Some of you are mutants and the reason I say that is because you have a mutation that causes this
muscle right here, called zygomaticus major, which by the way is responsible for smiling - you can
see that it connects to the side of the lip here so when it contracts, it would kind of
swing those lips up for a smile but if you have this mutation it can cause this muscle
to split. And if it does that, one end of the muscle will actually blend with the
cheeks right here so when it contracts it pulls the skin down and you get a dimple.
So that's right, those of you who have dimples,
you're basically an X-Men and you should be super proud of that.
If you've ever had something go down the wrong tube, this structure right here is
to blame. Its name is the epiglottis and it's made of elastic cartilage.
It's job is to actually block off the airway, which is what you're looking at here,
when you're swallowing food or drink and then it'll go down the correct tube here which is
called the esophagus. But if it fails to do its job, you can see exactly how the food or drink
could go in the wrong tube but this is going to cause a really strong cough reflex because
you do not by any means want any digestible material going into your respiratory tract.
Did you know that this bone that comes all the way at the top of your forehead comes around
and then forms the top ridge of your eye socket, which is called the frontal bone, used to be two
different bones? When you were born, there was a gap here - a soft spot called a fontanelle
that created two separate frontal bones that eventually fused to become this one gigantic bone.
Let's talk about how long bones, such as the femur, get longer during childhood and
adolescence. It has to do with what are called epiphyseal growth plates.
So, if we look at this kind of angle right here,
this is where that epiphyseal growth plate would be on the proximal side of the femur
and then down here would be roughly about where that distal epiphyseal growth plate would be.
Now, what would happen is these things would be loaded with hyaline cartilage.
And that hyaline cartilage would grow and then get replaced with bone which would make the
bone get longer. But those growth plates do close and they close somewhere around
16 to 19 years old. It depends on a variety of factors and once it does,
you're pretty much set in the length of that particular bone.
This gland right here is called the thyroid gland and it's going to rest just below
your Adam's apple or your voice box or larynx, whatever you decide to call it.
And if I were to remove all this connective tissue on top of it,
it would be purple in appearance. But this is going to be responsible for your metabolism,
which is essentially just a fancy way of saying how much energy do cells burn through.
Your heart is capable of surviving outside of your body for up to about five minutes or so
and that's without any assistance from the brain or medical intervention. And
that's because the heart is capable of something called self-excitation, meaning that it itself,
these muscle cells right here which are called cardiac muscle cells,
they're the ones who contract and decide when to contract, not the brain. This is all in effort to
reboot the brain if necessary. If you get some kind of head trauma or brain damage,
the heart will continually beat in an effort to bring that brain back online.
Your heart has nipples! I know that sounds crazy, but it's true. Look at this - I’ve cut a window
into the heart so we can see this. We see this structure right here,
this is called the papillary muscle. And papilla in anatomy means nipple. So,
someone looked at this a long time ago and decided that looked like a nipple. But what you can see is
that it's attached to all these strings. These are your heart strings - they're called the chordae
tendineae and then they're going to be attached to these connective tissue flaps called the cusps.
And what they're going to do is generate tension and pull on those cusps to keep them tight as
the ventricle contracts so that you don't have blood pushing back into the atrium.
You have somewhere between 500 and 1000 different species of bacteria
living and residing inside of this area of your body called your colon.
Now, these bacterial species do a variety of different functions but what they eat is going
to be leftover digestive material that your small intestine didn't absorb into your bloodstream.
So, we can see the end of the small intestine here and it's meeting up with the large intestine. And
then what will happen is there's plant fibers and other types of sugars and all sorts of material
that the bacteria will then break down and provide byproducts such as vitamins and even be important
in immune function. In fact, we do not know what all of the different bacterial species do
and some of them, we just find that if they're gone, it vastly impacts your overall health.
Did you know that as far as we can tell, there doesn't exist
a singular area in the brain that's responsible for intelligence. Instead,
the leading theory suggests that intelligence is more than likely a product of how well the
different areas of the brain communicate with one another. So that means the difference between
your average individual and some kind of super genius isn't about brain size, instead it's more
than likely just about how effectively and how efficiently do the various areas communicate.
