SCAPTLA. Tins or Snotn.nee BLADE, is a flat triangular bone, which, when the arm hangs loosely down, extends posteriorly and laterally from the first to about the seventh rib. It presents for examination an outer convex and an inner, smooth, and concave surface, three borders (a superior, an inferior or axillary, and a posterior), three angles, and certain outstanding processes.
It is divided into two unequal parts, the supra-spinous fosse, and the infra-spiuous fossa, by the spine, a crest of bone commencing at a smooth triangular surface bn the posterior border, and running across toward the tipper part of the neck of the scapula, after which it alters its direction, and projects forward so us to form a lofty arch, known as the aeromion process, which overhangs the glenoid cavity, or receptacle for the head of the humerus or main hone of the arm. This acrontion (so called from the Greek words aeros runos, the summit of the shoulder) obviously serves to protect the shoulder joint, as well as to give great leverage to the deltoid muscle which raises the arm. It is this process which gives to the shoulder its natural roundness. From the upper part of
the neck there prdeeeds a remarkable curved projection, termed the corticoid process, from its supposed resemblance to the beak of a raven (Or. Nrd.r). It is about 2 in. long, and gives nenehmnruts to several muscles. The upper border of the scapula presents a very remarkable notch, which in the recent state is bridged over with a ligament, and gives passage to the supra-scapular nerve. This bone articulates with the clavicle and humerus, and gives attachment to no less than 1G muscles, many of which, as the biceps, triceps, deltoia, serintus magnus, are very powerful and important.
The uses of this bone may be stated as follows: 1. It connects the upper extremity to the trunk, and participates in and is subservient to many of the movements enjoyed by the arm; 2. By its extended flat surface it furnishes a lateral protection to the chest ; and 3. It affords attachments to various muscles which modify the size of the thoracic cavity, and is thus concerned iu the process of respiration.