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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4
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1answer
154 views

How late in a human pregnancy can a zygote split?

This page indicates that the first two days is "very early" for a zygote to split, and that conjoined twins are the result of an "extremely late" split: If the zygote splits very early (in the ...
2
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2answers
225 views

Can the human body enter “Power Save” mode? [closed]

Once a year, I am fasting for 24 hours. No food or drink at all for whole 24 hours. Recently I thought about what is happening to me during those 24 hours, and realized there might be something ...
11
votes
3answers
767 views

Why we do not get hurt from HCl secreted in the stomach?

I read in my book that during digestion our stomach secretes hydrochloric acid ($HCl$). Why we do not get hurt from it? It was also said that mucous provides protection, but from where is it coming?
0
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1answer
138 views

Cancer in myogenic heart cells? [duplicate]

Why cancer does not occur in myogenic heart cells? Is there any special ability in heart cells to resist cancer ?
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3answers
160 views

Why didn't humans evolve to reproduce identical twins all the time?

According to the selfish gene theory, it seems like because identical twins sometimes get produced, a mutation to a gene that says, "if you have an identical twin, be fully altruistic towards them" ...
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0answers
50 views

Proteins and Blood Acidification

Is there evidence to suggest that excessive consumption of Whey, or similar proteins will lead to acidification of the blood?
1
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1answer
488 views

Why do sneezes come out the mouth?

As anyone who's ever sneezed can tell you, it's caused by irritation in the nose. And the answer to a question on this very SE attests that "sneezing is a reflex, partially autonomous, to clear the ...
5
votes
2answers
530 views

Can people with AIDS get tattoos?

When I do a Google search, most of the results are about whether or not people can get HIV / AIDS from getting a tattoo through dirt needles. I am, however, curious whether or not it is possible to ...
5
votes
2answers
137 views

How can a chromosome translocation in somatic cells lead to disease?

Looking at this picture... ...I get the impression that the part of chromosome is attached to other chromosome, but it is not mutated. When we assume that all genes in the translocated part are ...
0
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1answer
66 views

Cut strand of hair longevity?

Quick and useless question : what can be the longevity of a cut strand of hair, assuming we kept it in (good) normal conditions ? Any idea ?
4
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0answers
40 views

How does drug-induced photosensitivity work?

Some drugs (tetracyclines, for instance) can cause photosensitivity reactions—that is, some patients become extremely sensitive to the sun, developing rashes or inflammation after spending time ...
2
votes
1answer
41 views

Does alcohol really do more damage to the body of a child compared to an adult?

Beside the fact that children and teens (people under the age of 18 year) usually have less body weight than the average adult, is there a biologically fundamental difference between the damage done ...
0
votes
1answer
148 views

How long do human egg cell grow up?

I read article about alcohol harm where written that child may bear with birth defect cause mother used to drink alcohol 10 years ago so egg cell stay damages that long. I don't believe that human ...
3
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0answers
24 views

Why does our body exhibit bilateral symmetry? [duplicate]

Externally, we (humans) look symmetrical. However, internal organs don't show the same patterns of symmetry (heart being on the left side while the liver is on the right side, etc.). It is a bit ...
1
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0answers
26 views

What is the lifetime of the vasopressin receptor V2?

I was looking at the production of vasopressin receptor 2, also known as V2R or ADH-R. What I found is that it is coded by the AVPR2 gene and degraded by the Alix protein (source). But I did not get ...
6
votes
1answer
431 views

How to identify the age of a “living” person?

An Indian old man claims he is 180 years old now. 180 years old We are not able to tell he is 180 or 181 probably. But can we tell he is 90, 120, 100 or 150? Different people may age differently. ...
4
votes
0answers
76 views

Why do people die? [duplicate]

what is the reason people die naturally even though they have no known disease? I see people become physically weak at times they get old and die eventually in case they are not attacked by any known ...
2
votes
1answer
131 views

Will a 0.2g/mL sugar concentration cause vomiting in humans?

