BIOL 152 Muscular System (2023)

Introduction

Content

Welcome to today's discussion on muscles.

And the muscular system today we'll be looking at blossom, sections 10.1 and 10.2 in 10.2 we're only going as far as excitation coupling I'll show that to you then we're going to jump down to looking at cardiac muscle in 10.7 and a few facts about smooth muscle in 10.8.

The other sections will be skipping over and I'll also be mixing in a few images from a separate powerpoint a set of images that are also posted below this video and the exam two folder.

So let's get started with muscle tissue.

Muscle.

Tissue is really the third of three different tissue types that we've been looking at rather significantly recall back in lab two.

We spent a lot of time looking at epithelial tissues and connective tissues.

You did briefly look at the three types of muscle tissue, and that hasn't changed.

Uh today, we'll be looking at just a few more details about smooth muscle and cardiac muscle.

The majority of our time, however will be dealing with skeletal muscle.

Skeletal muscle is of course, the type of tissue making up all of your body muscles that you're learning in labs, four and five.

For example, the biceps brachii, the gastrocnemius, etc, all those muscles that you're naming in lab are skeletal muscles.

So let's, take a look at muscle tissue.

And as we go through this again, we're focusing on the anatomy, and we will not be worrying about the physiology, that's, the section that we'll be primarily skipping over.

So you know that muscle is one of four primary tissue types, you know, the other three, you know that there's also epithelial connective and nervous tissue.

And you know that muscle comes in three flavors.

You've got skeletal muscle cardiac muscle and smooth muscle.

You should know where those different types of muscle are found in the body.

And you should recognize them under the microscope as well.

Now recall too what are the characteristics? What are the characteristics let's? Go back? What are the characteristics of epithelial tissues? And if you'll go back, we learned seven different epithelial tissues and their characteristics were that they were avascular tightly, packed cells.

Remember this story sitting on a basement membrane and highly mitotic, right, they they replace themselves very readily, whereas connective tissues recall their list of characteristics were loosely packed cells, surrounded by a ground substance with protein fibers in there.

So you've learned a number of different connective tissues now, we're going to take a look at muscle tissues, and they have some special characteristics about them as well.

Number one, muscle tissues are excitable excitability simply means that they are going to change, um their electrical activity from signals received from the nervous system.

We haven't talked about how this works yet, but just know that muscles are going to going to receive signals from the nervous system.

And that signal is going to excite the muscle.

And when muscle tissues are excited, they contract that's, what makes muscle tissue so unique in that, it changes its shape, right? It's excitable.

And that is true of all three muscle types, uh, cardiac smooth and skeletal.

You have seen these tissues under the microscope before let's just review briefly, uh in the top panel you're, looking at a micrograph of skeletal muscle, you recognize it because of the strong striping striation patterns.

You also see long, skinny cells that are multi-nucleated in the bottom.

This is cardiac muscle.

What is sticking out to me is that you have y shaped cells.

You see branching going on in the cells.

You do not see that in skeletal muscle.

And you do not see the, um, you also don't see the multi-nucleated nature within cardiac muscle.

And then in smooth muscle and we'll see different micrographs.

You've got images in green you're going to have images in pal and in other resources as well.

But what we have here are single cells, which are sort of cigar shaped and we'll see these in isolation as well.

But you see single nuclei.

And you do not see the strong striation patterns at all.

Hence, the name smooth muscle.

We've also learned already that skeletal muscle is voluntary, whereas smooth muscle and cardiac muscle is involuntary.

So, in addition to being excitable, right when muscle tissue gets excited, it contracts, right? It gets shorter.

This is where the power comes in so muscle fibers contract.

Number three, all muscle, muscle, uh, tissues, exhibit elasticity.

They are able to return back to their original shape when they relax.

And finally, muscle tissues are extensible.

That is when one muscle is when one muscle is shortening, there's, another muscle that is extending becoming longer.

And that is what happens with opposable muscle.

Groups, you'll be understanding that better.

When you look at opposing muscle groups, for example, the hamstrings and the quadriceps femoris group, or when you think about the biceps brachii versus the triceps brachii, I want you right now just to flex your flex, uh, your biceps brachii, right? Put your arm out at 90 degrees, your elbows at 90 degrees, flex your biceps.

And I want you now to bring your your wrist toward your shoulder as you're doing that.

Your biceps brachii is shortening.

But your triceps is extending right.

So the opposing group is extending so all muscle tissues have basically these four characteristics.

These are important to know, muscle, cells are contractile.

And the three e's they're, excitable elastic and extensible we're going to be comparing and contrasting muscle types.

It's, really what I want you worrying about here as we think about cardiac versus smooth versus skeletal muscle know, this as well all muscles require atp, all muscles require energy and all muscles require calcium to contract.

Boy, if I say calcium, I hope that you're immediately thinking, oh, yeah, skeletal system right? The skeletal system stores that calcium and that calcium is released into the blood through the action of osteoclast cells.

And I talked last time, too about individuals who are on osteoporotic perosis medications, right? If they're on some sort of osteoclast inhibitor because their osteoclasts are inhibited they're, not releasing calcium into the blood as they should normally.

And as a result, their muscles will be affected by the lack of calcium.

In addition to being important for muscles to contract is also important for nerves to conduct their electrical signals and calcium is also necessary for wound healing and clotting of blood.

So all of these important functions are affected.

If someone is taking an osteoporosis medication now, when we look under the microscope we're going to see those striations that much we've heard before, but what's actually causing those striations, it turns out that there are proteins within muscle, uh, two proteins called actin and myosin we're going to discuss those quite a bit here in a few minutes.

But acne myosin are arranged in a very regular pattern.

And that regular pattern is what gives both skeletal muscle and cardiac muscle, the tell-tale striations or striping pattern that one sees under the microscope.

Now skeletal muscle is, in addition multinucleated.

And while smooth muscle does, in fact, have actin and myosin it's, not arranged in the same way.

So smooth muscle is lacking striations.

Hence, one of the other characteristics of smooth muscle on the first exam you are asked to compare cardiac and skeletal muscle in a in a statement, and you can expect something like that also for the second exam, when comparing all three muscle types, definitely take a look at these videos, they'll help.

You visualize the distinctive characteristics between these types of muscles and make sure that you are reviewing the questions as well, like I said, uh, actin and myosin are present, but they're, not arranged in the same regular fashion in smooth muscle.

So the uh, cells appear quite smooth.

Uh, the cells are single uniform cells.

And they are said to be, um, fuse of form and shape you'll see that word coming up in a minute, but they are that cigar shape or fuse of form in shape again.

Watch the video on smooth muscle, appreciate the differences and that's the end of 10.1, a very quick review of the muscle types, I'm going to click over to the set of images that are attached and just say a couple more things and then we'll go back to look at uh, the other part of blossom, but in your body again, we're comparing and contrasting all the muscle types.

