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Questions tagged [anatomy]

The study of the structure of organisms and their parts.

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78
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2answers
23k views

Why is the heart not in the middle of the body?

All mammals that I can think of have a high degree of bilateral symmetry (In fact, almost every animal I can think of is like this). So why is the human heart not exactly in the middle of the body? ...
57
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4answers
13k views

How come large herbivores have such thin legs?

Edit: This question is very similar to this and related to this one (though the latter focuses on homology instead of scaling laws). However, the answer to this question is far more comprehensive, in ...
41
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5answers
7k views

Why Is Most Life Symmetrical Externally But Not Internally?

Mammals, reptiles, arachnids, insects, etc are all as far as I am aware symmetrical in appearance. Take a human for instance, make a line from the top of our head right down the middle. However, ...
35
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2answers
3k views

Is C. elegans always observed with precisely 302 neurons? Are there ever individual viable exceptions?

This answer mentions that the C. elegans hermaphrodite has exactly 302 distinct neurons. This has made it a very effective model for a variety of types of biological research, including neurology and ...
26
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5answers
12k views

Why are there no known animals with an odd number of legs?

In my 6th grade science book it is said that there are no three legged animals, and that no animal with an odd number of limbs exists. I checked Wikipedia and could confirm this: There are no ...
26
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1answer
17k views

Does the octopus have an anus? What does it look like?

Octopuses are cephalopods, which have separate anal and oral openings. Indeed, descriptions of the cephalopod GI tract clearly depict an anal opening. However, I am very confused about how this ...
19
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2answers
15k views

Evolutionarily, why do male rats and horses lack nipples?

Developmentally male rats don't have nipples because (reddit) Testosterone release in the fetal male rat happens before the stage of mammogenesis where the teat is formed whereas other species halt ...
18
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2answers
1k views

Do the majority of fish lack scales on their heads?

Based on pictures, it seems to me that a vast majority of fish species that have scales do NOT have scales on their heads. Is that fact true? To make this properly answerable: lets' define a "...
15
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1answer
404 views

Evolution of long necks in giraffes

In this question, the OP uses giraffe necks as a supportive example of evolution. Is the mechanism described in this post accurate? At some point, I thought I remember hearing that giraffes did not ...
14
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3answers
5k views

How many cells does the smallest animal have?

Note: question rewritten to prevent misunderstanding and make it more answerable I know that some small animals like C. elegans display surprising sophistication with a very small number of cells. ...
14
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2answers
819 views

What is the morphological difference between Leydig cell in human and pig?

The pig is only an example, just an animal. Leydig cells have protein inclusions (Reinke crystals) that are mostly made of crystallised lipofuscin. They are secretory inclusions i.e. cells formed in ...
14
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4answers
1k views

Skull mystery on beach

The skull was found on a beach on the Sechelt inlet on Canada's pacific coast. A marine environment. What species is this skull from?
13
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2answers
5k 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 ...
12
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5answers
16k 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 ...
11
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2answers
3k views

Where can I find the list of all tendons in the human body?

https://www.healthcentral.com/article/aging-can-take-major-toll-on-womens-tendons (mirror) claims that: There are about 4,000 tendons throughout the body. This claim is echoed by a fair amount of ...
11
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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 ...
11
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2answers
3k views

Is there a correlation between muscle fibers and body types?

I have been told the number of muscle fibers a particular muscle has varies from person to person. Unfortunately, the person who told me this did not know much more than this. Initial searching on the ...
10
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1answer
335 views

Why don't dragonflies wings collapse?

How do dragonflies manage to fly at such high speeds without their wings collapsing? Their wings are thinner than paper, but they do not even flutter. What gives them their strength?
10
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2answers
3k views

What are the atmospheric requirements for large dinosaurs?

What are the atmospheric requirements for large dinosaurs? and are the atmospheric constituents for supporting large dinosaurs any different from the atmosphere today?
10
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0answers
312 views

Anatomical Angle Made by the Fingers of an Extended Palm

Does the angle made by the fingers (excluding the thumb) of an extended palm (as shown in the figure below) have a name (such as the Lovibond or Cobb angle, for instance) ? I have already checked ...
9
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2answers
10k views

What is the anatomical term for a two jointed leg?

Allow me to apologize in advance for the layman's terminology. I'm wondering what the anatomical term for a cat- or a goat-style hind leg is. Cats, goats, t-rexes, and many many other animals don't ...
9
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2answers
48k views

Do male mammals other than humans have nipples?

When I grew rabbits, I had a pair, one male and one female. And while the female's nipples were quite prominent, especially after giving birth, I don't remember the male having any nipples at all. Do ...
9
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2answers
7k views

Why do adult insects have 6 legs?

Apparently, there is an advantage to having 6 legs in the insect world. What is that advantage, if anything? Why would such an advantage exist for insects, but not for other, larger land animals? ...
9
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1answer
916 views

Can frogs see clearly under and above water?

If humans attempt to see underwater, the image is blurred due to refractive differences in air and water that disrupt the normal refractive effect of the lens in the eye. A diving mask overcomes this ...
8
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2answers
418 views

Can you tell if a corpse was male or female by only examining its skull?

There are articles that says women have more rounded corner faces than men, than women noses are usually shorter, etc. But are those (and other features) tendencies or deterministic features that ...
8
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2answers
1k views

Why do small organisms make faster movements than big organisms?

