Examining a long bone

There are four main sections of a long bone

  1. Diaphysis – long central shaft
  2. Epiphysis – forms the larger, rounded ends of long bones
  3. Metaphysis – area between the diaphysis and epiphysis at both ends of the bone.
  4. Epiphyseal Plates – plates of cartilage, also known as growth plates which allow the long bones to grow in length during childhood.  Once we stop growing (between 18-25 years of age) the cartilage plates stop producing cartilage cells and are gradually replaced by bone.

Cross-section of a long bone

Starting from the outside and examining the layers


There is a thin outer layer of dense connective tissue called ‘periosteum’. This layer can be divided into two layers: an outer ‘fibrous layer’ containing mainly fibroblasts and an inner ‘cambium layer’, containing progenitor cells which develop into osteoblasts (the cells responsible for bone)