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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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155 views

What's a “constitutionally small penis”?

I'm reading some urology papers and came across one involving penis growth (Kim & Song, 2008); here's an intro passage that I'm confused about: A total of 58 patients with constitutionally ...
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48 views

The truth behind human urine and marking territory?

So some years ago, I remember watching a survival show in which the host said that human males produce a type of chemical in the urine that animals such as wolves can acknowledge as a territory marker....
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Why do children not have the Acid Mantle?

Post puberty humans begin to secrete a substance called Sebum which changes the neutral PH of our skin from ~7 to 4.5-5.5. This has that advantage of serving as a protective line against pathogens and ...
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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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841 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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524 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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78 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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32 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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58 views

At what point does muscle mass overcome muscle strength to affect speed?

I'm trying to think in terms of "how fast" someone can do something, like swing a bat or push a crate. Someone might have a lot of muscle mass, but that also increases how much mass an arm has to move ...
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116 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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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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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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44 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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51 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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330 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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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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188 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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2k views

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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347 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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25 views

What phosphorylates tau protein & and what causes tau to be phosphorylated?

I want to know what phosphorylates tau protein and its 6 isoforms. I know kinases cause phosphorylation events, and in tau it can be phosphorylated in a healthy neuron in the trans conformation, but ...
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Can sperm cells penetrate the cell membrane of non-ovum cells?

Sperm cells have tiny bags of enzymes on their tip (the acrosome) which allow them to penetrate the ovum. My question is whether or not the process that allows sperm cells to penetrate the cell ...
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Why can humans tolerate eating onions but other mammals like dogs and cats cannot?

Onions are one of the many foods we shouldn't feed our pets. Looking it up, I learned that onions cause hemolytic anemia in MANY species: cattle, sheep, horses, dogs, cats, and even some primates. If ...
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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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620 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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261 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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269 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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829 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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88 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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47 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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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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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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815 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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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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273 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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369 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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126 views

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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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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230 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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96 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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80 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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118 views

Smallest pressure differential that humans can detect

While cooking dinner under an extractor on its lowest setting, I noticed that none of the steam (referenced by the amount of fogging on a nearby window, compared to the absence of the fan, was ...
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311 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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126 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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137 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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68 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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57 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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122 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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254 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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143 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 ...