I hesitated to ask this question because it seems so obvious and intuitive. However, I am not able to explain this tendency. Background It seems to me that small organisms make faster movements than ...
8
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2answers
12k views

Why do we have more sweat glands in our palms?

Why is it that we have more sweat glands in areas such as the palms of our hands and the soles of our feet? I just learned that there are more there but I am curious as to why that is.
8
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1answer
71k 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 ...
8
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5answers
10k views

Why do most mammals have long snouts?

It seems like most mammals, e.g. dogs, have long snouts. My pet dog's snout would seem to me like an evolutionary disadvantage, since her canine teeth are way out at the end of her jaw, which acts as ...
8
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1answer
4k views

Can humans live without their right atrium?

The right atrium is one of four chambers (two atria and two ventricles) in the hearts of mammals (including humans) and archosaurs (which include birds and crocodilians). It receives deoxygenated ...
7
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1answer
4k views

What is the rest state for eyelids - Open or Closed?

If one were to not apply any efforts on the eyelid muscles, will they remain open or closed? In movies when we see a person die, either case could happen - their eyelids could be open or closed when ...
7
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1answer
9k views

Can defibrillation be done with a car battery?

Can successful defibrillation be done with a car battery? Is it POSSIBLE for this to work? Let's say you are stuck on a very remote place and something happens to someone... Moreover, can you jump ...
7
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1answer
2k views

evolutionary reason behind sharing the same path for food and air?

What is the evolutionary reason behind sharing the same path for food and air? For example, we have a nose and lungs, yet they are linked by the pharynx, which is shared with the mouth and oesophagus....
7
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2answers
16k views

How do other primates treat their fingernails?

Do all primates have to trim their fingernails in some way, or do some primates' fingernails wear off through natural use? Also, is constant nail growth common to all primates?
7
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1answer
11k views

How many abdominal sclerites would be there in a cockroach?

Every tegmina of a cockroach has sclerites which are analogous to the bones of humans. Every abdominal segment of cockroach consists of two lateral sclerite plates called pleura along with a dorsal ...
7
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1answer
3k views

For fish, does a bony skeleton have any advantages over a cartilage skeleton?

I have learned that two important lineages of fish are the bony fishes (Osteichthyes) and the cartilaginous fishes (Chondrichthyes). Many websites mention an advantage of the cartilaginous skeletons ...
7
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1answer
1k views

Skeletal muscle without antagonist

Is there any skeletal muscle that does not have an antagonist? Excluding circular muscles such as around eye and mouth. The reason why I am wondering is because in biology normally nothing is ever ...
7
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1answer
1k views

How can bats hear such high frequencies?

I attended a talk that glossed over some biology as it was talking about a certain protein. The speaker mentioned humans can hear up to, often less than 20kHz frequencies, whereas bats can hear up to ...
7
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1answer
1k views

What is the name of the appendage that mantis shrimp use to rub their eyes?

In this short clip, you can see the mantis shrimp using some sort of feathery arm/claw to rub its eyes. Looking at a diagram here, it appears possibly that it's using maxillipeds. Someone with ...
7
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1answer
762 views

Do antigens protrude through the capsule/slime layer in prokaryotic organisms where these features are present?

In prokaryotic organisms that have a slime layer or capsule, do intrinsic/extrinsic proteins and other molecules that could be used as antigens protrude through the capsule? I assume that they must ...
7
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1answer
17k views

Do male humans have a mons pubis?

Wikipedia writes: In human anatomy, and in mammals in general, the mons pubis (also known simply as the mons, and known specifically in females as the mons Venus or mons veneris), is a rounded mass ...
6
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1answer
31k views

Examples of animals with 12-28 legs?

Many commonly known animals' limbs usually number between 0 and 10. For example, a non-exhaustive list: snakes have 0 Members of Bipedidae have 2 legs. Birds and humans have 2 legs (but 4 limbs) Most ...
6
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4answers
38k views

Which organs do cats not eat on their prey?

My female cat is a very active hunter and brings me her prey daily. Except for shrews and birds, she always eats them entirely. This afternoon she brought me this: It was quite large (maybe between ...
6
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3answers
392 views

Symmetry of species [duplicate]

I've got a silly question, sorry for that. I know, that we probably have no the right answer and the current answer could be "that's evolution, external conditions". I'd like to speculate, why most of ...
6
votes
1answer
103 views

When is an anatomic entity named “laterale” vs. “lateralis”?

I'm trying to learn the latin names of anatomical entities and I have a hard time remembering whether it's "Os cuneiforme laterale" or "Os cuneiforme lateralis". In that case it's "laterale". But in ...
6
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3answers
1k views

Did dinosaurs have more than one brain? If so, why?

I once remember reading (15 years ago) that dinosaurs had two brains. One for their head and another one for their digestive functions. What is the current opinion on this theory? Has more evidence ...
6
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1answer
77 views

Are there any anatomy books focusing on etymology?

I noticed that I can remember names for a very long time if I now their etymological background, the reason is easy I love etymology, especially when it is connected to mythology. However when I learn ...
6
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1answer
6k views

Why does the sacrum fuse together?

Everywhere I look describes how the 5 sacral vertebrae start fusing together during adolescence and are totally fused by the time you're 30 or so. But nobody seems to explain why this happens. It ...
6
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1answer
6k 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, ...
6
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1answer
4k views

What is the average Leg-to-Foot Length/Width Ratio?

I'm making a program that estimates a probable size (widest width and longest length) for a human's foot given the length and width of the leg to which it is attached. However, try as I might, I can't ...