1.02 Structures of Skeletal System

Welcome to the video lecture for unit 1.02 in our objective for this unit is to remember the structure of the skeletal system. Our essential questions for this unit are, what is the process of bonus formation? What are the structures of the long bones and what are the structures of the skeletal system? First thing on our side says, I did empty osteocytes. Well, let's break down that word. Osteo means bone and sights mean cell. Bones consist of a microscopic cell called oscillates. This is from the Greek word osteon, meaning bone. In osteosarcoma is a mature bone cell. Bone is made up of 35% organic material, 65% inorganic mineral salts, and then there's some water in there. The organic parts derived from a protein called Bozeman collagen. It's a fibrous material. Between these collagen is fibers, there's a jelly like material. The organic substances in a bone give it certain, give it a certain degree of flexibility. The inorganic portion of the bone is made up from mineral salts such as calcium phosphate. Calcium carbonate, calcium fluoride, magnesium, phosphate, sodium oxide, and sodium chloride. These minerals give bone, its hardness. The bony skeleton can be compared to steel reinforced concrete. The color of genus fibers may be compared with flexible steel supports. And those mineral salts can be compared with concrete. When pressure is applied to bone, the flexible, organic material prevents bone damage while the mineral elements resist crushing under pressure. So we need both of those things. Bone develops at different rates and times as part as a person goes through their stages of development. The cells that allow human bone formation are present after three weeks of fetal development. So we already start at three weeks when your mother is pregnant with you at three weeks. You already start making these human bone cells. Now we're going to look at ossification and are going to discuss this process. We're going to figure out, well, how do we know this is even happening? And then we'll give you some examples. Ossification is when minerals replace previously formed cartilage. And as bone ossifies, they become hard. Ossification begins after 6 weeks, sorry. Excuse me, 5 weeks of fetal development. Mesoderm cells form a cartilage center in the place where bones will ultimately form. So you kind of have a skeleton, but it's actually just kind of made out of cartilage. It's not bone yet. Those cartilage centers will grow and develop into cartilage pegs. And those cartilage pegs look like mini bones. Those pegs will calcify, they get hard and we have something called osteoblasts. It's osteo and then B, STS, osteoblasts. These are bone cells that deposit new bone, so they're kind of like bob the builder. So that's a good way to remember that because osteoblasts begins with a B, they build bone. That's a B and you can think about bob the builder. So as these pegs get harder, we have osteoblasts and then we have osteoclasts, which is osteo and then CLA STS. Osteoclasts are bone cells which secrete an enzyme that will digest bony material. So the way I like to remember osteoclasts is that they consume. They both start with C, sorry. They consume. So as those pegs calcify and osteoblasts and osteoclasts move in, both work together to sculpt the new bone. So we have osteoblast bone material and osteoclast comes around and kind of eats up that extra stuff. Calcium and phosphorus are important to stimulate bone growth and maintenance. Also specific parts of the endocrine system will regulate the rate of bone growth. Well, how do we know that ossification is occurring? Long bones actually will grow in length and they ask 5 times the center to the ends. So if you're long bones are growing and we're going to talk about where your long bones are, ossification is performing. Long bone formation occurs through a process called endochondral ossification. So the first step or primary ossification it begins with osteoclasts, carving out a cavity in the center of those cartilage pegs. That carving out of a cavity will then become the diaphysis of a long bone. The diaphysis of a long bone. Blood vessels begin to grow into the bone and they enter the cavity. This will provide nutrients for bone growth and maintenance. Osteoblasts, those bob the builders come in, they enter and they start secreting bone tissue to replace the cartilage that the osteoclasts broke down. First, compact bone, which is that hard outer outer shell of the long bone is deposited. And then it's converted into spongy bone, which is a lightweight honeycomb appearance. As the cavity gets larger. At the same time, osteoclasts in the periosteum produce a sheet like layer of bone on the surface of the diaphysis. Okay, a whole lot of words going on here. Perry ostium, Perry was learned meant around ostium is that bone tissue. So osteoclasts in that area around the bone produces a sheet like layer of bone on the surface and the diaphysis is going to be the long part of the bone and we'll look at that and a few slides we get to, I'll actually show you what I'm talking about. The bone elongates, it gets longer and widens with this process. The elongation occurs at the epiphysis epiphyseal plate and I'll show you that's your growth plate. It pushes in opposite directions. This will continue into our late teens or early 20s. This is how our bones grow. There's another thing called secondary ossification in this occurs late in fetal development, sometimes right before you're born. Osteoclasts form small cavities in the epiphysis, then bone vessels, sorry, blood