An Introduction to Bone and Skeletal Tissue - Online Tutor, Practice Problems & Exam Prep

Bone is a living, dynamic tissue that supports the body, protects organs, produces blood cells in bone marrow, stores minerals like calcium, and acts as levers for muscles. There are five types of bones based on shape: long bones (e.g., humerus), short bones (e.g., carpals), flat bones (e.g., sternum), irregular bones (e.g., pelvis), and sesamoid bones (e.g., patella). Understanding these functions and classifications is essential for grasping skeletal anatomy and physiology.

What is Bone?

Hello, and welcome to our unit on bone and skeletal tissue. Now, before we dive in and learn any new material, I always like to remind people and orient people to the fact that bone is living dynamic tissue. I say this because, so often when we think of bones, we think of a skeleton—something that's been dead, maybe for 100 or even 1000 years, or a Halloween skeleton. It's not something that we associate with life, but bone is living tissue. It has blood in it. If you break it, it's going to bleed.

It has living cells in it. Those cells reproduce and replace themselves. The skeleton you have now is different than the skeleton you had 10 years ago. Bone responds to its environment. How you use bone is going to affect its structure.

Alright. So, with that in mind, what we're talking about is the skeletal system, and the skeletal system comprises approximately 206 bones. There's a little variation from person to person, and also the associated cartilage. To illustrate that, we have a person here showing us his bones. We can see the skeleton.

We can see the 206 bones of the body. Now, I've told you there are 206 bones in the body, but we are not learning the 206 bones of the body in this unit. You are going to learn them later. We'll go over that later in another unit. Right now, we're talking about bone generally.

What is bone? What are the types of bone? How is bone built? What does bone do? So, to start with that, let's talk about the major functions of bone.

Here we have 5 major functions. It's always difficult to put a number on it because someone may count something a little differently, but this is the way I like to think of it. First up, bone supports the body. To illustrate that, we have a flying buttress on a cathedral here.

Bone is the hard thing in your body that holds you up and gives you its shape. And for some things, they will only work with that structure. Your lungs, for example, need the structure of the ribs to work. Second, bone is going to protect soft organs. To illustrate this, we have a knight in armor here.

That armor protects his body. Well, your body has things like your rib cage or your skull to protect the soft organs inside, and they do a pretty good job of it. Right? You can take a punch to the head. Now, you don't want to.

It may hurt you, but for the most part, in the end, you'll be okay because you have a cranium that is going to protect that soft, really delicate brain inside. Another thing bone is doing is it's going to produce blood cells, and that's going to happen in the bone marrow. We can illustrate that here. We show a factory, and a factory is producing these blood cells coming out from that bone marrow, which is located inside of bones.

Bone is also going to store things. Specifically, it's going to store fat or triglycerides and also minerals, specifically Ca+2. To illustrate that, we have a refrigerator filled with food, and the fat that it's going to store in your body, that's going to be in the form of another type of marrow. That calcium, well, that's just in the matrix of the bone. You have a ton of calcium, and your body can use it.

Finally, bone is going to act as levers for muscles. To illustrate this, we have a little guy here, and he's lifting up something with the help of a lever. Now bones work with muscles. Muscles do one thing: they pull. What do they pull on?

They pull on your bones, and when they do that as a lever, well, your arm bends. We're not going to talk about that in as much detail in this unit. In this unit, we're really going to focus on the structure of bone, how bones are built, and what bones do physiologically. I'm looking forward to it. So let's get to it.

An Introduction to Bone and Skeletal Tissue Example 1

This example says for each bone below, state whether you think the primary function is support, protection, or acting as a lever. You may choose more than one function if necessary. Alright. Quick note. In this chapter, you do not need to know the specific function of each individual bone.

You will learn that later. But for now, we just want to think about this stuff a little bit generally. So let's go through our options and see what we've got. First up, we have the phalanges. The phalanges are your finger bones.

Well, what do you think? Support, protection, or acting as a lever? Well, your fingers do lots of movement, and when the body moves, it's because muscles are pulling on bones acting as a lever. So for the fingers, I'm definitely going to put an l for lever. Not really doing a lot of support or protection.

Next up, we have the vertebrae or the bones of your back. What do you think? Support, protection, or acting as a lever? Well, definitely some support, right?

