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Questions tagged [human-biology]

This tag is for questions about the general biological features of human beings (as opposed to the biology of non-humans).

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Anatomical Angle Made by the Fingers of an Extended Palm

Does the angle made by the fingers (excluding the thumb) of an extended palm (as shown in the figure below) have a name (such as the Lovibond or Cobb angle, for instance) ? I have already checked ...
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What happens to apetite hormones like ghrelin and leptin when a person in coma?

Don't coma individuals feel hungry? If so, how does the brain senses this condition (as coma is caused by neural death or damage) and switches off gene expression of ghrelin and leptin. Is there any ...
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102 views

Evolutionary explanation of the bicuspid on the left and tricuspid on the right

The left heart handles more pressure and logically it would make sens to have a valve with three leafs on the left (If I had got to choose, I'd have put three on both sides). Other than being more ...
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773 views

Which are the last cells of the human body to die?

When somebody dies, which are the last surviving cells of his/her body? Those of hair, nails, or some other obscure but resilient cells? Shedding light on why and how they are so vital might boost ...
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613 views

Does variation in human gut length vary predictably with diet of ancestors?

Background: Numerous online searches, textbooks and other sources seem to pin the average length of the human gut from mouth to anus (oroanal) between about 5-10m in length. To pick a reputable ...
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42 views

Can we predict a person's tolerance to cold exposure during excercise?

Being an amateur athlete and student of anatomy I've always wanted to know if there is a formula for determining an unconditioned body's tolerance to cold temperatures while exercising. I know the ...
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486 views

Why are lips covered with specialized skin?

I found out some interesting facts while studying our lips: They are covered in glabrous skin, while most of the skin surface is hairy; The outermost layer (stratum corneum) of the skin is far ...
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65 views

How is atrophied muscle different than normal muscle in a chemical or biological way?

I am a writer with a question for a story I'm working on. In it, the character suffers from muscle atrophy due to spinal damage. So that I can portray this accurately, what would cause this type of ...
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31 views

Recession of skin tan

In early October I was on a holiday near the equator and got tanned. Now, roughly 3 months later, the tan on my face and arms has gone almost entirely where my belly, chest and legs are still ...
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114 views

Can you “fight” a coma or serious illness?

In an article about the latest earthquake to strike Mexico, I read that a rescuer said to someone in a gurney, "Fight for your life, please!" I've seen similar things in TV shows and movies where a ...
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706 views

Why do hand/fore-arm muscles “lock up” after very high-powered effort?

Inspired from Why does it hurt the next day after doing significant exercise? with its excellent answer: In climbing, you can put tremendous load on the hand/fore-arm muscles (specifically, flexor ...
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42 views

A hypothetical nerve damage question

If a 100 pound bucket is dropped on someone's hand, what will this do to the nerves, will they get crushed, will they die? And how will this affect that person's ability to feel or move their hand?
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How much time does it take for the naive T Cell to get activated?

Suppose a naive T cell comes in contact with an APC. How much time does it take for the T Cell to get activated and within how much time does the T cell move away from the APC due to incompatibility ...
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201 views

Is Near-infrared focused light safe for your eyes?

I found a new product, but I'm afraid it's not safe. Can you help me understand what the safety limits are when it comes to near-infrared light focused on your eyes is? I'm assuming the wavelength ...
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132 views

What happens to the brain during sleep versus unconsciousness?

How does being unconsciousness differ from being asleep and whether it causes breaks in consciousness?
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47 views

What are necessary parameters for a tissue scaffold to be biodegradable?`

I am a mechanical engineer with little biological experience, but I have recently been looking at tissue scaffoldings. My current understanding is as follows, but may be flawed. I would appreciate ...
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89 views

Does anxiety about weight or eating cause people to become overweight?

A while ago I saw this TED talk about the futility of dieting. The speaker suggests that a body maintains a homeostatic weight point and returns to that weight after dieting has stopped: Turns out ...
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150 views

What is the biological basis of “energy” that extraverted humans draw from social engagements and introverts expend?

This question is related to this question about introverts becoming exhausted after extended social events on cognitive sciences stack exchange. As I read more on the topic of human extraversion-...
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Do Asian women have more difficult births than Europeans?

I recently heard a claim that Asians in general have more difficult births than Europeans. Is this true? I have found a few studies(1,2) on the effect of ethnicity on birth outcomes but they seem to ...
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320 views

Virucides - Herbal and otherwise, for HHV6 type virus or any inner-cell virus

Does anyone know where I can find a reliable list of virucides (not anti-virus) that can be used by humans? This virucide must be able to affect viruses that are already inside the cells. St John's ...
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108 views

What is the average volume of the human Psychic tear? (“emotional tear”)

My goal is to find out the volume of the average human "emotional tear" (Psychic tear - sadness, happiness), specifically when crying. I found a lot of information about Basal tears (constant ...
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541 views

Can Wasps smell fear?

There are two conflicting things I have heard. One more anecdotal: Wasps can smell when you are afraid of them The other from reading popular science magacines: Humans don't produce any ...
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219 views

How long can one go with necrosis?

In general, when a limb dies, how long does it take before it falls off? Can you go years with a black and useless limb, or does it just.. fall off right away?
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195 views

Does drinking dry water have same effect as drinking regular water?

Dry water consists of water droplets that have been coated with silica nanoparticles, which prevents the droplets from forming a liquid. If a human swallows dry water, does it have the same effect as ...
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85 views

How to determine if twins are identical or fraternal if only one is alive?

I had a twin brother who died at birth. I've missed him all my life, and have been curious to know if we were identical or fraternal. Is there a test to determine whether we were identical or ...
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77 views

How can just new born baby can walk ?