vessels, and osteoblasts come in and convert that cartilage to bone. This progress is slower than the primary ossification, and it will continue through adolescence and stop into the early 20s. The epiphyseal plate or the growth plates fuse together creating an epiphyseal line. Bone thickening and sculpting continues throughout a person's lifetime. So throughout our lifetime, we're always building and breaking down bone. The whole time. It just slows down at a certain point. Osteoblasts become osteocytes in mature bone tissue. As your sites are responsible for bone maintenance, more than bone formation. Remember osteoblasts are those bob the builders. So once we build that bone, we really don't need so many of them. They actually will become osteocytes where they can consume some of that bone and shape it. We're going to talk about something called the fontanels. Actually, let me go right to it. Here we go. These are fought and nails. It is where in the head oops, let me go back, sorry. In the head here, you have a lot of bones that make up the head. And they eventually will come together. And you'll have this spot where they're not quite fused together yet. I'm sure you've heard of a baby soft spot. It is actually the test medical term the medical term for a soft spot is a fontanelle and just that's where that soft spot is where the bones have not fused together. Well, this when they fuse together and they become hard, works a little bit differently. It's called intra membranous ossification. And it's much easier than that endochondral ossification. It doesn't need cartilage for bone formation. It replaces those right here, the sheet like membrane, that it's connective tissue. It actually will replace that with bone tissue. The connective tissue membrane is put down where future bone's going to grow. Osteoblasts settle in that membrane and they deposit spongy bone material. Blood vessels and osteoclasts will move in to help with growth. And then a thin cap of dense bone is of positive on the surface of that intramembranous bone by osteoblasts in the periosteum. That's a whole lot of stuff. So let me just go back. And tell you to not go back, but I'm going to tell you a little bit more about font nails. The good thing is you're not really going to be tested on the ossification stuff. I do want you to just be familiar with it in case you see it that ossification is that process where bone actually goes hardens. So fontanelle is the soft spot in a baby's head. And the bones in the head have not hardened because it needs to allow for some flexibility during the birth process. Okay, that's a big mate or sometimes babies have big heads. Okay, we've got to be able to get that baby through the vaginal through the birth canal. And what happens is because these are soft, they actually are movable. One can slide over the other one. To allow the baby to come down through the birth canal. As the bones harden, they'll move closer together and then the fat nails will close. That posterior fontanelle, here we have posterior fontanelle is back here. Right there. That one closes in about one to two months. That's the first one to close. The last one to close is this an anterior. Up here in the front. Everybody knows that as the baby's soft spot. That one's the last one to close, and that one closes in 18 to 24 months. We have some more fought nails though. I mean, we know the one up here, the anterior. You have the posterior which I showed you, you also have a sphenoidal fontanelle right there. And you have one on each side. Like this is also can be called the anterior lateral fontanel. And it closes about three months. And you can have an posterior lateral fontanelle, which is right back here, and that one closes also about three months. So we actually have, let's see. We have one, two, three, four, and then you have these on the other side, 5, 6. So we have 6 soft spots when we're as a baby, even though all we really think about is this anterior. And let's go back to last unit when we talked about anterior and posterior. We're using those tournaments right now anterior. This is up in the front. Posterior, this is in the back, and then lateral is on the side. All right, so we have different types of bones. Well, let's talk about their possible function. One, let's see, a skeletal system actually has 5 different functions. And we're going to talk about in the next unit we talk more. We go more in depth about the functions. But we have the 5 functions in general are it supports bone support, bones protect, bones allow movement and anchorage of muscles. Bones provide me general storage. And bones are the site for hemolysis. Hemolysis is the formation of blood cells. Okay? So that's actually where our blood is formed is actually in the bone. All right, you already heard me talk about long bones. This is a long bone. As you can see in compare to other ones, this is definitely a long bone. Long bones are found in the arms and the legs. Specifically, the arm has the humerus. And the radius. The radius is located on the thumb side of the arm, okay? So if you look down at your thumb, that bone that's on that inner side there, that is your radius. And then your humerus is your upper arm bone. In the leg you have two long bones, those are your femur, which is that big bone. That's your thigh bone. And then you have your tibia. That is the bone that runs along the side of your big toe. That's how I remember where my tibia is because it's goes with my big toe. You have flat bones. Flat bones are the located in the skull. That's what you see right here. This