[Warning: This episode contains material that may not be suitable for all audiences. Viewer discretion is advised. Seriously.] [The Brain Scoop Grossometer: EXTREME – some blood, skin removal, visible organs] This series of episodes is brought
to you by the Field Museum, the Harvard Museum of Comparative Zoology
and the National Science Foundation. – Hey! We’re here at Harvard’s Museum of Comparative
Zoology with Dr. Kenneth Angielczyk. – I am the Associate Curator of Fossil Mammals
at the Field Museum of Natural History. – And we’re here today
to do some experimentin’ on some dead animals. To learn
more about those fossil mammals. It’s gonna be great. Let’s go! [Wait!] [Before we start the dissection] [we have to explain synapsids.] – In the episodes that
we’ve been doing so far we’ve talked a lot about synapsids
but you might not know what they are. So a synapsid is a member of a group of animals
that includes living mammals as their sort of living relatives but also a number of fossil forms that in some cases look very different. And all of our different kinds of synapsids
are characterized by one feature, this opening back here,
in the back of the skull, just behind the eye socket. That’s an area where jaw
muscles attach to the skull and all synapsids have those. So if you compare an animal like this, this is Eothyris, one of the most primitive
synapsids that we know about, to a living mammal, you can see the skull looks very different. But we have that same synapsid temporal opening
back here in this skull the way we did in Eothyris. So this is an animal
called Massetognathus, which is a more derived, or a
more advanced kind of synapsid. You can see that it has a skull that
is much more similar to our living mammal. Synapsids have undergone a massive amount of
evolutionary change over the course of their history, and so there is actually very
few features other than that, that you can point to
in all synapsid specimens. – And that’s kind of why
we’re here today, right, so we’re going to be looking
at some of the changes in the other parts of the
skeletons of these animals. And primarily what is it
that we’re going to be looking at? – We’re interested in the evolution
of the backbone of synapsids. So, living mammals have very distinct
vertebral columns or backbones today that have lots of different regions and they have very specific
functions in each of those regions. And if we look at
more primitive synapsids, they have a much more uniform
backbone or vertebral column. We can only get so much
information out of the fossils. We need to look at some living animals that have their soft tissues, like muscles, attached
to the backbone or vertebral column. And what we can do is learn about how the
backbone functions in those animals and then go back to our
fossils and essentially model how those vertebral columns
would have been working when they had all of their
soft tissues attached. – So, we’re going to the Prep Lab. [43 minutes and half of a sandwich later] We are here in the Preparation Lab at Harvard’s
Museum of Comparative Zoology with Dr. Katrina Jones.
Katrina, what is it that you do? – Hi Emily. I’m a researcher
here at the Museum and I study the anatomy
and evolution of mammals. – And that is what we have
here in this bag in front of us. – Exactly, yeah. So this is a fisher cat. And today we’re going to be
dissecting out its vertebral column so that we can do experiments on it. – But it’s not– it’s not a fish, kind of, it’s a derived fish, and it’s not a cat, it’s like a big ferret. – Yeah, kinda like a giant ferret, otter. So the skin was taken off and has gone to be used in our collections and
all the organs have been taken out but now we need to remove the head, the limbs, and get down
to the vertebral column which is what we’re interested in. – Let’s do it! – Should I grab this end…
– Yeah, you can grab and pull it out! – Oh, oooh! Oh, boy! You can kind of already– you–
if I’m gonna hold this guy up– you can already sort of see– Whoops, now it’s bleeding on the table. [laughter] um, that the– the ribs, the thoracic vertebrae and all
the muscles that attach to them are kind of contained in that area and then
there’s nothing here at a lumbar region. – Yeah, so mammals actually have a region
that’s free of ribs called the lumbar region and that’s different than some of
the ancient mammal ancestors that you were looking at earlier,
the synapsids which had ribs pretty much all the way along their– their, um, trunk. – Yeah, then you can kind of see
where like that would’ve– that would’ve perhaps inhibited a bit of movement, a range of motion down there.
