Development of the Ribs
Ribs are derived from the sclerotome portion of the paraxial mesoderm which form the costal process of the vertebrae. The ribs are form mainly from the costal process of the thoracic vertebrae. Primary ossification centers appear in the body of the ribs and mostly become cartilaginous during weeks 13-14 of development.
Note that:
Development of the sternum
The sternum develops from the somatic mesoderm in the ventral body wall. Two sternal bars are formed on either side of the midline and these later fuses to form the cartilaginous model of the manubrium, sternabrae (body) and the xiphoid process (fig. 14). These bars are connected to the end of the costal cartilages.
Centers of ossification appear cephalo-caudally before birth except in the xiphoid process which appears during childhood.
Note that :
Ribs are derived from the sclerotome portion of the paraxial mesoderm which form the costal process of the vertebrae. The ribs are form mainly from the costal process of the thoracic vertebrae. Primary ossification centers appear in the body of the ribs and mostly become cartilaginous during weeks 13-14 of development.
Note that:
- The ribs are more horizontal and less curve in neonate than those in adult
- Breathing is primarily due to the musculature of the diaphragm and abdominal
wall in neonate
- Secondary ossification centers appear for the head and tubercle of the
rib at puberty
- True ribs (1-7th)-attach through their own cartilages to the sternum. False ribs (8-10th)-attach to the sternum through the cartilage of another rib or ribs. The floating ribs (11th and 12th)-do not attach to the sternum.
Development of the sternum
The sternum develops from the somatic mesoderm in the ventral body wall. Two sternal bars are formed on either side of the midline and these later fuses to form the cartilaginous model of the manubrium, sternabrae (body) and the xiphoid process (fig. 14). These bars are connected to the end of the costal cartilages.
Centers of ossification appear cephalo-caudally before birth except in the xiphoid process which appears during childhood.
Note that :
- In the neonate, the manubrium contains usually one main ossification center. Ossification at the lowest segment begins shortly after birth and that of the xiphoid process during the 3rd year of life.
- If fusion is incomplete, a minor fissure or perforation may be present in the sternum.
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(Copyright © 2011 by U. Bala)