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Thinking about the dead and working with dead bodies is something that we obviously do on a
day-to-day basis here. So, you can imagine that we get tons and tons of questions from students
obviously about the anatomy of the human body because this is an anatomy lab
but I can't tell you how many times we get questions that start something like
this - "Is it true that after the body dies, this or that can still occur?"
You've probably heard some of these claims. Claims of body still moving, making noises,
things still growing, and even physiological processes still occurring? So in this video,
we feel anatomically obligated to start a series on the most common myths that we hear about bodies
after they die and before we jump into it, I wanna mention one last thing - we
wanna say thank you and recognize all those who donate their bodies to science and education.
We would not be able to educate students in the same way
without their priceless anatomical gift. And with that said, let's jump right into this.
[Intro]
Myth number one, hair and nails continue to grow after death. Let's just jump right into this one
with one of our skin dissections that we have here. So, this is a skin dissection from the
left side of the head or in other words is the left side of the scalp here and if you
look closely, you can definitely see there are hairs still in this portion of the skin.
Now, a cool FYI about how bodies are prepared - When body donor
programs prep bodies for cadaver labs such as ours, they remove the hair
of the head essentially with clip kind of the equivalent of like a buzz cut
and you can see that those hairs remain on this particular dissection. Now, one other cool thing
about this dissection is that the body that this came from, we've had since December of 2012
and I can assure you, since that time and right after we even received the body, there
was zero hair growth coming from this portion of the body or anywhere else for that matter.
So, for us to even more fully understand why this is a myth, it helps to understand some
basics about how hairs grow. So, if you come to our cute little skin model here,
you can see little fake hairs erupting from our model here but this portion of the hair
is referred to as the hair shaft. In other words, hair that's outside of the skin is referred to as
the hair shaft and this portion inside the follicle is referred to as the hair root.
All of us have a pretty good idea that if we pulled that hair or plucked that hair out,
we'd have this hollow space or this hollow bag and that's essentially the follicle and it would
be empty until a new hair grew but speaking of hair growth, for us to fully appreciate that,
we wanna go down to the base or the bottom portion of the follicle and we'll zoom in there.
The base of the follicle or that bottom portion is referred to as the bulb and
the bulb has some important structures or cell layers that we need to discuss.
There's something called the hair matrix and that is a layer of germinal cells. In other words,
cells that can grow and divide and as those cells divide, think of one cell copying itself,
it pushes a cell up into the follicle and it's gonna make another copy though. So, the cell
that was first copied here will get pushed up from another copy and pushed up and pushed up
and pushed up and as those cells continue to grow and divide and grow into the follicle, that
contributes to the length of the hair or other words, we see it as the hair growing outward.
There's another structure we have to mention and this is an indentation or a nipple-like
indentation in the bulb and that is called the papilla of the hair and inside that papilla are
important little structures called capillaries or tiny little blood vessels. Those tiny little
blood vessels are essential for the hair matrix or those cells that are dividing
because it provides the nutrients for cell division and if we don't have those nutrients,
say what happens when somebody dies and blood flow ceases, hair growth and cell division
cannot continue on and that is again why we don't get hair growth after a body passes away or dies.
Now, nails work very similar. If I show you this other cadaver dissection here, you can obviously
see the fingernails here. Let me pull that into view here and here's the main portion of the
fingernail but just underneath the skin kind of at the base or below here which we would say proximal
to the nail is the nail root and even further proximal, a little bit further down here on the
screen, you would actually see something called the nail matrix. Very similar to the hair matrix.
Those nail matrix, again, will divide and continue to add length to the nail over time but again,
without a blood supply those nail matrix cells can't divide and contribute to nail length.
So, that helps us debunk myth number one.
Myth number two: Bodies sitting up in a morgue or in a lab. I mean could you imagine if this
actually happened? Full disclosure though, this is not the first time that I've done this before,
I may have done it on a Halloween when we had students come through during a lab class - grown
adults screamed like children as they felt the zombie apocalypse was upon them but when it comes
to this, literally sitting up after death, whether I did it quickly like I did in this example or
even if I did it more slowly and more zombie like, those are still substantial muscle contractions
of multiple muscle groups. Like my abdominal muscles had to get involved, my hip flexors
and since I did it zombie like, I had to you know, get my shoulder flexors involved as well.
Now, that's just not going to happen when somebody has died or passed away
because even just to engage those muscles, I had to send a signal from the motor cortex of
my frontal lobe, down my spinal cord, out various nerves to engage those various muscles. So again,
not happening after somebody died and if somebody does raise up on a lab table,
they're not dead or we're dealing with things of biblical proportion if you're a Ghostbusters fan.
Now, some people might say,
"Jonathan, what about rigor mortis? Isn't that what happens? Muscles contracting or stiffening
after death?" Well, we need to discuss what rigor mortis is actually truly capable of
and how forceful of a muscle contraction that could cause and to do that, we just to talk
about general physiology when it comes to muscle contractions and how that applies to rigor mortis.
So, if you take a look at this right arm that we have here, we've got various muscles that we
could choose from because each muscle, whether it's a muscle like the biceps
or hip flexor abdominal muscle, they're all gonna engage in a similar way.
So, let's stick with the biceps cuz that's a muscle we all know and love
and if you look closely here, I'm probing specifically the medi - or the red portion,
kind of brownish in this particular cadaver, but this the contractile portion or the muscle belly
and each muscle belly of a muscle is made up of multiple muscle cells or muscle fibers.