– Yeah, definitely that’s one of the factors, but also the individual
shape of the vertebrae and how they fit together is really
important for determining how much mobility can happen at each joint and that’s what we want
to get a handle on today. Okay, so you want to take–
we’ll start with a forelimb. – He pooed on me. Yeah, sure.
– Yeah, he probably did poo on you. Sorry about that. – That’s okay.
– It happens. First thing we’re gonna do is we’re
going to remove a forelimb. So what we’re going to do is cut
down the midline along these – this is the pectoral muscles. So… loosen this up… release that connection… – Well, that’s, wow, that’s cool. So I can
actually see the different muscle that you just cut off. – So, yeah, so that was the pec
major that we just, we just… we call it “retracted,” just retracted it, and so now I’m gonna cut through
this connective tissue of the neck so that we can remove the
connection with the forelimb there. – So what is it you’re kind of cutting
the fascia between the muscles? – Mhm, so some muscle attaches
into bones to move bones but some muscles actually
attach to other muscles and they do that by attaching to these
like thick sheets of connective tissue that we call fascia. And that sort of helps them to move. And it’s kind of cool when you
think about all the different things that mammals do with
their arms, like bats flying or like, you know… Wales swimming…
– Wales swimming… – Yeah, exactly. Like a brachiating primate
swinging through the treetops… There’s a lot of different functions.
– A lot of googling, a lot of facebooking… – Mhm. Exactly. Yeah, so, this muscle serratus ventralis
actually has muscle fibers that insert in each rib,
so it kind of looks jagged and that’s where the
name comes from. – So it goes all the way from
the back to individual ribs. – Mhm. Then this is quite cool here.
This is what’s called the brachial plexus. So this is a really dense web of nerves, so this is how you get nerve impulses in to move the muscles and sensation out.
– Wow. – So I’m actually going to cut
through the brachial plexus. Sorry brachial plexus! – Oh nooo!
– Off you go. – Now he can’t use his arm.
– Yeah. Very sad.
– ‘Cause he’s dead. Also that. – Notice how I’m dissecting
a lot with my scissors. – Yeah. – Even though it’s called dissect,
ideally you just want to split tissues along their natural planes more than
actually cutting through tissues. – So you’re just, you’re
just separating things. – Separating things, yeah. – Whoa, this looks nothing
like an arm anymore. – Yeah. It’s easy to get disoriented once you have it
detached from the trunk. – Yeah, it’s also missing his little hand. – Okay, so we’re gonna work on this other limb now. Maybe if you wanted to have
a go at doing something, you… – I’d love to! – This is the pec muscle, which is here,
which sort of flexes the arm like this. So what you’re going to do is
detach it from– from the trunk. Start with the scalpel and
then when it starts coming loose you can actually just get
in there with the scissors. – So like that?
– Mhm. – And then use the scissors…
– So then you can… I’ll take that… And you use the scissors
and you kind of pull it towards me to get some tension and
then you sort of… – Did you do… I’m trying to mimic your technique. – Yeah, you sort of spread apart — to feel how the tissues just spread
along the natural plane and then where there’s
a connection, you just snip. – Like right there? – Yeah. So– Yeah. So that’s where the muscle
is actually inserting onto ribs. So we have to cut that. – This guy has an
obscenely thick neck. – Yeah. I feel like this is an aggressive,
really muscly male that we’re… – Like he was probably getting some stuff done. – Mhm. Probably didn’t want to mess with him. – No. – Okay, so we’re definitely making
progress now. – What’s holding it on down here still is the… the serratus muscle. Exactly.
– Serratus muscles. Yeah. – And what we have over here…
We saw earlier… – The connective..
– The brachial plexus! – Yeeah, that one! – That’s amazing. They are–
I mean you call them cables. They are like cables. – Mhm. It’s like data cables.
– Data cables. Communicating information
from the brain to the– -If i spend too much time
thinking about that, I just have an existential crisis. Like, oh gosh, there are so
many things happening in my body right now
that I don’t think about! And then I’m cutting them! Oh noo! Okay.
