Bone structure consists of a number of layers. These include the periosteum, compact bone, spongy bone and an inner core of bone marrow. Here we explain the anatomy of bone and the function of each part. It is important for bones to be strong to support our body weight. In some cases, their main function is to provide protection such as the skull and ribs. However, they must also be light enough to make movement possible.
The structure of a long bone consists of several sections:
- Diaphysis: This is the long central shaft.
- Epiphysis: Forms the larger rounded ends of long bones.
- Metaphysis: Area between the diaphysis and epiphysis at both ends of the bone.
- Epiphyseal Plates: Plates of cartilage, also known as growth plates which allow the long bones to grow during childhood. Once we stop growing (between 18 and 25 years of age) the cartilage plates stop producing cartilage cells. Over time, they are gradually replaced by bone.
If you cut a cross-section through a bone, you would first come across a thin layer of dense connective tissue. This is known as the Periosteum. It consists of two layers; an outer ‘fibrous layer’ containing mainly fibroblasts, and an inner ‘cambium layer’ containing progenitor cells. The progenitor cells develop into osteoblasts (the cells responsible for bone formation). The periosteum provides a good blood supply to the bone and a point for muscular attachment.
Compact bone structure
Under the periosteum is a thin layer of compact bone (often called cortical bone). This provides the bones strength and consists of tightly stacked layers of bone which appear to form a solid section. However, they do contain osteons, which are like canals, providing passageways through the hard bone matrix.