Fig. 1

Vertebral anatomy, ossification centres and growth cartilage. a-b. Vertebrae consist of a body and a neural arch. b. The cranial and caudal articular facets (dark and light green) meet at the articular process joints. b. Adjacent vertebral bodies articulate with the head of a rib at the caudal and cranial costal foveae (dark and light blue) to form the costo-vertebral joint. a-b. The rib tubercle articulates with the costal fovea of the transverse process (red) to form the costo-transverse joint. c-d. The primary ossification centre (1°) is responsible for forming the ventral 2/3 of the vertebral midbody, whereas d. the secondary ossification centres (2°) cover the entire cranial and caudal ends of the vertebral body. c-d. The body and arch meet at the neuro-central synchondrosis (labelled). c. The neural arch forms from a pair of primary ossification centres (1°) located within the left and right demi-arches, respectively, and c-d. the spinous process, transverse process and cranial and caudal articular processes have secondary ossification centres (2°). d-e. Between primary and secondary ossification centres, there are metaphyseal growth plates or physes (P) and superficial to secondary ossification centres, there is epiphyseal growth cartilage (EGC). e-f. The growth cartilage of the physes and synchondrosis (S) contains patent vessels or eosinophilic streaks (arrowheads) representing the cartilage canal blood supply. f. The synchondrosis is bidirectional and contains one proliferative zone (PFZ1) contributing to the neural arch and a second proliferative zone (PFZ2) forming the dorsal 1/3 of the vertebral midbody. a-b. Tracing of T7 from photograph; a. cranial view, b. lateral view. c-d. Simplified indication of ossification centres from CT scans on top of tracings; a. mid-body transverse plane, b. lateral view. e-f. Para-sagittal histological section from T4-T5 of a 12 kg mixed-breed piglet; e. 10x; f. 100x magnification, haematoxylin and eosin