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8

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 ...


7

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 ...


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 ...


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

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

You're confusing an emergent system with a determined system. Your cells have programming which emerges as the form you see. You are using determinism to decide what your form should be. Determinism gives one reaction for every action. Biology is emergent, not deterministic. The biological mechanisms which are responsible for healing exist in a different ...


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

Melanin is the main compound responsible for the color in hair. It is synthesized from the amino acid tyrosine. The absorption of tyrosine is around 280nm, which is a shorter wavelength than humans can see. Tyrosine can not absorb or preferentially scatter visible light in order to appear colored. It appears colorless as it scatters visible light ...


3

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 ...


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 ...


3

Short answer Slowly adapting mechanoreceptors in the skin mediate the perception of static pressure stimuli, while rapidly adapting skin receptors mediate swiftly changing (e.g., vibratory) stimuli. Background There are various skin receptors. Hairy skin, such as that encountered on the arm, contains at least four specialized mechanoreceptors, namely ...


2

There are all sorts of things that can stimulate melanocytes, most notably UV rays (ie from the Sun). So yes, melanogenesis can very over age and exposure to the Sun. Young infants often are lacking build ups of melanin in their skin, eyes, and hair, which is why these things darken with age. There are other more pathogenic ways to change melanogenesis, ...


2

Vitiligo is a loss of skin pigmentation that causes patches of lighter skin as the immune system attacks melanocytes. It can eventually progress to cover the entire body. Edit: Ongenae, K., Van Geel, N. and Naeyaert, J.-M. (2003), Evidence for an Autoimmune Pathogenesis of Vitiligo. Pigment Cell Research, 16: 90–100. doi: 10.1034/j.1600-0749.2003.00023.x ...


2

As dd3 said the density of mechanoreceptors dictates skin sensitivity to touch (also look at penfield map. It is a nice illustration of how different senses are mapped to the brain and to what extent each region is sensitive to stimulus). Skin thickness is also different in different regions. This article says that Dikkopf1 (a Wnt pathway antagonist) ...



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