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13

There are two types of sweat glands: (1) eccrine sweat glands and (2) apocrine sweat glands. Eccrine sweat glands are present from birth in humans and secrete sweat that is mostly water and functions in evaporative cooling. Apocrine sweat glands are found in the armpits and groin regions and become active in humans at puberty (although the distribution ...


9

1) Is this plausible? It is absolutely plausible. His particular condition was called Vitiligo (as stated in your quote) and isn't that uncommon, albeit not usually as severe. Skin pigmentation expression changes over time, sometimes dramatically. 2) Is it likely to be an actual disease, or would there be so many mitigating factors that it is ...


7

With about 20 square feet of skin constantly exposed to potential irritation, itching must serve an important protective/defensive function. The "scratch reflex" (I'm not sure I would call it that) is necessary to life and limb. Itch is a major somatic sensation, along with (and different from) pain, temperature, and touch. Itch can be an acute sensation, ...


6

For question 1 it's just a biochemical response from thermoreceptor nerves in the skin, temperatures that are likely to cause lasting damage from prolonged exposure cause a neurological response - in this case it's pain. In address to question 2 it is most likely down to the physiological response of vasoconstriction. When the body is cold the body ...


6

Short answer Humans sense temperature differences. Background (Including edits based upon comments) Because the question is "Do humans perceive temperature or heat-flux?", I will answer the answer from a psychophysical perspective, i.e., by dealing with sensory awareness. Just as with many other sensory systems, temperature sensors in the human body ...


6

The human skin is indeed made off a number of different layers, the three most important are epidermis, dermis and hypodermis (also called subcutaneous fat), see the figure (from here) for details: All three layers can be subcategorized further, I'll only give a few details here. More can be found for example in the Wikipedia article on skin. Epidermis: ...


5

This is a normal part of the inflammatory process. Inflammation is your body's localised defensive response to tissue injury of any kind, and it is characterised by four cardinal signs- redness, swelling, heat and pain (severe inflammation involves a fifth, loss of function). Your body is performing three main processes here: Mobilisation of the body's ...


5

This depends on a number of factors. Here are the first two that come to mind: 1) Is the cut deep enough to reach the dermis (this is the layer below the epidermis) where scar tissue will form? 2) What is your general state of health, and was there an infection at the site of the cut, which would have altered the normal healing process. Basically, not ...


5

The reason for laser hair removal/growth products not being safe for darker skin tones is the ability for darker skin tones to absorb more light from the laser than lighter skin does BEFORE the light is able to reach the depth at which the hair follicle is located. Light from lasers must pass through the epidermis where melanocytes are located before they ...


5

This is the modified answer in response to the discussion: Facts: There are warmth and cold receptors in the body at two places: The Peripheral receptors and the Central Receptors The peripheral receptors are present in skin and the central receptors in the body core at multiple sites the notable site being the hypothalamus The Temperature receptors have ...


5

It's a phenomenon called Frisson. From the wikipedia page. Frisson (French for 'shiver') is a sensation somewhat like shivering, usually caused by stimuli. It is typically expressed as an overwhelming emotional response combined with piloerection (goosebumps). Stimuli that produce a response are specific to the individual. Frisson is of short ...


5

Pores don't change size; that is, the diameter of pore does not increase or decrease in hot or cold environments. Your skin, where pores are located, is not muscle but an organ so the pores don't contract or expand. Pores can become clogged with dirt, oil, and debris (make up). When pores are clogged, you are more inclined to notice which would cause the ...


5

The genetics of pigmentation is relatively complicated, as the pathway for the pigmentation (regulation of the pigment production, ratio between the melanins, maturation, trafficking and distribution of the melanins from the melanocytes to other cells) is quite long and also subject to different regulations. All the mutations found to date (at least to my ...


4

As a general rule, you might want to check wikipedia before posting here. On the other hand, I am glad you made me look the answer up. Goose-bumps warm you up a little. "During the formation of goose bumps, the body is warmed from the muscle tension in piloerection." There are other reasons, which do not directly serve humans, but may be a remnant ...


4

Afaik the tongue is not more heat tolerant than other parts of the body, so the minimum temperature to cause burn is about drinking a beverage having 45°C temperature for a long time (more than 5 minutes). The pain threshold of tongue is around 47°C, so you will feel when it really burns. According to studies the hedonic value of coffee has a maximum by ...


