Best Frog Dissection: Part II – Internal (Jr. High, High School and College Review)

Best Frog Dissection: Part II – Internal (Jr. High, High School and College Review)

September 8, 2019 0 By Stanley Isaacs


(upbeat music) – Let’s go ahead and start. – Shall we start on the bullfrog here. – Let’s put this off to the side, yeah. – All right. – So as far as the first initial cut. – Yeah, so you wanna cut, you know, The body cavity is right in here, it’s a fairly large body cavity. So we want to expose that and you can use scalpels or scissors, I like scissors, just gives
you a little more control. – Any concerns as far
as depth or anything or? – Yeah, well you don’t want
to jab down in, you know, into the cavity itself and you try not to stay within the muscle there. But with frogs, the skin’s pretty loose. – Oh, you kinda show that. – Oh, sure, yeah. The skin’s pretty loose. So usually you can just
kinda get down there, and that’s when you
can do the initial cut, and so you can get down
and cut through that skin. And see if I can get a little sharper. – [Man Learning] It
isn’t very thick is it. – [Man Dissecting] No,
the skin is very thin and – [Man Learning] Any chance
of hurting anything here? – [Man Dissecting] Not really,
I think, you don’t want to cut down into the
muscle layers too much if you can help it. But as you cut around that. – [Man Learning] What I find
kind of unusual is that, in comparison to like the human anatomy is that’s nothin’ really attached. I mean, – Right, yeah, the skin doesn’t
have a lot of connective tissue or anything to
it that makes it hard, in fact, once you, you know you really get going on these things, you can pretty much just
kind of tear it like that. You can just pull it loose,
so that’s another option too. So especially if you wanna
study the muscles system and you wanna you know,
skin the entire frog, you can do that. You get a little bit of attachment
up here around the limbs, one thing you can do with the scalpel is kind of cut up here. – [Man Learning] Should
I lift it up a little? – [Man Dissecting] Yeah, you can lift that up a little bit so it
shows a little bit better. But if you cut up there
around, like a ring around, you know, kind of cut all
the way around the limb then that will make that
skin come off a lot easier. And so all we gotta do is
make a few incisions there. And don’t want to cut you here. – [Man Learning] Yep – [Man Dissecting] Cut
away from you there. And so, I’ll do the
same thing on this side. Maybe if I can get down there. – Yep, I’ll kinda hold it up here. – Yeah let me get back
to my scissors again here and cut up around. Yeah so the main, in this
case we’re not trying to be terribly careful about it. We’re just kind of, cutting up here so that we can, you know, expose these internal organs. – [Man Learning] You can
definitely see the muscles there. – [Man Dissecting] Yeah veins and muscles coming up in there. – [Man Learning] So the kids
should be easy to identify what should they cut,
what shouldn’t they cut. – Yeah, yeah you can see the skin again, it’s pretty shiny here. Kinda get that. Roll it
just quite roll off that internal membrane there yet. There he goes. There we go. So we’ll just pull that up up there. – [Man Learning] That’s
coming off real nice. – [Man Dissecting] Yeah
see there’s no point in being too fancy at this point. – [Man Learning] There it is yeah. – [Man Dissecting] Yep. – [Man Learning]
Definitely see the muscles. – [Man Dissecting] Got some muscles. – I’ll kinda hold that up. – Sure let me just clean up the, I’ll just clean that up a
little bit, there ya go. – I’ll kinda hold it up here. You can see that skin’s removed. – Yeah, so skin’s removed from the area. We probably wanna take it
just a little bit further down this way, to expose the abdominal area. Let me just, for tonight,
today that should be good. You can skin the legs too and
look at the muscles there too, but for right now we’ll stop there. And so here’s, unlike a lot
of the other areas we see, pretty thick body wall here of muscles. So these are the abdominal muscles. This is called the Linea Alba. This line that runs where the
muscles meet in the middle. And you can kinda see
– [Man Learning] Kinda see it. It’s a little shiny here, you can see how these
muscles kinda run this way. Those are the Rectus Abdominis. Or abdominal muscles, the
famous six pack in humans. – [Man Learning] Kinda see it there. – [Man Dissecting] You
can see how that would be if those were developed. Highly those would stand
out like a six pack. And then up here, these
large muscles that move the front limbs, is the Pectoralis. Our muscles that we use
to move limbs as well. From the middle bone, you
know, out to the arms. So they pull the arms inward. And so that’s a strong muscle. – Which means too, we’re seeing bone, definitely bone, cartilage, both. – Yeah bone, definitely
bone, smaller bones here, but there’ll be bones that support that, and of course now with these
animals being tetrapods, four-limbed animals unlike fish, which use their tail, now the muscles are big sheet-like muscles that move the limbs themselves. And so the trunk muscles
become less important. Those big strong muscles
that move the limbs, particularly here in the back, are the ones that power the
locomotion on the animal. – Should we go ahead and open up then? – Yeah so now, see really
I say at this point, today we’re not as
concerned with the muscles, so we wanna basically cut
through down here somewhere. – Should I kinda hold that up, – Yeah see it’s always kinda
hard not to block the camera. Here you don’t wanna go too deep. Just get through the muscle layer, there you can kinda see the muscles. You can see the body
cavity starting to open up. – [Man Learning] A
definite cavity in there. – [Man Dissecting] Yeah a big. – [Man Learning] It’s hard to
make a mistake here really? – [Man Dissecting] I think so.
