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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2answers
11k views

What happens to the holes in the skull where teeth were developing?

In Skeptics.SE, a question regarding the skulls of children arose. Depicting a scary skull where the permenent teeth are "hidden" inside the jaws and the milk teeth are in the their place. After all ...
1
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1answer
185 views

Characteristics of life

If all of the characteristics of life are required for something to be defined as living, how can we account people or other life that can not reproduce?
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3answers
2k views

How come that we “feel” it when someone's watching us [closed]

The question is relatively easy (the answer however..). We all know this feeling "being watched" and more often than not this is a real thing. If someone is staring at us from the side or from the ...
1
vote
1answer
2k views

Are there more/less favourable phases of menstrual cycle to donate blood?

I was wondering whether it makes a difference when during the menstrual cycle a female is donating blood in terms of: Blood quality (iron or hormones levels) Her health/safety I am aware that ...
18
votes
3answers
471 views

Are human fetuses more likely to be male? [duplicate]

Question: From a physiological point of view, when sex is determined in a human fetus, is it equally likely to be male or female? Studies in this area typically measure age at birth, where the data ...
2
votes
2answers
701 views

What is the best color for a PPG signal (photoplethysmography)?

What is the best color for a PPG signal? Red, green, blue or infra-red? I'm asking because commercial oximeter sensors usually use a pair of red and infra-red LEDs. But recently, I've seen a lot of ...
5
votes
3answers
2k views

Fetal development, gastrulation and embryonic disc

I am completely confused by the images circulating on the internet of human gastrulation. First, lets see how it happens in deuterostomes. This image depicts the process: (image is from Wikipedia) ...
8
votes
3answers
413 views

Why people like to see pornographic scenes, but do not feel the same about eating scenes?

This question may seem funny, but I think biology must have good answers. I think no more explanation is needed. I really thought about this and searched for an answer, but there is nothing yet. If ...
0
votes
1answer
510 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?
3
votes
1answer
110 views

What causes sinus pain and congestion?

When the sinuses flare up, it can get very painful. Thus, my question - what biological mechanisms cause the congestion and especially the pain associated with sinusitis?
6
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2answers
906 views

Do animals get sick from eating dirty food or eating off the floor?

Humans have very strict tradition of hygiene, such as washing hands before eating, using utensils, and in general keeping as much distance between food and dirt as possible. At the same time, most ...
2
votes
1answer
63 views

Use of pigs for obtaining transplant organs

It is being said that organs can be obtained for transplant from the pigs. What is special about pigs that we are using them? Why can't we use monkeys or chimpanzees with whom we share a more recent ...
2
votes
2answers
139 views

Lactose Intolerance

What nutrition is given to infants who are lactose intolerant? I understand, in today's day and that age we have non-lactose formula milk, but what happened, before lactose-free milk was created, to ...
6
votes
2answers
346 views

Is there a preferred sleeping position for humans?

I remember hearing various sleep related advice as a child, like "sleep on your right side", or " have your head pointed in X direction". Is there any biological reason why sleeping on one side ...
1
vote
1answer
4k views

Is Diabetes sex linked disease

There are two types of diabetes mellitus. a. Type 1 diabetes mellitus b. Type 2 diabetes melliuts Is either of them a sex linked disease? Can either one be inherited? My book says, "this disease is ...
3
votes
0answers
99 views

What are the physiological effects of wine?

I have read that alcohol in general and wine in particular can have advantageous as well as detrimental effects on human health. Is this true? What are the physiological effects of consuming wine in ...
3
votes
1answer
2k views

Why do you need you room dark for melatonin release?

There is a light pollution movement that says lighting at night obstructs melatonin production. They say: What makes you fall asleep are changes in the level of the hormone melatonin ...
2
votes
3answers
117 views

Is it possible to make humans extinct artificially?

Verging on the realm of science fiction, my question is that is there any theoretically possible way, biologically/chemically, with which the entire human race can be killed without affecting the rest ...
2
votes
2answers
228 views

Why are animal births not taken as seriously as human births?

When humans give birth, more than often medical assistance is needed. Others gather around and frantically look for any way to help. But when an animal gives birth, it is usually seen as a moment ...
3
votes
1answer
121 views

In theory, would it be possible to create an injection of Vitamins, Minerals, sugars etc so that eating was no longer necessary?

I am wondering, out of pure curiosity, whether with current medical & biological science, (or indeed with accepted probable future developments in those areas), in theory, would it be possible to ...
0
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1answer
25 views

Stopping the effect of hormone

Many hormones released by endocrine organs travel down in the blood and bind to specific receptors on the target cells. What then breaks that binding of the molecule with the receptor ? ( thus ...
3
votes
2answers
970 views

Physiological indicators of happiness and well being

If I understand it correctly, levels of serotonin in the brain can indicate if a person is happy. What other physiological measures indicate happiness or well being for a humans? I am looking for ...
5
votes
1answer
65 views

Diabetes-diabetes comorbidity

Is it possible to have both type-1 (insulin-dependent) and type-2 (non-insulin-dependent) diabetes mellitus? That is, to have both insulin resistance and zero (or negligible) insulin production? If ...
3
votes
1answer
138 views

How are memories stored in the brain?

I've been thinking about this for a while and I can't figure out how a memory can be stored in the brain. I understand that important memories are favourably retained, such as a near death ...
1
vote
3answers
86 views

Are there “multi-frequency” signals within a human brain?

I know that neurons can exhibit tonic and phasic firing, and also that a neuron is sometimes called an integrator. This makes me interested to know if there are activities in the brain that depend on ...
0
votes
2answers
882 views

What part of food gives the blood red color?