This website here stating video of New born baby walking breaking the internet. How can just new born baby can walk ?
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How can you gain 1 lb of bodyweight from eating less than 1 lb of food surplus?

A commonly referenced "fact" is that a caloric surplus of 3500 kcal is equivalent to a 1 lb gain in bodyweight. But I'm confused. If you get 3500 kcal worth of, say, fatty acids, which are 9 kcal per ...
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46 views

First infection of malaria

As I know Plasmodium falciperum survive in either a host animal, human or mosquitoes. But how does malaria come to infect either of them initially? I am interested in knowing evolution of malaria. ...
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124 views

I read that the average cell will divide between 50-70 times before cell death. How, then, can human cells be constantly dividing?

Aren't those 2 statements contradicting each other? See https://en.wikipedia.org/wiki/Hayflick_limit and e.g. http://book.bionumbers.org/how-quickly-do-different-cells-in-the-body-replace-themselves/....
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739 views

Drinking water after eating banana

Why elders advice not to drink water after eating banana? Is there any science behind or is it a myth? Found a website supporting this (so called?) myth.
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75 views

How does the body determine where to deposit fat reserves?

People's bodies store fat in similar areas, but often there are subtle differences in which areas are first or slightly more effected. This seems to also be apparent with morbidity, where certain ...
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237 views

What is the lifespan of Skeletal Muscle Cells?

I have read that skeletal muscle cells cannot multiply and are generally not created after early development. However, I have also read that they have a "lifespan" of 10-15 years. Could this lifespan ...
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274 views

Why do hair on head not get pilo-erected?

Whenever we have "goosebumps", there is a momentary piloerection, due to which hair on our elbows and legs get "erected" and "stand" almost perpendicular to the surface of our skin. But why do our "...
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90 views

Why does pink colour reduce aggressiveness?

According to this Wikipedia page, a shade of pink colour known as "Baker-Miller_Pink" has been known to reduce aggressive behaviour. Is there any biochemical reaction responsible for this? ...
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70 views

Why spermatogenesis is an independent process while formation of ovum is dependent on fertilization by sperm?

At the time of ovulation,secondary oocyte is arrested at Metaphase II and goes into the fallopian tube.If fertilization occurs, sperm binds with secondary oocyte and releases Anaphase promoting factor ...
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54 views

how long after death can a body exhibit an immune response

I suppose this is part of a larger question - at what point do the body's coordinated systems (Endocrine, Autonomic nervous system etc) begin to fail? Within hours? Days? Minutes? Of course this ...
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93 views

How many various types of Memory B cells does an average person has in his body?

Memory B cells are a B cell sub-type that are formed within germinal centers following primary infection and are important in generating an accelerated and more robust antibody-mediated immune ...
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63 views

To what extent is excretory control a learned vs. instinctive behavior?

Human babies are clearly not born knowing whether/how to hold in urine and feces, and teaching them to do so requires a nontrivial (really nontrivial...) amount of work on the parents' part. But once ...
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263 views

Difference between dysentery and bloody diarrhea

The difference between diarrhoea and dysentery is quite clear; but the appearance of blood in stool or bloody diarrhoea is a very confusing term when compared with dysentery. Are they different in the ...
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75 views

Does increased calorie intake cause increase in libido in humans?

I'm interested in the effect of increased calorie intake on sex hormones and chosen mating strategy in humans. I'm aware that humans have a dual mating strategy - somewhere between pair bond and ...
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108 views

T cell sensitivity and persistence to specific bacterial proteins

Currently, the standard tests for Lyme Disease measure antibody production after exposure to a bacteria, Borrelia burgdorferi. Often, the tests are performed too soon after infection, before ...
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66 views

Why are kidney discard rates so high?

A recent report from UNOS states: The kidney discard rate has returned to pre-KAS levels, dropping from 20.2 percent in the first six months to 18.4 percent in months 7-10. To me, this seems quite ...
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51 views

Can body temperature affect the quality of sleep?

If so, how does it influence our sleep? And what can we do to improve the quality of sleep by adjesting our body tempurature?
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315 views

How long does conception take?

I know that conception is a multi-step process. A sperm fuses with an egg. Its contents diffuse into the cytoplasm. Dad's DNA is transported to the nucleus. Proteins are gradually made from Dad's DNA....
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119 views

Is it possible that weak memory is due to interference between signals in the brain?

"Weak memory", as used in this question, refers to the inability to retrieve a memory that a person otherwise knows he has memorized earlier. An example of this is some fact snippet that the ...
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229 views

How does estrogen influence collagen synthesis?

Through what mechanisms does estrogen interact with collagen synthesis? Especially in the context of elevated estrogen levels and genesis of purpura simplex .
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129 views

Why does human hair grow and behave differently depending on its location?

Why does human hair behave differently depending on its location? For instance, head hair grows to an indefinite length, but eyebrows maintain a particular length and appearance. Head hair and ...
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1k views

Which types of blood vessels can regenerate in humans/mammals?

Which types of blood vessels can regenerate in humans/mammals? From what I understand, arteries and arterioles can be created later in life, while this is not necessarily the case with veins. However ...
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118 views

Viagra for pain management

Not all men who take Viagra experience any sexual side effects about 40% have no change of sexual abilities on the pill. However like many women the drug in such cases cause a strong pain reduction ...
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199 views

Human female chest model or data representation?

I am looking for professionally used representation of female chest (I know how it sounds ;). Generally - a model comprehensive enough to effectively represent human chest, with focus on breasts. ...