That’s why I like scissors, ’cause you press up
against the skin, you know, you don’t try to go too deep. If you’re using a scalpel
then you just wanna be real careful not to go, wanna
hold that up just a second? Now what we got here, probably the urinary bladder, is attached, I’ll have to go
ahead and cut that I think. There, and we’ll pick that up later, but the urinary bladder
down there stretching. So pretty much just anything that sticks you wanna just kinda pull it away. At this point do we wanna go, we could go all the way
up to the Pericardial, or we could wait on that. – [Man Learning] Maybe
identify the parts down lower. – [Man Dissecting] Yeah we can get, maybe, to that ’cause the heart
is in up above the.. You’ll feel these, – [Man Learning] So right
now you’re basically just removing the muscle
from the whole area. – So here you can see the muscles and here’s where the bone is right here. So in order to get, the
heart’s kinda right here, but in order to see the heart better, you usually cut through some bone. – Kinda equivalent of a sternum. Yeah, it’s called the Coracoid, but it’s equivalent of a sternum. They don’t have a rib cage. Frogs don’t have a rib cage like reptiles birds and mammals do. We can see quite a bit there, but we’ll probably take a little
bit more of that off later. – [Man Learning] That’s a
nice looking heart actually. – [Man Dissecting] Yeah, yeah. – [Man Learning] So were
we correct? Male or female? – [Man Dissecting] Uh sure
looks like a male so far, ’cause female’s usually have the ovaries. You can see them earlier.
We’ll see in a minute. One thing, we’ll see this, a lot of these frogs
we’ve been getting lately, there in solid condition, but you see all this structure in here. These big finger-like looking, projections are fat bodies, and you can see they’re paired. They’re on both sides. And so they would depend
a lot on the condition of the animal so if the
animal’s in good condition, probably gonna be storing
energy in those fat bodies. Certainly with females
would be doing that as they get ready to reproduce, but as you can see they
take up a lot of space, so I think the best thing, let’s lay him down for just a second. I think the best thing to
do is probably take fat body out at least on this one side. You can pretty much just, – Kinda angle it this way. – Oh sure, can you see him? So I pretty much, I’m
just kinda goin in there and loosening it up. Just trying to see, they’re not so directly attached to anything, and so you can pretty much
just kinda probe them loose. – Should I grab a hold of this here. – Okay can, okay, I’m just
gonna cut that fat body. Leave kind of the base of it. – [Man Learning] Leave one
side to kind of reference. – [Man Dissecting] Yeah for
now anyway I think we can. We’ll see if we wanna
clean it up even more. So anyway, yeah so you
can see how large that is. – Absolutely
– A lot of energy in that. – So I can kinda hold him up here again. – I’ll even cut this one out of here just so we get a little better view. Okay. Yeah so now we can see things quite a bit better. This one’s kind of reddish
which is a little different. Oh there’s some more fat
body, let me get that out. – [Man Learning] I was
thinking the same thing. He was a little redder than
the ones we have seen before. – [Man Dissecting] We should
be able to get another one later on. This again, he’s a very young,
must be a very young male. That is the testes right there. – [Man Learning] That’d be paired then. – [Man Dissecting] Yeah
so there’ll be another one on that side among the fat body. So that’s very small. So that animal is not really
in reproductive condition. – [Man Learning] Some of the
students might get confused with something very
similar, looks very similar. – [Man Dissecting] Yeah
and that’s the spleen. We’ll try to pick that up
later, but that’s the spleen. So, let’s lay him down, or
yeah hold him up like that. Course this very, right
away you see this very big structure here at the front,
and it’s got three lobes to it. Right and a middle and a
left, and this is the liver. And livers are in almost all vertebrates, the largest organ, I mean you see, largest internal organ anyway. So you’ll see these really large livers for storing fats, detoxifying things, producing um, bile which is
stored in the gallbladder. So very large livers and
so this is, you know, takes up a lot of the anterior part. – Which is nice for comparative. – Yeah easy to find and kinda see. And then if you lift the liver up, should be able to find,
although it’s a little tricky, here it is, wow, okay right
there is a little sac. That’s the gallbladder. So the bile that the liver produces is stored in that gallbladder. Then there’s ducts here
that carry that bile down to the digestive system. It’s helpful in digesting fats. It’s a emulsifier breaks fats down. That type of thing. So bile’s important. So, got the big liver, and then another big structure
right here you can see is the stomach. So again the food comes
down the esophagus, stored in the stomach,
some digestion begins. – [Man Learning] Similar function to ours? – [Man Dissecting] Very similar. Big storage, elastic would expand, and then the stomach then gives rise to the small intestines. You can see all of this then long, the intestine is elongated,
then curls up on itself, to the duodenum kind of part. – [Man Learning] It does
