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.

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3 votes
1 answer
752 views

Can the axial length of the human eye decrease?

I understand that the axial length of the eyeball grows until you are around 20 years of age, which is why hypermetropia decreases with age but myopia doesn't. My question is: can the axial length of ...
0 votes
1 answer
73 views

Why does Sanjay Gupta's brain look so unusual? (brain model shown on CNN) The subdivisions don't look like the lobes I learned in school

above: Screenshot from CNN's May 18, 2023 Feinstein’s office confirms broader health complications, contradicting senator’s denial below: from anatomyinfo.com's Parts of the Brain Neurosurgeon Dr. ...
3 votes
0 answers
79 views

Can drugs be administered through penis?

I was reading this paper on routes of drug administration and noticed that it mentioned intravaginal drug administration. It looks like this is a good way to take drugs because there are a lot of ...
-1 votes
1 answer
43 views

Volumes of the four heart chambers

We know that the left ventricle which feeds blood into the aorta is typically the largest chamber of the heart. I'm looking for the typical absolute and relative sizes of the four heart chambers.
5 votes
1 answer
4k views

Why do I breathe out of BOTH nostrils?

After reading the question why do I only breathe out of one nostril I realized that breathing out of both isn't common. I have always breathed out of both, and when I get a stuffy nose, or a runny ...
6 votes
1 answer
488 views

Is there a quantitative report for cortical homunculus?

Almost all websites that I see for cortical homunculus only show the final picture with some qualitative descriptions such as "hands have more dexterity and occupy more motor cortex." But is ...
2 votes
1 answer
20k views

How large is the variability in human bone thickness, and is "big boned" a real thing or not?

My girlfriend is arguing that there are "big boned" people, I read some articles that there is no such thing but she still didn't believe in me because she saw some articles too that big boned people ...
0 votes
1 answer
123 views

What's the terminology for the deformity between the halluces and index toes caused by sandals?

In Japan, especially in the past, people tended to wear wooden sandals or the like, which separated their halluces from their index toes. As a result, there is often a gap between their halluces and ...
0 votes
0 answers
26 views

Why vasa recta is absent in cortical nephrons?

My teacher taught me that nephrons that have a short loop of Henle are called cortical nephrons, and they added that it might not even have a vasa recta, or that it may be much reduced. I do not doubt ...
0 votes
0 answers
12 views

Are white rami communicantes only specific to the sympathetic system or are they found in parasympathetic system too?

According to the doctor that explained autonomic nervous system to me in medical school, white rami is found in both sympathetic and parasympathetic, it connects spinal nerves to sympathetic chain ...
1 vote
2 answers
471 views

Why does 360 degree rotation not seemed to ever have evolved?

Of the designs of species that have evolved, I am curious why a 360 degree rotation, like a joint that can spin, does not seem to have evolved, for example wheels or a propeller. Like, is there some ...
0 votes
0 answers
37 views

Estimating Weight of Human Skeletal Muscle?

Is there a way to measure the weight of skeletal muscle? I understand body fat and lean body mass can be measured by: skin fold calipers, electrical impedance, table lookup based on formula of weight,...
14 votes
1 answer
189 views

Do patella bones form in people born with the inability to walk?

The patella is a sesamoid bone that typically doesn't completely from and ossify until ~3-6 years of age (e.g., Source). My long-standing understanding (supported by a claim in Saladin's college A&...
4 votes
1 answer
91 views

What is the actual molecular mechanism for muscle relaxation?

A number of my students asked what happens to the sliding filaments when muscles relax. For example, in an individual sarcomere, do all myosin heads release all at once or one/few at a time? More ...
0 votes
1 answer
261 views

Does the human abdominal cavity use pressure to maintain posture?

Several of my PT friends have referenced a physical therapist p who has studied breathing named Mary Massery. In her articles, she has referenced the idea of "intra-abdominal pressure" http://www....
4 votes
1 answer
978 views

How to maximize lung oxygen intake?