Did you know that when you inject Botox, you are literally paralyzing the skeletal muscle
tissue? Botox stands for Botulinum Toxin and it's a neurotoxin produced by certain species
of bacteria. And what it does is it affects the neurons that attach to the individual muscle cells
and it causes them to be incapable of releasing the neurotransmitter acetylcholine.
And without acetylcholine, muscles don't work which means they're paralyzed.
So then the integument, so that means the skin and all the soft tissue on top of it,
those aren't going to have much tension on it because the muscles are just kind of hanging out
and what that does is it just reduces the appearance of wrinkles and age lines.
If you had to guess, how many bones do you think are located in just your hand? 15? 20?
30? 40? Well, the answer is 27. You have eight carpal bones or wrist bones,
you're gonna have five metacarpals - these are the bones that are deep inside of your palm,
and then you're gonna have three bones in each of these four digits but only two bones in that
thumb. But when you add it all up, you're gonna end up with 27 bones in just your hand alone.
I want to show off this incredible brain model provided to us by anatomy warehouse to show the
different areas of your frontal cortex with which you as a human have the largest frontal cortex in
the entire animal kingdom. This red area is called the motor cortex. This is your pre-motor area
and all the pink is going to be the prefrontal cortex - which is especially big in humans.
But this area on the side, this is called broca's area. And Broca's area is almost
always found on the left hemisphere although occasionally it can be found on the right
and it's going to be associated, as you can see, with speech - which makes sense because you
as a human being are the most communicative species on the entire planet earth.
I want to use this extremely cool model of the brain given to us by Anatomy Warehouse
to talk about strokes. So, all these red lines are showing you the vascularization of the cerebrum,
the cerebellum down here and then we can even see it for the brainstem out front.
Now, when it comes to strokes, there are two main types; we have what are called ischemic strokes
and hemorrhagic strokes. An ischemic stroke occurs when
something is blocking - typically a blood clot, but something is blocking the blood vessel
preventing the blood from being delivered to the neurological tissue underneath.
A hemorrhagic stroke on the other hand is when the blood vessel ruptures
and so then there will be bleeding on the brain. And that means the blood can't get
exactly where it's needed to go and it then can't deliver oxygen to the neurological tissue.
Have you ever wondered why we as humans still have a tailbone if we no longer have a tail? You see,
this little bone here is called the coccyx and the reason we still have it is because it serves
as an attachment site for various soft tissues like muscles and tendons and ligaments that all
attach right along it and then fan out along that pelvic bowl. And these muscles have a
variety of different functions - from helping you urinate and defecate to literally just
providing a base - a literal floor so the organs that are above it don't just fall straight out.
Do you think it's possible for this organ right here called the bladder to literally explode
due to having too much urine inside of it? Well, this is definitely possible
because it has happened to many people in the past - many documented cases of it.
That doesn't make it all that probable for most individuals. The reason being,
for the individuals that did have this rupture, most of them had some kind of
underlying disease or dysfunction or condition. For your average individual, the sphincters in
the urethra instead would weaken causing the bladder to empty and you'd just pee your pants.
So let's go ahead and orient you to what you're looking at. We can see part of the uterus here,
we can see some of the bladder, you can see the upper part of the vagina,
we can even see part of the colon - but what I want you to look at is this little
pouch here called the recto uterine pouch or also sometimes known as the Pouch of Douglas.
Now, this little area normally accumulates fluid every single month for the female,
but it also can serve as a place of attachment and
accumulation of endometrial like tissue if they have endometriosis.
So what is a bursa? A bursa is a fluid-filled sac that reduces friction between neighboring
structures - like the skin of my elbow and the bone underneath. You find them over the knee,
the hips - lots of different places where you might have to reduce friction between
neighboring structures. If they get inflamed, you call it bursitis. Every once in a while they get
filled with fluid and you have to drain them. I’m going to show you that in just a second.
So, here's a bursa on the right elbow of a cadaver. You can see we cut a little
hole in there - there'd be some oily fluid in there that would help reduce friction
as the skin moves over the elbow when you straighten and bend the elbow.
Doing okay?
- Yeah.
I want to use this incredible facial muscle model
to talk about this circular muscle going around the eye called orbicularis oculi.
And based on its name, you can tell they named it because it's orbiting the eye,
but you can also see from its fiber orientation that it's going to close the eye. And that could
be a reflexive close, as in you're blinking or maybe if sweat starting to pour down, this muscle
can contract and tightly shut and prevent that sweat from getting inside of your eye.
