The study of the internal structure of organisms.

learn more… | top users | synonyms

4
votes
1answer
80 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 ...
3
votes
1answer
22 views

What does it mean for muscles origins and insertions to be the other way around in the right than left limb?

Herbert Srebnik writes in Concepts in Anatomy: In the right limb, the muscle's origin is proximal to the joint and the insertion is distal to it. In the left limb, the muscle's origin is ...
7
votes
1answer
554 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?
0
votes
0answers
9 views

Do bears generally have sesamoid bones in their fore and hind feet?

I can't seem to find any information specifically (that shows photographic evidence) of whether bears (of any kind) have sesamoid bones in their feet. And whenever I read information that says that ...
3
votes
1answer
73 views

Does size matter?

As I compare the morphologic differences between mouse models and the human disease for which they are analogous, I have become interested in what difference interspecies size has on molecular ...
1
vote
1answer
41 views

What is the role of gills in terrestrial Crustaceans?

Why do Crustaceans that live on land have maintained their gills? In aquatic species, the gills play a pivotal role in respiration, but terrestrial crustaceans have tracheal lungs. So why do they have ...
11
votes
2answers
109 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?
3
votes
2answers
66 views

Do nematodes have organ-level organisation?

Some introductory biology books state that nematodes have a pseudocoelom. So, they have a false body cavity. So, does it also mean that they have organ level body organisation?
1
vote
1answer
61 views

Explanation of the ‘cherry red spot' in Tay Sachs disease

In Tay Sachs disease, a hallmark symptom is a cherry red spot in the macula of the eye surrounded by a halo of white. I understand that the ganglion cells, which are higher in numbers around the ...
4
votes
1answer
97 views

Cross section through the right arm question

Is the largest drawn vein on first attached pictue v. brachialis or did they make a mistake and it's actually v. basilica? Picture 1: Cross section through the right arm (source: Thieme, General ...
3
votes
1answer
16 views

Is the thecal sac ectoderm?

The thecal sac, or dural sac, is the membranous sheath of dura mater that surrounds the spinal cord and the cauda equina. The thecal sac contains the cerebrospinal fluid in which the spinal cord ...
3
votes
1answer
43 views

Why are vertebrae, specifically, so important in classification?

A fundamental level of animal classification is the distinction between vertebrates and invertebrates. The vertebrata are, arguably, often classified as higher life forms than the invertebrata. But ...
26
votes
3answers
3k 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, ...
5
votes
2answers
112 views

Does the hepatic portal system form capillary beds?

Does the hepatic portal system form capillary beds? If so, is the capillary bed coordinated with that of arterial capillaries? What review paper might I look in?
2
votes
1answer
141 views

Anatomical differences between herbivores and omnivores [closed]

What are differences of herbivores vs omnivores? I do not mean dietary differences (obviously), but physical ones. E.g., afaik herbivores have a much longer digestive tract than carnivores; then ...
3
votes
0answers
40 views

How does glucose delivered intraperitoneal (i.p.) get into the peripheral circulation?

Intraperitoneal delivery of drugs or fluids is something that occurs much more frequently in veterinary medicine than clinical medicine. In veterinary medicine or scientific studies using animals, ...
3
votes
4answers
6k 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 ...
14
votes
1answer
2k 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 ...
0
votes
0answers
26 views

What is the term for toes that pull together with an upstep?

I fairly recently learned the term digitigrade, to describe the anatomy of a creature that stands on its toes rather than on the flat of its foot, like cats and ...
2
votes
1answer
372 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) ...
4
votes
1answer
78 views

What causes the opaque green colour in Lepidoptera?

Link here to what I mean by 'opaque' colouration on the insect, the colour intensity remains constant despite changes in light intensity and angle (not shown by the picture but the moth exhibits this ...
1
vote
0answers
13 views

Does this habit present any harm? [closed]

Sometimes I am able to put one knee down on the floor, rest my weight on that knee, and then relax it in order to make the knee cap go up and "crack" the knee. I can do this with both knees, I think ...
5
votes
3answers
274 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 ...
1
vote
0answers
33 views

Why are belly buttons on the stomach (why does the umbilical cord end up attached to the stomach)?

Belly buttons are at the site where the umbilical cord was attached to us as we developed inside our mothers. The same is true for all placental mammals. Why are belly buttons on the stomach? Why ...
0
votes
0answers
28 views

What is the lack of nipples in male horses and mice? [duplicate]

do male mice and horses create nipples in embryonic period then lack the or Whether these structures(nipples) are created from scratch?? Thank you!
0
votes
0answers
30 views

Why do male rats and horses lack nipples? [duplicate]

I have read many articles about why male rats and horses lack nipples, however, I still don't understand why! Do male rats, mice, and horses have nipples in early embryonic life and then lose them?
5
votes
1answer
128 views

Are CN3, CN7, CN9 and CN10 the only Parasympathetic Cranial Nerves?