There are over 700 skeletal muscles that have been named in your body.

You can thank me later that we're only learning 60 or so muscles.

The muscles that we are learning in the lab in labs, 4 and 5 are the more superficial muscles, their muscles.

Most of them you can you can identify from surface, uh features of the body.

And this is in general, but we're gonna be focusing mostly on skeletal muscle, we'll be looking at this in much more detail, but a muscle cell a muscle cell is also called a muscle fiber.

So this is nomenclature that's really important.

But you'll hear me say, a muscle fiber or a muscle cell.

This is where this gets confusing for some students up until now a fiber.

Whenever I said fiber, I was referring to a protein fiber.

I was talking about collagen or elastin or reticular fibers.

Okay.

But in the context of muscle tissue, a fiber is the muscle cell.

And in skeletal muscle, the muscle cells are as long as the muscle is.

So if you think about your sartorius muscle, the sartorius muscle is a long strapping muscle in the thigh in a taller person that sartorius muscle can easily be 12 inches long.

That means that the cells in that muscle are also 12 inches long.

So muscle cells, aka muscle, fibers are very very long or can be very very long.

And we've already seen that, uh, skeletal muscle cells are multinucleated and here's.

What happens in development? There are myoblasts now that's, not a word we're going to see again.

But those are the cells that make skeletal muscle right? Myoblast, just like fibroblasts, make fibers chondroblasts make cartilage and osteoblasts make bone myoblasts make muscle.

And what's interesting is that when these cells combine to make the long long long, skeletal muscle, fiber, the nuclei are maintained.

So this is or these are multi-nucleated cells.

And I like this next table, only because it gives us a quick visual and again.

So much of what I want you to learn in.

This unit is comparing and contrasting the three muscle types in even more detail than you know.

So skeletal muscle in this representation, right, we're, looking at three we're, looking at a portion of three cells.

These cells are long, skinny they're running into the next room.

And we see the multiple nuclei along the cell.

Now skeletal muscle is considered considered strong right? This is strong muscle, it's, very quick.

It's, voluntary and it's discontinuous.

What meaning this you can have your arm down to your side all day.

And you only have to use your biceps brachii occasionally, okay, your biceps brachii is not continuously, working versus the cardiac muscle.

Right? The cardiac muscle.

We still see the striations.

We see these etch-a-sketch looking lines if you know what an etch-a-sketch is, but this looks like an etch-a-sketch line to me.

These black lines represent the intercalated discs.

You can also see that there's some odd branching pattern, a little bit going on here within the cardiac muscle cells.

And if you were to characterize cardiac muscle, you would say that it's also strong, it's also quick, but it's continuous isn't.

It right cardiac muscle works for us.

24.

7.

It never gets a break.

So cardiac muscle is continuous.

Whereas skeletal muscle is discontinuous.

And you already know that cardiac muscle is involuntary, you can go to sleep, and you don't have to worry about your heart beating.

And then finally there is smooth muscle.

And here you can much more easily see.

This is why I wanted to go to the slide, but you can see that these cells are individual they're short.

They are what we call fuse of form or the cigar shaped.

Notice they have two tapered ends.

The single nucleus is found right in the center of the cell and note that there is no striation patterns within smooth muscle.

So how would we describe smooth muscle, it's, weak it's, slow, right? It is not.

This is like the the the turtle in the in the hair, sort of thing.

This is the turtle.

Uh, this is slow moving muscle, it's relatively weak.

But it keeps on working and it slowly gets the job done.

And as you know, it's involuntary.

So this is a nice slide to compare and contrast, the three muscle types, let's, go back now to blossom, don't, forget to review the questions.

Okay and let's.

Take a look at 10.2 skeletal muscle.

So again, we're gonna be looking at 10.2 skeletal muscle and then we're going to jump down to cardiac and smooth muscle, make this just a little bit larger for your eyes and mine as well again, we're not going to finish even this chapter we're only going to go down to a portion of this.

So you know, skeletal muscles, right when you think muscles, you're, probably thinking skeletal muscle.

And then this is the kind of muscle that's, allowing for all those things that is under voluntary control this even these muscles, even help control or begin the processes of swallowing urination defecation.

Now there are some smooth muscles that also contribute to these processes.

But we are able to control aren't.

We swallowing and urination and defecation.

If all things are working well.

So these are part of these are voluntary control muscles.

It takes a lot of energy to make your muscles work properly.

So there's a lot of atp that suggests that there'll be a lot of mitochondria right? Your skeletal muscles are full of mitochondria making tons of atp and there's.

So much energy that is being expended that heat is produced.

And you know that if you're exercising, you get hot and sweaty, and if you get cold your skeletal muscles begin to shiver as a way of creating heat, let's, take a look at what makes up a skeletal muscle, a muscle and let's, just think for a second think your biceps brachii right, just have this image of your biceps brachii in your head.

As we think about this, skeletal muscle is not just made up of muscle cells or muscle fibers, but there's also blood vessels and nerve tissue and other connective tissues running in.

And through your muscles.

Remember, your muscles are an organ right? Think of your muscles.

Each of the named muscles as being an organ.

And as such in a muscle, there is going to be epithelial tissue.

There is going to be connective tissue.

There is going to be nervous tissue.

And of course, there's going to be muscle tissue.

Let's, take a look at the three layers of connective tissue that are found within a muscle.

These layers of connective tissue are going to enclose and give structure to the muscle and help to compartmentalize the cells in groups.

So let me name these three groups and then we'll look at a number of pictures to help you understand the significance of these three layers of connective tissue.

Number one, there is a layer of dense irregular connective tissue.

Now recall dense irregular connective tissue is also what you primarily find in the dermis.

But also here there's a layer of dense irregular connective tissue.

And this layer is called the epineum.

The epinesium epi on, or upon like the epidermis is on the dermis.

So the epimysium is on the entire muscle.

Okay, it separates muscle from other tissues.

It allows muscles to slide past each other.

So it separates one muscle from another muscle inside the muscle.

There are bundles of muscle fibers called fascicles fasci from the vocab, meaning, a bundle or a band.

So we have a bundle or a group of muscle fibers.

A fascicle inside the muscle is covered by another layer of connective tissue called the perimysium.

Now, you know, peri means around like perimeter.

So this is a layer of connective tissue that goes around.

The fascicles goes around the fascicles, and then finally internally around and protecting each.

And every muscle fiber, there is the most delicate layer of connective tissue.

And that layer is called the endomysium endomysium.

Okay.

So we have these three layers, epi, peri and endomesium and let's.

Take a look at how this works in different colors.

Here is a muscle.

Okay.