Okay, so I want to show you something pretty cool - what you got to do is just stick your hand out
in front of you and then just start flipping your hand back and forth. We call this action
pronation and supination. Supination is though you're holding a bowl of soup
and pronation is like you're pouring it out. But what I want you to know is that this entire action
is just one bone moving and that's called the radius. And so, we can see that right here.
This is the radius and then this one's going to be the ulna.
Now, watch as I twist it, you can see that radius is just flipping back and forth while
the ulna is staying completely still. And you can do this for yourself - if you stick your arm out
in front of you, I want you to touch your elbow and then as you move it along, you're feeling the
ulna right there, and I want you to go ahead and flip your arm back and forth like this
and the ulna is staying put. But if you put your hand onto the radius, which is on the thumb side
and move that back and forth, you can feel the radius flipping and flopping inside of your arm.
You see this gigantic organ here? This is the liver, except this liver was not healthy when
this individual passed and we can tell because of this dust coloration right here, right here,
we can see another one right there and even over here. In fact, these are all
cancerous tumorous nodules because this individual passed away from colorectal cancer
which likely began here in the sigmoid colon but then metastasized and spread to their liver.
Let's talk about something that's been suggested to play a role in knee pain - it's called
the quadriceps angle. So, if we pretend this cadaver or skeleton has a kneecap,
because obviously they don't, if we were to draw a line from the center of that kneecap
and go straight up to this point here called the anterior superior iliac spine
and then drew another line going from the center of that kneecap down to the tibial tuberosity,
we would essentially have two lines - one going in this direction and another going
in this direction and that would create an angle. And that angle is called the quadriceps
angle and it's a measurement, essentially of how the femur rests inside of the hip joint.
Now, if I move the femur around, you can see how that would change the angle.
What that means is - and it's been suggested - that say like with females who have wider hips
or maybe you have some kind of issue with how the actual hip joint rests.
That could possibly create pressure differences inside of the knee
which may relate to different types of pain and cartilage wasting inside the knee.
Using this amazing facial dissection model from Anatomy Warehouse, I want to show you
the strongest muscle in the body and that's based on leverage. Not because it's made of
anything different than these other muscles, but this is the muscle masseter. Its leverage
is absolutely insane and that's because this is the primary muscle for chewing or mastication.
And what it's going to do is it's going to elevate your mandible causing it to slam shut or basically
just close your mouth. And it works in tandem with this muscle here called temporalis. So,
these two muscles are really really important for chewing and in fact, the more you chew
the stronger this is going to get which is why you can even see in competitive eaters,
this get to be super thick and strong giving them a more square jawline.
When you get really cold, your muscles are going to start contracting very quickly in an attempt
to warm you up. So you can picture all these muscle cells just going across all just kind of
contracting back and forth. And what's happening is they're consuming energy in the form of ATP
or Adenosine Triphosphate. And when you consume ATP, you actually give off heat. So you can just
picture all these muscle cells just bouncing back and forth and it gives off heat and that's an
attempt to raise your body temperature and bring you away from potential hypothermia.
I want to show you just how thin the epidermis actually is. So, you're looking at skin from the
mid to upper back and if I turn it to the side here, you can see this cross section, and the
majority of that thickness is actually the second layer down called the dermis. So I’m going to get
really, really close and you're going to see this yellow line on top here. That yellow line is the
epidermis. That only gets to be around 50 to maybe 100 cells thick on average depending on the area
of the body which makes it obscenely thin. The majority of the thickness of your skin is going to
be the dermis and then the next layer down which technically isn't skin but called the hypodermis.
Your stomach is capable of two different types of digestion;
chemical and mechanical. So, chemical digestion is going to happen when stomach acid is going
to be secreted into this hollow inside and that's going to bathe the food and break
it down into this pasty liquidy substance called chyme. Mechanical digestion happens
due to these gastric rugae - these stomach folds you're looking at here just grinding against one
another as well as the stomach contracting and moving it around almost like a cement truck.
So, I want to go ahead and remove this chest plate, and the chest plate includes the sternum,
the ribs as well as all of these abdominal muscles. So, as I go ahead and grab this,
I can turn it over, and as I do that, we can now see the inside surface of the rib cage and
sternum and you'll notice as I kind of tilt this back and forth, you're going to see a
shimmer. And that's from the light hitting the tissue on the inner surface called the pleura.
