02.02 Bone Structure

In this lesson we're going to talk about bone structure, and the gross structure and classification of the bone.

So when we're talking about the structure of the skeleton, we want to look at two different types. You got the axial skeleton, and appendicular skeleton. The axial skeleton contains the skull, vertebral column, and rib cage. The appendicular skeleton refers to all the limbs, the pelvic girdle and the shoulder girdle. Now let's take a look at some bone classifications.

When we start talking about bone classifications, we're talkin about the different types of bones that you're going to see throughout the body. First off is long bones. This is going to include anything like the humerus, radius, ulna, femur, tibia, fibula, metacarpals, and metatarsals.

The next classification where to look at are the short bones. These are the carpals and tarsals.

The flat bones are different types of skull bones, the scapula, sternum, and ribs. What you're talkin about the flat bones of the skull, what we're really looking at are the lacrimal bones, nasal, frontal, parietal, and occipital bones.

We also have different types of irregular bones, which are your pelvic bones, your vertebral, your sacrum and coccyx. And we were talking about skull bones, we're talkin about the ethmoid bone and sphenoid bone. We're also talking about the maxilla, mandible, and temporal bones.

Also don't forget we have these bones called the sesamoid bones. These are bones that are encased by tendons. These are also known as floating bones. You have two of them, and it's the patella and the hyoid bone.No we start looking at the structure of a long bone, this is what we really think about what we think about bones.

First we'll start off with the diaphysis. The diaphysis is basically the long middle shaft of the bone, and it's hollow and contains bone marrow. This is known as the bone marrow cavity, or the medullary cavity. Young bone marrow is known as red bone marrow and aged bone marrow is known as yellow bone marrow.It has spongy bone, it's also covered by endosteum, which contains osteoblasts which are needed for growth and repair.

Now each end of the long bone you're going to have the epiphysis. You have a proximal and distal end, and on each end is a very thin layer of compact bone with most of the phone internally being spongy bone. Articular cartilage covers the outside of them, and it's always occurring at the joint and it helps to reduce friction. This articular cartilage is made of hyaline cartilage.

Another important structure of the long bone is something called the periosteum. The periosteum covers the outside of the bone except for areas where there is articular cartilage. It's made up white fibrous connective tissue and it contains blood vessels what vessels and nerves. It also contains osteoblasts which are really helpful for growth and repair and there are collagen fibers which connect the periosteum to the bone. This is also the site of tendon connection. New pair of the long bone let's take a look at the other types of bones.

No more talking about all of the other types of bone, were talking about short bones, irregular bones, and sesamoid bones. For the most part, they're all equal and composition. There's an internal spongy bone which contains red bone marrow, and the external bone is compact bone covered by the periosteum. That's what makes it hard.

So now you have a better understanding of what's involved with all the different types of bones, let's take a look at how these two different types work together within a single bone. So we look at this cross-section of a long bone, it looks like a hollow cylinder. That hollow cylinder in the middle is the bone marrow cavity. There's trabecular bone or spongy bone at the edge of the bone marrow cavity, and in the osteon with covers that spongy bone. Around that is the compact bone. Now if you remember from the previous lesson about bone cells, you have these things called haversian canals which you can see here. These are the ones that run up and down or vertically through out the bone and they supply all of the blood vessels and nerves to all of the bone. Then you have these things called volkmann's canals and they run horizontally and they can interconnect the haversian canals. This is a way for blood to get from the blood vessels to the bone marrow cavity.

Now there is also other types of layering, or Lamela. and the two types we're going to look at here are the interstitial lamellae and the circumferential lamellae. If you look here in between each one of these osteons, is interstitial lamellae, and what it does is it helps to provide strength in between each osteon.On the outside here you can see something called circumferential lamellae, and then is the outer edge of the cell. They reinforce and provide strength in the outside.


Okay so let's recap.

We're talking about bones, we want to look at the different types of classifications. You've got long, short, flat, irregular, and sesamoid. Remember with amp you always looking at structure and function, and we look at the structure will look at the diaphysis which is the middle shaft of any long bone, the epiphysis which are the ends of the bone, and the periosteum which is a covering.

Bone consists of both spongy and compact bone with long bone being a little bit more complex.

When we look at the blood pathways, what we're looking at is how do we get blood to the Bone tissue. This is delivered via the haversian and the volkmann's canals.

And don't forget about the other lamella structures, which of the interstitial and circumferential structure which help to provide strength in between cells, and around cells.

That's it for our lesson on bone structure. Make sure you check out all the resources attached to this lesson. Now go out and be your best selves today, and as always happy nursing.