is the frontal bone. It's in the skull. Flat bones are in the skull. Your ribs are considered flat bones. And your shoulder blade or your scapula. That is considered a flat bone. Irregular bones. Their name that because they don't have a real, they have different shapes. I mean, you can see. This is irregular. It's very weird shaped. Your irregular bones, you have them in as you see on this picture, in your vertebra. So your backbones are irregular. You also have another irregular shaped bone, and that is your mandible. Your mandible is your lower jaw. It's that bone that sticks up your lower jaw. That's the mandible. And it is classified as an irregular bone. You have short bones, short bones, you will find those in your carpals and tarsals. So in your hand and your feet is where you'll see those. All right, let's identify the structures of the long bone. All right, a typical long bone contains a shaft. Which is called the diaphysis. So, here you go. This part right there. The diaphysis. You can see it right there, how it's spelled. This is a hollow cylinder of hard compact bone. It is what makes a long bone strong and hard, yet light enough for movement. At each end of the diaphysis, is an epiphysis. Here we go. Up here. Right here. And down here. So the heads of those are the epiphysis. In the center of the shaft is the broad medullary canal. See, number 6, medullary cavity or canal, okay? This is filled with yellow bone marrow, mostly made up of fat cells. The marrow also contains many blood vessels, and some cells which form white blood cells called leukocytes. The Yelp arrow functions as a fat storage center. The Endo ostium, let's see. It is right there. The Endo ostium. Is the lining of the marrow canal that keeps the cavity and tact. So it's like the wrapper on there. Endo meaning inside. So inside of the boat, Endo ostium, the medullary canal is surrounded by compact or hard bone. Ever since canals branch into the compact bone. And they carry blood vessels, which nourish the osteocytes or the bone cells. Where less strength is needed in the bone, some of the hard bone is dissolved away, leaving spongy bone. Here you go, spongy bone. Kind of looks like spider webs. And I will show you in class. I have a long we have a part of a long bone so that you can see this. Spongy bone. But if all of our bone was this hard compact bone, they'd be really heavy, and we'd have a hard time walking around. So what happens is we have this very thick or dense compact bone. On the outside and then we have a spongy bone on the inside to make it lighter. The ends of the long bones contain the red marrow. And this is where some red blood cells called erythrocytes. And also some white blood cells are made. The outside of the bone is covered with the periosteum, peri means around. And periosteum is a tough fibrous tissue. Which contains blood vessels, lymph vessels, and nerves. The periosteum is necessary for bone growth repair and nutrition. Covering the epiphysis is a really thin layer of cartilage and it's known as articular cartilage. This cartilage acts as a shock absorber between two bones that meet to form a joint. When two bones meet to form a joint, they are called to be articulating. So, this is why this is named articular cartilage. So right? Over the ends of the bone, we have this articular cartilage. And it's down here too. I'm not sure if you can see it real well. Put it down there also. So that's what makes up a long bone. The diaphysis remember is the shaft or that long part of it. The epiphysis are the ends. And the Endo ostium lines that inside marrow cavity, periosteum is that tough outer covering of the bone. Okay? Here's a better picture of it. So here is that compact or dense. This is the really tough stuff right here. And here's your spongy bone, kind of looks like cobwebs a little bit. And here you have your periosteum that outside or Perry around the around the bone, the periosteum, your compact or hard bone, and your spongy bone. Here's another view of it right here. Here's your Endo osteometric wrapper. Okay, your compact bone that really thick bone got some yellow bone marrow in there, and your periosteum that outside that around layer. Okay? So that's your long bone. So your skeleton can be broken down into two parts. Sorry, I apologize about my chair making noise, guys. The axle skeleton. That's what you see in blue. Your axle skeleton is made up of 80 bones. And its name axel, because it lies along the central line or the access of the body. So it contains your head, so and trunk area, okay? So along the axis or the center of your body, this is your axial skeleton. All right, so you see your head and you're gonna see your ribs, all right? Your backbone. We're gonna talk, let's talk more about that. Skeleton here are sorry your skull. This is the front view. We've got your skull. Contains cranial and facial bones. Right here, you have your frontal bone. This makes up your forehead. The frontal bone is one bone, and it forms a front part of your skull, and it forms your forehead. You let's see what we can see else on here. Temporal bone. Over here to the side. You have two temporal bones. One on each side. These two bones on either side of your skull, they form the sides and the base of your skull. They also are where your ears are housed, right? And when you have a headache, you rub on your temples. Okay, your temporal. That's your temporal bone. A lot of times you'll see that muscles might be named for the bone layover. So we're going to start with a very basic. We're going to start with a skeleton and we're