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Questions tagged [human-anatomy]

This tag is for questions about the general anatomical features of human beings as opposed to the anatomy of non-human animals.

16
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2answers
5k views

How is eye color in humans inherited?

In high school we studied the inheritance of eye color, as it was explained to us in the most simple way: blue eye color is a recessive, monogenic, autosomal trait. Now I know that it is a bit more ...
20
votes
5answers
8k views

How did the cardiovascular system evolve?

How has evolution created our blood, lungs and the heart? We can't exist without blood, which transports the oxygen to all areas of our body. However, the blood needs a lung, which gives it the ...
13
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2answers
1k views

Why do we have two of some organs, but not all?

We have two eyes, but we don't have two hearts. Why do humans have two of some organs, but not all?
8
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4answers
16k views

Bad Eyesight and Evolution

Why do many humans have bad eyesight, such as near-sightedness, which hampers performance in a wide variety of tasks? Shouldn't there be evolutionary pressure towards better eyesight?
20
votes
1answer
6k views

Why can hair grow without limit while eyebrow cannot?

I cut my eyebrow and it grows until reach a certain length. Hair can grow without limit. Why can hair grow without limit while eyebrow cannot?
38
votes
3answers
74k views

If the brain has no pain receptors, how come you can get a headache?

I've read many years ago in books, that the brain has no nerves on it, and if someone was touching your brain, you couldn't feel a thing. Just two days before now, I had a very bad migraine, due to a ...
13
votes
2answers
57k views

Why does human facial and head hair continue to grow?

Many people can grow extremely long head hair and facial hair. Are there evolutionary theories as to why this is the case? It seems like having long hair could be a disadvantage, and extremely long ...
1
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2answers
32k views

Will I grow taller? How can i tell? [closed]

I'm 17 and I'm about 160 cm and my weight is 47 kg . I just want to know if I will still grow taller ?
4
votes
3answers
881 views

Mechanical cause of loss of consciousness

Consciousness is an electrical and chemical interaction in the brain, caused by neurons firing and chemical interactions. How does a mechanical "force" cause this to stop working? i.e. How does a ...
268
votes
3answers
237k views

Why do I only breathe out of one nostril?

I was just sitting with my hand next to my nose and I realized that air was only coming out of the right nostril. Why is that? I would think I would use both, it seems much more efficient. Have I ...
18
votes
3answers
607 views

Why would diffusion be faster across a non-specialised tissue?

The standard protocol for a person experiencing chest pains is to chew a 300mg aspirin tablet, the argument being that chewing rather than swallowing the tablet results in the aspirin entering the ...
6
votes
2answers
16k views

Is it biologically possible for an adult's eye color to change?

Can it be that the adult eye can change color? Specifically my question is about a unilateral color change, such that the color of one eye remains constant, while the other changes color over time. ...
6
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1answer
5k 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, ...
17
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2answers
11k views

Will humans and animals be harmed by frequencies outside their hearing range?

The human ear (for example) is sensitive to frequencies from 20Hz to 20kHz. Any sound beyond that limit would not be heard by us naturally. Will it harm us (effect our ability to hear) when we hear ...
6
votes
1answer
7k views

Why does the ring finger not move independently?

Why is it that we need to move little finger in order to move ring finger with it? For example, put your palm on a table and fold your middle finger inside. You won't be able to move your ring finger ...
3
votes
1answer
7k views

Circulation through the liver in light of drug metabolism

I have a lingering question which stems from an answer that I gave to What hydrolyses aspirin within the digestive tract and blood stream? When a drug or any other substance is absorbed into the ...
46
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2answers
10k views

What is the function of epidermal ridges on human fingers (that produce fingerprints)?

What function is served by the epidermal or capillary ridges on human fingers, the supposedly unique impressions of which are known as fingerprints?
8
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1answer
53k views

Dorsal vs Posterior and Ventral vs Anterior

From prior reading, I thought that Dorsal is the same as Posterior and Ventral is the same as Anterior. However, when I checked in google images for these anatomical terms for a horse (just to ...
5
votes
0answers
642 views

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 ...
13
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2answers
4k views

Using anatomical terms for human organs and parts of plants

I know how to apply anatomical directional terms (e.g., dorsal/ventral, anterior/posterior, etc.) for animals as a whole (bipeds and quadrupeds). Recently, I've been studying plant physiology, and I ...
11
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5answers
12k views

Why is the opposite of plantar flexion called “dorsiflexion”?

