the sceletal system which is made up of bone performs several basic functions the skeleton serves as a structural framework of the body by supporting soft tissues like the skin and providing the attachment points for the tendons of most galal muscle bone protects our most important internal organs for example the skull protects the brain and the rub cage protects the heart and lungs moscal muscle attaches to Bone and when that muscle contracts it will shorten and pull on a bone to create movement at a joint bone tissue stores several minerals including most of the body's calcium and phosphorus stores within certain bones red bone marrow produces red blood cells white blood cells and platelets and within other bones or in other regions of a bone we find yellow bone marrow which is a storage site for triglycerides or fat now within the sceletal system there are many different types of bone these bones can be classified into five main types based on their shape so our five main types include a long bone flat bone a regular bone sesamoid bone and a short bone so our long bone has a length greater than its width examples of a long bone include the femur which is your thigh bone which is the largest bone in the body as well as the relatively shorter bones of the fingers and the toes long bones function to support the weight of the body and to also facilitate movement in conjunction with our scalino muscle flat bones are generally quite thin and are composed of near two parallel layers of compact bone enclosing a layer of spongy bone flat bones provide protection for the organs or the tissues underneath them as well as a large surface area for the attachment of muscle examples of flat bones include the bones of the skull the sternum and the rib cage and also the bones of the pelvis a reg bones as their name suggests have an irregular shape they don't fit into any of the other categories and they often have a complex shape which helps protect an internal organ or tissue so for example our vertebra which are the irregular shaped bones of the spine they surround and protect our spinal cord sesamoid bones are bones which develop in tendons where there is considerable friction tension and physical stress functionally our seso bones protect the tendons from excessive wear and tear and they can also often change the direction of the pull of a tendon which can help improve the man the mechanical advantage at a joint so make that joint more effective examples of sesamoid bones include the small round bones found in the hands and the feet however the most common and well-known sesamoid bone is your patala which is the bone which forms your kneecap lastly our short bones are somewhat Cube shaped they're nearly equal in length and width they consist of spongy bone tissue except at the surface which is a very thin layer of compact tissue when located together short bones provide stability and a small degree of movement the carpal bones in your wrist and the tassel bones in your ankles and feet are all examples of short bones so recapping that all in text for you our long bones are longer than they are wide they support the weight of the body and facilitate movement in conjunction with muscle our flat bones are flat funnily enough they serve to protect the tissues underneath and serve as a large attachment size diet for muscle our irregular bones are irregular complex shapes they also often serve as protection for internal organs sesamoid bones are ended in a tendon they protect that tendon from wear and tear short bones are about as long as they are wide they provide stability and a small degree of movement now of those different bone types long bones play a particularly important role because they contain both red and yellow bone marrow and they facilitate much of the movement of the body through their attachment to muscle so learning objective number three is to describe the structure and function of each part of a long bone so here is a long bone remembering a long bone is longer than it is wide and a typical long bone is made up of a diaphysis which is the Bone's body or shaft it's this long cylindrical section here and then two epes which are the proximal epis and the distal epis or the two ends of the bone which end of the bone is proximal or Cal will depend on which end is closer to the point of attachment so this bone here is our humorous this end here will attach into our shoulder this will attach into our elbow so this is proximal it's closer to that point of attachment being the shoulder this end is distal because it's further away we then have meta feces which are actually not labeled here and I don't particularly need you to be able to ident ify these but the medes are the regions of bone between the dapes and the epiphyses in growing bone each metaphases contains an epipal plate which is a layer of Highland carage which allows the bone to grow in length so that's why this region is important now we will cover bone growth later on in this series of lecture recordings but when a bone stops growing in length which is is typically between the ages of 14 and 24 the cartilage in that epipal plate is replaced by bone and that resulting layer of bone is known as the epipal line we then have articular cartilage which is it found at either end of a long bone the articular cartilage is a thin layer of Highland cartilage which covers that epipa EP p feis and is called articular cartilage because it's found where two bones will articulate or meat the function of this articular cartilage is to reduce friction and absorb a small amount of shock at a freely movable joint so if this section here is where your humorus will meet the two bones of your lower arm this layer of articular cartilage will Dru the friction between those bones As you move your elbow now surrounding the bone we have the periosteum Perry means around and remember OST refers to Bone so this is the layer of tough connective tissue which surrounds the entirety of the bone except for where we find articular cartilage it's composed of an outer fibrous layer and an inner osteogenic layer which consists of cells which allow the bone to grow aside from containing cells which help the bone to grow the Peri oium also serves to protect the bone nourish underlying bone tissue and also serve as an attachment site for both ligaments which connect bone to bone and tendons which connect muscle to Bone the end osteum is then the thin membrane that lines the inner surface of the bone so Endo refers to within OST again referring to Bone the endosteum contains a single layer of bone forming cells and a small amount of connective tissue lastly we have the mallerie cavity which is a hollow cylindrical space within the diaphyses of the bone this area contains fatty yellow bone marrow and many blood vessels aside from storing that yellow bone marrow this cavity also reduces the weight of a long bone by reducing bone density where it's least required now we also have compact bone and spongy bone labeled on this image here we're going to speak more about these two types of bone tissue more shortly but I just wanted to highlight here that the different types of bone are found in different regions so our compact bone is found all the way along the outside of a bone so you can see it's that thick tissue here and here and then thinner around the edges our spongy bone is this spongy looking tissue it looks like a kitchen sponge that's found on either end