going to learn it. That way when we move on, things will make sense because they're usually named for the bone that they lie over. You have your nasal bone. Right here. You actually have two bones, two nasal bones, and they form the bridge of your nose. This is where your sunglasses sit. Okay? You have your vomer, let's see. Where is he? Here's your vomer right here, this little guy. That's one bone, and it forms the inferior or the bottom part of your nasal septum. If you. Never mind, forget, I'm sorry. Let's go on. Zygomatic. Why are we not? Do you guys see it? I don't see zygomatic. It may show it from the side. But zygomatic, you have two bones that form your cheeks. You have your mandible, which we learned was an irregular bone, right? Makes up your lower jaw. And this is the only movable bone in the face. Your mandible is the only movable bone in your face. Everything else stays still. It can't move. This is the only one that moves. And then making up your upper jaw, you have your maxilla. It's two bones. You have a left and a right, so they come together and that forms your upper jaw. Parietal, you can see it here. We're going to look at another view. This is the frontal view. We're going to be able to look at a lateral view. But right here you have a parietal bone. There are actually two of those. And you have one on each side of your head, and it forms a sides and the roof of the skull. Here we go. Here's a lateral view. Here's a side view. Here's that parietal bone. So you can see it makes up the side and also the roof. So you have one on the left, one on the right. Here's your frontal. Here's your zygomatic arch right here. They showed it on the lateral view that makes up your cheekbone. It's called the zygomatic arch. One more bone that makes up the skull is the occipital bone. This is the back, the occipital bone. You have one occipital bone, and it forms the back part of your skull. So those are the bones that you will be responsible for learning. Once again, I'm going to go, let me see what's on this next page. Here's a superior view, so we're looking at it again. Here is your frontal bone. Here, here's your parietal bone, and there's your occipital bone. Lateral view again, parietal, frontal occipital, temporal. Okay, let me go back. So I'm just going to review your axle skeleton again. It is this is your skull is made up of cranial and facial bones. You have two parietal bones that make up the sides and the roof of your skull. You have one frontal bone that forms the front part of your skull in it forms your forehead. You have one occipital bone that forms the back part of your skull, you have two temporal bones, one on each side, that form the sides and the base of your skull. This is where your ears are. You have two nasal bones which form the bridge of your nose where you, this is where your sunglasses sit, you have one vomer bone, which forms the inferior or the bottom part of your nasal septum. The nasal septum is that if you put your finger in your nose, that stuff in the middle, that divides you into left and right, that's your nasal septum. You have two bones that make up your zygomatic arch one on each side, these form your cheeks. One bone, and your lower jaw, that is called your mandible, and it is the only movable part in your face. And you have two bones that make up your maxilla, or your upper jaw. Let me catch up with where the slide is. We have a really kind of unique bone. It's called the hyoid bone. And what's used in the book about it, it's the only bone in the body that is U shaped. And its purpose, the reason we have a hyoid bone is to support the muscles of your tongue, your larynx, and your fairings. And here you can see in the picture, this is the hyoid bone. And when we meet in class, I will show you on the skeleton all of these in the hyoid bone. But it is the only shaped bone. In the body. Included in our axle skeleton is your vertebral structure or your backbones are in here, your spinal vertebra. The spine or the vertebral column is strong and flexible, it supports its head and it provides for attachment of the ribs. The spine is also the spine also encloses the spinal cord of the nervous system. The spine consists of small bones called vertebra, which are separated from each other by pads of cartilage tissue called intervertebral discs. These discs serve as cushions between the vertebra and act as shock of the virtues. The vertebral column is divided into 5 sections and their named to the area of the body where they're located. I'm going to go back to that. Let's go to this one. So in the top up here, we have the cervical vertebra or cervical spine, and these are labeled C one C meaning cervical one C 7. C one through C 7. These are located in the neck area. C one actually has a special name. It's called the Atlas. It is the first cervical vertebra that articulates or is jointed. With the occipital bone of the skull. In this permits us to nod our head. Then we have C two, that has a special name. It's the axis. This is the second cervical vertebra. And it is the odontoid process, which forms a pivot on which the Atlas can rotate. So Atlas and axis work together. And because we have the access we can turn our head from side to side, because the Atlas rotates only on this axis. These are the only two vertebra that have their own name. So don't freak out. You're not going to have to learn names for all of these. Just C one, Atlas, C two, axis. All right? And then we have C three, four, 5, 6, and C 7. Below the cervical spine or cervical vertebra, we have the thoracic vertebra. Remember we