This infographic claims that the sugar content in a can of Coca Cola would cause vomiting if not for the phosphoric acid. In The First 10 minutes: 10 teaspoons of sugar hit your system. ...
1
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0answers
20 views

Why does a limb sting when it “falls asleep”? [duplicate]

Closely related to this question, but unanswered other than @Matthew-piziak providing a description and link that says: What is Paresthesia? Paresthesia refers to a burning or prickling sensation ...
1
vote
1answer
136 views

Can my eyes adjust instantly to my friend's glasses? [closed]

My eyesight is pretty much perfect, but I noticed that whenever I try any of my friends glasses, from really thin to extremely thick, my eyes seem to adjust to them within seconds and let me see ...
3
votes
2answers
1k views

How does Bernoulli’s Principle apply to the cardiovascular system?

Below are graphs which illustrate the cross-sectional area, velocity, and fluid pressure through each vascular segment of the cardiovascular system. It makes sense that velocity and cross-sectional ...
2
votes
1answer
75 views

Is there a schema for how human behavior is genetically determined?

It seem one can distinguish three different kinds of genetic determinism of common patterns of human behavior: behavior that is directly wired into our nervous system, e.g. face-related mirror ...
9
votes
1answer
166 views

What bacteria do unborn babies contain?

This Scientific American article states that "[human] infestation [by bacteria] begins at birth". This would suggest that unborn babies are free from any bacteria. However, if the mother catches a ...
2
votes
1answer
247 views

Do the enzymes and compounds in saliva help with stain removal?

Does spitting on stains help with removal? Saliva is high in amylase that should help with the breakdown of protein rich stains like blood and semen. It also contains antimicrobial enzymes and ...
3
votes
0answers
110 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 ...
2
votes
2answers
95 views

What would happen if brain neurons did not reduce their sensitivity to neurotransmitters after prolonged exposure?

From my understanding, neurons decrease their sensitivity to neurotransmitters by reducing the amount of receptors on the cell membrane in response to sustained neurotransmitter activity. One ...
0
votes
0answers
75 views

How to mimic / approach some animals/insects' anabolism?

This article states that some shelled animals - spiders, scorpions, crabs, worms and other creatures - have metal atoms in their claws, jaws and fangs. I believe through anabolism, since they eat ...
3
votes
1answer
388 views

Do our belly buttons consist of scar tissue?

I read an interesting post on Facebook the other day saying that we all have a visible scar since birth - our belly button. This got me thinking (and research for me only found results regarding belly ...
5
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0answers
76 views

Is there a mechanism by which mammals lose interest in a partner after mating?

I'm reading the book called "Cupid's poison arrow", which revolves around a rather simple assumption: most mammals, including humans have a genetic program that is responsible for ever increasing ...
2
votes
0answers
25 views

Why are humans mostly right-handed? [duplicate]

Most sources I've seen say that about 90% of humans are right handed, and 10% are left handed. Why is this? My only guess would be that it has something to do with different parts of the brain ...
1
vote
1answer
94 views

Is each generation getting older? [duplicate]

So we know that our sperm and egg cells get set aside relatively early so that they aren't going through unnecessary cell divisions and causing DNA damage or telomere shortening, but since each new ...
15
votes
2answers
841 views

Why does mouldy food make you sick?

Bread gets mouldy pretty quickly, and my parents (both of whom are nurses) throw out a loaf of bread after a spot of mould is seen (because "if you can see one spot, it means the whole thing is ...
2
votes
1answer
37 views

Why is there a compound highlighted in red in a KEGG Module search?

Considering the following module: http://www.kegg.jp/kegg-bin/show_module?M00115+C00003 why is the compound C00003 marked in red?
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0answers
130 views

Which of these methods is both effective and reliable in elongate muscle and tendon for use in humans: growth factors or stem cell technology

Which method is it the most effective, but also the most reliable for elongating muscle and tendons for clinical trial; using modern growth factor technology or using modern stem cell technology? ...
1
vote
1answer
20 views

What information does the KEGG Module statistics page show?

