Development of bone


Development of bone


      Two types of bones cells named osteoblast and osteoclast take part in the formation of bone. Both these cells remain active during growth.  Osteoblast makes bone and osteoclast does the work to absorb bone of which the shape and proportion of the bone remain present. 

     Hyaline cartilage or fibrous membrane provide appropriate atmosphere for the development of bone. The bone which develops in the fibrous membrane is called membrane bone and the bone which develops in the hyaline cartilage is called cartilage bone. The process of the bone’s development is called ossification. There are two kinds of ossifications.

Intramembranous ossification:

      If the bone tissue (cribriform or compact) is developed by the embryonic connective tissues, this process is called Intramembranous ossification. The valt-crescent portion of the skull and clavicle and flat bones of the face are developed by this kind of ossification. There is a good supply of blood in the connective tissue membrane of which the bone gets developed properly. The process of ossification starts on some definite centers in it and it keeps on increasing by the multiplication of cells present in the membrane until a sensitive net of bone originates. Finally a flat bone comes into existence and there are two layers of compact bone tissue on the up and below side of the bone and there is a spongy bone tissue in the middle. There is a periosteum before the compact bone.

Intracartilaginous ossification:

        When bone tissue gets developed by the hyaline cartilage, this process is called Intracartilaginous ossification. In this process, bones take the place of cartilages. In a developing embryo, all the long bones are in the form of rods of cartilages in the early stage and there is a membrane named pericardium on it. At the center of rods, a center of primary ossification appears which is called diaphysis which is finally is the shaft of any long bone. Calcium gathers in the matrix and cells of bones get developed. Periostium originates from the Pericardium. Osteogenic cells are found in its deep internal layer which gets changed into osteoblasts during partition and because of their multiplication the bone gets increased in both thickness and length. Long bones are developed by the Intracartilaginous ossification.   

         Developing long bones originate by meeting one diaphysis and two separate epiphyses which all three get jointed altogether finally. Later on in the process of development, a secondary center of ossification originates in each epiphysis which keeps on marching towards the diaphysis and towards the end of each epiphysis. Epiphyses of both sides are covered by the hyaline cartilage which gets changed into articular cartilage. Diaphysis and epiphysis of both sides are connected to each other by the epiphyseal cartilage. This layer of cartilage changes into the bone gradually and epiphysis cartilage disappears completely till the period of child’s birth and both diaphysis and both epiphyses get changed into fully developed bone.

       After birth, long bones keep on developing until they become complete bone. The bone keeps on increasing in length until the layer of cartilage remains there. The diaphysis also gets increased in length too and new bone keeps on making on the both ends by the epiphysis cartilage. Epiphysis cartilage changes into bone when the process of growing bone gets complete and the bone does not disappear later on. It happens between 18 to 25 years. The growth in different bones completes on different times and the growth of different ends of a bone completes on different times. For example: the lower epiphysis of humrus (bone of arm) joints in the age of 18 years but its upper epiphysis does not joint even after 20 years.   

       Calcium has an important contribution in making and developing and hardening the bones. In addition to, the growth of bone depends on the health and body growth because the bone develops in the proportion of organs. Hormones of pituitary and thyroid gland affect the growth of bone.