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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What stops the coagulation process?

Whenever there are minor/major injury to blood vessels, the platelets, fibrin, thrombin, etc. are recruited. They then seal the wound and block bleeding. What tells them that their job is done?
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103 views

Other than Acetylcarnitine what other orally-bioavailable Acetyl donors exist to assist in the conversion of CoA to acetyl-CoA?

I asked a question on bio stackexchange a few days from which I was hoping to be able to arrive at an answer for this question myself but I have had no such luck so now I am going to just ask ...
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2k views

Why we have no enzyme to digest cellulose?

As we know, cellulose is the most abundant polysaccharide in nature. Why don't we have any enzyme to digest cellulose?
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34 views

How is oral cancer development and turnover rate of oral epithelium related

How is oral cancer development and turnover rate of oral epithelium related? Does their inverse relationship have genetic evidence?
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65 views

Are simple esters like those used as flavouring agents metabolised into their constituent carboxylic acids and alcohols in the human body?

By this I mean to ask whether say ethyl butanoate is hydrolysed in humans into ethanol and butyric (butanoic) acid. This is of interest to me as a pharmacology researcher because butyric acid, for ...
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2answers
161 views

Eating rarely but a lot, or often but little

I wonder if it matters if an average person eats the same amount of food distributed between a few (2-3) meals during the day, or constantly having small snacks. I'm interested in several aspects of ...
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0answers
46 views

Why do fresh cavities form from the margins of sliver amalgam fillings on teeth?

Silver amalgam fillings predominantly contain silver a known bactericidal agent and mercury which a known toxin and has bactericidal property. So how is it that the plaque bacteria survive near the ...
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4answers
158 views

Are biological systems engineered? They are often reverse engineered at a molecular level!!

Understanding biological systems, molecular biologists need to “reverse engineer” them. Is this evidence that the systems were engineered to begin with?
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1answer
578 views

What is a “mechanistic study”?

I believe a "mechanistic study" means a study where a medicinal product is being used but the purpose of the study is to investigate the patient or disease, not the medicinal product. How does this ...
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0answers
125 views

What tests can be performed to test the purity and quality of the raw peptide HCG (Human Chorionic Gonadotropin)

What tests could be run to test the purity and type of HCG? We are looking to purchase HCG from China but the purity and quality varies between labs, we are able to receive samples of the raw peptide ...
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2answers
140 views

Why do our eyes “wrap” hue from UV to IR?

On the high-wavelength side of things, we see almost-infrared as reddish, with a slight tinge of magenta. On the low side, we see violet fading into the same magenta color. Why is that? You can see ...
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1answer
58 views

What is an explanation of the dual role of calcium hydroxide in teeth?

Calcium hydroxide induces dentine formation in permanent teeth, while it causes resorption of tooth in deciduous teeth. How is this dual role explained?
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57 views

Can we identify an individual from their palm lines

Can we identify an individual from their palm lines. Is there any uniqueness for palm lines among family members ?
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80 views

Can the colour of skin change with age

Can the colour of skin change with age? Can a dark skinned person become fair or vice versa? Can Melanocyte production vary?
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1answer
57 views

The difference between “Hunger” and “Appetite”

When I am "hungry", I need something to eat physically. But what about "appetite"? I think it is a psychological phenomenon. Is that correct?
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2answers
76 views

Why does the mixture of infant formula with saliva provide an ideal breeding ground for disease-causing micro-organisms?

From: http://www.nal.usda.gov/wicworks/Topics/FG/Chapter4_InfantFormulaFeeding.pdf Discard any infant formula remaining after a feeding. The mixture of infant formula with saliva provides an ideal ...
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1answer
187 views

Why is the liver the only internal organ of the human body to regrow?

Related to my earlier question, "How does the human liver regrow?", am curious as to why the liver is the only major organ that has this capability? Why is it that other major organs, such as the ...
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1answer
82 views

When was the purpose of bone marrow discovered?