Why is the action of flexing the foot so that the toes move anteriorly/superiorly (i.e. in the direction opposite that which they move during plantar flexion) described as "dorsiflexion?" In the same ...
8
votes
1answer
2k views

What happens to bones that do not heal?

I would like to know the steps the body takes to heal a broken bone and what happens if it cannot heal properly. I am not looking for advice or explanations on resting and not doing activity, I am ...
12
votes
1answer
1k views

Why are there nail growth differences between humans and other mammals?

When a cat is growing, his nails are growing with him to some extent. A grown cat has a fixed nail length that is not extending. By contrast, human finger nails just keep on growing, so we have to ...
8
votes
1answer
2k views

Are males taller than females in humans?

Is there any scientific evidence that in humans males are taller than females? And if so, what is the reason that they are taller (please include genes or hormones that accounts for human growth and ...
5
votes
2answers
794 views

Extraretinal photoreception in mammals? [duplicate]

A Finnish firm Valkee sells light-ear-plugs against thing such as jetlag. I asked a researcher in Aalto university how do they really work and he responded ...
5
votes
3answers
6k views

Why does the apex of the human heart usually point to the left?

In the majority of human beings, the apex of the heart (left ventricle) points towards the left side of the body. Sometimes however (approx. 1/12000 births), a person is born with a condition known ...
5
votes
2answers
992 views

Can someone who cannot talk still whistle?

Can someone who has a damaged larynx, which does not allow them to talk, still create a tune when they whistle? I know that the larynx is what allows a person to manipulate their pitch and volume, ...
7
votes
1answer
2k views

What is the function of the human eye white?

If you have a look at the eyes of most animals, you never see the white part unless the eyes are averted. In contrast, humans always have the whites visible because the iris is quite small. The only ...
6
votes
1answer
13k 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
3
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2answers
8k views

Why can't people talk while inhaling?

Why do we have to exhale in order to talk? From looking on Wikipedia, it seems like it has something to do with the glottis, but I'm not clear on the mechanism that makes speech sound so different ...
3
votes
1answer
714 views

Is there a genetic reason explaining the difference of the height of male and female?

The male and female height difference seems to be around 1.08 if all cultures are counted from these stats: https://en.wikipedia.org/wiki/Human_height Can this ratio, 27/25, be explained by genetics ...
2
votes
0answers
46 views

How much does a human brain's metabolic rate vary? [duplicate]

Possible Duplicate: How does brain energy consumption depend on mental activity? Our brains consume about 20% of our energy when we're at rest. How variable is a human brain's energy consumption? ...
6
votes
1answer
787 views

Mechanism of Tear Gas (chloropicrin/Trichloro methane)

Tear gas (CCl3NO2) makes people cry, and crying doesn't seem to be a simple procedure. There has to be a triggering process somewhere. Can someone explain its mechanism / how it works?
5
votes
1answer
2k views

Why do men grow facial hair?

Ancestral facial hair. Our closest ancestors, the chimpanzee and bonobo, both grow facial hair around the mouth area. What is noteworthy is that this is the case in both males and females of the ...
5
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2answers
3k views

Where do the 31 spinal nerves start/meet?

Which part of the brain is the first place (from top to bottom) where all 31 pairs of spinal nerves (on each side) meet? Or if they all start at one place - where is that? Nominally, the beginning of ...
4
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0answers
402 views

Why are sutural bones more common in lambdoid suture? [closed]

Why are sutural bones (Wormian bones) are more commonly present at lambdoid suture? Is the tortuous nature of lambdoid suture a reason for that? Evidences for my claim: They(sutural bones) occur ...
3
votes
0answers
98 views

How do we sneeze?

When a stimulus triggers the sneezing pathway, known as the trigenimal nerve network, how do the droplets from a sneeze get created within the nose? What affects the size of these droplets?
3
votes
1answer
10k views

Are transgender people born physically different from others?

Are all children born with only either male or female body parts (other than exceptions), or is there actually a natural third gender with the physical characteristics of both genders, e.g. the child ...
1
vote
1answer
57 views

How correlated are the lengths of tendons in different part of a human body?

How correlated are the lengths of tendons in different part of a human body? E.g., if the we consider two humans, A, and B. Human A has a patellar tendon of length 2 cm, and human B has a patellar ...