look loose in there, but it is connected isn’t it? – [Man Dissecting] Yeah
connected by these Mesenteries. You can see these Mesenteries
extensions that go, so here you can see more and more. There’s that fat body again,
but all that coiled tube there, is the intestine. So a lot of time, a lot of
surface area for absorption, a lot of food spends more time in there as it’s broken down and absorbed. And then again a nice
differentiation in kind of areas, between here the small
intestine now giving rise to the large intestine, or colon. And so, right here is the large intestine and that’s where the food
after it’s been absorbed, the undigested food is there. Water is reabsorbed to save water, and then the feces, the undigested food, then can pass out through the cloaca. – Okay and the common opening for.. – Yeah common opening for now we’d have the urogenital system too. So digestive system really, you know, you swallow the food,
stored in the stomach, passes through the small intestine where it’s digested and absorbed, and then food in the large intestine for reabsorption of water. At this point, oh we didn’t look at the
pancreas either did we? We did talk about the spleen
being underneath here. – [Man Learning] Pancreas a
little harder to find then? – [Man Dissecting] Yeah here’s the spleen. Yeah pancreas is kinda weird. They’re in the Mesenteries
of the intestine. So you gotta kinda
sometimes work it around a little bit here to find. I think it’s right there. Yeah there it is. – [Man Learning] Oh yeah. – [Man Dissecting] It’s kinda
blood colored in this one which is kind of weird. So it’s very, it can be
kind of fleshy colored, and it’s right there. – [Man Learning] A little
harder to see in this one. – [Man Dissecting] Yeah
and the pancreas there along the line, and the pancreas then, another one that produces hormones, insulins and things to
help with digestion. – And as far as, you’ve mentioned before, about the having external like nostrils, is their lungs in, – Oh yeah, yeah. – How are they developed? – You wanna get to the respiratory system. The liver kind of hides those. Let’s maybe, cut that and
move that back a little bit. There they are way up there. We might have to wait, there he is right there. – [Man Learning] So
again, similar to ours? – [Man Dissecting] Yeah
similar lungs. They’re elastic. They’re not nearly as structured as hours. These are very kinda more just like sacs. Ours have a lot of
internal structure to them. Part of that’s because
frogs use their skin so much for oxygen so they
don’t need complex lungs. You can see, and these
would expand of course as they’re inflated, and they’re paired, so there’d be a lung on each
side. Right and left lung. So here’s the right one, that’s the left. – [Man Learning] So is
there any reason we can’t remove some of this
and identify the other. – Yeah I think that’s
probably a good idea. Let’s take maybe the, we’ll
just go ahead and take the whole liver and the
digestive system out I think. – Okay. – And so here, I’ll get the, let’s see if maybe we can
get the stomach up near the source and then, – [Man Learning] So
basically you’re removing the digestive system. – [Man Dissecting] Yeah
and then we’ll kinda see, – [Man Learning] That way we
can see the paired testes. – [Man Dissecting]
Right and kinda cut some of the mesenteries and as that comes down here, cut some more mesentery out, and then right here’s the large intestine, so that’s where it exits and cut that. So there’s our digestive system. You can actually see the
stomach and the intestine and the large intestine. – There’s the kidneys show up nicely. – Yeah so then we can
just clean up a little of those fat bodies, I think again. There we go. And yeah, and then these
show up really well in these. These paired kidneys. – [Man Learning] They function the same similar to ours then? – [Man Dissecting] Right
they filter the blood, body fluids, take out
waste and remove those, so the kidneys, and that
would be the urinary bladder, would pick up, store some of that water, and then again be released through the common opening, the cloaca. So a lot of times frogs that young, frogs or toads in particular, they’ll pee on you when you,
you know when you pick them up, because they’re storing a lot of water in that urinary bladder and one of their defensive response is then
to release that water, which is being stored. It’s also why you find them
in wet areas a lot of times. They can absorb food through
their skin, or absorb water, I’m sorry through their
skin and pick that up. Yeah so nice view here of there’s the testes, part of you know that side,
part of the urogenital system, and then the paired kidneys going down to the urinary bladder. And other than that you kind
of see that’s pretty much where we’re at. – Should we go ahead and
cut up the upper region? – Yeah go look at the
circulatory system now. We’re gonna get that liver out of there. So you can see the heart
right up here above the liver, but I always like to
open it up a little bit, you have to use scissors and
cut through the bone now. Kinda hear that crunch. – [Man Learning] This is looking at three chambers in this one? – [Man Dissecting] Yes, yes, amphibians. – [Man Learning] A little more advanced. – [Man Dissecting] Fish have two chambers. Amphibians and reptiles have three. So they have two atria.
