The medial two-thirds of this fossa are marked by several oblique ridges, which run lateralward and upward. The ridges give attachment to the tendinous insertions, and the surfaces between them to the fleshy fibers, of the Subscapularis. The lateral third of the fossa is smooth and covered by the fibers of this muscle.
|Figure 1 : Left scapula. Costal surface.|
|Figure 2 : Left scapula. Dorsal surface.|
|Figure 3 : Left scapula. Lateral surface.|
At the upper part of the fossa is a transverse depression, where the bone appears to be bent on itself along a line at right angles to and passing through the center of the glenoid cavity, forming a considerable angle, called the subscapular angle; this gives greater strength to the body of the bone by its arched form, while the summit of the arch serves to support the spine and acromion.
The dorsal surface is marked near the axillary border by an elevated ridge, which runs from the lower part of the glenoid cavity, downward and backward to the vertebral border, about 2.5 cm above the inferior angle.
The surface between the ridge and the axillary border is narrow in the upper two-thirds of its extent, and is crossed near its center by a groove for the passage of the scapular circumflex vessels; it affords attachment to the Teres minor.
Its lower third presents a broader, somewhat triangular surface, which gives origin to the Teres major, and over which the Latissimus dorsi glides; frequently the latter muscle takes origin by a few fibers from this part.
The broad and narrow portions above alluded to are separated by an oblique line, which runs from the axillary border, downward and backward, to meet the elevated ridge: to it is attached a fibrous septum which separates the Teres muscles from each other.
The head, processes, and the thickened parts of the bone, contain cancellous tissue; the rest consists of a thin layer of compact tissue.
The central part of the supraspinatous fossa and the upper part of the infraspinatous fossa, but especially the former, are usually so thin as to be semitransparent; occasionally the bone is found wanting in this situation, and the adjacent muscles are separated only by fibrous tissue.
The following muscles attach to the scapula:
|Pectoralis Minor||insertion||coracoid process|
|Serratus Anterior||insertion||medial border|
|Triceps Brachii (long head)||origin||infraglenoid tubercle|
|Biceps Brachii (short head)||origin||coracoid process|
|Biceps Brachii (long head)||origin||supraglenoid tubercle|
|Rhomboid Major||insertion||medial border|
|Rhomboid Minor||insertion||medial border|
|Levator Scapulae||insertion||medial border|
|Trapezius||insertion||spine of scapula|
|Deltoid||origin||spine of scapula|
|Teres Minor||origin||lateral border|
|Teres Major||origin||lateral border|
|Latissimus Dorsi (a few fibers)||origin||inferior angle|
Movements of the scapula are brought about by scapular muscles:
Elevation, Depression, Protraction, Retraction, Lateral rotation, Medial rotation, Upward Rotation, Downward Rotation, Anterior Tipping, and Posterior Tipping
Additions have been made from "Nickel; Schummer; Seiferle; Lehrbuch der Anatomie der Haussäugetiere.
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