Structure of Bones

by Geoffrey Meyer, PhD

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    00:02 In this lecture, I am going to talk about bone. But I am going to concentrate on mature bone and the function of mature bone. In a later lecture, I am going to talk about bone formation and bone growth. Bone is a very specialized connective tissue. Like all connective tissues, it is composed of cells, fibres and matrix. But in the case of bone, the matrix is calcified. And because of that it enables bone to have some very important functions in the body. It can protect vital organs of the body, the thoracic cavity protects the heart and the lungs. The cranium protects the brain. Bone always forms the skeletal components of the body and in unison with the muscle affects movement of the body. It is also a very important mineral reserve for both calcium and phosphate and it provides a compartment for bone marrow to form blood cells. I am going to talk about these latter functions in a lecture later on. Let us look at really what I want you to understand with this initial lecture on bone. First of all, I want you to appreciate that there are two types of bone, compact bone and spongy bone. And I will describe these two types during this lecture.

    01:51 The very fundamental structural unit of bone is the osteon and I will also describe that and its something that you really should understand because it will explain to you really how bone forms its functional role in the body. And equally important you must understand how bone cells receive their nutrients. As I said earlier, the matrix is very hard.

    02:18 It is calcified. Unlike other connective tissues such as loose connective tissue or even cartilage, there is no aqueous component of the extracellular matrix. So nutrients including oxygen cannot diffuse through that matrix. So I am going to explain in this lecture, how bone cells get their nutrients from the blood when they are embedded in this very firm calcified matrix.

    02:52 So again let us look at what characterizes bone. First of all, it is vascular. Unlike cartilage, it has a blood supply. It has a very large blood supply. If you break a bone, it bleeds. Again like connective tissues, it has cells, fibres and matrix.

    03:18 The cells are called osteocytes and these osteocytes live within the bone matrix and often you see just a small clear space. This is a lacuna and a lacuna is really a space that is occupied by the bone cell or the osteocyte. Normally the osteocyte would occupy the entire space but during processing of bone, often the cell is completely lost from its territorial area in the bone matrix and just the small little space or a lacuna remains. Sometimes however in some of these little lacunar spaces, you can see remnants of the osteocytes.

    04:10 Again, like cartilage, the most important functional part of bone is the matrix.

    About the Lecture

    The lecture Structure of Bones by Geoffrey Meyer, PhD is from the course Bone Tissue.

    Author of lecture Structure of Bones

     Geoffrey Meyer, PhD

    Geoffrey Meyer, PhD

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