What method of breathing provides a sudden surge of oxygen into the lungs filling it as full as possible in volume and density. Deep breaths? Shallow breaths? Breaths taken while bent over? Deep ...
0 votes
0 answers
11 views

Human Body Muscle Mass: How to calculate new BMR?

Does anyone know how to calculate BMR that accounts for the total lean muscle mass? Specifically for someone that has been performing resistance training and their values may differ than norms? I ...
4 votes
0 answers
101 views

Why are lymph nodes located where they are? [closed]

According to the National Cancer Institute, a subdivision of the National Institutes of Health, clusters of lymph nodes are found in the neck, underarm, chest, abdomen, and groin. Why are lymph nodes ...
-2 votes
1 answer
245 views

How can a joint extend or flex?

The idea of a joint flexing or extending doesn't make sense to me, I can see how a leg or an arm might extend or flex but how does a joint extend or flex ? "The hip joint is most stable when it is ...
308 votes
3 answers
286k 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 ...
0 votes
0 answers
25 views

Why is the sinoatrial node in the right atrium?

Is it just an evolutionary remnant? If so, why would it have been disadvantageous for humans to have it in the left atrium?
4 votes
2 answers
7k views

Why does the kidney of a cow have lobules, why the kidney of a human hasn't any?

The kidney of a cow has lobules, while the kidney of a human hasn't any. I can't think of any reason why it would be good for a kidney to have lobules. It would be good if the kidney needed to have a ...
0 votes
0 answers
39 views

Where do salivary glands get all the water?

Humans typically produce a large amount of saliva per day (1.5+ liters in adults). I've searched around but can't find a direct answer to the question of where, since saliva is 99% water, all the ...
-2 votes
2 answers
67 views

Scientific terms for front-brain, mid-brain and back-brain

I am looking for a (semi-) scientific way of phrasing "front part of brain" (part 1), "middle part of brain" (part 2) and "back part of brain" (part 3) as denoted in the ...
25 votes
2 answers
4k views

Why do blood vessels in the eye not obstruct vision?

As light enters the eye, it reaches the photoreceptors at the "base" of the retina, which then pass that signal to the bipolar and ganglionic neurons -- the latter of which send the signal ...
1 vote
2 answers
604 views

Is the human iris concave or convex?

Most drawing and 3D modeling tutorials show the iris to be concave. But all the diagrams I Googled show the iris is at best flat, otherwise even a little convex (discounting the optical distortion in ...
2 votes
1 answer
79 views

Need help identifying vascular structures in brain matter

I am working on PET images of the brain. The neuro-oncologist I'm working with identified 2 large high-intensity regions as vascular structures. I've been meaning to ask what structures these are ...
0 votes
1 answer
882 views

Solar Celiac Plexus location in body

Where is the Solar (Celiac) Plexus located in relation to the ribcage? I am reading this on the internet, and trying to learn more. "The solar plexus — also called the celiac plexus — is a ...
0 votes
0 answers
96 views

How can children scream so loud and so long?

Recently I saw a small baby shrieking extremely loudly (my ears hurt) for at least 4 minutes . How is it possible? If I yelled so loudly, I would be defeated by throat ache after less than a minute. I ...
0 votes
1 answer
80 views

How do tapeworms aid weightloss?

The 5 second answer people come up with is, "well they consume calories you otherwise would have". This logic works great if we're discussing the impact of my brother consuming part of my ...
6 votes
1 answer
80 views

Human biology - liver regeneration after laprascopic segmentectomy

I am trying to understand to what extent human patients can regenerate liver mass after laprascopic segmentectomy: what part of liver will be regenerated and how fully. My work with sources is not ...
1 vote
1 answer
771 views

Did the capacity to be "knocked out" arise because it conferred an evolutionary advantage?

From first principles, it seems surprising that a blow to the head would cause unconsciousness rather than just impaired function. I've heard a lot of analogies to computers -- "Your brain has to ...
5 votes
1 answer
8k views

How are arms different from legs?

