Human Anatomy - Kotsan I. Ya. 2009

Anatomy of the Trunk Skeleton
Articulations of the Thoracic Bones

The following joints are distinguished in The thoracic cage.

JOINTS OF THE Ribs with the Sternum. The cartilaginous PARTS OF THE true ribs (from II to VII) articulate with the sternum via small sternocostal joints (articulationes sternocostales). These are simple, plane, multiaxial, and slightly movable joints (allowing elevation and depression of the ribs). The articular capsule is thin and represents a continuation of the periosteum of the sternum into the perichondrium of the costal Cartilage. Anteriorly and posteriorly, these joints are reinforced by radiate sternocostal ligaments (ligg. sternocostalia radiata). The cartilage of the first rib directly fuses with the sternum, forming the first sternocostal synchondrosis (synchondrosis sternocostalis costae primae). The cartilages of the false ribs (VIII–X) interconnect and join with the cartilages of the overlying ribs via interchondral joints (articulationes interchondrales), forming the so-called costal margins (arcus costaks).

The Articulation of the ribs with the vertebrae is accomplished through the costovertebral joints (articulationes costovertebrales), which consist of two joints: the joint of the costal HEAD and the costotransverse joint.

The joint of the costal head (articulatio capitis costae) is formed by two costal facets (demifacets) of two adjacent thoracic vertebrae and the articular surface of the costal head. The heads of ribs I, XI, and XII articulate with a full facet on the body of the corresponding vertebra. The joint of the costal head is plane, combined, and multiaxial. The articular surfaces of the costal facets and heads are covered with fibrocartilage. The articular capsule is thin and attaches along the margins of the articular surfaces. The joint is reinforced by the intra-articular ligament of the head of the rib (lig. capitis costae intraarticulare), which extends from the crest of the costal head to the intervertebral disc, dividing the joint cavity into two chambers (this ligament is present in the joint cavity of ribs II–X), and by the extracapsular radiate ligament of the head of the rib (lig. capitis costae radiatum), which fans out from the anterior surface of the costal head to the anterolateral surfaces of the adjacent vertebral bodies and the intervertebral disc.

The costotransverse joint (articulatio costotransversaria) is formed by the articular surface of the costal tubercle and the costal facet of the transverse process (present in the upper ten ribs). The shape of the joint is cylindrical. The articular surfaces are covered with hyaline cartilage. The articular capsule is thin and attaches along the margins of the articular surfaces.

The joint is reinforced by the following ligaments:

a) the superior costotransverse ligament (lig. costotransversarium superius), which extends from the Inferior surface of the transverse process to the crest of the neck of the underlying rib;

b) the lateral costotransverse ligament (lig. costotransversarium laterale), which extends from the costal tubercle to the apex of the transverse process;

c) the costotransverse ligament (lig. costotransversarium), which lies between the posterior surface of the neck of the rib and the anterior surface of the transverse process of the corresponding vertebra.

The joint of the costal head and the costotransverse joint are anatomically separate, but movements in them occur simultaneously; therefore, functionally they form a combined costovertebral joint. In shape, this joint is cylindrical, and rib rotation occurs around a single axis passing along the neck of the rib. During these rotational movements, the anterior ends of the ribs, together with the sternum, execute excursions upward and downward. When the anterior ends of the ribs elevate along with the sternum, the volume of the thoracic cavity increases (inspiration); when the anterior ends of the ribs are depressed, the capacity of the thoracic cavity decreases (expiration).