That sort of is what keeps your body upright, so I'm going to put an s for support. I'm also going to put a p for protection. Your spinal cord goes down the middle of your vertebrae, and that bony protection is one of the things that protects it. And you probably know if you break your back, that compromises that protection and it can have some serious consequences. Now acting as lever, there are muscle attachments on the vertebrae and they do help you bend and stand up straight.

So there is a little bit of lever action, but I'm not really thinking that that's a primary function, so I'm going to leave it off. Next up, we have the parietal bones. These are the bones on the side of your cranium. So what do you think? Support, protection, or acting as a lever?

Well, not many muscle attachments there, so I'm not going to say acting as a lever. Support, I mean, it does give you the shape of your head, but really what it's doing is protecting the brain inside. So I'm going to put a p for protection. Next up, we have the mandible or your jawbone. What do you think?

Support, protection, or acting as lever? Not really a lot of support going on there, unless you consider supporting the teeth. And for protection, unless you're getting punched in the face a lot, not a lot of protection going on. What it's definitely doing is acting as a lever when you chew your food. Alright.

We have ribs. Ribs, support, protection, or acting as a lever. Well, definitely some support, right? The ribs give you the shape of the thoracic cavity, the shape of your chest.

We'll learn in the respiratory system, your lungs don't work unless you have rigid ribs giving them shape. Also protection. Right? I've stated before, pound on my chest, my heart is just fine because those ribs, the sternum are giving protection. So I'm going to put a p as well.

Now acting as a lever, again, there are some muscle attachments on there. They sort of base some muscles, but not a lot going on there in terms of levers for the ribs. So I'm going to leave that off as a primary function. Our final bone here is going to be the humerus. That's your upper arm bone.

What do you think? Support, protection, or acting as a lever? Alright. Well, really, those bones of the limbs, arms, and legs are definitely just mostly acting as levers. The more movement a bone has, the more it's acting as a lever.

Not a lot of protection, not a lot of support going on there. Alright. With that, we run through these bones. Again, you don't need to know the specifics of every bone, but you do want to be thinking about bone functions in general. And we have more questions to follow.

I'll see you there.

Which substances are stored in bones?

• A. Blood and Sodium
• B. Triglycerides and Calcium
• C. Sodium and Calcium
• D. Triglycerides and Sodium

Types of Bones

We're now going to learn how to identify different types of bones, and we're going to start by just saying that bones are characterized based on their shape. Now eventually, you're going to learn how to identify all the different bones in the body individually. We're not there yet. Right now, we just want to be able to pick up a bone and put it into one of these 5 categories based on shape. So let's take a look.

We have this anatomical model. We can see the skeleton, and then we have 5 bones pulled out as an example. Let's go through each one. First up, we have a long bone. And as our example bone here, we can see the humerus.

The humerus is your upper arm bone. A long bone is going to be shaped much like a rod. And by that, I mean, it has a shaft and then it also has these expanded ends. So when you look at the humerus, you can see the shaft and the 2 expanded ends on each end. Now, this is often like the type of bone that a kid will draw.

It's sort of the classic bone shape is a long bone, shaft with expanded ends. Now importantly, not all long bones are long. The bones of your fingers and toes, those are long bones, even though the bones are quite short. They're called long bones because of their shape. They have a shaft and widened ends.

Long bones, you're going to find in your arms and your legs. Okay. That brings us to the short bones. The short bones also based on shape, They are going to be roughly, we're going to say cube shaped here. You might say sphere shaped.

Sometimes I just sort of say lump shaped. Now, of course, every short bone is very specifically shaped based on what bone it is, where it is, and what it does. But because they're all sort of just these small sort of lump shaped bones, they tend to be the hardest bones to identify individually one from another in a disarticulated skeleton. Short bones, you're gonna find in the wrists and the ankles, the car

An Introduction to Bone and Skeletal Tissue Example 2

In this example, we're going to identify whether bones are long, short, flat, or irregular. As we look, we have an anatomical model where we can see the skeleton, and we have 4 bones pulled out. So let's go through those bones one by one. First up, we have the scapula, also just called your shoulder blade.

So I happen to have a model of a scapula here, so we can take a look. Take a look at this bone, and what kind of bone do you think it is? Well, when I look at it, pretty much every way I look at it, this bone is really thin. There really isn't a fat place on it. It does have this kind of crazy spine here, but even that is thin in at least one dimension.