How are arms and legs defined physiologically? For example, we say humans have two arms and two legs, while cats have four legs, and some monkeys (appear) to have four arms (although I guess they ...
0 votes
1 answer
52 views

In human anatomy what is the purpose of measuring shoulder abduction and shoulder adduction separately if they cover the same range of motion?

In human anatomy what is the purpose of measuring shoulder abduction and shoulder adduction separately if they cover the same range of motion? For example, this video Goniometry Shoulder Abduction &...
9 votes
1 answer
2k views

Can skeletal morphology change in adults?

I'm just a curious layman, so be gentle. I read around that things like the cranial1 and pelvic2 morphology change with age, but I also read seemingly contradictory information that bones are '...
2 votes
1 answer
2k views

Ear ossicles a part of Skull?

Is there anything special about not considering ear ossicles as a part of skull? I could not understand the reasoning behind such classification.
0 votes
0 answers
58 views

Is the human mouth more burn-resistant than other animals which don't eat cooked food?

I burnt my mouth on some hot pizza and it got me wondering if we have been eating cooked food long enough to have evolved a better resistance to oral burns than other species. Have there been any ...
2 votes
2 answers
33k views

What is inside the male’s body in the space where females have the ovaries and the uterus?

The male penis and scrotum are external, whereas the female sex organs are placed "inside" the body. As females have the bladder, rectum etc. just like males, does this mean overall females ...
13 votes
5 answers
21k 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 ...
1 vote
0 answers
19 views

Is there any meaningful ratio between the width of a vertebra and its height and depth?

Given the location (i.e. their entry points, but not their trajectories) of two pedicle screws, we are trying to come up with a way to approximate the sagittal distance of the vertebral foramen to the ...
1 vote
2 answers
419 views

Are bronchioles and alveoli covered by respiratory epithelium?

Which parts of respiratory apparatus are covered by respiratory epithelium and which are covered by other kinds of epithelium?
0 votes
0 answers
82 views

Is there a functional reason why the right side of the heart has a tricuspid valve while the left has a bicuspid one?

Is there a functional reason why the right side of the heart has a tricuspid valve while the left has a bicuspid one? Why is it necessary that the right atrioventricular valve be 3-cusped?
9 votes
2 answers
516 views

Do breasts size depend solely on fat amounts?

I've read the first answer here on quora and it suggests that (not during pregnancy and breastfeeding) breasts differ in size only due to the amount of fats. However, there can be firm or soft breasts ...
5 votes
1 answer
2k views

Chest muscle and female breast size

Do female chest size have anything to do with muscle? I know many female athlete and their average breast size is much bigger than normal female that does not tend to play sports. Do this have any ...
2 votes
1 answer
163 views

What is inside digestive system while it's empty?

Up to this point, all my life I assumed that stomach and intestines are filled with air. I got this impression from all the anatomic drawings in schoolbooks and encyclopedias that show empty stomach ...
10 votes
1 answer
7k views

Do the right-handed people tend to use the right side teeth of their jaw to chew food more often than the left-handed people?

And vice versa, do the left-handed people tend to use the left side teeth of their jaw to chew food more often than the right-handed people?Or the frequency of food chewing distribute fairly to both ...
26 votes
1 answer
11k views

Why do stars disappear when I look at them?

I've noticed that when I'm out at night stars seem to vanish when I focus on them. I assume the reason is physiological and not astronomic. Why does this happen? I would expect that things would be ...
3 votes
2 answers
446 views

Does the palate truly house the sense of taste?

Source: Your “palate” is the roof of your mouth, and by extension, your sense of taste. I was reading Etymonline's entry for palatable {adj.}, which cites and derives from palate {noun}: ... ...
1 vote
0 answers
34 views

Which of dB or dBA are more useful for predicting damage to hearing?

With no information about noise other than its loudness measured in decibels or in A-weighted decibels, which can be used to more accurately predict how much hearing damage may be caused? Even though ...
0 votes
0 answers
66 views

Can the effect of an allele on height be context-dependent?

Some data is available on the effect alleles have on height. For example Common DNA Variants Accurately Rank an Individual of Extreme Height However after browsing the literature I was not able to ...

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