learned about the thoracic cavity, the chest, that's where these are located. And you have 12 of these. And they are labeled T one through T 12. They are located in the chest area. These articulate or join up with the ribs. Down here we have 5 vertebra and they get bigger. They start very small and they get bigger. Here we got some big ones here. This is your lumbar vertebra. They are located in the back that lower back lumbar lower. There we go. Both with L they have large bodies that bear most of the body's weight. Next, we have the sacrum right here. The sacrum is a wedge shaped bone formed by 5 fused bones. So there's actually 5 bones, but they're all fused together. They're all stuck together. And it forms the posterior pelvic girdle, and it serves as an articulation point for the hips. So our hips are actually joined up with your sacrum. And then you have the very bottom and you guys may know this as the tailbone. It's actually called the coccyx, and it is formed by four little fused bones. I'm going to go back to this to show you more kind of up close what a vertebra looks like. So the spinal nerves actually enter and leave the spinal cord through this opening right here. The foramen foramen just means it's a fancy word for hole. So your nerves that go through there. So you can see that this bone protects those nerves, okay? When we study a model of the human skeleton, note that the spine is curved instead of straight, a curved spine has more strength than a straight one would have. Before birth, the thoracic and the sacral regions are convex curves. And as an infant learns to hold it up its head, that will cervical regions become concave. When a child learns to stand, the lumbar region also becomes concaved. This completes the four curves of a normal adult spine. And we will talk about disorders in the next unit, because I'm sure some of you have heard of scoliosis, which is a curvature of the spine, an abnormal curvature, and we'll talk about those. A typical vertebra, which you see. Right here in 6.6 right here. This is a typical vertebra. It contains three basic parts, a body, that's up here, a foramen, which is a hole, and several processes. The large solid part of the vertebra is known as the body. The central opening for the spinal cord is called the foramen, above the foramen protrudes two wing like bony structures, and these are called transverse processes. Let's see, right here, and right here, transverse processes. The roof of the foramen contains the spinous process or the spine. Spine is processed right here, or the spine, okay, when you guys are feeling down your back and you feel that bone sticking out. Ladies and gentlemen, it's this, the spinous process. And there's also an articulate process. I don't think let's see. I don't see it on here. So. All right, but there's an articular process. Let me see, I'm going to look on my thing. Ah, right here. These two things right here. The articulate articular process. This is where they join up with the other bones. So that is why your vertebra looks like up close and personal. Let me give you a helpful hint for remembering the spinal column, because if you're like me, you need a helpful hint, you need a memory jogger. Cervical spine has 7 thoracic has 12 and lumbar has 5. K, each CTL. I eat breakfast at 7. I eat lunch at 12. I eat dinner at 5. That's how you can remember how many are in each one. Now you have to figure out a way to try and remember, you know, cervical is on top, cervical actually means neck, thoracic, that's the chest, that's the middle, and then lumbar is the lower, which has L, the lower back, which has 5. So you just have to try and figure out you got to try and remember that we go cervical, thoracic lumbar, and then you have your sacrum and you have your coccyx. Okay? We have 7, 7 vertebra in the cervical, so you eat breakfast at 7. That's the first thing you do. Next, you have lunch. Which is at 12, right? And that would be relate to your thoracic in the middle. And then your lumbar in the lower is dinner, and you eat that later, right? And that's at 5. That may help you. It may not, okay? I just wanted to give you. A helpful hint there. Here you could see in this x-ray, you can see despite then you can see those vertebra right there. You see all them, and these are actually your ribs coming off of it. Let me go back one, your ribs. Your ribs, there are 12 pairs of ribs, okay? 12 pairs of ribs. The first 7 are called true ribs because they actually connect to the sternum or the breast bone by cartilage. The next three are false ribs because they actually just connect to the 7th. The very last trip. And then the next two are actually called floating ribs. They don't really connect to anything in the front. And we will look at the skeleton in class. And you can see that more closely. All right, so 12 pairs of ribs. Okay. So we just finished talking about the axle, skeleton, which is basically the head. The neck. The chest, which includes your ribs, and then your backbone. So let's move on to the appendicular skeleton. That's what you see in beige, the non blue, so this is kind of all the extras on the body. The appendicular skeleton is related to the limbs, or the appendages of the body. So we're talking about like arms and legs pretty much. The appendicular skeleton is made up of a 126 bones. We'll start with the shoulder girdle. The shoulder girdle is also known as a cat is called the pectoral girdle. It consists of four bones, two curved, clavicles, which are your collarbones, and two triangular scapula, or your shoulder bones. On the skeleton