It has been my thought for a long time that this is the case, but I am unsure currently, since the parasympathetic tract of colon sigmoideum does not seem to have connection with CN 10. It connects ...
2
votes
1answer
257 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 ...
21
votes
5answers
4k 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 ...
0
votes
1answer
73 views

Is the prostate problem unique to humans?

In human males the urethra goes through the prostate rather than around it, which tends to create problems for older men as the prostate enlarges. Is this only a human problem or do other animals, ...
2
votes
0answers
53 views

Front versus back in animal anatomy [closed]

Throughout various species, there seems to be a clear distinction between the front and the back. The musculature of the front, when engaged, closes or curls up the body, protecting it, while the ...
5
votes
2answers
966 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? ...
0
votes
0answers
20 views

Organ secretions

If an animal secrets an enzyme from an organ that is entirely dedicated for the same secretion, can one or cannot one just use the gene coding for that protein to obtain the protein in vitro. How much ...
4
votes
2answers
441 views

Why do snakes not have eyelids?

Why is it that snakes do not have eyelids? Is it due to that fact that they are not as evolved as we humans and other organisms that have eye lids, or is there any other significance behind it if ...
3
votes
1answer
100 views

Please identify organ

This is the gut area of an Eastern Grey Kangaroo taken of a property in the Southern Highlands of NSW, Australia. The top red organ appears to be the spleen but what is the elongated tubular organ ...
1
vote
0answers
33 views

Is lung size/shape a factor in long-continuous running of animals?

Apart from other factors, does lung shape/structure/size play any role in long-continuous running animals. Is there any similarity in lung structure between different long-continuous running species? ...
0
votes
0answers
30 views

How much force can connective tissue withstand?

I have been studying a 3D anatomy model. Based on visual observation, it doesn't look like the bones would be able to stabilize themselves at all without the connective tissue like ligaments. In the ...
1
vote
0answers
20 views

What is the radius of the Ora Serrata and lens in rabbits?

I'm interesting in estimating the surface area of the hyaloid membrane connecting the vitreous and aqueous chambers. This is a crude estimate however i'm struggling to find parameter values for ...
4
votes
1answer
3k views

How does this headless fish still move?

There is a (VIDEO) on Facebook where the fish starts to flail around despite no heart or internal organs. What causes the fish to flail around the way it does? My theories: It is because of ...
0
votes
0answers
22 views

What is the permeability of proteins across the hyaloid membrane of vitreous to retina?

Does anyone know of any experimental work to test the permeability of the hyaloid membrane between the vitreous humour of the eye to the retina to proteins? Currently the largest molecule I can find ...
3
votes
2answers
413 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?
2
votes
1answer
173 views

Does “squinting” make you concentrate better on a logic test?

We have all had those moments of intense concentration on some tough exam, perhaps a college test or whatever... Why is it that when we squint, it feels like we can focus and concentrate better on ...
5
votes
1answer
306 views

Why did Opabinia have 5 eyes?

I recently read about a fossil called Opabinia. What intrigues me is that it had five eyes. I was under the impression that most features, such as eyes, ears and legs are always even-numbered, i.e., ...
6
votes
1answer
404 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 ...
0
votes
1answer
35 views

is left brachiochephalic vein and left pulmonary artery is same?

I am reading about ligamentum arteriosum which connects the left pulmonary artery and descending aorta. But I am seeing that if any figure shows left brachiochephalic vein it does not show left ...
2
votes
0answers
56 views

Differing number of “things” in mammals [closed]

I'm not a biology expert, but I have often wondered about the following facts of life: All mammals have precisely 5 fingers on each of our 4 extremities. Granted, some may not be seen, but the bone ...
12
votes
3answers
1k 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. ...
1
vote
0answers
40 views

Bolyerine Snakes maxillary bone, split?

How is the maxillary bone split in the Bolyerine Snakes described in T.H Frazzetta's "From Hopeful Monsters to Bolyerine Snakes?" In T. H. Frazzetta, "From Hopeful Monsters to Bolyerine Snakes?" He ...
3
votes
0answers
106 views

Total number of pleura in the exoskeleton of cockroach

Basically as far as i know cockroach consists of 10 terga and 9 sterna but what are the total number of pleura present in the cockroach. Pleura are situated between tergum and sternum of a body ...
0
votes
2answers
525 views

Horns in animals and birds [closed]

Are there any carnivores with horns (whether extinct or currently alive)? Do any flying creatures have horns? By horns I mean horn like structure.