So this entire bracketed area we're, looking at let me make this larger we're, looking at a skeletal muscle.

Notice that inside the muscle, I see the circular arrangements.

Okay, notice too that there are blood vessels.

You see red and blue.

And there are also some nerves running through here as well that aren't shown in this particular picture around the outside of the entire muscle, shown in this pinkish color, purplish color.

That is the epineum.

If we then take just a section one of these bundles from within the muscle and pull it out.

This is a fascicle.

This is a fascicle.

And we see that the fascicle is surrounded by the green colored layer of connective tissue.

And that is the peri museum.

Okay.

So that is a muscle fascicle.

That means that each of these structures inside the fascicle is itself, a muscle cell.

So let's kind of we're zooming in this is the entire muscle here here is just a fascicle pulling out.

So this image is the same as this image.

And inside the fascicle we see that it is a group of cells.

So each of these is a cell, and the cell is surrounded by a layer of connective tissue called the endomesium.

So what is protruding here is actually the muscle cell, aka the muscle, fiber, okay.

And what we see is that the muscle cell itself has its own cell membrane.

And we notice something here about this cell membrane, it has little little holes in it we'll come back to that.

Uh, we sort of saw something like that in the nuclear pores.

These are different.

But you do see that there are these holes along the outside cell membrane of a muscle cell inside inside a muscle, cell let's, take a look inside a muscle cell, which is also shown down here.

There are these long, skinny organelles.

This is a brand new organelle.

This is a specialized organelle that is only found in muscle cells.

So it was not described to you back in chapter 3 when you learned about organelles, remember, we learned about golgi and endoplasmic reticulum and mitochondria.

Well, muscle cells have this specialized organelle called a myofibril.

So within the muscle cell, what you see is that there are these myofibrils that are these long cylindrical structures along.

And throughout the cell, you also see mitochondria.

So these are the uh.

These bluish green guys are the mitochondria.

And then you also see, um, this network of tubes.

And this is the sarcoplasmic reticulum we'll.

See this in a minute, uh, the sarcoplasmic reticulum.

And the sarcoplasmic reticulum is important in storing calcium.

Remember, I told you that muscle cells need calcium.

In fact, they need so much calcium that they have these specialized organelles that store that calcium for the muscle cells.

So this is what the inside of a muscle cell looks like here's another picture of that.

And then we see this myofibril being pulled out what I want you to notice too is that the myofibril you can see the striping pattern.

So you can see that there's a light and a dark and a light region, and we begin to understand what causes the striations of muscle cells are these alternating overlapping arrangements of proteins that make up the myofibril we'll come back to that.

One more term to know is that the specialized membrane that goes around a skeletal muscle cell is called the sarcolemma sarcolemma.

Sarco is a prefix.

That means muscle, you'll see, lots of sarco terms in this unit.

You'll also see a lot of myo terms.

So sarco and mayo, both are prefixes referring to muscle or flesh and lemma is a term referring to the outside layer.

So the sarcolemma is simply the fancy name for the cell membrane of a muscle cell.

Now there are there's a really great video here that will help you visualize, uh, these three different connective tissue layers.

As we think about, why do we need these connective tissue layers? Well, remember that your muscles need a lot of oxygen.

They need a lot of energy.

They need a lot of nutrients.

So there has to be a lot of blood flow into your muscles.

And every cell every one of those muscle fibers needs a constant supply of oxygen and nutrients.

So there has to be blood vessels that travel down to the individual cells within a muscle.

If you think about your muscle, right, it's, a big it's, a big band, right, thousands and thousands and thousands of cells bundled together running along the muscle.

So each of those cells needs its own energy supply.

So these, uh, perimysium and endomesial layers.

What they do is they help to provide a space, a sort of a pathway so that the blood vessels and nerve tissues can also go to the muscle we're, not going to focus on this in this unit.

We will when we get to the nervous system in a couple of weeks.

But every muscle cell is also directly connected to a nerve cell and it's that nerve cell that tells the muscle to contract.

So we also need a way for those nerve cells to travel down inside deep into the muscle to activate to excite the muscle cells.

So take a look at these questions and definitely take a look at the associated videos in this unit.

Here's a term that I introduced last time, and that is an aponeurosis and a napo neurosis is just like a ligament or tendon, sort of in that it's made of the same material.

So an aponeurosis is made up of dense regular connective tissue.

And the job of an aponeurosis is to connect one muscle to another muscle.

Right? These are muscle to muscle connectors.

I want you just to look down to your abdominal region, right? And you know that there are no bones covering your gut organs.

But you do have and you'll see this in lab four.

There are four layers of muscle that make up your abdominal wall in the in around your gut.

And those four layers of muscles.

The most superficial is the rectus abdominis, your left and right, rectus abdominis are connected by that linea alba, right that white line that travels down the middle of your abdominal region.

And that white line is an aponeurosis and the other muscles, the external and internal obliques.

All those muscles are connected one to another through layers of apple neuroses.

Okay.

So you'll see that in lab.

But I just want to introduce that word again, we saw in a slide last time as well again, every skeletal muscle cell is richly supplied with blood vessels for the uh delivery of oxygen and nutrients and the removal of wastes and every single muscle cell must be directly connected to a branch of a nerve cell again, we'll talk about that when we get a little bit further into the nervous system, so muscle cells are just a different kind of cell right? These are not going to be those prototypic cells that you labeled back in blossom chapter 3, or in your green lab manual, right, they're, not spherical or cuboidal shaped cells.

They are long, and they not all right.

But a long muscle has very very long muscle cells within it, and they have a pretty good diameter.

And they can be like.

I said up to a foot long.

If you think about the sartorius that long strappy muscle in the thigh, I've already mentioned the myoblast story and how the cells are fused together.

But the nuclei are maintained.

There is some unique terminology that goes along with muscle, cells, they're just so unique.

They have their own vocabulary and you're going to see that sarco term used a lot.

So I've already shown you the sarcolemma, the sarcolemma is that cell membrane of the muscle cell or the muscle fiber and the inside rather than just being called the cytoplasm is referred to as the sarcoplasm again, very similar term, just sarcoplasm rather than cytoplasm.

And inside there is a smooth endoplasmic reticulum.

But this smooth endoplasmic reticulum is specialized.

And let me go up and show this to you.

I showed it to you briefly.

But in this picture, all this purple webbing, all this purple webbing that we see around the myofibrils that is the smooth endoplasmic reticulum of a muscle cell.

So that's a very different looking organelle.

And I told you that that is where calcium is stored.

Well, it turns out that that specialized smooth er in muscle cells is called the sarcoplasmic reticulum.

So rather than just the endoplasmic reticulum, the smooth endoplasmic reticulum.

We call the sarcoplasmic reticulum.

