we'll finish the axial skeleton with the look at the sternum and ribs sternum has three main parts the manubrium is the most superior region bodies in the middle and the xiphoid process is the most inferior portion manubrium means shield and xiphoid means shaped like dagger some violent imagery from the early anatomist there's also a notch out of the manubrium called the jugular notch which is where the jugular veins drain the blood from the head and brain down towards your chest we can then look at the ribs but first we should take note that the ribs do not directly contact the sternum there's chunks of cartilage called costal cartilage and those are what connect the ribs to the sternum and this is important because if you look very closely at the costal cartilage you'll note that some ribs have one chunk of costal cartilage connecting them to the sternum but if you look at the lower ribs especially very low you'll see that there are chunks of cartilage that merge with other chunks of cartilage and other chunks of cartilage and then eventually they'll make their way up to the sternum so we have names for these different types of ribs true ribs are the first seven pairs of ribs and those typically have more or less a single piece of cartilage connecting them to the sternum false ribs can be defined a few different ways you can call false ribs all the lower ribs pairs eight through twelve or you can get a little more nuanced and say well some of those pairs of ribs like pears 8 through 10 they do have cartilage that will connect them to the sternum we can call them false ribs but ribs 11 and 12 have no cartilage at all they're just kind of floating there and so those can be called floating ribs so in other words some sources you'll look at will say that the floating ribs are ribs 11 and 12 other places we'll call those false ribs and more specifically floating ribs you you can do either in this course now let's look at a basic rib take note that there's a bunch of stuff on one end of the rib little bony bumps here and there but the other end is pretty flat and nondescript I like to think of this as one end has a bunch of bony chunks because it needs to attach to the vertebrae and you know how vertebrae are classified as an irregularly shaped bone so they've got a bunch of their own bony tongue sticking out here and there but on the other end the rim attaches to cartilage think of cartilage this is like being really sticky and the rib just kind of connects to it like that so the sternal end of the rib is the very flat nondescript end that attaches to the costal cartilage the other end attaches to the vertebrae and more specifically we can see the rib has a head followed by a neck and then a chunk of bone called a tubercle on the and the tubercle are facets articular facets so the facets are where the rib is going to articulate with the vertebrae anytime you see the word articular or articulation you should be thinking about a joint between bones and anytime you see the word facet you should be thinking that's the exact spot where the bones are touching in the articulation the ribs have a sharp curved region called an angle we also learned that where the mandible suddenly curves up towards the skull that's called an angle the bottom region of the rib is called the inferior margin and in one region there's this groove kind of dug out of the inferior margin that's called the costal groove just means the groove on the rib and there are some blood vessels and nerve that are tucked up in that costal groove so now we've looked at the sternum and the ribs but the last thing I want to do is look at how this rib attaches to the vertebral column so from this superior view we can see a thoracic vertebra which makes sense because only thoracic vertebra are in the rib region we can see its body and its spinous process and even things like the lamina region here in here and the pedicle regions here and there but the structures were most interested in right now are where the rib is attaching so remember costal means rib and the thoracic vertebrae have a superior costal facet and an inferior costal facet and a transverse costal facet so each thoracic vertebra has three places it will come in contact with ribs but as you can see here the head of the rib actually attaches to two vertebrae it's attaching both to the inferior costal facet of this vertebra and it's attaching to the superior costal facet of the other vertebra you and remember the ribs also have that chunk of bone near the head called the costal tubercle and it's the costal tubercle then that articulates with the vertebra at the transverse costal facet you you if you look at this superior vertebra we can see now it has a superior costal facet and a transverse costal facet and those are standing there ready and waiting for the next rib to plug into so each rim articulates with two thoracic vertebrae in each vertebra has three different articulation points you so axial skeleton lots going on but now we can move on to the appendicular skeleton