we observe two broad flat triangular surfaces. The scapula. And you can see it on this picture. It is, you'll see it better from the back, but it's right here. It kind of looks kind of looks like wings a little bit. They permit the attachment of the muscles that assist in our movement and they serve as a place of attachment for the arms. The two clavicles or your collarbones are attached at one end to the scapula and the other end at the sternum. Or your breastbone, and they help to brace the shoulders and prevent excess forward motion. So your clavicles are to your collarbones, and we'll be able to feel those and we'll check them out on the skeleton in the classroom. And then your shoulder blade, your scapula. On your arm, the bone structure of your arm consists of the humerus, the radius, and the ulna, okay? The humerus, the radius, and the ulna. The humerus is located in the upper arm and the radius and the ulna are in the forearm. You can see it right here. Here's your radius, I mean, sorry, excuse me. Your humerus, you have your ulna and your radius. The humerus, the only bone in the upper arm is the second largest bone in the body. The upper end of the humerus has a smooth, round surface called the head, which articulates or joins up with the scapula, or your shoulder blade. The upper humerus is attached to the scapula socket by muscles and ligaments. The forearm consists of two bones. The radius and the ulna. The radius is the bone running up the thumb side of the forearm. Its name derives from the fact that it can rotate around the ulna. This is an important characteristic permitting the hand to rotate freely and with great flexibility. The ulna by contrast is far more limited in its motion. It is the largest bone in the forearm. And its upper end at its upper end, it produces a projection called the cranium process forming your elbow. When you bang your elbow or the old cranium process, it is usually referred to as hitting your funny bone. The Ukrainian process articulates or joins up with the humerus. So there you go guys, in your shoulder girdle, you have your clavicle, your collarbones, you have your scapula, your shoulder blades, your upper arm, that bone is called the humerus. Your lower arm or your forearm has your radius, which is on the thumb side, and your ulna, which is on the other side, and that has the old cranium process, which makes your elbow. You also have your hand. Interesting enough, the hand and the wrist actually has like 27 bones. Okay? Let me see if we have a, oh, here's a nice picture. So here is your collarbone, right? Your clavicle. Here is your scapula. You can see it right there. Here is your humerus. I don't want to go back. They're not going to show you Andy. Any hand. X-rays, but we'll look at it in class. The human hand is a remarkable piece of skeletal engineering and dexterity. It contains more bones for its size than any other part of the body. Collectively, the hand has 27 bones. The wrist bone or carpals consists of 8 small bones arranged in two rows. They are held together by ligaments, which permit sufficient movement to allow a wrist a great deal of movement and flexibility. There is only there is only slight lateral movement. So side to side movement in the carpal bones. However, we can go about we can learn about the movements, but we can flex and extend our wrists without any problem. We can't move them side to side so much. Attached on the palm side of the hand are several short muscles which supply mobility to the little finger and the thumb. The hand consists of two parts, the palmar surface, which has 5 metacarpal bones, and 5 fingers with 14 phalanges. Each finger except the thumb has three phalanges. And the thumb only has two. There are hinge joints between each flange, allowing the fingers to be bent easily. The thumb is the most flexible finger because the end of the metacarpal bone is more rounded, and there are muscles attached to it from the hand itself. Thus, the thumb can be extended across the palm of the hand, only humans and other primates possess such a digit known as an opposable thumb. And we will look more in depth at the hand in the classroom. In this lecture. But we will definitely look at that. The pelvic girdle, the pelvic girdle. When you're young in your youth, the pelvic girdle consists of three bones. It's found on either side of the midline of the body. The bones include the ilium, the ischium, and the pubis. And this isn't I'm going to move forward for a minute and see, here we go. The ilium. The ischium, which you have right here, and the pubis. Ilium, they look like elephant ears, ischium that goes to this lower part right here, and then this little curve here, your pubis. These bones eventually will fuse with the sacrum to form a bull shaped structure called the pelvic girdle. Eventually, these two sets of bones form a joint with the bones in front, and it is called the symphysis pubis. And with the sacrum in the back. The pelvic girdle serves as an area of attachment for the bones and muscles of the leg. It also provides support for the viscera, or the soft organs of the lower abdominal region. The obvious anatomical difference between the male and the female pelvis is that the female pelvis is much wider than that of the male. Why? Because women have to have babies, right? So this is necessary for childbearing or pregnancy and childbirth and we need room to hold that baby in there and we need room to push it out too. In addition, the pelvic inlet is wider in the female. The pelvic bones are lighter and smoother than those of the male also. So, there