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Connections of the ribs to the vertebral column and sternum
Last reviewed: 23.04.2024
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Due to the presence of movable joints of the ribs with the vertebral column and the sternum, changes in the volume of the chest and respiratory movements are possible.
The ribs are connected to the vertebrae with the help of costal-vertebral joints (artt. Costovertebrales), which include the rib head joints and rib-transverse joints.
The joint of the rib head (art. Capitis costae) is formed by the upper and lower costal fossa (half-planes) of two adjacent thoracic vertebrae and the rib head. From the scallop of the head of the rib of nine (II-X) ribs to the corresponding intervertebral disk in the joint cavity is the intraarticular ligament of the head of the rib (lig. Capitis costae intraarticulare). This ligament is absent in I, XI and XII ribs, whose head does not have a scallop. Outside, the capsule of the joint of the head of the rib is strengthened by a radial ligament of the rib head (lig. Capitis costae radiatum). This ligament begins on the front surface of the head of the rib, fan-shaped diverges and attaches to the bodies of adjacent vertebrae and the intervertebral disc.
The costal-lateral joint (art. Costotranversaria) is formed by the tubercle of the rib and the costal fossa on the transverse process of the IX thoracic vertebrae. A thin articular capsule is attached at the edges of the articular surfaces. The capsule is strengthened by an edge-transverse ligament (lig. Costotranversarium). The costal-transverse joint and the joint of the rib head are combined, movements in them are carried out jointly; It is possible to move around a common axis passing through the centers of these joints. When the posterior ends of the ribs rotate relative to this axis, the anterior rib ends, which are connected to the sternum, are lifted.
Joints of ribs with sternum. The ribs are connected to the sternum with joints and synchondroses. The cartilage of the 1st rib fuses with the sternum (synchondrosis). Cartilages of the II-VII ribs, connecting with the sternum, form the sternocosthenal joints (artt sternocostales). The articular surfaces are the anterior ends of the costal cartilage and the costal incisions of the sternum. Joint capsules are a continuation of the perichondrium of the costal cartilage, which passes into the periosteum of the sternum. The joint capsule is strengthened with radial sternocostal ligaments (ligg. Sternocostalia radiata).
In front these ligaments, fused with the periosteum of the sternum, form a dense membrane of the sternum (membrana sterni). The joint of the second rib, formed at the level of the sternum angle (joints of the handle with the sternum), has an intraarticular sternocostal intraarticulare (stigma).
The anterior ends of the VII-X ribs do not unite directly with the sternum. They connect with each other with their cartilages. The cartilage of the VIII rib fuses with the rib of the VII rib lying above. Sometimes between the cartilages of these ribs are formed interchilar joints (art interchondrales). The anterior ends of the ribs are connected to each other by the outer intercostal membrane (membrana intercostalis externa). The fibers of this membrane are directed from top to bottom and forward. The posterior ends of the ribs are interconnected by an internal intercostal membrane (membrana intercostalis interna). The fibers of this membrane go from bottom to top and back.
The movements of the ribs occur in the costal-vertebral and sternal-rib joints. Amplitude of chest movements: during the inspiration phase, when the front ends of the ribs and sternum are lifted, the chest moves upward by 1 cm, the sternum extends forward by 5 cm, the chest circumference increases by 10 cm.
In the act of inspiration, the following muscles participate: the external intercostal muscles, the muscles that lift the ribs, the upper posterior jagged muscles, the stair muscles.
In the act of exhalation, muscles are involved: the transverse muscle of the chest, the internal intercostal muscles, the lower posterior jagged muscles, the rectus abdominis muscles, the outer and inner oblique muscles of the abdomen, the transverse abdominal muscle.
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