And lastly, I'll be showing in a few minutes, this structure called a sarcomere, a sarcomere we'll see that in a minute in more detail.

So again, sarcosarco sarcosarco, make sure that you watch this video it'll help.

You understand all these layers and structures of a muscle cell looking here again, we see a muscle cell again, this got everything labeled up for us.

So here the outside layer, the cell membrane is referred to as the sarcolemma again.

There are little openings in the sarcolemma we're, not going to be learning about the significance of those.

This semester that has to do with the way, the electrical signal travels through the muscle cells and that'll be a conversation that you'll learn in depth in physiology.

We again, see the mitochondria now they're labeled in this particular view.

And all of this webbing all of this purple webbing is the sarcoplasmic reticulum.

And then here I can see a single myofibril being pulled out for demonstration again.

All this purple webbing is the sarcoplasmic reticulum do not worry about these terms, t-tubule terminal cisterna or triad we're, not going to discuss those three terms.

So just know that that's the sarcoplasmic reticulum, the purple webbing a couple of questions for you.

And then we get to the sarcomere so let's think about what this word means sarco, we know means flesh or muscle mere or myrrh.

If I said to you, uh, there is a polymer of something that means a molecule of many repeating parts.

So this ending mer right, myrrh, basically means part.

Okay, apart.

So this is basically the heart of the muscle.

And this is a microscopic portion and we're going to say that the sarcomere is the functional unit of a muscle fiber.

This is mentioned in video, 10.5, make sure you review this.

But a sarcomere is the microscopic functional unit of a muscle fiber.

We've seen, um, a functional unit back in the skeletal system.

I don't know if that word was used, but back in the skeletal system, we learned about an osteon right that circular arrangement of the bone within the within the compact bone.

So the osteon is the functional unit, the the the microscopic unit that is the building blocks for bone.

Likewise, the sarcomere is the microscopic building block of skeletal muscle.

So let's, take a look at what a sarcomere is.

And for this I'm going to jump to a slide, then we'll come back and we'll.

Look at these videos together.

Okay.

So let me jump down to the slides.

And let me go to the sarcomere and that's toward the end down here.

In fact, you know what before I go there, let me just go ahead and review.

These connective tissue layers, uh since that's, kind of in our head, and it makes sense to do this right now.

So again, this is just another set of images to help.

You really understand these different levels of protection and different levels of structure within a skeletal muscle.

First of all, I see a bone back here right? This is I hope you recognize it? This is the femur right? It's.

The only bone with that big head.

We see that hyaline cartilage here on the head here's, the neck of the femur here's, the greater trochanter here's, the lesser trochanter.

I think this is also just a good place to pause and think about for a moment, what you know if you were to take a little bit of this cartilage and put it under the microscope.

What would you see? You should be able to tell me what you're going to see that is hyaline cartilage.

Remember, hyaline cartilage it's that glassy type of cartilage, the most common type of cartilage you're going to have chondrocytes living in lacunae, right, it's going to look like little eyeballs looking at you.

And then, if you took some of the compact bone, you know what to expect right? You would see canaliculi and lamella and central canals and osteons.

A muscle is attached to bone through a tendon.

And you know that a tendon is made up of dense regular connective tissue.

And if you looked at a tendon under the microscope, what would you see? Right? You would see what I always say looks like wavy bacon, but you're going to see those tightly arranged collagen fibers with fibroblasts right being the cell type again.

This is all review.

This is this is where you should be.

You should be able to think, okay, if I saw this under the microscope, that's cartilage.

If I saw this, this is compact bone.

If I saw this, this is tendon, you know from labs, two and from exam, one, what those tissues are and what they look like under the microscope.

Okay? So the tendon connects the muscle to the bone.

The tendon is continuous with a layer of connective tissue that I have not yet discussed.

This is called the deep fascia, the deep fascia.

And this is simply the layer that's going to encase the entire muscle.

In addition to the deep fascia.

Now we have the epimysium perimysium and endomysium.

So if we take a look here, here's the muscle, the outer edge of that muscle.

If I look at the outer layer of the muscle, that's, the epimesium within the muscle, I have these circular arrangements called fascicles.

Each fascicle is surrounded by perimysium so that's sort of the the periwinkle color here.

And then I know that each of those structures inside the the fascicle is an individual muscle cell.

So here is a fascicle.

And then sticking out of it is an individual muscle cell.

And I know that there be endomysium surrounding each of those muscle cells.

I look at this muscle cell, and I see two nuclei right? Even here.

The artist has shown us two nuclei, reminding us that this is a multi-nucleated long, skinny cell.

And while I can't see it here, I know that inside the muscle cell are individual organelles called myofibrils.

Again, let's go let's go through this again.

So, uh, here's.

Another bone.

And what bone is this one, I see a rounded head, but it's certainly not as big as the head.

I would expect to see on the femur.

This is the humerus.

The humerus is the other long bone that's part of a ball and socket joint.

And this is part of your glenohumeral joint.

This is the humerus.

And here you have the turbicals, the bumps that are found on the on the on the humerus.

And here we see a tendon coming down.

Same idea.

Tendon connects a muscle to a bone.

We have the deep fascia.

And then we get to the muscle itself.

The muscle is surrounded by a layer called the epimesium within the muscle.

There are fascicles all right circle here for us.

This is a fascicle.

It would be surrounded by perineum perimysium.

We see the muscles nerves and blood vessels traveling through here.

And then within that peri within that fascicle, there are individual muscle cells.

This is a muscle cell being pulled out.

And we know that the muscle cell is surrounded by endomysium.

And then here for the first time we see the we see three myofibrils have been pulled out of the muscle cell so those, and we see the striping patterns right? We see the striations on the myofibrils.

You also see the artist left us two nuclei to appreciate that.

This is a multinucleated cell a moment ago, too.

I mentioned that this is the deep fascia.

Well, if this is the deep fascia, uh, you've been around anatomy long enough to now to know that if there's a deep fascia, there must also be a superficial fascia.

So what in the world is superficial fashion? Well, you already know this by two other names back in the integumentary system.

We looked at the hypodermis, which is also called the subcutaneous layer, right? And you know that that's mostly adipose a little bit of loose areolar connective tissue.

Well, another name for that same layer is superficial fascist.

So superficial fascia, subcutaneous, layer and hypodermis are the same name for three different things.

Let's, try to understand what this superficial fascia is so I'm going to take a transverse cut through the thigh.

Here we go looks like a hamstick doesn't.

It right? Big old, ham steak.

There is the bone right, there's the femur.

And we see that there are all of these muscles in the thigh and you're learning that right, you're learning the muscles in lab, five you're going to be learning about 13 muscles that are sitting in the upper thigh region.