A right and left atria, and then only a single ventricul. So the blood is separated in the atria, but it then comes back. So the pericardia, the heart surrounded by the pericardium, pericardial sac, and as we kinda clean that away you can start to see the
different parts there. I’ll get my little forceps here. Pull some of that, pull some
of that connective tissue away. – [Man Learning] This will
expose the atria on top then? – [Man Dissecting] You have
to be a little careful here. You don’t want to tear anything. Yeah it should expose
the atria and the sacs. – [Man Learning] We’ll
break and then we’ll show, – [Man Dissecting] Yeah
we’ll show the injected one. Which will show the blood vessels better. Sometimes the uninjected
ones show the heart. So here’s our liver again for reference. Then our coracoid, the
bone right across here, then right underneath that is the heart. So you can see it’s a
pretty large structure. Vertebrates have a closed
circulatory system. Blood always staying inside the vessels pumped under pressure, so
there’s rapid circulation times. And so you have the right
atria, the animals right, and so blood would enter from there, go into the ventricle, as it’s
pumped out of the ventricle some of it would go to
the lungs and the skin and pick up oxygen,
return to the left side, back into the ventricle
and then out into the body. So there’s somewhat a
little bit of a mixing of oxygenated and deoxygenated
blood in the ventricle, but it’s still, you’re pumping the blood out to the body under much more pressure now with this three chambered heart. So it’s definitely an advance. – Anything else for you to mention as far as any of the systems then or does that cover most of ’em? – Well I’m trying to think.
We’ve got the lungs here. Our lungs here again show up a little bit, a little better in that view. – [Man Learning] Paired. – [Man Dissecting] Pair, Pair of lungs. The liver. We took out
the digestive system. Here’s the kidneys and
the urogenital system. So of a male anyway, I think we’ve pretty much, pretty much covered that. – This point we’ll probably
break then and we’ll come back and show a comparison. – Yeah come back and we’ll show a female and then we’ll show an
injected specimen as well so they can see the difference between… – The larger.. – Oh yeah and we may well
take a look at our big frog too just for, just for fun. – Sounds good. – All right. – Now we’re gonna look
at difference between male and female. – Yeah. Male and female here comparison. Two similar sized bullfrogs,
but you can see in this case, the female in reproductive
condition on the left over here is much more full body cavity, with full of the fat
bodies and the ovaries and things like that. So let’s take a look at
her just real quickly. You can see again here’s
the liver for comparison and here are these large fat bodies again that are pretty extensive. I think I’ll just go
ahead and remove those. Might need a scalpel for that. – [Man Learning] That’s
again storage for fat. – [Man Dissecting] Yeah storage of fat, again not only for body condition, but in this case to produce eggs. – [Man Learning] I should ask too, as far as producing eggs,
is this internal, external? – [Man Dissecting] Yeah well they produce, of course the female produces the eggs, but it’s external fertilization, so she will release
the eggs into the water and then the male will fertilize them. So the male usually is right there, usually even grasps
the female in his arms, and then as she, deposits the eggs, he will fertilize them. And then, we were talking
about earlier maybe, interesting with parental care in frogs, frogs are one of the amphibians, it does sometimes show some parental care, so they’ll guard the territory
where the eggs developing, keeping predators away. There are some tropical frogs
that move the eggs around, carry them around, sometimes
they move the tadpoles around. So there’s a varied and fairly extensive amount of parental care in frogs. Anyway, so here’s our female again. So as we take the fat
bodies away we can see again the body cavity really full
of, here are the ovaries. So all those follicles are there that’ll potentially become eggs. So female’s capable of producing large amounts of eggs, and you
can see they’re paired. We didn’t take everything
off on this side, but there’s ovary on each side. – [Man Learning] Kind of
have that grainy appearance. – [Man Dissecting] Yeah kind
of that grainy appearance again because of the follicles
being round and eggs. And of course the eggs
then released by the ovary will pass down to the
oviducts and so you’ll see those are pretty extensive again. It’s a large large