– Ooh, there we go. There’s actually like a web of muscle that runs
all the way of the neck called platysma and it’s what sort of allows you to op– one of the muscles that helps open the jaw. It’s kind of cool because
whales have really giant ones. – Whales? – Mhm. Helps them to push the
water when they gulp feed. – Like baleen whales? – Mhm. People think dinosaurs are cool
lbut really mammals are so much cooler. – Hear that, guy? You’re gonna start some stuff
in the comments of this video. – Okay, so there’s only
the serratuses left so what I’m gonna have you do is we’re gonna put it like that, you’re gonna hold it and then you’re
just going to run your scalpel… – Sure. – And just cut that… And then
that’s gonna bring the limb off. – Just like that.
– There you go. You can have a look. – Another limb. Two of ’em. Wow. – Okay, should we do a head next?
– Yeah. Lots of important things connecting
the head and the body going on here. – Yeah. I mean, I would hope there were important
things connecting the head to the body. Otherwise I’d be a lot more likely
that it could… fall off. – Yeah, that would be… that
would be bad news. So we’re working our way
through these layers of muscles, hoping to get to the joint that
connects the head and the neck. It’s called the atlanto-occipital joint. – There’s just one joint? – Mhm. – That attaches the head to the neck? – That attaches the head to the neck. Exactly. – What happens if you cut it? – Then your head falls off.
– No way. – You’ll see it’s quite hard to get to.
– Okay. We’re still working our way through
muscle layers trying to get to it. So… it’s not something that’s
gonna happen overnight. So you don’t have to…
– Okay. – Don’t have to lose
sleep over it, Emily. The top two vertebrae mammals– The two that are closest to the head
are really really really weirdly shaped. So that the one that connects the
head and the neck, the atlas, only allows movement like this [nods] and the one beneath it, the axis, only
allows movement like this [shakes head]. So it’s like the yes-joint
and the no-joint. And they work together to
produce all the other movements. – Like a bobblehead. So you’ve got a lot of these neck
muscles kind of dissected off. – Yep. And we can actually start to feel
the joint between the head and the neck so if you just pinch with your thumb
and your forefinger right there and I’m gonna do a
yes-action with the head and that’s where you’re feeling is
the atlanto-occipital joint moving and that’s what we’re gonna try and
cut through to separate the head off. – I mean it’s probably for the best that
it’s difficult for your head to be removed. – Almost through. Okay, I see. Ready? – Yes! Get it! There you go! Ooooh!
– That’s fine. – And it lost its head. There we go.
– So the head and all of the neck muscles. – It’s somehow more disturbing with
just like the neck muscles as a part of it. “How’s it going, Katrina?”
– Very cool. – I’m good, thank you,
dead fisher head. [untintelligible]
– Yeah, there we go. We’ll just leave this here. – Okay, I think it’s time for
you to do the honors. Remove the baculum. – Alright.
– Since you’re wearing the baculum earrings. – I’m– Yeah.
– So you’re just gonna cut along this connective tissue here so… Mhm.
– Here? I’ve never so surgically
clipped a penis bone off. – Great. And one on that side too. – Wow. I feel a bit…
– We can keep that, we can keep this as well. You know, someone might be
interested in studying it one day. You wanna cut through the urethra? – Here we go. – There we go.
– Keep going? – Yeah, just… just take it all off. – Take it all off. – There we go. Perfect. – Alright. Well… Just lay that out there. – All done.
– It’s the bits. This just saline solution, we gotta
keep those muscles hydrated. Hydration’s important
even post-mortem. – So this is like the equivalent
of hamstrings in humans – It’s kind of the groin area.
– Mhm. So I’m just running the
scalpel along the pelvis and cutting all the connections. Okay, and then we’ll cut the quads.
– That’s huge. – Okay, so now all that’s left
connecting is the head of the femur into the acetabulum, which is the… – So that ball and socket joint…
– Ball and socket joint. I’ve just cut into the
opening of the joint there. – I can see it, yeah. – So now we’re just cutting
the ligaments. Okay. So we’ve opened up… the capsule of the joint, the– So–
– Ooh. – This is the head of the femur. And that fits in here into
the acetabulum, and see… I put my probe under here,
there’s like a connection. – Yeah.