And again, if you look closely you can actually see those fibers in this
vertical orientation up and down and when those fibers contract,
it shortens the overall muscle and you move the skeleton. Now, to fully even more understand that
or understand rigor mortis and how this truly work, we're gonna have to go even a little bit
deeper and look at this at the microscopic level and zoom in and zoom in and zoom in.
So to do that, we're gonna go on a little magic school bus ride and head to the whiteboard. So,
to the whiteboard. Welcome to our rendition of a sarcomere. Now, what in the world is a
sarcomere? Well, remember, we went on a little magic school bus journey to the inside of a
muscle cell or muscle fiber and as you saw in the cadaver, muscle cells are the string-like
cells relatively long compared to other cells that have these sarcomeres inside of them.
These are the functional unit of contraction of a muscle cell and there are multiple sarcomeres
inside each muscle cell stacked end to end to end and this is just one. So,
imagine them connected at these end portions end to end to end throughout the length
of the muscle cell. Now, for us to fully understand muscle contraction and therefore,
rigor mortis, we gotta talk about these red structures in green and blue structures as well.
The red is referred to as the thick filament and the thick filament is made up of a protein
called myosin. One myosin protein or molecule kinda looks like a golf club.
So, the head of the golf club would be referred to as what we call a myosin head where you'd actually
hit the ball of the golf club and then the shaft of the golf club would be the myosin tail. So,
kinda think of a bundle of golf clubs just stacked together right here.
Now, the green is referred to as the thin filament and the thin filament is made up of a protein
called actin and each little circle or ball there is an actin molecular actin protein and you can
kinda see they're bound together and kinda twisted in on themselves. Myosin and actin love each other
and they want to bind together but I joke around with students and often say, well, we've got this
other protein complex that I nicknamed "the protective parents" and it's truly made up of
two proteins called troponin and tropomyosin often referred to as the troponin tropomyosin complex.
And why I call them the protective parents is that it's blocking those binding sites
making it so myosin and actin can't bind together.
So, this is the relaxed state of a muscle but if we wanna contract a muscle,
we send a signal through a motor neuron from the nervous system and when that signal comes down
onto the muscle and says "engage", it tells the muscle cell essentially to release calcium from
the structure called the sarcoplasmic reticulum, not to scale, just a little diagram here.
When the calcium is released from that nervous system impulse or that nerve impulse,
it floods around the sarcomere and it binds the calcium specifically to TTC and it binds to it
and causes a confirmational change or shape change just enough for it to move out of the way
so myosin and actin can bind together and if you think of all these myosin heads kinda coming down,
they would bind to actin and as soon as they bind, they ratchet
and this continue to create this ratcheting process where they ratchet, release, reset,
and ratchet further down and overall this whole sarcomere would shorten and if you
think of the other sarcomeres downstream shortening as well, that would create
this shortening of the whole muscle cell and therefore the whole muscle and we can move.
It's remarkable how fast that actually occurs. But one thing I didn't mention that's important
for rigor mortis is when the myosin and actin bind together and then ratchet,
to actually get them to release, you have to burn an ATP molecule. Some of you have
taken biology before and you may have heard of ATP but ATP is an energy source for our cells.
So, every time it ratchets, every time a myosin head binds, it cost an ATP to release it. So,
muscle cells can be pretty expensive from an energy standpoint but it does a pretty good
job cuz we have a lot of blood supply to muscles, lots of oxygen going in there and we can get this
ratcheting and shortening of the muscle. But to have a muscle relax, we actually to get the
calcium out of there cuz if it's in there, it's gonna keep binding to TTC and keep the muscle
contraction sustinct but we will actively pump it out back into the sarcoplasma curriculum which
cost even more ATP. So, lots of energy required to get muscles to work properly.
So, how does this relate to rigor mortis? Again, this is amazing how fast all this happens with
contraction and relaxation of muscle tissue but when we die or when a person dies, we no longer
getting blood supply, we're no longer creating ATP but what happens is the sarcoplasmic reticulum
becomes leaky. Kinda think of it as degrading a little bit and that calcium starts to leak out
into the sarcomere. What is it gonna do? The same thing as an active muscle contraction,
it'll bind to TTC and then myosin and actin will bind together but what's the
problem here and what's the difference between a living muscle contraction?
What did we need get that release of myosin and actin? You needed ATP.
We're not making ATP when we are dead. So, we get that initial tension and pulling from those
initial myosin and actin molecules ratcheting but we don't get that release and further binding
and ratcheting the whole length of the sarcomere creating that whole shortening. So, there's this
initial tension. Not enough to create full-fledged shortening of the muscle but an initial tension in
about the first three to four hours of death but then it starts to relax or loosen within about a
day or 24 hours and the reason for that is the proteins, myosin and actin, start to degrade.
There's enzymes that are being released from the death of the muscle cell and just degradation
of the protein cuz again, the tissue is dying or is dead and then it will just
release and then the muscle tissue will relax. So, rigor mortis is temporary
and not nearly enough to lift the whole body up off of the table.
Now, one last thing I wanna mention for all of you who love to go to the gym and work out your
muscles and get bigger, get huge... This is what you are eating protein for or when you're taking
protein supplements so you can create more sarcomeres. When you stimulate your muscle
tissue for growth, you're going to build more myosin proteins, more actin proteins, more TTC in
order to create more sarcomeres. More sarcomeres equal more muscular force equals more strength.
So, hopefully that gives you guys some cool ideas on muscular strength but also helps us debunk
myth number two. As you can see, there are plenty of myths about the human body and
trying to figure out what's true versus what's fake can be challenging and even frustrating at
times but learning how to think critically and applying your knowledge to real-world
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