinal cord, the nerve fibers that transmit pain messages — such as the pain from the burn — will enter the spinal cord in an area called the dorsal horn. There, chemicals, also known as neurotransmitters, are released. They activate other nerve cells in the spinal cord, which processes the information and then continues to transmit the information about the burn to the brain.

The thalamus is a sorting and switching station deep inside the brain. Finally, when the neurotransmitters have reached the brain, it forwards the message about the burn to specialized regions of the brain, all at the same time. The brain would then respond to the pain by sending messages that moderate the pain in the spinal cord.
Simply put, pain is transmitted from nociceptors to the spinal cord, to release neurotransmitters, which transmits the message to the thalamus in the brain, where the brain will then respond.
Now that I know what allows me to respond to pain, I started searching about burns.
I found out that there are burns are classified according to how serious they are, and how much damage is done to the nerves, tissues, and even fats.
Burns can be classified into 3 different groups:
1) Superficial burns (first-degree burns)
- Epidermis affected
- Nerves are not affected
- Reddened skin
- Pain is felt at the area of the burns
- E.g. Sunburn

2) Partial-thickness burns (second-degree burns)
- Epidermis destroyed, parts of dermis affected
- Nerves not damaged
- Skin becomes red and raw, blisters develop
- Intense pain felt
- E.g. Scalding

3) Full-thickness burns (third-degree burns)
- All layers of skin destroyed
- Nerves are totally damaged
- Charred, waxy skin
- Pain not felt where skin is charred
- Pain felt around area of charred skin
- E.g. Electric burns

So now I know that I have a partial-thickness burn. After providing treatment for the burn, I found out some interesting information while researching and comparing superficial burns and partial-thickness burns with full-thickness burns. Pain can be felt for the less serious burns, superficial burns and partial-thickness burns, but pain would not be felt for full-thickness burns.

The reason behind this is actually quite simple. In a superficial or partial-thickness burn, the nociceptors are working well, and are able to transmit nerve impulses to the brain to sense the pain. However, when a full-thickness burn occurs, the nociceptors have been burnt and damaged, and is no longer able to transmit messages to the brain. That is why pain is not felt in the full-thickness burn, which is much more serious than either a superficial burn or a partial-thickness burn.

Actually, feeling pain is not a bad thing. It is our body’s way to telling us that there is something dangerous, and we would be warned of the approaching danger. So, next time you’re wishing that your burn won’t hurt so much, you better think twice. Do you really want it to not hurt?

Audrey Wong-19-4H

http://www.umm.edu/dermatology-info/anatomy.htm
http://familydoctor.org/online/famdocen/home/healthy/firstaid/after-injury/638.html
http://www.nlm.nih.gov/medlineplus/tutorials/burns/er099102.pdf
http://www.mayoclinic.com/health/pain/PN00017

Me: I have this burning question to ask you, can you control your body? Or are you totally unaware of what you are doing?


Ian: I believe my gestures are conscious and I can move as and when I like— although great difficulties sometimes.


Me: Can you wave to me now?


Ian: (waves hand after some time)


Me: That’s great!


Ian: Yes. And as I am talking to you, I am controlling my lips. I may be slow when it comes to talking, but ultimately, I still control my body. Somehow my brain is just able to assert itself and take full charge of my body.

--------- END---------

Waterman has demonstrated how resilient the human body is. While to most people, being able to touch is critical for normal movement, Waterman has shown us how the amazing brain can utilize the other senses to help him cope with daily life.

Interact with me

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My life

This is me...

Hello everyone, I am Sarah Beth. I have decided to set up this blog as my own personal diary.

A few months ago, I did a full-body checkup. To my horror, I found out that I am suffering from a viral infection and I had to go through various tests. The doctor told me that I am suffering from a very uncommon infection which might cause me to lose my sense of touch, if I did not receive proper treatment at once. However, I believe I still have a chance to make a complete recovery.

Since then, I did a lot of research regarding the skin and it was then that I decided to create this blog for those that are interested to know more about our skin and our sense of touch.

I came across this song while reseaching.

Here’s to all who need the strength to continue walking down this long and hard journey.

Links

Visit these websites!

Sensory Receptors (Interactive tutorial)

Summary of the skin

Definition of the skin

Wikipedia- The Skin

Health related issues about the skin

Fun experiments to try out at home

Cells of the nervous system

Designer: US
Base codes: detonatedlove♥
Featuring: The skin