|Henry Gray (18251861). Anatomy of the Human Body. 1918.|
|behind; broad above, becoming narrowed at the point where the manubrium joins the body, after which it again widens a little to below the middle of the body, and then narrows to its lower extremity. Its average length in the adult is about 17 cm., and is rather greater in the male than in the female.|
Manubrium (manubrium sterni).The manubrium is of a somewhat quadrangular form, broad and thick above, narrow below at its junction with the body.
Surfaces.Its anterior surface, convex from side to side, concave from above downward, is smooth, and affords attachment on either side to the sternal origins of the Pectoralis major and Sternocleidomastoideus. Sometimes the ridges limiting the attachments of these muscles are very distinct. Its posterior surface, concave and smooth, affords attachment on either side to the Sternohyoideus and Sternothyreoideus.
FIG. 116 Posterior surface of sternum. (See enlarged image)
FIG. 117 Lateral border of sternum. (See enlarged image)
Borders.The superior border is the thickest and presents at its center the jugular or presternal notch; on either side of the notch is an oval articular surface, directed upward, backward, and lateralward, for articulation with the sternal end of the clavicle. The inferior border, oval and rough, is covered in a fresh state with a thin layer of cartilage, for articulation with the body. The lateral borders are each marked above by a depression for the first costal cartilage, and below by a small facet, which, with a similar facet on the upper angle of the body, forms a notch for the reception of the costal cartilage of the second rib. Between the depression for the first costal cartilage and the demi-facet for the second is a narrow, curved edge, which slopes from above downward and medialward.
Body (corpus sterni; gladiolus).The body, considerably longer, narrower, and thinner than the manubrium, attains its greatest breadth close to the lower end.
Surfaces.Its anterior surface is nearly flat, directed upward and forward, and marked by three transverse ridges which cross the bone opposite the third,