4

This depends on a lot of factors, including how you take your first sip. If you sip with air, you are altering the temperature of the liquid as you sip, as well as decreasing the volume of hot liquid in your mouth, so that the increased surface area of your exposed tongue can quickly alter the temperature of a borderline scalding liquid into a non-scalding ...


4

Flux is defined as amount of heat transferred per unit area per unit time. Our body does not perceive heat flux. It perceives temperature and tries to adjust heat exchange mechanisms until thermal homeostasis is achieved (in all warm blooded animals). This is a feedback controlled process. If it were to measure heat flux then the body cannot sense if it ...


4

Genetic modification of any cell to overexpress a fluorescent protein will not 'generate' light, per-say: fluorophores absorb particular wavelengths and re-emit in less energetic wavelengths, dispersing some energy as heat. (Perhaps there is some semantic choice here, but there is no transduction to light from another form of energy.) Bio-luminescence, on ...


4

Since there are different formulations for anti-aging creams, it would be helpful to focus on the specific compound or combination of compounds. According to a comprehensive literature review done in 2007, certain compounds (Vitamin C, alpha-hydroxy acids, Vitamin A, Vitamin B derivatives, and botanicals) have had varied success in literature ...


3

S. pyogenes cultured on Blood Agar should show beta-hemolysis. B-hemolytic colonies can be further identified as S. pyogenes by the results of negative catalase (hydrogen peroxide) test, positive L-pyrrolidonyl arylamidase (PYR) reaction (1) and sensitivity to Bacitracin (2). See ...


3

Hairs (with their nerve rich follicles) are sense organs, extending our sense of touch beyond the skin. When things disturb our hairs we feel them; bugs, breezes, close encounters. During fright or arousal goosebumps cause the hairs to stand on end, extending our sense of touch to it's furthest distance. In the process the hair shafts that are otherwise laid ...


3

One might argue that since replication takes place in erythroblasts (Brown, Anderson, & Young, 1993), that it's not actually a respiratory infection either. Fluids are simply more hospitable to the virus and more transmissible. As for the rash, perhaps it is because the P antigen receptor that erythrovirus uses to infect erythroblasts is also ...


3

It doesn't matter if its hand or any other human body organ, cold would hurt, the reason being that we humans being warm blooded animal require an optimal temperature-pressure balance to be maintained for our nervous system to work in its natural order. So when we have, in your case, cold hands its like a thermal shock to our hand as the above mentioned ...


3

Vitamin A: One study conducted in the 60's claims that vitamin A acid prevents formation of comedones in Acne Vulgaris [1]. Another one conducted in the 70's found no significant improvement of plantar warts when vitamin A acid was applied topically [2]. Vitamin D: Agents like calcipotriene associated with topical steroids are effective against psoriazis ...


3

Healing in the body is normally independent of the brain. Following an injury, a process of inflammation attracts lots of cells to the site of the injury (including platelets, white blood cells, clotting factors). There's also vasoconstriction (tightening of your blood vessels) to reduce blood loss from the injury site. Your skin cells continue to divide ...


3

This page is pretty complete with examples and references. In summary a lot of the evidence is empirical - you look at smokers and the quality of their skin and compare to non-smokers and the differences are statistically significant and reproducible. It seems as if this is old work, dating from the 1970s. So in many cases these are only observed ...


3

The increase in temperature is due to dilatation of the capillaries in an area of inflammation, here brought about by trauma and is one of the five cardinal signs of inflammation'. This is a natural process which helps to bring in more blood supply for repair and removal of damaged tissue components.


3

The short and unsatisfying answer is no-- it remains controversial due to lack of high quality randomized clinical trials. According to an article in UptoDate, a reliable resource for many physicians, last updated September 2014, there is an association between acne and intake of milk in which milk components could exacerbate acne. Unfortunately, there have ...


3

Sort of problematic is the "at a whim" part. Just a brief search to wikipedia on electric organs, here, we see that the electrocytes are controlled by a nucleus of pacemaker neurons. This is all unique to electric fish, and you'd have to express that whole system in a human being to elicit the same effect. You'd also have to consider how your organism is ...



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