I'm currently reading William Cheselden's book Osteographia or The Anatomy of the Bones, which was published in 1733 (for the pretty pictures, naturally; not up to date anatomy). When he addresses the ...
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1answer
203 views

Why are human eye colours limited?

Related to the question What causes the colors we see in eyes?, I am wondering why human eyes are restricted in colour. Most common eye colours are blue, green and brown. Why not yellow, orange, ...
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1answer
31 views

Is it possible to suffer from hyperthermia by spending too much of time in the hot springs?

People may tend to spend time in a hot water spring. Is it possible to get hyperthermia (like a sun stroke) due to this?
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41 views

Axial skeletal system

I was curious about a fact given in my biology textbook as to why the Japanese have 3 pairs o floating ribs unlike the rest who have just two?
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2answers
2k views

Is there any use of CO2 in human body?

We all know CO2 as a waste product of metabolism . Does CO2 have any helpful role , apart from having a role in pH of blood ?
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1answer
334 views

Human body power consumption in still state

I'd like to know what kind of power human body needs to maintain life, in still state (average daily power consumption of an average man is also of interest). In terms of watts. I've only managed to ...
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1answer
60 views

What does the evidence suggest about how Neanderthals became extinct?

According to "Neanderthals: Facts About Our Extinct Human Relatives" (Szalay, 2013), Neanderthals dominated Europe during the last Ice Age, but may have died out before the arrival of Homo Sapiens ...
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1answer
336 views

Can food swallowed when a person is upside down reach the stomach?

If a person positions himself upside down and swallows food, will it reach the stomach against gravity? If so how?
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Why does it hurt when you take sweets, if you have cavities in your teeth?

When you have cavities in your teeth taking any sweetend drinks or food causes sensitivity or pain. What could be the reason?
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1answer
56 views

Can someone provide resources on human electromagnetic frequencies?

Pardon all of my questions below. I'm basically looking to find online resources regarding my inquiry. If you can answer any of them off the bat, that would be awesome!! It seems that humans and ...
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1answer
132 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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479 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 ...
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1answer
869 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 ...
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2answers
450 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 ...
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1answer
316 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?
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149 views

Why are diabetic people often overweight?

I was looking at diabetes the other day, and I noticed something strange. Lower amounts of lipase are a symptom of diabetes, as is overweightness. However, since lipase is the enzyme that breaks down ...
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1answer
340 views

Do hormones make men think of sex?

I remember hearing a saying that goes like "men think of sex every 7 minutes (or seconds?)". I take this saying to mean that men have sex related thoughts more often than women. I'm interested if ...
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1answer
5k views

What is the standard deviation of adult human heights within sexes?

The wikipedia article on human height reports mean height for many different countries by sex but it does not report standard deviations. What is the standard deviation of adult human heights within ...
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1answer
298 views

Why do people sleep with their eyes open?

It's a fact that some people sleep with their eyes open, but why does that happen? Is it normal behavior, not a symptom of any sort of disorder? Are there any (dis)advantages to sleeping with eyes ...
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2answers
608 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 ...
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1answer
79 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?
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1answer
239 views

Why does the stomach ache if you take a brisk walk after lunch or dinner

After eating your lunch or dinner, if you take a brisk walk, most of the time your stomach aches. Why does that happen? What happens with respect to the body metabolism?
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1answer
52 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 ...
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2answers
2k views

Can one die from pain?

Is it possible that a human or any other creature can die from pain? I googled and found different answers. Some articles say Yes while others say No.
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2answers
254 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 ...
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1answer
2k 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 ...
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1k 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 ...
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1answer
108 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 ...
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2answers
146 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 ...
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7k views

Why do toenails grow much slower than fingernails?

As the title suggests, I've noticed that my fingernail grow much faster than my toenails. For instance, I usually trim my fingernails every two week or so, but for toenails the number would be about 6 ...
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23 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 ...
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170 views

Why do life savers hurt?

Why does holding a life saver peppermint candy to my tongue hurt? Does it have something to do with the chemical makeup of the candy?
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3answers
107 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 ...