Henry Gray (18251861). Anatomy of the Human Body. 1918.
attachments of their anterior extremities, and it is convenient therefore to consider separately the movements of the ribs of the three groupsvertebrosternal, vertebrochondral, and vertebral.
FIG. 316 Lateral view of first and seventh ribs in position, showing the movements of the sternum and ribs in A, ordinary expiration; B, quiet inspiration; C, deep inspiration. (See enlarged image)
FIG. 317 Diagram showing the axes of movement (A B and C D) of a vertebrosternal rib. The interrupted lines indicate the position of the rib in inspiration. (See enlarged image)
FIG. 318 Diagram showing the axis of movement (A B) of a vertebrochondral rib. The interrupted lines indicate the position of the rib in inspiration. (See enlarged image)
Vertebrosternal Ribs (Figs. 316, 317).The first rib differs from the others of this group in that its attachment to the sternum is a rigid one; this is counterbalanced to some extent by the fact that its head possesses no interarticular ligament, and is therefore more movable. The first pair of ribs with the manubrium sterni move as a single piece, the anterior portion being elevated by rotatory movements at the vertebral extremities. In normal quiet respiration the movement of this arc is practically nil; when it does occur the anterior part is raised and carried forward, increasing the antero-posterior and transverse diameters of this region of the chest. The movement of the second rib is also slight in normal respiration, as its anterior extremity is fixed to the manubrium, and prevented therefore from moving upward. The sternocostal articulation, however, allows the middle of the body of the rib to be drawn up, and in this way the transverse thoracic diameter is increased. Elevation of the third, fourth, fifth, and sixth ribs raises and thrusts forward their anterior extremities, the greater part of the movement being effected by the rotation of the rib neck backward. The thrust of the anterior extremities carries forward and upward the body of the sternum, which moves on the joint between it and the manubrium, and thus the antero-posterior thoracic diameter is increased. This movement is, however, soon arrested, and the elevating force is then expended in raising the middle part of the body of the rib and everting its lower border; at the same time the