Sternal Bars

Definition

Sternal bars are a pair of cartilaginous bars that develop on either side of the midline of the embryonic chest wall, forming the foundation for the sternum. These structures play a crucial role in the embryonic development of the axial skeleton.

5 Must Know Facts For Your Next Test

1. The sternal bars develop from the ventral (anterior) portion of the somites, the segmented blocks of mesenchyme that give rise to the axial skeleton.
2. The sternal bars begin to form around the fourth week of embryonic development and continue to grow and fuse towards the midline.
3. The fusion of the sternal bars is a gradual process, with the superior portion fusing first, followed by the inferior portion.
4. Failure of the sternal bars to fully fuse can result in congenital abnormalities, such as sternal clefts or ectopia cordis.
5. The sternal bars eventually undergo ossification, transforming from cartilage to bone and forming the mature sternum.

Review Questions

• Describe the role of the sternal bars in the embryonic development of the axial skeleton.
  • The sternal bars play a crucial role in the embryonic development of the axial skeleton. They develop from the ventral portion of the somites, the segmented blocks of mesenchyme that give rise to the axial skeleton. The sternal bars begin to form around the fourth week of embryonic development and continue to grow and fuse towards the midline, gradually forming the sternum. This fusion process is essential for the proper formation of the chest wall and the protection of the vital organs within.
• Explain the process of chondrification and ossification as it relates to the sternal bars.
  • The sternal bars initially develop as cartilaginous structures through the process of chondrification, where mesenchymal cells differentiate into chondrocytes. Over time, the cartilaginous sternal bars undergo ossification, a process in which the cartilage is replaced by bone. This transformation from cartilage to bone is crucial for the formation of the mature sternum, as the sternal bars eventually fuse and become the bony structure that protects the vital organs in the chest cavity.
• Analyze the potential consequences of a failure in the fusion of the sternal bars during embryonic development.
  • Failure of the sternal bars to fully fuse can result in congenital abnormalities, such as sternal clefts or ectopia cordis. Sternal clefts occur when the sternal bars fail to fuse completely, leading to a gap or opening in the sternum. Ectopia cordis is a rare and severe condition where the heart is located outside of the chest cavity, often due to a failure in the fusion of the sternal bars. These congenital abnormalities can have significant implications for the health and development of the individual, as they can affect the proper formation and protection of the vital organs within the chest cavity.

Related terms

Sternum: The sternum is the flat bone located in the central part of the chest wall, formed by the fusion of the sternal bars during embryonic development.

Chondrification: The process by which mesenchymal cells differentiate into chondrocytes, leading to the formation of cartilage.

Ossification: The process by which cartilage is replaced by bone, transforming the sternal bars into the bony sternum.