And if you've ever had a ham steak, you can appreciate that you are seeing these segments of muscle right that are separated by connective tissue and fat between the muscles right are are individually sort of separated from each other well that layer of fat all around the thigh that is your superficial passion, right? So it's the same as the hypodermis or the subcutaneous layer, superficial fascia, same as the fat that is underneath the skin right? The hypodermis and the deep fashion again.

We see is that dividing connective tissue that separates the muscles from each other.

So they can all do their individual work.

Right? Some of these muscles would be contracting others would be extending.

And so we need to have the ability of muscles to slide over each other while still being in close contact with each other again, let me go through a few more of these pictures.

This will help us.

I think pull this all together.

So here, what I find is that these pictures sort of look all the same, uh, initially.

And you have to start looking at features in the individual images to figure out what layer you are at.

So here it tells us that this is a muscle fiber.

Well, if this is a muscle fiber, we know that a muscle fiber is surrounded by a layer of connective tissue called the endomysium.

And we know that there's a cell membrane in here that if we had a label here, this would be the sarcolemma inside that muscle, cell we're going to see a bunch of myofibrils here's, a couple of them sticking out.

We also are shown here.

Some nuclei right, multinucleated cell.

This particular image does not show mitochondria.

Okay.

So again, we have to realize that every feature is not shown in each picture.

There's, also a cell out here.

I'm just going to mention it.

This is called a satellite cell.

A satellite cell is a muscle stem cell.

So if you damage your skeletal muscle, it does have the ability of regenerating or repairing itself.

So these satellite cells right, they're out in the periphery and like a satellite floating around the outside.

And this is just a little clue that there are stem cells in your muscles.

Okay, let's.

Zoom out let's.

Zoom out.

So now, uh, the picture is telling us that this is a muscle fiber or a muscle cell.

All those individual components are the myofibrils.

We see two nuclei here and many nuclei along that cell.

And we know that this would be endo mesium surrounding each of these cells pictures telling us that this entire thing is a fascicle.

So we know that this would be surrounded by perineum and then let's zoom out one more time.

So here's, our muscle cell on the inside here is a fascicle, surrounded by perimesium here's, the entire muscle, surrounded by epinesium.

In addition to the epimesium, we would expect to find some of that deep fascia here.

And then that would continue with the tendon back here.

Lastly, if and I like this drawing, because it shows us the artery vein and nerve traveling through here.

So again, we're getting a sense of why we need these connective tissue layers, they're, providing a space for these vital connections, right? Arteries, veins and nerves to travel down deep into the muscle tissue.

So this if this was not labeled as a fascicle, how would you know what this is? And if this was not labeled as a fascicle because it's labeled up here as perimesium, you know that this layer is surrounding a fascicle and then down here, if this didn't say, muscle fiber, how would you know that this was a muscle fiber? A few things one, the endomysium is labeled as the connective tissue layer around the cell itself.

And then those myofibrils are sticking out here.

It also lists sarcoplasm again, that's the cytoplasm of a muscle cell.

And it also says sarcolemma, which is the outside layer, the cell membrane of a muscle cell.

And then finally that satellite cell is labeled in this picture.

Satellite cells are the stem cells that can help to regenerate damaged, skeletal muscle tissue.

I should say now while we're here cardiac muscle does not have satellite cells.

And this is why heart attacks are so devastating is that when cardiac muscle cells are without oxygen, they die off and cardiac muscle is not able to regenerate itself.

So again, that's, why a heart attack is so devastating, a skeletal muscle will regenerate, but a cardiac muscle cell and tissue does not okay.

So let's hop on back to blossom and let's, look at this sarcomere story.

And what we're looking at here, uh, this is going to take a little bit of imagination to figure out what we're looking at here.

But again, a sarcomere is the functional unit within the muscle cell.

In fact, let's figure out where a sarcomere is a sarcomere is what makes up the myofibrils.

So the myofibrils are those organelles running the entire length inside muscle fibers.

And each myofibril is composed of sarcomeres arranged end to end.

Okay.

So each myofibril is composed of these sarcomeres.

These parts of the muscle around end to end as a muscle shortens what's happening as a muscle contracts.

What's happening is that all of the sarcomeres within the entire muscle cells, all of those sarcomeres contract.

So it's, actually, the sarcomere that is getting shorter.

And all of these hundreds of thousands of sarcomeres are simultaneously shortening.

And that leads to the contraction of the muscle within the sarcomere we have overlapping proteins.

And these proteins are called the myofilaments, the myofilaments and myofilaments come in two flavors, actin actin and myosin.

Okay, actin and myosin actin is referred to as the thin filament and myosin is referred to as the thick filament within the sarcomere.

So let's, take a look here.

So let's, this is a a drawing to help us visualize and understand what a sarcomere is again.

A sarcomere is a part a functional unit part of a muscle sarcomere.

It goes from this green line here over to this green line.

Here, those lines are called z lines.

Think of like the alphabet, the end right.

So from end to end this bracketed area is a sarcomere within the sarcomere I'm, seeing overlapping proteins, the purple make this larger.

The purplish one right here.

The thin protein, this is actin primarily.

And we see a bunch of these actins, and then the thick protein that's running in the middle, this orangey red that is myosin.

So we see myosin and actin overlapping within the sarcomere structure.

Now I think perhaps you're beginning and another picture is coming.

It will help you to even better understand this.

But what you're seeing when you look at skeletal muscle is you're, seeing overlapping regions and regions that are not overlapping between these proteins.

And that is giving you the light and dark banding patterns, the striations that are visible under the light microscope.

As we zoom in right.

The thick filament here is myosin it's, a thick protein.

And then thin filament is made up of this purple protein called actin and there's.

A couple of other proteins that are part of the thin filament called tropomyosin and troponin tropomyosin and troponin are not going to be something you need to worry about this semester, okay, what they do.

And why they're there that'll be a big part of the physiology story.

Next semester just know that the thin filament is primarily actin, right this thin protein.

So what is going on here? It turns out that when muscle contracts and we're not going to get into the nitty-gritty of this, but as muscle contracts, these proteins grab onto each other.

And they pull toward the middle toward the m line.

They pull toward the middle toward the m line and here's the sarcomere here, but there's also a sarcomere over here.

Okay, it's not shown there's, a sarcomere over here and there's another sarcomere over here.

And if you take a long string of these sarcomeres that's, what's making up a myofibril a myofiber.

So the video up here will help you see this in this video again, here's, your thick filament.

Here is the thin filament here is the z line and you're going to see how the sarcomere shortens as muscles contract.

This is called the sliding filament theory.

The sliding filament theory, okay, I'm going to jump to a couple images to help you understand this in a different way.

And these are here in the powerpoints.

What I like about this particular image is that it's showing you a cartoon representation of a sarcomere, but it's also showing you a micrograph of muscle tissue.

