Bones begin life as cartilage. As the young baby develops in the mother’s womb, the skeletal system becomes organised into a framework of cartilage. Before birth, there is a certain amount of hardening of the limb bones to allow the animal to stand shortly after delivery. However, the greater part of the skeleton is cartilage at birth. After birth, hardening of all parts of the skeleton begins. This process continues throughout life until, in old age, very little cartilage is left and the bones are old and brittle. The process of hardening cartilage into bone is called ossification. Osteoblasts secrete the osteoid into this membrane to form a spongelike network of bony processes called trabeculae.