amount of coiled oviduct. So the eggs will move down the oviduct toward the posterior end of the animal and as the eggs mature and
the yolk is put on them and somethings like that. So all that’s taking place as it travels down this long long tube. The oviduct, and the oviduct
again will exit at the cloaca. So the female’s, the mature
eggs then would be shed into the environment through
the cloaca by the female. So in this case this
female’s probably getting really close to the reproductive. – [Man Learning] ‘Cause
we have seen a few, but not nearly this big. – [Man Dissecting] Yeah. It’s gonna vary again, your frogs, whether they’re, what season
they’re in, how old they are, and things like that. So you may not always see
ovaries that well developed. It’s real easy to see an ovary. Much different than the testes. – Here I’ll lift this one up for you. – So the male again, just much less stuff. We took the fat bodies
out of this one already, but here’s the again the two kidneys, and then here is a very small testes here. This is fat body again. So then the testes and the
ducts are hard to pick up, and the sperm would move down
along the urogenital track, and into the cloaca
and then the male would release sperm into the
environment as well. So these males probably
not in reproductive condition in this case because
the gonads are so small. As they approach breeding
season the gonads get larger, produce larger amounts of sperm. – They may get confused
too by the spleen there comparison to the two. – Yeah you gotta be careful,
yeah about, about that. Oh here’s the spleen right here. Spleen’s darker. These will often be white. These probably had a
little blood going to them. Right now they might be
getting ready to grow, but the spleen’s dark
up in the mesenteries. The testes are down here more
associated with the fat bodies and closer to the kidneys. – [Man Learning] Again paired. – [Man Dissecting]
Paired, yep paired kidney. – And then as far as the injected. – Yeah and this is an injected frog. We can see now compared to
earlier what we looked at, you can see the heart, you
can see it does pick up a lot of this latex around the heart, but it allows you to
trace the blood vessels. So here is we see, we talked
about the blood coming into the right side of the
heart, the animal’s right, going down the ventricle,
then it comes out. As it comes out of the ventricle, it comes into these
large conus arteriosus, and then splits into
two systematic arches. One of these going up to
the front of the animal. I think this one actually goes
up to the front of the animal and the one on the
right side of the animal dives down into the body cavity taking oxygenated blood to all the tissues. And in fact, we haven’t tried this yet, but there’s kinda so much stuff there I don’t know if we can, we
can see all the blood vessels on how the color there. You can see the blood vessels now coming out to all the different organs, coming to the stomach,
coming to the pancreas, to the spleen in this case. So if you dig down in there enough you can see probably the large vessels, you know the large aorta, dorsal aortas, that’s carrying oxygenated
blood down into the system. – [Man Learning] This
looks single injected probably right? – [Man Dissecting] Yeah I was only seeing, not showing the blue
very well in this case. Yeah so I think it’s like single injected. So I think we’re hitting
mostly the arteries. – [Man Learning] But you
can really see in the lungs. There’s a lot of blood vessels. – [Man Dissecting] Lot of blood vessels. Again if you wanted to trace, you know, all the different arches
down into the legs, the femoral arteries and things, carotid arteries to the head, you could do that, but
it does take significant amount of work to do that, to clear up, to clean the blood vessels, and trace them to all the
different areas that they go. – Anything else you
wanna add about the frogs or is that pretty much
covered most of the system? – Well I think that covers it. Like I say again, very
similar to you know human, other vertebrates, you know. We have, you know, the
stomach and the intestine, the gallbladders, the
spleen, the pancreas, all those pretty much, you know different in sizes and things and length, but the same basic, basic
structure that we see in all vertebra. So frogs can be a nice
way to study that plan without you know into the greater expense and more probably greater amount of time dissecting a fetal pig or a mink, or something like that. – Well thanks so much Dale. – Well yeah these are great. They’re great animals. They’re interesting in a lot of ways. Fun to watch too. Just all the types of behaviors that they do out in the wild. – I hear ya. – Okay. (upbeat music)