And what you're seeing here are the striations.

Okay, the striping pattern that you see under the microscope.

Take a look here.

See here the myosin, which is in yellow in this artist's rendition and the actin, which is this red protein, notice it right here where I'm circling.

These proteins are overlapping there's, a greater density of proteins.

Look straight down.

This is lined up that gives you a dark band.

And then there are places where there are not overlapping actins and myosins.

And that provides a lighter colored band.

So again, when you see the striations of skeletal muscle and of cardiac muscle it's, because of the overlapping alternating overlapping regions of the sarcomeres down at the microscopic level, I mentioned already that smooth muscle does have actin and myosin.

But it is not in the same overlapping patterns.

Hence, smooth muscle is not striated.

These regions of the sarcomere have a couple of names.

This is pretty easy.

You see here wherever the myosin is that is called the a band.

I remember that a is a thick letter it's kind of a wide letter.

So the thick filament is the a band wherever myosin is that's.

The a band wherever actin is by itself.

That is an I band.

Actin is a skinny letter or I sorry, I is a skinny letter right? And and so the I band, uh, the skinny thin protein, okay, actin.

And then we see here again from z to z.

So from z to z from this z to this z that makes up the sarcomere again, there's a sarcomere here, there's.

Another sarcomere here, there's another sarcomere over to each side and you'll see that in the visualization in the videos.

So what happens when a muscle contracts again, here's, the same idea here is the cartoon representation of the proteins.

Here is the striping pattern that you would see under the microscope.

Now let's begin to contract the muscle.

And as we contract the muscle, the actins and myosins are going to slide over each other.

And as they slide over, you see more of a dark pattern in the muscle under the microscope.

And then if you look at a muscle that is contracted as full and as hard look at the picture up here, right? Your biceps brachii.

You are contracting with all of your force all of your muscles as short as it can be.

And all of the actins and myosins are sliding over each other under the microscope you would see this right, you would see that there is a big area of overlap and very little area where there isn't overlap.

So you would see much less of the lighter colored bands.

So I think this is kind of a cool demonstration to see how muscle as it contracts would change under the microscope.

Okay.

So let's go back to blossom.

And again, this is just a visual representation of a sarcomere with actins and myosins.

I mentioned that your muscles are excitable.

And that simply means that there is a connection between nerve cells and muscle cells, we're going to talk about this in a little bit greater detail when we get to the nervous system.

And then next semester, you will deal with this in much more gory detail just know that where the muscle cell and the nerve cell come together, that's called the neuromuscular junction neuromuscular junction.

And I think it's really cool to think that every single muscle cell in your muscle is connected innervated by a motor neuron, that's, a that's a nerve cell at the neuromuscular junction.

Okay.

And when your nerves send an electrical signal to the muscle, the muscle gets excited.

And when muscles get excited, they contract, okay.

So that's sort of just a basic overview of skeletal muscle.

And we are not going beyond this.

So you'll see I put blue here.

But this is just a road map for me, the rest of 10.2 excitation, contraction, coupling, don't worry about any of these.

Therefore also don't worry about the questions.

Okay, that are down here.

So don't worry about that when it comes down to the very end of this, you do not need to worry about any of these questions because they all deal.

Well, no take that back.

You can answer question, three.

And you can answer question, four.

And you can answer question, five, I take them back.

So you can do three four and five, but the other questions you don't need to worry about because they are, uh on things that we're not covering.

And then you certainly can come down to this multiple choice, quad or this fill the blank question and practice labeling of these different structures.

So there is, there are some questions.

You can do here at the end.

And then you can also do the vocabulary checkup at the end of 10.2 jumping down now to cardiac muscle, not a lot.

You've already seen cardiac muscle.

And we are going to learn a lot more about cardiac muscle when we get to the heart and the cardiovascular system.

And then you will learn even more physiology about the cardiac muscle cell.

Next semester when you're dealing with ekgs and much more of the physiology of the heart there's, a couple things that you know and there's, really nothing new here to share with you that is cardiac muscle.

Cells are shorter than skeletal muscle fibers.

Usually cardiac muscle cells have only one nucleus, although occasionally there's a couple, but usually one.

And those nuclei are found more in the center of the cell in skeletal muscle, the nuclear shoved off to the edge, because of all those myofibrils in cardiac muscle, you're going to find a lot of mitochondria, because we need a lot of atp to constantly be produced to control and regulate the pumping of the heart.

And you know that there's branching, the cells are branched within cardiac muscle.

We don't see that in skeletal muscle.

And finally, there are these structures called intercalated discs we'll deal with what those do later, but just know that intercalated discs allow for the cardiac muscle cells to connect to each other.

So that when the heart pumps all of the cells are able to work, essentially as a unit right? We need all of the cells in the heart to work as a functional unit.

So here is a picture once again of let's, zoom in of a cardiac muscle.

You can see those intercalated discs pointed out here.

I see one two, three, four five.

And there are even more there's one up there, here's one up here right.

So, as you start looking around your eye starts to start to see these interpolated discs pretty easily.

I can see the y shaped or the branching also of these cells, the intercalated disks.

If we zoom in, I want you to know this.

What is an interpolated disk? It is a combination of a desmosome and gap junctions.

We learned about both of these back in epithelial tissues, remember that desmosomes were like rivets.

They were the reinforcement buttons.

If you will found between cells, the heart is constantly contracting under a lot of force.

Think about when you exercise right, your heart is pumping even harder and under a greater force.

It needs some reinforcements.

So there are desmosomes between the heart cells and gap junctions recall from epithelial tissues are ways for cells to communicate with each other.

So gap junctions allow for ions and electrical signals and metabolites to cross from one cell to another.

So if you were to zoom into an intercalated disk, this is just a cartoon representation, but you would find that it's composed of both desmosomes and gap, junctions, desmosomes and gap junctions.

And that is all I am going to worry about for the cardiac muscle.

When we get to the heart, we will learn that cardiac muscle is autorhythmic.

That means that your heart actually doesn't require connection to your brain.

Your brain is not sending the signals telling your heart to contract.

Instead, your heart has what's called a pacemaker right? The pacemaker in your heart tells the heart to beat.

And if a person has a faulty pacemaker, we can put in an external pacemaker, which helps to regulate the rhythmic contractions of the heart.

What your brain does send to your heart is signals to either increase your heart rate or decrease your heart rate.

But the actual signal for your heart to beat is coming from the heart itself will deal with this conversation later in the nervous system and in the cardiovascular system.

And then lastly, we've already said this, but I'll just say it again, calcium is critically important for the working of your cardiac muscle, and for your heart, the exact way it works.

We're not going to worry about this semester, but just know that calcium is a necessary component to the contraction of your heart.