– That’s called the ligament of the head of the femur and that actually keeps
the femur in its socket. So if you want to do the honors, this is gonna
sort of allow the whole thing to just pop open. You take the scalpel and cut through
the ligament right by where my thing is and it pops out. Once that’s cut. – That’s it. And then the femur’s so tiny compared
to all the muscle that’s around it. I mean the bone is just not even
as wide as my pinky finger. And then all these other
muscles are just coming in and… – Yeah.
– This is a powerful animal. – Okay, you wanna have
a try with the other limb? – Sure! – Yep. – I can feel the bone.
– And then if you wiggle… You can feel… Okay. So
you already got to the… to the joint there.
– Okay! – And now we’re gonna
open up the joint capsule. So can you– want to put
your finger and feel where it is? – The joint– Oh, it’s right there! – Yeah. Feel it?
– Yep. – Great. So then… Cut where
you felt the joint moving. – And you just keep cutting around?
– Yeah, so you just cut into the ligament, the… – There it is! I just don’t want to cut your finger. Right there.
– Right, right, right. – That’s good.
– Whaa, I did it! – There we go!
– Aaand the leg is off. – The leg is off. Right. – We’ll just put that over there,
make sure we’re hydrating those legs. – And so now what we have
left is the vertebral column, the pelvis and the ribs. And so before we do our experiment,
we’ll also remove the pelvis and we’ll remove the ribs. That takes kind of a long time so…
– Yeah. – We might skip to the… to the next specimen.
– Yeah. – ‘Cause we already have it,
like a cooking show. Already done.
– Mhm. – So this is the one that
we just dissected. – So the next step would be to actually remove the rib cage and to
start cleaning off some of these muscles. These are called epaxial muscles, which means muscles that
run on top of the spine. So I’ve started to do
that in this smaller fisher that we have from earlier and one thing that we can
see here which is super cool, notice how there are really
really long strips of muscle running all the way down the back. And this is kind of a
neat mammal feature. So if you were to look at the
epaxial muscles of, say, reptiles, those– the muscles
would be much shorter. But we have these really long–
they call them tracts of muscles. So that when the spine
wants to flex like this, they can contract and they can form
the flexion and extension action that we know is really important when
mammals are using their asymmetric gaits like galloping and bounding. So this is sort of before and
then after we remove the ribs and all of the muscles, we end up
with something like this. And then notice how flexion,
extension is happening a lot here but if we do twisting, there’s no
twisting happening down here and that’s because the vertebral
joints down here lock together and prevent twisting whereas those up here can
move by each other. – They– Yeah, they help enable the twisting.
– So you can sort of see them twisting. – So do you… Do you hypothesize that those
early synapsids like dimetrodon or edaphosaurus, that their spine was more
like the lumbar here or more like the thoracic? Like, was it more or less flexible? – It was less flexible, but
when you look at the vertebrae, they don’t look quite like
either thoracic or lumbar. From the shape of
the joints, we suspect that they might have been
able to do more lateral flexion but we don’t think that they
were able to do any of this… – So they kind of moved back and forth
– … bending. – like a lizard.
– Mhm. Exactly. And we hypothesize…
– And they weren’t galloping. – … that evolution of specialized
joints which allow bending, flexion, extension like this, might be related to the evolution
of asymmetric gaits of mammals. So the division of the vertebral
column interior regions is controlled by a set of
genes called the hox genes. – So it’s like, it was the evolution
of the genes that enabled the… the evolution of the morphology of the spine.
– Mhm. Well, yeah. I mean it’s the genes
which evolve and it’s nice here because we have such a direct link so we can clearly see that where
a particular gene is expressed, that’s where a particular
region forms in the adults. So if we can measure the
presence of different regions based off of vertebrae
in the fossil record, we can infer the expression of genes in
animals that lived millions of years ago. – So you’re doing genetic research on
animals that are like 200 million years old. – Indirectly, indirectly, by mapping out how
regionalization has changed through time. – That’s pretty exciting. That’s pretty cool stuff. – Very exciting. – Welcome to the 21st century. Awesome. [It still has brains on it.]