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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What are these tethers found inside/under the tongue?

When searching tongue ties I found this image: What are these bands that are often cut during tongue tie surgery? What is their purpose/why are they there?
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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 ...
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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?
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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 ...
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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 ...
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1 answer
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What's the terminology for this kind of deformity?

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 ...
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1 answer
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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 ...
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1 answer
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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 ...
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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 ...
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6 votes
1 answer
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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 ...
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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 ...
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1 answer
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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 &...
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Why do the median/medial and ulnar/lateral nerves' branch into different fingers/toes?

Each finger and toe gets two nerve branches each, one on each side. What I am curious about is the reason why the left and right branches, for any given finger/toe (except pinky fingers/toes), come ...
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What's the difference between mesenchyme and mesoderm?

The "mesenchyme" page in https://discovery.lifemapsc.com refers to mesoderm. It is said that blood, bones, and some other structures derive from mesenchyme, but then the tree from https://...
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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 ...
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1 answer
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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 ...
1 vote
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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 ...
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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?
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1 answer
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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 ...
1 vote
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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 ...
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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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What is the proper anatomical name of the "band of Richer" that wraps around the quadriceps femoris?

There's this fascial band called the band of Richer that wraps around the quadriceps femoris muscle above the knee (in this illustration, look for it near the left knee). It seems to stem from the ...
-1 votes
1 answer
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What is the difference between the cheeks and the near parts?

Linguistically, there should be the different property or feature between cheeks and the parts right near them for us to call cheeks “cheeks.” What is the main difference between cheeks and the other ...
1 vote
1 answer
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Is human skull size related to brain size?

Me and my dad have a disagreement about this. He thinks that if a person had a larger skull they would naturally have a larger brain. I think that he is assuming the evolutionary trend holds on an ...
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Are there any congenital anomalies that cause a lack of epicanthic folds in a child who would normally have them?

Wikipedia lists several medical conditions associated with epicanthic folds. Mount Sinai says that epicanthic folds in a baby who would not be expected to have them is a diagnostic tool that indicates ...
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1 answer
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Why can't I swallow the entire (liquid) contents of my mouth at once?

I've tested this out using water - I manage to fit a certain amount of water in my mouth, but if I try to gulp it all at once, I fail: I feel like spitting the water out (gag reflex?) There's a ...
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The location of pulmonary valve in comparison with the aortic valve

According to most transverse diagrams of heart, the pulmonary valve, in comparison to the aortic valve, angles towards the left side a little bit. Take, for instance, the pulmonary valve is more ...
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1 vote
1 answer
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Is it possible to see some renal pyramids in a transverse section those which cannot possibly be viewed in one longitudinal section at the same time?

This is just a random image I found on Google. It is showing that, in cross-section, several renal pyramids can be viewed. Is it so? According to the following longitudinal section of the kidney, I ...
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Cell location co-ordinates [closed]

I have just had the nails on both my big toes removed. I am much happier. But it got me to thinking, as there is no 'root structure' from which the nail grows, is there an x,y,z, type co-ordinate ...
37 votes
2 answers
6k views

Why do we have two kidneys but one liver?

Both the liver and the kidneys are involved in "cleaning" our blood. But why we have one liver and two kidneys? I can just as well imagine that we have two livers and one kidney. Is this ...
2 votes
0 answers
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Motion of Fallopian tube fimbriae

The fimbriae at the ovary end of Fallopian tubes are described as "sweeping" eggs from ovaries into the tubes: When ovulation is about to occur, the sex hormones activate the fimbriae, ...
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Why does bicep activate during dead hang?

Hanging from a bar causes my bicep to feel much harder than when simply holding my arm straight above my head relaxed, without a bar. This was slightly surprising to me: I used to assume that since ...
1 vote
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Brain centers vs areas (and how they relate to nuclei)

I'm looking for a reputable source that can provide succinct definitions differentiating the following terms in the central nervous system (CNS; particularly in the brain): Area Center Nucleus ...
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What determines walking direction in humans?

I've wondered about this for a while, without being able to come up with an answer. Is there a body part that single-handedly determines the direction we're walking in? Is it a group of body parts ...
-4 votes
1 answer
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Can a person survive without platlets in the bloodstream? [closed]

Can a person survive without platlets or thrombocytes in the bloodstream, if I guarentee that the person is isolated and won't injure? Any help will be appreciated. Thank you!
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1 answer
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What type of epithelium are the pancreatic Islets of Langerhans?

The human pancreas contains exocrine acinus cells (simple cuboidal epithelium) and Islets of Langerhans. Despite looking online I cannot identify what type of epithelium the Islets of Langerhans ...
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3 answers
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Why aren't the twin organs like both the eyes, ears, hands and legs lying both sides of a human body identical?

Both the eyes are not identical in geometrical shape and size i.e. physical appearances of both the eyes of a person are different from each other. The same difference is observable in both the hands, ...
3 votes
0 answers
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Are the foramina of Magendie and Luschka genuine defects of the ependymal epithelium?

Question: Are the foramen Magendie (or the median aperture) and the two foramina Luschka (or the lateral apertures) genuine defects of the ependymal epithelium? So the ventricular lumen truly ...
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1 answer
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Evolutionary selection pressure for human hair patterns?

Are there hypotheses or conjectures that postulate any selection pressures or benefits that account for the patterns of non-pubic human hair? Particularly: Humans do not grow notable (i.e., non-...
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1 vote
2 answers
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In human anatomy / biomechanics, what is the motion called when the arm swings sideways so the elbow moves in an arc of 90 degrees?

In human anatomy / biomechanics, what is the motion called when the arm swings sideways so the elbow moves in an arc of 90 degrees? So e.g. if a person was to elbow somebody behind them , or if ...
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2 votes
0 answers
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The exact points of muscle attachment and the "equal and opposite force" that skeletal muscles apply

I've been trying to make a simple simulation of the human body executing some motions in Mathematica (the details are irrelevant), but I need to know some more information about muscles and how they ...
1 vote
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Flexor/extensor group in lower arm and limb bud rotation

Have the flexor and extensor groups in the lower arm have rotated laterally 90° towards the humerus epicondyles independently of the rest of the lower arm? The pre-axial and post-axial veins are still ...
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1 vote
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What is the thinnest spot on the ilium called?

Is there a specific name for the spot on the human iliac fossa where the bone is the thinnest? (Or, is there a name for the thickness measurement of that spot, e.g. the left/right _________ is 2.1mm?) ...
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The position of the macula in comparison to the blind spot

Which is located in a higher postion? Macula or blind spot?
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1 answer
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Animal species anatomy [closed]

https://en.wikipedia.org/wiki/Animal Do all animal species have two lungs and two kidneys similar to human beings?
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1 answer
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Can a hinge joint technically allow rotatory motion?

Let's use a hinge joint and pivot joint as examples. When talking about the difference between them in terms of movements permitted, I see that on any websites and textbooks, the term 'rotation' is ...
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Is there any ethnicity difference in average pupil size?

I have seen some articles claim African Americans have smaller average pupils than whites while Asians have larger pupils. Is it true? link: Y. Li, D. Huang; Pupil Size and Iris Thickness Difference ...
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14 votes
1 answer
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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&...
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Is the diaphragm made of two muscles?

Is there a 'crural' and 'costal' parts of the diaphragm as suggested in this paper or is it just a single muscle?
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How do Human Skin Creases Vary?

I am studying human gross anatomy in order to produce an anatomically correct CGI model of the human body. As part of this, I'm attempting to understand the different features that define the ...

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