Rib Cage

Figure 1: Rib Cage

• Rib cage/Thoracic cage is consists of the Ribs, Costal cartilages, Sternum and the 12 Thoracic vertebrae.
• The space inside the thoracic cage is conical at the upper end and broader at the lower end and its function is to support the content of the upper abdomen and to assist the respiratory system.
• It has 12 ribs on both sides and their end at the anterior side is in the form of special cartilage called as costal cartilage and end at the posterior side is called as head of the rib.
• The Sternum is an elongated bony structure present at the anterior center and consists of three parts- Manubrium, body, and xiphoid process.
• The manubrium is a wider, the superior portion of the sternum. Clavicles and 1st pair of ribs are attached to the Manubrium.
• The body is an elongated central part of the sternum and the next 6 ribs pairs are attached to it.
• The xiphoid process is the inferior tip of the sternum. Rectus abdominal and front fibers of the diaphragm are attached to it. 
• The upper 7 pairs of ribs are called True ribs as they are directly in contact with sternum with the help of costal cartilages.
• The remaining 5 pairs of ribs are called False ribs because their costal cartilages are not directly connected to the sternum. 8th, 9th, and 10th ribs are indirectly connected to the sternum via 7th rib. And 11th and 12th ribs are not having the costal cartilages and not at all connected to the sternum, hence called floating ribs.
• At the backside, every rib is attached to the respective thoracic vertebra.
• Rib’s parts:
• Head- Articulates posteriorly with facets on bodies of 2 adjacent vertebrae
• Neck
• Tubercle -Articulates posteriorly with a transverse costal facet of the same numbered thoracic vertebra.
• Shaft
• Joints of ribs:
• Costovertebral joint (Joints of heads of ribs): Joint between Head of the rib and vertebra’s body.
• First ribs and the last three ribs have a single synovial joint with the corresponding vertebrae while the remaining ribs have two synovial joints: one with the corresponding vertebra and one with the immediately above.
• Costotransverse joint (Joints of tubercles of ribs):
• The joint between the tubercle of the rib, and the transverse costal facet of the corresponding vertebrae. The tubercles are absent on the eleventh and twelfth ribs and therefore no such joints occur for these ribs.
• SternoCostal joint: Joint between coastal cartilage of True ribs and Sternum.
• Joint of Sternum:
•  Xiphisternal joint: Joint between the xiphoid process and body of the sternum.
• ManubrioSternal joint: Joint between Manubrium and body of the sternum. This joint forms an angle called a Sternal angle or angle of Louis.
• The movement at the sternal angle allows the body of the sternum to move anteriorly and superiorly. This increases the volume of the intrathoracic cage and in particular, allows transverse expansion in the lower thoracic cage leading to maximal airflow.

References:

• Gnosis Medical Yoga Teacher textbook.
• https://www.britannica.com/science/rib-cage
• https://teachmeanatomy.info/thorax/bones/ribcage/