The study of the internal structure of organisms.

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Why can´t our dog bark with a high pitch while holding a stick in her mouth? [migrated]

When I throw sticks with our dog (a Swiss shepard) she usually barks at me with a high pitch when I´m about to throw the stick. Sometimes she still has another stick in her mouth and in that case her ...
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1answer
14 views

Accommodation mechanism. [closed]

Can anyone explain how contraction of the ciliary muscles causes relaxation of the zonules? Please explain it anatomically i.e. the attachments of ciliary muscles and its relation with the ...
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0answers
31 views

What is the circulation that allows for nutrient absorption and excrete of metabolic wastes in humans? [closed]

Pulmonary veins carry oxygenated blood from lungs to heart, while pulmonary arteries carry deoxygenated/CO2 rich blood from heart to lungs. On the other hand, systemic arteries carry oxygen-rich blood ...
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0answers
56 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 ...
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27 views

Do any non-human species have packed abs?

The classic "six-pack abs" in humans is due to tendons stretched across the abdominal muscles and low body fat. Do any other animals have a similar arrangement of tendons that could result in visible "...
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2answers
179 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?
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24 views

Why the name hypopharynx?

Why the tongue (like structure) in cockroach (or other insects) is called hypopharynx? In humans I know it's the lower part of pharynx, not a structure. Isn't this anatomical name misleading? Are ...
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1answer
50 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 ...
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1answer
34 views

Why do some drugs require you to take them in an “upright position”?

A friend of mine was taking the supplement Metamucil and on the container it says to take in an "upright position." Why would this be necessary? Doesn't your digestive system push food/liquid ...
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1answer
158 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
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1answer
42 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 ...
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1answer
612 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?
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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 ...
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1answer
80 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 ...
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1answer
47 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 ...
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2answers
124 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?
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2answers
74 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?
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1answer
82 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
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1answer
175 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 ...
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1answer
17 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 '...
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1answer
49 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 ...
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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, ...
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1answer
190 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 ...
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44 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, ...
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4answers
7k 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 ...
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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 ...
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29 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 ...
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1answer
690 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) ...
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1answer
81 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 ...
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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 ...
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3answers
277 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 ...
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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 ...
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29 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!
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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?
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1answer
130 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 ...
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1answer
340 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 ...
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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 ...
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1answer
93 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, ...
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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 ...
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2answers
1k 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? ...
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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 ...
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2answers
587 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 any?...
3
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1answer
102 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 ...
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36 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?
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33 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 ...
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0answers
21 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 ...
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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 ...
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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 ...
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2answers
672 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?
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1answer
198 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 ...