you can see the tailbone, but it forms like a bowl, and we'll see this on our mannequin. So the ilium is that upper bone of the pelvic girdle makes like elephant ears, the ischium is the lower bone, and then the pubis is that lower front bones. Once again, they are separate at birth, but as we get older, they fuse together. Let me go back. Two, here we go. Let's look at the leg. The upper leg. The upper leg contains the longest and strongest bone in the body. Your thigh bone is called the femur. Here it is. The longest and strongest bone in your body is the femur. The upper part of the femur has a smooth rounded head, and it fits neatly into a cavity of the ileum known as the acetabulum. And it forms a ball and socket joint. We're going to talk more about joints and a little bit. This femur is an amazingly strong bone. A direct compressible force applied to the top of the femur of in order to break that femur. It has to have anywhere between 15,000 to 19,000 pounds per square inch, applied to it in order for it to break. It's super, super strong. Your lower leg, your lower leg consists of two bones. The tibia and the fibula. The tibia is the largest of the two lower bones. And then so you have your tip bee, which goes to your big toe, that actually goes your whole foot, but you just remember it's on the side of big toe. And then your fibula is a smaller one that goes towards the back. And then here's your kneecap, your kneecap actually has a name, and it is called the patella, the patella is found in front of the knee joint, and it is a flat triangular sesamoid bone. The patella is formed in the tendons of the large muscle in front of the femur. In females, it appears at around two to three years of age in males and around 6. Okay. The patella attached to the tibia, it is attached to the tibia by a ligament. It ossifies as early as puberty. Surrounding the patella are four bursae, and we'll talk about those which serve as a cushion to the knee joint. You have your ankle. The ankle or it's also called the tarsus. Contains 7 tarsal bones. These bones provide a connection between the foot and the leg bones. The largest ankle bone is the heel bone or its other name is the calcaneus. The tibia and fibula articulate with a broad tarsal bone called the talus. Ankle movement is a sliding motion and allows the foot to extend and flex when we're talking. Your feet, feet take a great deal of punishment over from our bodies. With every mile we walk 200,000 to 300,000 pounds of stress, bears down on our feet. By the time a person is 50, they may have watched 75,000 miles. The foot has 5 metatarsal bones, which are somewhat comparable to the metacarpals of the hand. The way I remember this is metatarsals with a T have to do with your toes. Metacarpals are up in the hand. So they're the opposite. The metatarsal bones are arranged to form two distinct arches, which are not found in the palm of the hand. One arch runs longitudinally from the calcaneus to the head of the metatarsals and it's called the longitudinal arch. The other which lies perpendicular to the longitudinal arch is the metatarsal region, is known as the transverse arch, ladies and gentlemen, please do not worry about that. That's really getting more into depth, okay? So we just need to know that the foot is made up of metatarsals, the ankle are tarsals. And we'll look more in depth at that. So tarsals, the ankle bone, there's 7 of them, metatarsals, there's 5 foot bones. And we once again, just like in the hand, have phalanges, okay? Pelvic girdle. So what do we see here? Let's see. I see, here's your femur. And I see a patella, which is your kneecap. And then this thick bone that's a little bit darker is your, which one is that ladies and gentlemen? That is your tibia. And then the smaller one is your fibula. Okay? There you go. Tibia and then fibula is behind it. Sometimes you may see if somebody breaks her leg, they had a tib fib fracture. Sometimes we shorten it that way. Pelvic girdle, here is what you got going on up here. Your ileum, your elephant ears. And your ischium down here, and then your pubis. Okay, remember females is wider. You can see a nice picture of that difference right here. A man's is a little bit taller and thinner and ours is short and wide, okay? We got to leave room for that baby to come out. A male's pelvic arch very small, less than 90°. Ours is more than 90°. Once again, to allow that baby to be born. Now we're going to move on to joints. Joints or the articulation is joints are the point where there's contact between sorry. There's contact between two bones. A joint or an articulation is where there's a point of contact between two bones. Joints are classified into three main types according to the degree of movement. We have system, which are movable joints, amphi arthrosis, which are partially movable joints, and then sin arthrosis, which are immovable. They don't move. And we're going to go through each one of those. So, that's what we have on the computer right now. Our freely movable joints. We have four types of these. We have a ball and socket, a hinge, a pivot in a gliding. Most of the joints in the body are dye arthrosis. Type joints. Okay, once again, the ball and socket, the hinge pivot and gliding are the four types of dye arthrosis or freely movable joints. And the ball and socket, its named from the way that the bones connect. One bone has a ball at one end, and then the other has a concave socket. So you have the ball from the femur and the your hip bone or your ilium right here has that socket. This joint allows for the greatest