Answer
Part 1: Orientation and foundational concepts
Bone is a living, vascular connective tissue whose blood supply is essential for growth, remodelling, fracture healing and resistance to infection. The vascular arrangement differs substantially between the growing skeleton and the mature skeleton because the physis acts as a vascular and anatomical barrier during growth. In an examination answer, the blood supply should therefore be described separately for the adult and paediatric long bone, followed by the two mechanisms of bone formation.
General principles of skeletal vascularity
The principal arterial sources of a long bone are the nutrient artery, periosteal vessels, metaphyseal arteries and epiphyseal arteries. Their relative importance varies with age, the region of the bone and the presence or absence of an open physis.
| Vascular source | Origin and distribution | Important clinical relevance |
|---|---|---|
| Nutrient artery | Usually arises from a branch of a major regional artery, enters the nutrient canal and divides into ascending and descending medullary branches. | Supplies marrow and the inner cortex through endosteal and Haversian vessels; injury may contribute to diaphyseal osteonecrosis. |
| Periosteal vessels | Small branches from vessels in the surrounding muscles and soft tissues enter the outer cortex through Volkmann canals. | Supply the outer cortical one-third, particularly when the… |