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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1answer
72 views

Acrosomal enzymes and the female reproductive tract

My textbook wrote that the reason why acrosomal enzymes are so securely contained within the sperm (thus needing capacitation to facilitate their release) is to prevent any premature release in the ...
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0answers
34 views

Why do some men have patchy beards?

Why do some men have patchy beards? Or more specifically, why would some hair follicles lack sufficient 5-alpha reductase while others nearby don't when their genetic code is identical and they are ...
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0answers
25 views

Number of pair of chromosomes in sex cells of human [closed]

Just wondering how many pair of chromosomes in sex cells of human? How many single chromosomes in sex cells of human? Thanks for your help! It is said the chromosomes in sex cells are haploid?
9
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1answer
11k views

Name (and meaning of the absence) of the white semicircle at the base of the fingernail?

At the base of fingernail, there is a white semicircle (see on the first picture). But sometimes there isn't one. My questions are: what is this white semicircle on the fingernail, and what causes ...
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1answer
76 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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0answers
31 views

If your atlas is out of alignment, will the rest of your spine be out as well?

I just found out about this association called Nucca. Basically, they are a chiropractic association - their whole idea is that if your atlas is out of alignment, then the rest of your spine is also ...
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0answers
18 views

Could humans metabolize gasoline? [duplicate]

Gasoline is mostly made of organic compounds/fats/oils. Food is also made mostly of similar organic compounds. Therefore, would humans be able to metabolize gasoline, or some of its components, for ...
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2answers
476 views

Can excessive carbonated drink consumption lead to elevated red blood cell levels?

I've recently had a blood test and the results displayed elevated levels of erythrocytes as well as hemoglobin. (As a result my hematocrit levels were also above average) At my workplace there is a ...
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0answers
22 views

peritoneal dialysis Vs Hemodialysis?

Their are basically two types of dialysis: 1.peritoneal dialysis 2.hemodialysis, My Question is Why the peritoneal dialysis needs to be carried out on everyday BUT hemodialysis is carried out on only ...
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0answers
10 views

Is there any range for Aortic Valve Gradient?

I understand aortic valve gradient is pressure on the value (measured in mmHg). What I would like to know is if there has been any research that identified a minimum and maximum pressure value as the ...
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1answer
1k views

Why does air from the nasal cavity not go into the oesophagus?

When we ingest food, the epiglottis covers the trachea and the uvula covers the nasal passage. But what happens when we breathe? Why does the air go into our trachea and not the oesophagus?
4
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1answer
273 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 ...
4
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1answer
1k views

How are arms different than legs?

Ok, this is a bit of a tangent question, but it came up yesterday and I didn't know the answer: How are arms and legs defined physiologically? For example, we say humans have two arms and two legs, ...
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2answers
93 views

What makes something food?

From my (limited) understanding, animals get energy from food by breaking chemical bonds between molecules. There's a lot of water here [citation needed], so it seems like natural selection would ...
2
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1answer
69 views

Why cold water results in cough [closed]

I have a pretty simple question which always kept me intriguing since childhood and I couldn't find its precise answer yet. Why do we cough by cold water. Recently I had flu and found very strange ...
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0answers
41 views

What happens to the human brain when unconscious?

What part of the brain gets affected and does it harm the brain? Thank you I just needed some extra info for a video I'm making.
3
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1answer
926 views

What are hot spots on human body?

Recently I have just discovered that a certain amount of the mobile phone frequency can be absorbed by human tissues. For example, this is the SAR info of iPhone 4s: Head: 1.180 W/kg 1 g Body: ...
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0answers
39 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?
3
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1answer
93 views

How two genomes adopt when cell goes to recipient's body from donor's body?

We often give blood to another following the blood giving compatibility chart. Heart transplant and similar transplants also brings one's cell to another's body. My curiosity is, when a cell goes to ...
6
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1answer
3k views

Why don't we have hair on palms?

We have hair all over the body except palms. What is the biological reason behind this? Thanks
5
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1answer
380 views

Getting goosebumps at will

I can get goosebumps at will, regardless of the environment. Its mostly visible on my arms, and I can feel it on my head. It requires some level of concentration to achieve this. My questions are : ...
3
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2answers
105 views

Does sweat contain DNA information?

I was reading this article : Perspiration The first question which came to my mind after reading the composition of sweat was whether it contains any information about the DNA or not? I haven't had ...
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3answers
5k views

If the top epidermal layer is burned away, what is it replaced with?

If the squamous (top) layer of epidermis, or skin, is burned or damaged in another way, will it then be replaced by the next layer of below? Also, from where does the basal membrane originate? Does ...
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0answers
10 views

Cellular aspartate level?

I know that aspartate is a product of urea cycle, gluconeogenesis and oxaloacetate. In addition, there are dietary sources such as meat and vegetables. I would like to know what are the other factors ...
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0answers
55 views

Why is my right hand's thumb on the left side and my left hand's thumb on the right side?

My daughter just asked this question, and I could not provide a thorough answer. My first speculation is that it allows one to manipulate an object using one' both hands simultaneously (if the thumbs ...
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1answer
2k views

What does vitamin B6 and B12 absorption depend upon?

I'm looking at my question about homocysteine metabolism and am doing a followup inquiry into vitamins B6(Pyroxidine) and B12(Cyanocobalamin). I've found this interesting bit about vitamin B12 and am ...
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1answer
60 views

Is it possible to grow a fertilized human egg entirely outside the woman's womb?