So when I see a bone like this where every urethra is pretty thin, it's slightly curved, it's pretty flat, well, that's a flat bone. So I'm going to mark it with an F. The scapula is an excellent example of a flat bone. Moving on, we have the sacrum, and I have a model of the sacrum here. What type of bone do you think this is?

Well, the sacrum is the bottom of your spine, also the back of the pelvis. It's actually made by 5 vertebrae fusing to form one bone. And when I look at it, it's this kind of crazy shape. Sometimes I think it reminds me of a dragon's head or something like that. It would be really hard to describe this shape in any kind of detail quickly.

And when you see something like this that is definitely not flat and is just well, it's a really irregular shape, that's an irregular bone. So I'm going to mark it with an I. Sacrum, vertebrae, facial bones, and the hips, those are the irregular bones in the body. As we go over, we have the femur. The femur is the largest bone in the body.

It's your thigh bone. So what type of bone do you think this is? Well, when I look at it, I see that it has a shaft with two wide ends. When you have a bone with a shaft and wide ends, that's going to be a long bone. Now that may be kind of obvious for the femur because it is the longest bone in your body, but long bones don't have to be long.

Right? The tip of your pinky, the bone in there, that's a long bone and it's really short. The thing that makes it a long bone is, like the femur, it has a shaft with two wide ends. So, the femur, a long bone. That brings us to our last one here.

These are the tarsals. So if we look at this model of a foot here, the tarsals are the bones at the back end here. And as I look at these bones, well, I'll ask you first, what do you think they are? As I look at them, they don't really have any kind of distinct shape. They're kind of lump-like.

I believe above we described them as cube-like. You could also sort of say they're sphere-shaped. They have very specific shapes, but it's nothing to write home about. It's nothing too complex when you look at it. When you see a bone like that, relatively small, kind of lump-like, that is a short bone.

The short bones are the bones of your wrists and your ankles. Okay. With that, we've identified some bones. We have some practice problems to follow, and I'll see you there.

Where would you be most likely to find an irregular bone?

• A. Wrist or ankle.
• B. Spine.
• C. Ribs.
• D. Arm or leg.

Which of the following statements is true?

• A. Sesamoid bones are found in all joints in the body.
• B. Bones of your skull and ribs are both examples of flat bones.
• C. Your arms and legs contain mostly flat bones.
• D. Short and long bones have the same basic shape but differ in scale.

Here’s what students ask on this topic:

What are the major functions of bone in the human body?

Bones have five major functions: support, protection, blood cell production, storage, and leverage. Bones support the body by providing structure and shape, much like a cathedral's flying buttress. They protect soft organs, such as the brain and lungs, similar to how armor protects a knight. Blood cells are produced in the bone marrow, acting like a factory. Bones store minerals, particularly calcium (Ca²⁺), and fat in the form of triglycerides. Lastly, bones act as levers for muscles, enabling movement by providing points of attachment for muscle contraction.

How are bones classified based on their shapes?

Bones are classified into five categories based on their shapes: long bones, short bones, flat bones, irregular bones, and sesamoid bones. Long bones, like the humerus, have a shaft and expanded ends. Short bones, such as carpals, are roughly cube-shaped. Flat bones, like the sternum, are thin and slightly curved. Irregular bones, such as the pelvis, have complex shapes. Sesamoid bones, like the patella, develop inside tendons and can vary in number among individuals.

What is the role of bone marrow in the skeletal system?

Bone marrow plays a crucial role in the skeletal system by producing blood cells. Located inside bones, bone marrow acts like a factory, generating red blood cells, white blood cells, and platelets. This process is essential for maintaining healthy blood and immune system function. Additionally, bone marrow stores fat in the form of triglycerides, providing an energy reserve for the body.

What are sesamoid bones and where are they commonly found?

Sesamoid bones are small, round bones that develop inside tendons. They are named for their resemblance to sesame seeds. These bones can vary in number among individuals. The most well-known sesamoid bone is the patella, or kneecap, which is located inside the patellar tendon. Sesamoid bones help reduce friction and modify pressure, enhancing the tendon's mechanical advantage.

How do bones store minerals and what is the significance of this function?

Bones store minerals, particularly calcium (Ca²⁺), within their matrix. This storage function is crucial for maintaining mineral balance in the body. Calcium is essential for various physiological processes, including muscle contraction, blood clotting, and nerve transmission. When the body needs calcium, it can be released from the bones into the bloodstream, ensuring proper function of these critical processes.