range of motion out of all the joints, all the joints you have, the ball and socket joint allow for the greatest range of motion. The only place you will find a ball and socket joint in the body is the shoulder and the hips. Those are the only ball and socket joint. In the body. The hips and the shoulder. Here you have an example of the ball and socket joint. This picture that you have here is actually a artificial hip joint that when somebody has a hip replacement, this is what they do. They put in its metal. And here is your ball, and then there's your socket. Here is a real email. Femur. Got your ball, and then there's your socket from your hip. Okay? So once again, remember ball and socket is the most allows for the most movement, the joint that has the most movement in the body, and you will only find ball and socket joints with the hip and shoulders. The hinge joint moves in one direction, okay, flexion and extension. So moving your arm out and bringing it back up, it's like a door hinge. It's how it got, you know, probably named because this is how a door works. You know, you can only move a door so far, right? And then it won't go any further. This is the same thing. In the body, you will find hinge joints in your knee and your elbow and also the outer joints, your finger. Okay? He enjoys in your knee, your elbow, and the outer joints of your finger. It allows for only one direction. Here is a hinge joint. This is somebody's elbow right here. Unit uniaxial means one way, okay? So we can only move it so far, right? Once again, your elbow and your knee. Pivot joints. Bones that actually rotate across each other. They rounded portion of one bone in a pivot joint fits into the groove of another bone. And so their bones that rotate against each other. So you've got your elbow. You've got your wrist and your fingers. You also, let's look at this. You have the head of the radius, rotates within the groove of the ulna, so you have your radius and ulna, and that's what you have right here. Radius and ulna, and also remember when I talked about the vertebra. C one and C two Atlas and axis have the same pivoting. Okay, that allows C one rotates on C two. Gliding joints, bones with a flat surface that slide across each other. An example of a gliding joint would be the joints of the hands in the feet. Now remember that the gliding joint is still a dye arthrosis category of a joint, okay? Freely movable. Now we're going to move into amphi arthrosis. These are partially movable joints. Your amphi arthrosis joints would be your ribs meeting with the spine, and then also the pubis. So they can move a little bit, member synthesis, it has to kind of move to allow the baby to come out on a female. And then our ribs definitely need to be able to move because we have to be able to breathe, right? So you can see your chest moving up and down. So there has to be some little bit of movement between the articulation or where two bones meet up. So NPR means partially movable and the partially movable joints that you have in your body are your ribs to your spine and your synthesis pubis. Sin arthrosis means in movable. They don't move, okay? Throws his joints are connected by fibrous connective tissue. A great example and the one example that you have in your body that joints that do not move would be in your skull, okay? Once they fuse together, they are an immovable joint. We need that for protection in our skull. When we're younger, they're not fused together to allow the baby to be born, and then as the baby grows older, there is that fibrous connective tissue that will join those two bones together. And form what this is called is actually called a suture line. Okay? So here you have a frontal suture, it's a suture is where these two bones meet up. And we'll look at it on the skull. You can actually see these lines. On a skull. So sine arthrosis means immovable. These joints do not move. Freely movable, dye arthrosis, kind of movable, and arthrosis, not movable at all, sin arthrosis. Bursa, bursa is a small synovial fluid sac that are located at friction points around joints between ligaments and tendons and bones. They actually act as cushions to decrease stress on the structures. We have these located in the shoulder and knee. They are lined by a synovial membrane, but here you see a number four on the picture is the bursa. All right, so it's just a fluid filled sac. And you're probably going to ask me, well, what's a synovial membrane? Good question. A synovial membrane is a capsule that encloses a joint. It is a double layer of connective tissue that lines a joint cavity. And it actually produces what's called synovial fluid. Synovial fluid is a lubricating substance. So it keeps those bones from grinding on each other. When you pop your fingers pop your neck when you pop, that's actually an air bubble in that synovial fluid causes that popping. You definitely need that synovial fluid to lubricate those joints. You may have issues with your joints later on in life. If you tend to crack your knuckles and things like that. Oh, all right. Essential standards. So we should have learned what is the process of bone formation, what are the structures of long bones and what are the structures of the skeletal system? And we will talk about this in class. Make sure that you have taken notes during this lecture. Make sure you summarize this lecture and write at least one question that you have related to the lecture that you just listened to. I'm sure you have more than one, write them down and we will be meeting up in class and discussing these things.