The pleura is a serous membrane that attaches to the inner surface of the rib cage then the
surface of the diaphragm then comes right back around and attaches to the surface of the lungs.
So, you have the same tissue has two layers to it and there's a space in between those layers
that's going to be filled with a fluid - that's the serous fluid. And what happens is that fluid
acts to kind of limit and prevent friction from the lungs pressing against the ribs,
but also provides surface tension - which more or less attaches your lungs to the rib cage so
when these intercostal muscles contract and move the ribs, the lungs go with it and you breathe.
When learning your skeletal muscle anatomy, you're going to learn about two terms called Origin
and Insertion. Origin just means the end of the muscle that does the least amount of movement when
compared to the other end that does the most and that's going to be the insertion. So, if we look
at this muscle here called sartorius - sartorius is going to originate up here at the anterior
superior iliac spine. That's just the part of the hip that it comes off of. And then it's going to
insert all the way down here past the knee in this area called the medial, to the tibial tuberosity.
The thing is, while this is almost always the more mobile end, you can put your body into a
position where this end is actually more mobile. Which would mean this by definition would become
the insertion and this would be the origin which is why a lot of people choose to not
say origin and insertion anymore and instead just discuss it in terms of the ends that it attaches.
But chances are if you're taking an intro class, you're going to hear about origin and insertion.
If you had to guess, and I’ll give you time to guess, how many bones do you think are going to be
inside of the foot? 15? 20? 30? 60? 80? Hopefully not that high,
that would be ridiculous. The answer is 26. You have seven, what are called tarsal bones
or sometimes ankle bones, so that includes like the calcaneus, the cuboid, the navicular
and then you're gonna have five metatarsals going across here.
But when it comes to the digits, you're only going to have two in the big toe,
but then three in the rest of the digits. And so, when you do the math, that adds up to 26.
Now when you compare that to the hand, the hand had 27 and that's because the hand has eight
carpal bones. So, the only difference is eight carpal bones and down here seven tarsal bones.
Okay, so you're looking at the heart but you'll notice that it's covered in
a connective tissue layer. This is called the pericardium. So,
I’m going to go ahead and just reflect that pericardium back. And as I do so you're going
to see this tissue right here which is called the aorta, specifically the ascending aorta,
and as I push it, you're going to notice it compresses and it bounces back.
Now, this is the biggest artery in the body. It's about the size of a garden hose and what's going
to happen is as the left ventricle, which is just below all this epicardial fat, which is normal by
the way - as that left ventricle contracts, it's going to push oxygenated blood to the
ascending aorta, which is then going to start splitting and going to the arms and going down
before it can start distributing to the many different tissues including the legs. So,
it all begins right here with that ascending aorta.
Let's go ahead and take a look at some of the anatomy of the lateral neck. So, we can see this
muscle here called the sternocleidomastoid, and we've cut this, and that allows me to
reflect it back and you're immediately going to see this twine - and that's not - I mean,
you don't come with the twine but that's normal in the sense this is where the embalmers injected
the embalming fluid into the carotid artery and then they just closed it up with that twine.
We can see an artery here - this is called the subclavian artery as it's
turning into the axillary artery, but I want to focus on this right
here. And this may not look all that special as I try and spread this out,
but this is a bundle of nerves or at least the beginnings. This is the roots trunks
and the beginnings of the divisions of a giant network of nerves called the brachial plexus.
This little thing right here is going to turn into 17 different nerves that
are going to innervate parts of your back and your entire arm. And as we can see,
it's coming just behind this muscle here called anterior scalene and then as I grab it,
it's also coming between this muscle here called the middle scalene.
If you could unfold or uncoil your brain, which you can't, that's a physical impossibility,
but if you could unravel all of this, it would equal about two square feet which is
mind-blowing to me because all of that just when it's coiled together
becomes this three-ish pound organ that fits into your skull.
This bone right here is not your jaw, instead this is called the mandible.
Your jaw is actually going to be up here. You see, you have one maxilla on this side and then
on the other side, you have another maxilla and then they fuse together to form one solid bone,
but maxilla is actually Latin for jaw. So your jaw houses your upper teeth, not your lower teeth.