Questions tagged [anatomy]

The study of the structure of organisms and their parts.

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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, ...
kittycat's user avatar
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22 votes
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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 ...
asparagus's user avatar
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2 answers
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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?
Ray Kay's user avatar
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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 ...
senshin's user avatar
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2 answers
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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? ...
DrZ214's user avatar
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8 votes
2 answers
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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 ...
Remi.b's user avatar
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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 ...
Danny W.'s user avatar
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84 votes
2 answers
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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? ...
DrZ214's user avatar
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36 votes
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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 ...
uhoh's user avatar
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27 votes
1 answer
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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 ...
Superbest's user avatar
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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 ...
user31782's user avatar
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2 answers
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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 ...
mic's user avatar
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15 votes
1 answer
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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 ...
Daniel Standage's user avatar
14 votes
2 answers
6k 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 ...
MrAP's user avatar
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13 votes
1 answer
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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 ...
MrAP's user avatar
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11 votes
1 answer
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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 ...
Maxim V. Pavlov's user avatar
10 votes
2 answers
29k 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 ...
mkrell's user avatar
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6 votes
1 answer
397 views

Comparative leg sizes

When I was a child, my father showed me the classic essay "On Being the Right Size", J. B. S. Haldane. It talks (among other things) about how large animals need stockier legs to support their weight....
Ross Millikan's user avatar
5 votes
1 answer
880 views

What limits the size of fish compared to marine mammals?

The largest extant fish species is the whale shark (Rhincodon typus). With a length of 13 meters and a mass of about 20-30 metric tons, the whale shark is relatively small compared to the largest ...
Bart Jacobs's user avatar
5 votes
1 answer
238 views

What is this insect wing, based on its vein pattern?

I've heard that it's possible to identify insect species uniquely based only on the vein patterns of their wings. Is this true? If so, what is this? The image is taken from an unsolved Internet ...
A. B.'s user avatar
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1 answer
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What is the function of the Hyoepiglottic ligament?

The hyoepiglottic ligament (ligamentum hyoepiglotticum) is an elastic band that connects the epiglottis to the hyoid bone. Although I can find information about the clinical significance of this ...
theforestecologist's user avatar
3 votes
0 answers
109 views

How does Anabantoideis' labyrinth function? What does it look like?

Anabantoideis are fish with an organ that allows them to take oxygen directly from the air outside of water. However, I cannot find much on how this functions, nor can I find any clear image of what ...
E.UCIT's user avatar
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3 votes
1 answer
2k views

Is there a difference between pig and cow anatomy that makes religious slaughter of the latter less painful?

This question is not for the squeamish. I was told that non-Kosher animals like pigs have a different anatomy in their neck compared to kosher animals like cows such that the Shechita method of ...
A L's user avatar
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2 votes
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Terrestrial Vertebrate Limbs

This question is regarding the conversation that took place here: Why don't mammals have more than 4 limbs?. I'm not sure if someone mentioned this and I just missed it, but everyone is talking ...
lovesgenetics27's user avatar
1 vote
1 answer
571 views

Why do dragonflies have these special little spots on their wings?

The wings of several kinds of dragonflies I've seen here in Taiwan all have an apparently special little pigmented spot near the ends of each wing. Does this spot have a name and a function? below x2: ...
uhoh's user avatar
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1 vote
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Does a full tear of the gluteus minimus tendon has any functional implications?

From what I read on Wikipedia, all functions of the gluteus minimus are mirrored by the gluteus medius. Additionally, the gluteus medius is larger than the gluteus minimus (see comparative images here)...
Franck Dernoncourt's user avatar
1 vote
1 answer
64 views

Does a full tear of the gluteus minimus tendon result in a long-lasting inflammatory response?

Does a full tear of the gluteus minimus tendon result in a long-lasting inflammatory response? This answer mentions: An isolated gluteus minimus tear still causes functional problems because of ...
Franck Dernoncourt's user avatar
0 votes
1 answer
413 views

Why porifera is classified to have an incomplete digestive system although it has no organs?

Why are we using the term "incomplete" for digestive system only? We could have also said that for circulatory system that it is either incomplete or present as a simple system. What I mean ...
Lakshya Kumar Singh's user avatar