Roughly, what I know is, when we eat food it goes into our: Stomach > Small Intestine > Large Intestine > Rectum. So, it just moves through a digestive pipe. What I don't understand is, what part of ...
2
votes
1answer
2k views

fibroblast cells and fibers

I am interested in fibroblast cells in human arteries. Here are the things that I am not clear at the moment and I could not find any answer from the literature: What are the dimensions of these ...
0
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1answer
38 views

Distribution of nutrients throuought a drink made of plants?

In an attempts to eat my veggies for the day in one shot, I blended together a bag of salad with some water. The mixture separated by density, a thick top layer containing the bits of leaves, and a ...
3
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0answers
210 views

Can someone explain the color-changing unit (CCU) to me?

I've been physically carrying out serial tenfold dilutions on samples of Ureaplasma to work out the color-changing units (CCU). As a definition, the CCU is the highest dilution at which there is a ...
1
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1answer
55 views

What are the biological and nutritional benefits of having numerous smaller meals a day?

I have heard here and there that instead of consuming 3 largish meals (the traditional 3 meals a day), that consuming several smaller meals throughout the day is beneficial for health (and weight ...
3
votes
1answer
146 views

Differences between right and left handed people

Are there any articles reporting any significant differences in behavior, attitudes, intelligence, appearance, etc., between right and left handed people?
2
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1answer
594 views

What do rs id, allele coded 0 and allele coded 1 mean?

So, for a project I've been working on (different story), I've been looking at the HapMap Project, and their free online files. In their README file, they talk about how for each legend file for each ...
11
votes
1answer
265 views

In which order did the cells of the immune system evolve?

Thinking about how complex the interactions between different types of immune system cells (T-helpers, T-Killers, Phagocytes, B-Cells etc.) are, it's fascinating how they all combine to get the ...
3
votes
1answer
7k views

What is the functional difference between hemoglobin and ferritin?

I read that both hemoglobin and ferritin are for storing iron in the body. So, what is the difference between them in terms of storing/binding iron?
2
votes
2answers
98 views

E. coli, risk of infection?

There has been a warning about E. coli contaminated water in South Florida. Now I'm wondering are there empirical data or historic cases which show a correlation between E.coli levels in tap water and ...
3
votes
1answer
422 views

Are there records of monozygotic twins in which one experiences androgen insensitivity syndrome

I have given my high school biology students the thought experiment of "What would happen if a researcher induced twinning of a female zygote and then replaced one of the X Chromosomes with a copy of ...
5
votes
2answers
293 views

How does fever physically work?

What is the physical mechanism that causes temperature to rise during a fever? I know that somehow the hypothalamus "orders" to increase the standard body temperature regulation, and this should ...
22
votes
2answers
11k views

If a human takes antibiotics are all bacteria in the body killed?

From my basic understanding, antibiotics kill living things, bacteria for example. Do the antibiotics consumed by a human-being distinguish between what they kill? Or do they just kill every bacteria ...
5
votes
1answer
833 views

Is human face more resistant to cold than other body parts?

Walking outside tonight in -15˚C I realized an interesting observation: While I felt cold on most part of my body, my face (although the only uncovered part) didn't really feel cold. It registered the ...
6
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1answer
170 views

Does muscle growth trigger angiogenesis?

So heavier people generally have more blood than lighter people (this is why heavier people generally need to take higher doses of medication for the same effect of medication). They also have more ...
2
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0answers
60 views

Movement of stem cells from mother to fetus

Recent results from J Lee Nelson and colleagues (Sci Am. 2008 Feb;298(2):64-71; available as full text through Google) show that cells from the mother were found in a person aged 46. Logically, these ...
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1answer
352 views

How do changes in temperature affect body weight in humans?

What would be effect on weight of individuals if we bring a fully adapted (to cold climate ) human individual and a fully adapted to very hot climate individual to a moderate climate region?
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0answers
45 views

What parts of the brain are involved in regulating blood pressure in mammals?

I'm reading this Wikipedia article on blood pressure and its regulation, and it mentions that medulla is involved. however, I vaguely remember reading another article on Wikipedia and it mentioned ...
-1
votes
1answer
502 views

Are we evolving to age slower, or to live longer aging at the same rate?

I wonder why most of us find senior people lovely and charming. Is it because to love grandpa and granny is vital to our survival as a species, in the same way as we love babies? If so, it would mean ...
9
votes
2answers
454 views

Does arterial blood always flow away from the heart?

Is there a negative net flow of blood in human arteries at any point of the cardiac cycle? I realise that blood flow can be turbulent, e.g. in the aorta or around stenotic arteries, but then the ...
2
votes
1answer
891 views

Ammonia smell after physical exercise? What is the explanation? [duplicate]

After exercising vigorously one can sometimes smell ammonia and it feels like it's coming from within the nose actually. There is no indication that others can smell it when I do (i.e. seems to be ...
7
votes
1answer
204 views

Why are some menstrual cycles irregular?

A friend of mine asked me this today, and I didn't know. I remember studying the menstrual cycle a few years ago, but I can't remember the details (other than it was very hormone-related), and so I ...
5
votes
1answer
174 views

What effect do oligosaccharides, like those found in legumes, have on the composition of intestinal flora in humans and if so how so?

I know that intestinal flora metabolising oligosaccharides, like those found in legumes, is the cause for the well known fact that legumes cause flatulence, but does an oligosaccharide-rich intestine ...
1
vote
1answer
110 views

copper spiral birth control not toxic?

I Always thought that copper was toxic to the human body. So how can it be safe to place a copper object (birth control spiral) into a uterus for a duration of 5 years?
5
votes
1answer
433 views

What could account for an apparent loss of mass at death?

An interesting tidbit floating around the internet these days is that Dr. Duncan MacDougall apparently weighed people shortly before and after death, and found an average of a 21 gram discrepancy, to ...