Type X collagen is important for bone mineralization and is produced by hypertrophic chondrocytes in the zone of hypertrophy.
There are 4 zones of the physis. The first is the RESTING ZONE, which is characterized by widely dispersed chondrocytes, abundant matrix, and is relatively inactive in cell or matrix turnover. The second zone is the PROLIFERATIVE ZONE. It characterized by longitudinal columns of flattened cells, significant endoplasmic reticulum, high ionized calcium. The third zone is the HYPERTROPHIC zone. It is characterized by enlargement of cells, persistent metabolic activity, accumulate and calcium, synthesize alkaline phosphatase and type X collagen, aiding in mineralization. The final zone, in the METAPHYSIS, comprises the primary and secondary spongiosa layers. These layers are characterized by vascular invasion and bone remodeling, respectively.
Illustration A shows a histological view of the phyeal zones. Zone C is the proliferative zone, Zone D is the hypertrophic zone, and Zone E is the metaphysis.
Answers 1,2,3,5: collagen type X play the greatest role in the zone of hypertrophy.
Dietz FR, Morcuende JA: Embryology and development of the musculoskeletal system, in Morrissy RT, Weinstein SL (eds): Lovell and Winter’s Pediatric Orthopaedics, ed 6. Philadelphia, PA, Lippincott Williams & Wilkins, 2006, p27
Rathjen KE, Birch JG: Physeal injuries and growth disturbances, in Beaty JH, Kasser JR (eds): Rockwood and Wilkins’ Fractures in Children, ed 6. Philadelphia, PA, Lippincott Williams and Wilkins, 2006, pp 99-132