Many science-fiction movies show the possibility of growing a newly fertilized human egg entirely outside the womb of the woman. This means that you have to create the exact circumstances for the ...
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2answers
257 views

Are unilaterally deaf people able to determine where sound comes from?

My question is on people deafened in one ear, but normal hearing in the other. Time and level differences between the two ears are only part of how the human body can localize the source of the ...
13
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1answer
19k views

What is the composition of human feces?

Are there any studies or general information on the composition of human feces? I'd specifically like to know the percentage of carbohydrates and amino acids relative to the amount that was ingested ...
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2answers
59 views

What physical traits are derived from the Neanderthal DNA in human DNA?

Some researches had found that Human DNA has a bit of Neanderthal DNA. So they suggested there would have been crossing between Homo sapiens and Neanderthals. Now the Neanderthal looked a bit ...
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2answers
61 views

Does night sleep provide more energy-regain than sleep during the day? [closed]

After reading this, I know that sleeping is an universal function, and that basically everything with a brain has the need to sleep. However, I am still confused to what extent it is necessary to ...
14
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1answer
952 views

I don't want to know what bacteria is called but if the bacteria from unborn babies have benifits on health? [duplicate]

This question is not the same as the duplicate. I was told that when babies are born they are born with bacteria in their stomach. When a child takes antibiotics are there unique bacteria destroyed ...
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2answers
79 views

Use of sunlight in biological processes

Sunlight is used by green plants in photosynthesis, but it is also used by animals in the synthesis of Vitamin D. Are there any similarities between the two processes and how is the light energy ...
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0answers
19 views

How much yogurt would one have to consume to have a noticeable effect on neurotransmitters [closed]

I read several recent articles that proposed a link between bacteria in our gut and neurotransmitters in our brain. For instance http://www.ncbi.nlm.nih.gov/m/pubmed/24997036/ I am curious how much ...
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3answers
467 views

How does a person get AIDS?

I am inquisitive to know about how a person contracts AIDS. Among the common masses it's still the belief that having sex with multiple partners causes the disease but that is not the case when read ...
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0answers
23 views

How do I “reinoculate” a petri dish with new bacteria?

Hypothetical question, intended to find a general procedure rather than case-specific recommendations: I have a petri dish full of growth medium with a large population of gram-negative, anaerobic ...
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0answers
48 views

Why is a wound much more painful when damp?

Why is a wound much more painful when damp? This is a very strange phenomenon. For example: I have a little wound, not painful at all. But, when it is just damp, it is much painful.
5
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1answer
137 views

How do omega-3 fatty acids reduce cholesterol at the molecular level?

I have heard that omega-3 fatty acids found in fish are a good way to prevent/reduce cholesterol problems. My question is how do omega-3 fatty acids do that: what are they doing on a chemical level ...
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0answers
12 views

How large are medullary thymic epithelial cells in volume?

I'm looking for a rough average volume of medullary thymic epithelial cells (mTECs/MECs) in humans and mice. It would also help to know how they differ in form (are they spherical, long stretched, ...
6
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1answer
73 views

Why is there no symmetry in pigmentation when comparing people north and south of the equator?

If you are at the equator and start moving north, the further you travel, the lighter the skin of the indigenous peoples. Considering that we live on a ball, why do we not find the same traveling ...
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0answers
14 views

Relationship between Human Sleep Cycles & Sunlight

What is the relationship between the human sleep cycle and Sunlight? Why do humans tend to sleep for longer hours during the night than the day. Since we rely on Artificial lighting during the night ...
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0answers
43 views

Are all the atoms in your body replaced with others over a 30 year period?

I was reading Creation - Life and How to Make It by Steve Grand. (This is the book that inspired Jeff Bezos to start the AWS initiative. ) In it he makes the following statement: Anyhow, by now I ...
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2answers
936 views

What is the cause that angina pectoris is felt in your left arm?

When someone has heart problems sometimes they feel pain in their left arm. But why is the left arm painfull?
2
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1answer
52 views

Fasting gastric pH versus normal gastric pH

I want to know if someone is fasting (no food or drink for a whole day) will they have a higher or lower pH than a person who is eating regularly? If so what is an estimate of both of those pH's in ...
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0answers
16 views

Is it true that our tooth enamel shows a 7 days rhythm?

Is it true that in fossil remains of the Turkana Boy a kind of growth rings are found in tooth enamel which have a rhythm of a week? This also appears to apply to other primates? If so what is the ...
0
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1answer
112 views

If human proteins are synthesized from only 20 different amino acids, then how can there be such variety of proteins in human cells?

I know that human proteins are synthesized using only 20 different amino acids. However, how can there be thousands of different proteins in human cells, if we only use 20 amino acids to make them?
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0answers
23 views

Are there biological safeguards to compensate for male primate infertility?

I'm trying to understand human sexual selection, and the following question has been on my mind for some time. I don't know the exact terminology to do a quality scholarly search on the subject. Are ...
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3answers
2k views

What would happen if one eats silica gel?

What happens if one actually does go about eating the beads in those "do-not-eat" packets?
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1answer
42 views

Why does the blood not clump and result in death?

In this question's accepted answer, it is said that the blood type will slowly change to that of the donor's. When the blood in the person is about 50% his own and 50% that of the donor's. i.e, 50% A ...
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0answers
20 views

What kind of cell has the most different receptors?

All hormones and neurotransmittors has their own receptor. Now some of the cells has a few different receptors but others has many sorts of receptors. So what are the most receptive cells? Are that ...