this video is sponsored by brilliant find the link in the description below 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 i want to mention one last thing we want to 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 [Music] 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 the skin dissection from the left side of the head or in other words 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 clippers 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 want to 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 or 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 going to 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 cells 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 to 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 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 have 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 a hip flexor abdominal muscle they're all going to engage in a similar way so let's stick with the biceps because that's a muscle we all know and love and if you look closely here i'm probing specifically the meaty or the red portion kind of brownish in this particular cadaver but this is the contractile portion or the muscle belly and each muscle belly of a muscle is made up of multiple 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 these 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 these 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 got to 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 kind of 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 kind of 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 kind of see they're bound together and kind of 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 want to 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 this structure called the sarcoplasmic reticulum not the scale just a little diagram here but 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 conformational change or a 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 kind of coming down they would bind to actin and as soon as they bind they ratchet and this can 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 costs an atp to release it so muscle cells can be pretty expensive from an energy standpoint but it does a pretty good job because 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 have to get the calcium out of there because if it's in there it's going to keep binding to ttc and keep the muscle contraction sustained but we will actively pump it out back into the sarcoplasmic reticulum which costs 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 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 kind of think of it as degrading a little bit and that calcium starts to leak out into the sarcomere what is it going to 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 to 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 test 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 because 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 want to 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 situations is one of the most important things you can do during your pursuit of scientific truth and that's why i'm such a big fan of today's sponsor brilliant brilliant is an interactive online learning platform for stem subjects that is science math logic and computer science their courses on scientific thinking are the perfect way to start your journey to training your scientific mind these courses are far from boring they are completely interactive and engage you in a way that is both challenging and fun and take it from someone who's had to go through a lot of school you need that perfect blend of challenge fun and interactivity that these brilliant courses provide working through these courses will help you develop the problem-solving and critical thinking skills necessary to tackle any scientific challenge that comes your way if you're interested visit brilliant.org iha or click the link in the description below and the first 200 people will receive 20 off their annual subscription thanks for watching and we'll see you in the next video [Music] you