Fig. 76.—Lateral Surface of the Scapula, with the Areas of Attachment of Muscles.
a, M. infraspinatus; b, M. supraspinatus; c, origin of M. biceps; d, M. acromiodeltoideus; e, M. teres minor; f, M. levator scapulæ ventralis; g, M. spinodeltoideus; h, M. acromiotrapezius; i, M. rhomboideus; j, M. teres major; k-l, line of insertion of M. spinotrapezius.
Origin ([Fig. 76], a).—By fleshy fibres from the whole infraspinatus fossa, and by a raphe between it and the teres major ([Fig. 75], d), and sometimes by fibres from the teres minor ([Fig. 80], c), triceps, spinodeltoideus ([Fig. 75], e), spinotrapezius ([Fig. 68], j), and subscapularis ([Fig. 77], a).
Insertion ([Fig. 83], c).—By a flat tendon which passes over the capsule of the joint, into the ventral half of the infraspinatus fossa on the great tuberosity of the humerus. (The dorsal half of the fossa is covered by a synovial bursa.)
Relations.—Outer surface with the spinotrapezius ([Fig. 68], j), spinodeltoid ([Fig. 68], i), acromiodeltoid ([Fig. 68], g), teres major ([Fig. 75], d), and levator scapulæ ventralis ([Fig. 68], f). Inner surface with the scapula. Glenoid border with the teres minor ([Fig. 80], c), the teres major ([Fig. 75], d), and the long head of the triceps ([Fig. 75], g).
Action.—Rotates the humerus outward.
M. teres minor ([Fig. 80], c).—A small muscle from the glenoid border of the scapula to the proximal end of the humerus.
Origin ([Fig. 76], e) by a sheet of tendinous fibres from the glenoid border of the scapula beginning about one-fifth the length of the border from the glenoid fossa and extending to its middle. It is often attached to the infraspinatus ([Fig. 80], b) and the caput longum of the triceps ([Fig. 75], g).
Insertion ([Fig. 83], d) by a short tendon into the tubercle just distad of the infraspinatus fossa on the great tuberosity of the humerus.