there are two types of bone that I want you to be familiar with there's compact bone and spongy bone
and we're gonna spend the majority of our time talking about compact bone but before we get
into the details of what makes up the compact bone I want us to understand the difference between the
two but before we get into that I wanted to talk about terminology anatomy a lot of time has many
different names for the same thing so as if you ever read a different textbook I want you to be
familiar with the different terms that can be used for the same thing so when we're talking about
compact bone sometimes you can hear compact bone referred to as cortical or dense bone and then
in terms of spongy bone you may hear the terms trabecular or cancellous now a lot of times I will
use the term trabecular because really this type of bone is composed of trabeculae or these tiny
spicules of bone tiny spines of bone so let's look at an actual bone so this is a femur that has been
sectioned sagittally sectioned and it's really nice in terms of showing you the two different
types of bone so you can see when I'm talking about when I'm talking about these trabeculae
these little spines of bone right here and these this is going to be that trabecular or spongy bone
whereas you can see this much denser compact bone there so really making up that you know
strong portion of the diaphysis or the shaft of the bone now differences between the two why are
they located in different areas well that compact bone is as you would think it's a bit more solid
so it's going to be really important in terms of resisting bending and this is going to form the
external layers of all bones so even bones that are made up of almost exclusively spongy bone
are gonna have a layer of compact bone so every single bone is going to have a layer of compact
bone also important in terms of the bulk of the shafts or the diaphyses of all long bones so
you can see right here this is compact bone and you'll have it in the majority of the long portion
of long bones whereas spongy bone is going to be important in terms of strength in terms of
compression so you'll have these in areas where you have joints so on the ends of bones or these
epiphyses these are gonna be made up of almost exclusively spongy bone except for a small layer
like I was saying that compact bone so right around here even though the majority of this
is made up of spongy bone you're going to have compact bone on the edges now these are going to
contain larger spaces and this is important for two main reasons first this really reduces the
weight of the bone if you think about it if all bone was made up of compact bone or that heavier
bone we wouldn't be able to move it move as freely as we do so it really reduces the weight it also
serves as protection of that red bone marrow or of yellow bone marrow so remember in our previous
presentation red bone marrow is important in terms of blood cell formation so really important
in terms of protection of that now where are you gonna find spongy bone the majority of your short
bones so your carpal bones or examples of short bones flat bones so the majority of your skull
cap or calvaria are composed of flat bones and irregular bones and the best example of irregular
bones are your vertebrae or the bones that make up your spinal spinal column and last but not
least these epiphyses or these ends of long bones are going to be made up of spongy bone as well