Bone Basics

Bones are composed of hard living tissue which forms the skeleton and provides the framework and structural support to the body. Bones are made up of calcium and phosphorus and are arranged in a way to make them strong and resilient so that the skeleton can absorb impact without breaking. The outer surfaces of bones have a constant supply of blood which feeds them the nourishment they need to survive.

The Skeleton

The skeleton is made up of two different types of bone (see Figure 2):

1. Cortical (compact) bone is a thick layer of tissue that covers the outside of most bones and the shafts of long bones. Eighty per cent of the weight of the skeleton is cortical bone. 

Figure 1: Leg bone shaft

2. Cancellous (trabecular) bone looks like honeycomb and is found at the ends of long bones and within flat bones and the vertebrae. This spongy mesh-like bone provides strength in a way similar to steel rods within a concrete structure. The bone marrow inside bones is where red blood cells are produced.

Figure 2: Basic bone structure

The skeleton acts as a calcium bank or storage tank and needs to be regularly fed calcium to stay strong. If the food and drink we consume do not contain sufficient calcium, the body withdraws stores from the bones to meet its needs.

Due to the fact that the entire skeleton increases in mass throughout childhood, there is a constant demand for calcium for growth and bone maintenance.

Now go to Building Bones.