Physiology Essay Example | Topics and Well Written Essays - 1000 words

Physiology - Essay Example While osteoblasts are bone-forming cells, osteocytes are mature bone cells and osteoclasts break down and reabsorb bone (†Bone Growth and Development†). Ossification is basically of 2 types, intramembranous and endochondral. In both these, the formation of bone tissue is similar. First, there is increase in the number of cells and collagen fibers. Then, the cells differentiate into osteoblasts. These cells form an organic matrix called the osteoid in which the bone salts are deposited. Some of these osteoblasts remain in the matrix and transform into osteocytes (Gardner, 856-862). The replacement of sheet-like connective tissue membranes with bony tissue is known as intramembranous ossification and bones formed by this method are known as intramembranous bones. Some of the flat bones of the skull and irregular bones fall into this category. These bones are initially formed as connective tissues membranes, later on the osteoblasts migrate to the membranes and deposit bony matrix around themselves and change into osteocytes. Replacement of hyaline cartilage with bony tissue is known as endochondral ossification. Most of the bones in our body are formed in this manner and hence these bones are known as endochondral bones. The bones are first formed as hyaline cartilage models as early as in the 3rd month of gestation. This is surrounded by a membrane called the perichondrium. Later, this becomes infiltrated with blood vessels and osteoblasts and then is called the periosteum (†Bone Growth and Development†). Primary center of ossification is the region in the bone in which the process of ossification starts first and this is indicated by an increase in the cells and fibers. Ossification continues from this center toward the ends of the bones. The time at which the primary center appears depends on the bone. The parietal and frontal bones, maxilla, and mandible appear during the embryonic period. In the long bones, the primary center of ossification