骨骼的结构和功能

so in this video we're going to be talking about skeletal structure and then the function of those skeletons and specifically human skeletons is what we're interested in but before we talk about human skeletons let's talk about bug skeletons or the skeletons of arthropods or insects and so I'm going to draw a little ladybug here and our little ladybug being an arthropod has what is called an exoskeleton and the exo and exoskeleton actually first the fact that this skeleton is outside of the ladybug so EXO is actually greek for outside or external humans on the other hand we are vertebrates and as vertebrates we have this amazing network of bones located on the interior of our bodies and so we have what are called endo skeletons and endo is Greek for within or inner referring to the location of the skeleton as being inside of our bodies as opposed to outside now as humans our endoskeleton performs a variety of pretty vital functions the first of which is it supports our body and provides a framework for movement so what does this mean our our body is supported by the network of our bones which allows us to sit up and stand and provide some sort of structure for our body and then the limbs of our body in particular and the various joints in our body provide a framework for movement that allows you to run around to kick a soccer ball to type on a keyboard another important function of our skeleton is that it protects our most vital organs so if you look at the skull for example it houses our brain and the ribcage protects our heart and lungs and other organs and the third function of our skeleton is that it performs a variety of physiological roles in our body namely the storage of calcium and what is called hematopoiesis which is the production of all the cellular components within our blood so our blood is made up of many different components plasma proteins among other things and the cellular components of our blood which are red blood cells white blood cells and platelets are all formed within the bone marrow of our bones and so those are the main functions of the bones that form our skeleton now one way of classifying bones is differentiating between those that form the axial skeleton and then those that form the appendicular skeleton now the axial skeleton is made up of our skull and rib cage and our vertebral column that is the axial skeleton it forms sort of the axis of our body right right in the center down the midline and then the bones of the four limbs and our pelvis form what is called the appendicular skeleton and so our four appendages form the appendicular skeleton which is attached to our central or axial skeleton another classification system for the bones in our skeleton is the difference between flat bones and long bones now what are flat bones some examples of flat bones are the bones that make up your skull the different bones that make up your ribs and then also the bones in your pelvis and so flat bones really are describing the shape of the bone these bones are made up of an inner spongy or cancellous bone and then the outer shell is made up of compact bone so there's an inner spongy cancellous bone and rachelle of compact bone and flat bone serve primarily to protect our organs and serve as a site for hematopoiesis now long bones on the other hand some examples of those would be the humerus in your upper arm or say the femur in your lower leg and if I draw a long bone out here there are a few different terms to be familiar with when you're referring to different parts of a long bone the long middle portion of a long bone is called the diaphysis and then the end of a long bone is called the epiphysis and there is the small area of bone in between the two or in the middle of the diathesis and the epiphysis is called the metathesis and the metathesis contains the growth plate which is present in the long bones of children and these long bones are made up of the same inner spongy cancellous bone with an outer shell of compact bone just like flat bones and these long bones really are the ones that provide a framework for a movement like we talked about before and they also serve as a site of hematopoiesis and speaking of hematopoiesis where exactly does this metal pieces occur I mentioned that it occurs in bone marrow which is contained within bones and there are two different types of bone marrow there is what is called red bone marrow and then yellow bone marrow now red bone marrow serves as the primary site for hematopoiesis which makes sense because the red blood cells from that appeases actually make red bone marrow look red to the naked eye so you can remember that red bone marrows for blood or hematopoiesis and you can typically find red bone marrow within flat bones and then in the epiphysis of long bones and then yellow bone marrow on and is primarily a site for fat storage made up of fat cells called adipocytes and generally you can find yellow bone marrow within the diocese of long bones