Blood supply to bone (see Fig. 1-K)

Blood supply to bone (see Fig. 1-K)

The blood supply to bone is of critical importance in maintaining the health of normal

bone and in assisting the repair process after damage, fractures, etc. There are 3 sources

of afferent blood to a typical long bone:

a) Nutrient Artery (usually single)

This passes to the medulla via the nutrient foramen where it branches to proximal

and distal medullary arteries through the marrow. These further divide to provide

the major blood supply to the diaphysis and may anastomose with epiphyseal and

metaphyseal arteries at each end of the bone.

b) Metaphyseal Arteries

Numbers of these enter the proximal and distal metaphyses at all sides. Their

final branches anastomose with the medullary arteries. Normally this anastomosis

is at a capillary level so the metaphyseal arteries make little contribution to the

medullary blood supply but if the nutrient artery is blocked they can enlarge to

take over the medullary supply.

c) Periosteal arterioles

Pass to the diaphyseal cortex only at areas of strong fascial attachment. They

supply the outer third of the cortex where they anastomose with branches of the

medullary artery. Their extent and significance is questioned, but they may be

important in bone repair following fracture.

Figure 1-K: Blood supply of bone

In a young animal arteries do not usually penetrate the epiphyseal cartilage.

Most drainage of blood from the bone is by veins following the path of the arteries -

nutrient and medullary. The cortex is drained by venous channels and capillaries to the

periosteum, always centrifugal (medulla to periosteum).

Nerves are largely distributed to the blood vessels. The periosteum is richly endowed

with sensory nerve endings, and is second only to skin in sensitivity. This explains why

fractures, infections and tumours involving bone are so exquisitely painful, and always

require early attention to pain relief.

Young growing bones have a separate circulation to the epiphysis since arteries do not

generally penetrate the epiphyseal cartilage.