Figure 2.

Diagram depicting the proximal head of a growing leg bone. The epiphyseal vascular supply (ev) courses through epiphyseal vascular canals (ec) within the hyaline zone (hy) of the epiphysis (e), or through junctional canals (jc) directed toward the growth plate (gp) or physis. Branches of the ev terminate as epiphyseal vascular capillary complexes (evc) within the hyaline zone, or become penetrating epiphyseal vessels (pev) that terminate as a penetrating vascular capillary plexus (pvp) supplying the resting zone (rz), proliferating zone (pz), and prehypertrophic zone (phz, also known as the maturing zone) of the gp. The ascending branch of the nutrient artery (ana) divides repeatedly inside the diaphysis (d) to form metaphyseal vessels (mv) within the metaphysis (m). The mv terminate as the metaphyseal vascular capillary plexus (mvp) supplying the calcifying zone (cz, also known as the degenerating hypertrophic zone) of the metaphysis. The hypertrophic zone (hz) normally is not penetrated by the pvp or mvp, but may rarely be penetrated by transphyseal vessels (tp). Additional features include: a articular zone of epiphyseal cartilage; eb, endosteal bone; mc, medullary cavity; pb, periosteal bone; and rez, resorption zone of the metaphysis. Micro-anatomical terminology is consistent with the established anatomical nomenclature for avian bones (Beaumont, 1967; Lutfi, 1970a,b; Wise and Jennings, 1973; Howlett, 1979, 1980; Hunt et al., 1979; Duff, 1984a; Howlett et al., 1984; Thorp, 1986, 1988a; Ali, 1992; Farquharson and Jefferies, 2000).