So you can answer these questions down here.

Okay.

And let's.

Finally, go to well.

Let me go back to a couple slides just to reinforce this a couple extra slides about cardiac muscle.

And again, everything I've already said, these cells are individual they're.

Striated, they're, shorter usually have one sometimes two, nuclei, y branching and they're autorhythmic with the intercalated discs.

And just another picture of this don't worry about the eye and the a and the z here, but just see that you have the branching.

You have the striations you have single nuclei, usually that are in the center of the cell let's finish up with smooth muscle.

So we'll go down to smooth muscle, 10.8, just a little bit here.

So I've already blued out quite a bit of this section we're, not going to go into the physiology of this, but smooth muscle.

It is named because there are no striations.

Where do we find it? We find it in the walls of hollow organs.

Think in your bladder uterus, stomach intestines, it's inside lining, your arteries and veins, it's lining, your trachea, it's lining, um, you know, all of the all the tube like structures in your body have smooth muscle.

There there's also some smooth muscle in your eye.

All of these.

Oh and also don't, forget in the skin back the erector pili muscles.

The muscles that are attached to every single hair when you're scared those little smooth muscles, pull on the hair and cause your hair to go erect all of those muscles that I'm talking about here are smooth muscle again.

What we see in the artist rendition are these fuse of form or these cigar shaped cells, one nucleus, okay, and they have actin and myosin, but it's, not arranged in the same way.

Therefore you do not see the striation patterns under the microscope.

Watch this little video about smooth muscle tissue when we get to the digestive system we'll once again, look at smooth muscle, obviously, the stomach and the intestines have smooth muscle and we'll see this again.

When we get there, a couple of things to remember all three muscle types need calcium.

So yes, calcium is necessary for smooth muscle as well.

We've seen these spindle shaped or fusiform shaped cells.

They have a single nucleus.

They are much much smaller much much shorter than skeletal muscle cells, and they do not have the striations.

Okay.

So those are all the facts that I want you to know about smooth muscle.

The blue areas are crossed off.

And we see that smooth muscle cells, shorten just like all muscle cells, shorten, um that long, skinny cell kind of puckers up.

And that is the contraction of a smooth muscle cell.

Again, don't worry about the blued out regions.

Those are to be skipped.

We know that smooth muscle is involuntary.

And again, we find this smooth muscle along the walls of your organs all over the place and we'll talk about a little bit more about this when we get to the nervous system as well.

So again, don't worry about all of these good things.

And I believe that's it.

Oh, I told you earlier that smooth muscle is slow right so visceral smooth muscle produces slow, steady contractions, think again, turtle in the hair.

This is the turtle just keeps on going keeps on going slow and steady slow and steady.

And this is the kind of muscle.

You find that pushes food through your digestive system.

As an example, it is possible for smooth muscle to increase in, um the size of the cells.

And this is most obvious in pregnancy.

So the uterus, uh in a non-pregnant uterus.

The cells are quite small, but uh during pregnancy.

The cells of the uterus get much larger.

The smooth muscle cells get much larger and increase the layer of the uterus called the myometrium that's, the muscle layer of the uterus.

So that is the end of smooth muscle and going to those slides again, back to smooth muscle I'm, telling you just a couple things here.

I've already said, it short, muscle fibers, fuse the form there's that word fusiform or cigar shaped cells, one centrally located nucleus, thin and thick filaments the actinomycin are there, but not aligned.

So that you see the striations contractions are slow.

This muscle is resistant to fatigue.

It just keeps on going keeps on going keeps on going because it's slower it doesn't require as much atp, therefore, you would not find as many mitochondria in smooth muscle cells, compared to skeletal or cardiac muscle cells.

And these cells just move slower, right? They're slower to contract slower to relax.

And you already well know that it is involuntary.

So that brings us to the end of, um, the blossom.

Chapter 10, there's, one, more section we're going to look at and that's 11.1.

Just briefly here also in the powerpoint slides are the four special characteristics of muscle tissue already been through that.

Again, just want to point out that these extra slides are highlighting some of those very important things.

I want to confirm that we've been through all of these things.

What happens to your muscles as you age as you age there's, a slow, progressive loss of skeletal muscle mass.

Now you can slow this down by continuing to be active and exercising.

But there will be a slow, progressive loss that progressive loss can be more more quick.

If you are not exercising, the power and size of the muscles will decrease the muscle that is lost is most often times replaced by fat right? So as you lose muscle mass, you become more flabby.

And that is the adipose that replaces the muscle as a result.

Not only are your muscles weaker.

But your cardiovascular performance also is going down.

Don't, forget your heart is a muscle as well, your decrease, uh, sorry, your tolerance for exercise will decrease and your your fatigue will increase right that makes sense right as we get older we're, just not running around quite as quickly.

And we certainly get tired and are slower to recover than we were when we were younger.

You also are more prone to injury and the muscle elasticity decreases.

So with age, we see a lack of stretchability right that extensibility and elasticity of the muscles decreases making it just a little bit more stiff as we get older the last little bit for this.

Uh, chapter is we're going to jump down to chapter 11.

Now in chapter 11, this is primarily the naming of muscles.

It goes through the muscles of the axial region, the muscles of the appendicular region, I'm, not going to be talking through these sections as this is basically what you've been doing in labs, four and five.

But I do want to just mention one more time or go in here into 11.1 just a little tiny bit and remind you of a couple of things that you're also seeing in lab.

And that is your skeletal muscles.

Now this chapter is about skeletal muscles.

Skeletal muscles, attach most of them, not all of them attach to bones and where those muscles attach to bones.

Those are predictable places right? All of us have the same bones with the same muscles attached.

And when those muscles contract, they pull certain bones with them to allow the movements that we discussed in the last presentation in moving your body in all of those joint structures so origin and insertion origin and insertion is what I want to discuss here with you.

And you've seen this in lab as well.

So where muscles attach where the tendon attaches we're looking here at the biceps brachii and the brachioradialis, these are two muscles that are important in flexion of the elbow.

So as you flex your biceps, brachii, biceps, two heads, right? By means two seps means head.

Brachii is the region where this muscle is found these two muscle.

These two heads of the biceps brachii have two different tendons and you're learning in lab about the origin.

And the insertion of these the origin for the biceps brachii.

One is on the coracoid process.

And one is on the supraglenoid turbical and then, uh.

So that's, the origin of the biceps brachii.

The origin by definition is the place that doesn't move.

So as you flex your your elbow, right, your shoulders, not moving.

But what is moving is your forearm right? Your ante brachium is moving toward your shoulder.

So where the muscle attaches to the bones where there is movement.

This is referred to as the insertion and the biceps brachii looking over here, the biceps brachii specifically inserts onto a little bump right here on the radius referred to as the radial tuberosity.

