Blood supply of bone

Diaphyseal nutrient arteries : They are usually single (in 90% cases), enter through the middle third of the shaft of bone. The direction of entry is away from the region of the dominant growing epiphysis. For example, in humerus, the dominant growing epiphysis is in the head of humerus. So the direction of entry of the nutrient artery of the humerus is towards the elbow.  Mnemonic to remember the direction of entry of nutrient arteries – TOWARDS THE ELBOW I FLOW, AWAY FROM THE KNEE I FLEE. After entering the marrow cavity, the nutrient artery gives rise to ascending and descending branches and branches further on reaching the epiphysis. Here it anastamoses with the branches of the epiphyseal and metaphyseal arteries. The marrow is supplied by centripetal branches which drain into a central venous sinus. The cortex is supplied by centrifugal branches which pass along the harvesian canals and are interconnected by the vessels in the volkmann’s canals. The cortical vessels anastamose at the surface of bone with the periosteal vessels, which are formed by the arteries from the neighbouring muscles.

1. Direction of entry of nutrient arteries in long bones is away from the direction of the dominant growing epiphysis of the bone
2. Blood supply of the marrow is centripetal, where as that of the cortex is centrifugal.
3. In immature long bones, there is practically no anastomosis between the epiphyseal and metaphyseal arteries, due to the epiphyseal cartilage. But both vessels supply the ephiphyseal cartilage.
4. Venous drainage of the bone takes place via all surfaces other than those covered by articular cartilage.

Reference: Gray’s anatomy, 39th edition, Pages 94-97