Bone Structure and Histology (Nursing)

00:02 So, the structure of the bone is pretty simple.

00:04 Here we will talk about the long bone.

00:07 Now, please note that this is specific for long bone and flat bones may not have all of these different structures.

00:16 So, in the long bone, you have the shaft or the long part of the bone.

00:22 This is referred to as the diaphysis.

00:25 At each end of the bone, you have the two epiphysis.

00:31 And the region that separates the diaphysis from the two epiphysis are referred to as the metaphysis.

00:42 The long bone also consist of other parts.

00:45 So, at the ends of each of the bones on the epiphysis, you will have the articular cartilage.

00:52 This is going to be important for joints.

00:56 Also on the outside of the bone you have a connective tissue layer known as the periosteum.

01:06 Inside of the bone, there is a hollow space that we refer to as the medullary cavity.

01:13 And finally, inside of this medullary cavity, there is also a connective tissue lining known as the endosteum.

01:23 So before we get started in talking about the histology of the bone, I first want to go over a little bit of vocabulary that will help you navigate the following slides.

01:34 When you see the term Osteo, think bone.

01:38 When you see the term Chondro, think cartilage.

01:43 When you see Peri, think peripheral or the outside of the bone.

01:48 And when you see Endo, think inside of the bone.

01:53 And for suffixes at the end of the word when you see Blast, especially when we're talking about certain types of cells, these are normally precursor cells that are going to secrete matrix like collagen and ground substance.

02:09 When you see Cyte, think of those as mature cells.

02:16 So the bone is going to contain an abundant extracellular matrix that is going to surround different types of cells that are very widely separated.

02:27 The bone is mostly made up of three major components: There's water.

02:33 There is a large amount of crystallized minerals, those including calcium phosphate, calcium hydroxide, and hydroxyapatite.

02:44 And finally, we have collagen.

02:47 The importance of collagen is that calcification or the hardening of the bone requires the presence of collagen fibers in order to occur.

03:00 So there are four main types of cells found in our bones.

03:06 First we have, osteocytes.

03:08 which are mature bone cells.

03:12 Prior to that, we have the osteoblasts, which are the precursor to osteocytes and are going to secrete the matrix.

03:22 Prior to osteoblasts, we have osteoprogenitor cells.

03:26 These are a type of stem cell that normally differentiate into osteoblasts.

03:35 And then we have osteoclasts.

03:38 Osteoclasts come from a different lineage and are actually a type of white blood cell.

03:44 And this cell is going to be important for remodeling as this type of cell breaks down bone.

03:52 So in the bones, we have two major types of bone tissue.

03:57 We have compact bone, which is going to be good for providing protection and support.

04:03 It is very thick and very strong.

04:05 And then we have spongy bone.

04:08 Spongy bone is a lot more lightweight and is also going to provide some support for the tissue.

04:16 Compact bone is usually found on the periphery of the bone.

04:20 Whereas, spongy bone is often found inside of the bone.

04:25 The epiphysis of the bone or the ends of the bone are going to contain a large amount of spongy bone.

04:31 Whereas, the diaphysis of the bone or the shaft of the bone is made up of mostly compact bone with a little bit of spongy bone also in the medullary cavity.

04:45 So, the bone does have a blood supply.

04:49 There are several different arteries and veins that are going to go into and out of the bone.

04:56 In the periosteal area of the bone or that outer layer of the bone, you have periosteal arteries.

05:04 These are also accompanied by periosteal veins.

05:09 Coming into the center of the diaphysis or shaft to the bone through a hole known as the nutrient foramen, we have the nutrient artery.

05:20 This is going to be very important when we talk about bone formation.

05:25 Along with the nutrient artery, exiting from the nutrient foramen, we have the nutrient veins.

05:33 Also, in the metaphysis and epiphysis of the bone, there will also be arteries and veins associated with those areas as well.