The cell responsible for secreting the matrix of bone is the osteoclast

Osteoblast is the cell responsible for secreting the matrix of the bone. Bone is a dynamic tissue that is constantly reshaped by osteoblasts which produce and secrete matrix proteins and transport mineral into the matrix, and osteoclasts, which break down the tissues. The osteoblasts lays down the extracellular matrix of the bone, by secreting both collagen and ground substance. Osteoclast are the cell that that accomplish the process of resorption. 

Crossing over creates new combinations of genes in the gametes that are not found in either parent contributing to genetic diversity

Called for cell.