While browsing through the home page of KEGG Module, I clicked the button named Module statistics. Can someone tell me what does these numbers signify? What are they the statistics of?
0
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1answer
93 views

Would a human survive eating only living ants?

After reading an admittedly foolish question about 1 googol ants vs. 1000 humans, I had a question. Could a human survive solely on eating ants (common ants, not the stinging kind, or leafcutters ...
3
votes
2answers
77 views

Why are our bodies created to itch when histamine is released by our immune systems?

Why do bug bites and cuts itch when scratching them clearly doesn't help us survive? Did our early ancestors need to rely on this itching sensation, or is it just that the receptors for itches just ...
4
votes
1answer
240 views

What are the most important factors influencing a person’s gut microbes?

You are your bacteria! The probiotics and the antibiotics... There has been on going discussions about how our gut bacteria is important for a healthy lifestyle. Figure 1: Schematic diagram ...
2
votes
3answers
298 views

Blood urea nitrogen and usage of proteins?

I have been reading some books and am getting slightly confused. Here is roughly what I have read. The greater the blood urea nitrogen the greater the usage of proteins (since blood urea nitrogen ...
2
votes
1answer
94 views

How does Celiac's Disease cause people to stop growing?

In all of the sites I've looked on, one of the symptoms of Celiac's Disease is the failure to grow in children. Why would an immune attack against gluten cause stunted growth? Celiac.org states: ...
2
votes
2answers
141 views

Is there a short-term, very strong anesthetic, which can be blocked/delayed by other substances?

Question migrated from World Building SE. (For fictional use only, of course :) ) I am looking for an anasthetic which fulfills the following criteria: very strong effect, induces a comatose state ...
16
votes
4answers
2k views

Where’s the flaw in my proposed TB Treatment?

Ten years ago, I emailed a prominent lung specialist with my suggestion for a treatment for Tuberculosis. His lack of response led me to believe that the idea had no merit whatsoever – but I had no ...
4
votes
1answer
263 views

How significant is the genetic component of homosexual behaviour?

From some basic googling, I found that nobody has ever proven that people are born gay and that environment plays a great part in homosexuality. I wish to know if there is a genetic component to ...
7
votes
0answers
103 views

What is basis of multifunctionality of “master glands” in the endocrine system?

I have just started reading about the endocrine system and I am having some difficulty understanding the basis of distribution of glands and associated hormones. I am using multifuntionality to ...
0
votes
1answer
72 views

At what saltiness will water simply pass through us?

If water has a low salt content, it hydrates us. When water has too high salt concentration, like sea water, it drains water out of us instead when we drink it. At what salt concentration would water ...
2
votes
1answer
218 views

Why do some people burn and others tan?

Connected to What is happening when we get a tan? - Why do some people burn while other people tan? Very pale people tend to just burn while other people tan very nicely, what causes this difference? ...
12
votes
3answers
2k views

What is happening when we get a tan?

Almost everyone nowadays wants that nice summer tan, but what exactly is going on beneath the skin? I've heard a few different theories about tanning - such as a tan is nothing but the pigmentation in ...
1
vote
2answers
134 views

What is a substance that is safe to eat, not absorbed and not metabolized?

I would like to know whether there are substances that are safe for humans to consume, are not absorbed and do not interact with any digestive process. So, food is disqualified because although it ...
2
votes
1answer
153 views

(How) Does the human digestive system process petroleum jelly, aka petrolatum?

Does the human digestive system processes petroleum jelly? In other words, does it pass through the digestive system without any interaction, or is it absorbed and/or metabolized?
2
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2answers
63 views

Database of medically validated SNPs

I'm looking for all possible sources of clinically tested human SNPs. There is a handful of databases that store SNPs (like dbSNP), but I only need those that have validated presence/absence of ...