So the radial tuberosity and that's, the insertion for this muscle, so as the biceps brachii and the brachialis muscle here, the brachialis also goes down to the radial tuberosity as these muscles contract.

Your forearm is pulled up the muscle goes across the joint goes across the elbow joint to allow this movement.

Synergists are muscles that help work help do the work.

So a synergist, uh, the brachioradialis, the brachialis are muscles that help with the flexion of the of the elbow.

Look at these muscle names, guys, brachioradialis, right? It goes from the brachium down to the radius right? Don't, make this hard muscles will name themselves and you'll start to get a hang of how to name these muscles, many of them name themselves based upon where they're located or what they do.

Now, the muscles that oppose the prime mover is called an antagonist.

So as you are shortening, the biceps brachii there's.

Another muscle group here on the posterior brachium called the triceps brachii, and it will be the opposing muscle and that's called the antagonist, the antagonist and you'll see that the other really common antagonistic group that you're going to be learning about is the quadriceps femoris group that's in the anterior thigh versus the hamstring group, which is the opposing group.

And that is in the posterior thigh.

So the quadriceps femoris and the hamstring groups are antagonistic to each other.

And while I'm here, you should be able to name the four quadriceps from morris muscles.

This should become really easy for you again.

Those four muscles are the rectus femoris, plus the three vastuses, the vastus lateralis, sebastian's medialis and the vastus intermedius.

And you should be able to rattle off also the three hamstrings, the three little pigs, right? Three, little hammies.

This is the biceps brachii.

Sorry, biceps.

Femoris.

Sorry.

I almost did it biceps femoris, the semitendinosus and the semimembranosus.

So here are a couple of those antagonistic pairs, biceps and triceps, hamstrings and quadriceps.

And then in the wrist, uh, the flexor muscles and the extensor muscles that we're not going to be talking about as much this semester.

And lastly, we've already talked about fascicles right? Fascicles are bundles of muscle cells.

Turns out that there are a few different arrangements of fascicles within skeletal muscles.

Let's, take a look.

So some of your muscles have parallel parallel fascicles.

A good example that is the biceps brachii.

Some of your fascicles are convergent.

The pectoralis major is a good example of that.

So what you see is that all of the fibers are converging onto a tendon that's in a more localized place.

These are typically triangular shaped muscles.

There are circular fascicles, uh, the two circular muscles.

You're being learning are the orbicularis oculus and the oculi and the orbicularis auras right the circular muscles of the mouth and of the eyes.

And then there are three that have the term pennate in them.

You also heard this in the lab pre-lab presentation for muscles, but penny means feather shaped.

So you see here, bi-penny, you see the fibers are running at oblique angles toward the central tendon.

Okay.

So bipennate, two two sides if you will unipennai just one.

And then there are also multi-penny muscles.

The deltoid's a good example of that, because the deltoid, uh has three parts to it three parts and you'll see that when you're working through some of the actions of the muscles.

So that brings us down just read through the different shapes of these muscle types.

And this is where we're going to stop at the lever.

So do not go do not go based or beyond this again.

This is our stopping point and the rest of the chapter on levers.

Don't worry about that last little bit.

You can answer questions, one through eight.

Okay, nine is on lever.

So don't worry about that one, but you can answer questions one through eight, and you can certainly do the labeling activity down here.

And you can do the vocabulary.

The rest of chapter.

11 is a good thing to review.

And that is everything to do with the naming of muscles that's.

What you're learning in lab.

Lastly and very important.

I put it here at the very top of these slides.

I forgot to mention this, uh, when I was doing the skeletal system presentation, it was in that set of slides at the very end I'm, putting here at the top of the muscle slides, because this is an important concept that will be a part of the next exams.

Exams, two, three, four and five will all have what I call connection questions connection questions as we learn these body systems, we learn the integumentary system.

And then the next week we learn the skeletal system.

And then the next week, we learn the muscular system.

And oftentimes as we learn about these body systems in isolation, we lose the the we lose the idea or the important idea that these muscles that these different systems are not working in isolation, but they're all working together to maintain your overall homeostasis and your title, your total metabolism.

So here is a slide, which shows us some connections between the skeletal system and a number of other systems.

This is not an exhaustive slide.

There are many other examples.

Let me go through a few of these.

So we have learned that the skeletal system stores calcium and uh, calcium is important, not only for bones.

But also for many other things like muscles.

We've in the nervous system.

And it turns out that vitamin d, you know, is made in the skin.

So vitamin d is made in the skin or is activated in the skin.

But it also plays a role in absorbing calcium into your body.

So there's a connection right between the integumentary system and the skeletal system revolving around calcium availability.

The nervous system.

I've already told you that there are nerves traveling through your bones.

And you also know, for example that your cranium protects your brain or that your rib cage protects your heart and lungs.

So there's, definitely a lot of connection between the skeletal system and the nervous system cardiovascular system again, the heart is protected by the rib cage and the sternum.

But also remember that inside your bones is where you are making blood cells.

And that would also be that hematopoiesis is also a connection between the skeletal system and the cardiovascular system.

The digestive system again is absorbing the calcium from your diet that is necessary for bone strength, your ribs are working to protect your lungs.

And we understand too that the pelvic bones are protecting the reproductive organs.

These are just a few examples of how systems connect to each other on exam.

Two, there will be short answer questions.

You know, these are coming.

Let me tell you about them.

You can ask about these in s, I or in lab as well.

I will ask you the following questions name, another system that interacts with the skeletal system and give me the specific interaction of those two systems for that.

You would simply say, uh, the skeletal system interacts with the integumentary system because vitamin d is activated by the skin and is important in calcium absorption, or you could say that the cardiovascular system and the skeletal system connect because the hematopoiesis that occurs in the skeletal system is, you know, building or creating the blood cells necessary for cardiovascular system function.

There will be two questions for the skeletal system.

I will ask the same question for the integumentary system.

And I will ask the same question for this muscular system so you're going to have six connection questions on the next exam.

They will be short answer.

You will need to provide the specific example.

I don't want general statements.

In other words, don't say to me, the skeletal system protects the brain right? You must tell me what is it about the skeletal system? You've got to say the cranial bones protect the brain don't, tell me that the skeletal system protects the heart, a kindergartener knows that you need to tell me just a little bit more tell me that the sternum and the rib cage protect the heart.

So be a little bit more advanced in your connection, drop the words into your statement that that indicate that you're learning how these specific things connect together.

As we go through the semester I'll expect more and more complexity from your connection questions.

But for now again on exam, two, there will be six connection questions, two for integument, two, four, skeletal and two for the muscular system that does bring us to the end of all things muscular again.

These extra slides are posted for you as well as the video in the exam 2 folder.