Pectoralis minor

It is well known that sometimes individuals are bom lacking certain abdominal muscles. This is regarded, of course, as abnormal. It is not so well appreciated, however, that in the normal populations there may be a high degree of variation. Anson,3 for example, shows how the pectoralis minor muscle varies in an unselected population In 42 per cent it overlaps the 2nd, 3rd, 4th, and 5th ribs in 28.5 per cent it misses the 2nd rib in 15 per cent it misses the 5th rib and in 5 per cent it misses both the 2nd and 5th ribs. There is no one normal pattern. 

Clipping through the hardened fibers of the pectoralis major and exposing thereby the pectoralis minor, its fibers were seen to be almost, if not quite, as dried out as were those of the outer muscle. ... 

Fig. 4.3 Anatomic relationship of the axillary vein to the pectoralis minor muscle. The pectoralis major has been removed. Note the cephalic vein draining directly into the axillary vein at approximately the first intercostal space. (From Belott PH. Unusual access sites for permanent cardiac pacing. In Barold SS, Mugica J, eds. Recent advances in cardiac pacing Goals for the 21st century. Armonk, NY Futura Publishing, 1997, with permission.)...

The cephalic vein, a conunon venous access site for pacemaker implantation, drains directly into the axillary vein just superior to the pectoralis minor. The axillary vein is an excellent site for venous access, but is usually not considered because it is a rather deep structure. The surface landmarks of note are the infraclavicular space, deltopectoral groove, and the coracoid process. 

From the anatomic point of view, the muscles of the shoulder may be subdivided into two main groups intrinsic musdes (subscapularis, supraspinatus, infraspinatus, teres minor, teres major and deltoid), which originate and insert on the skeleton of the upper limb, and extrinsic muscles, which join the upper limb with either the spine (trapezius, latis-simus dorsi, levator scapulae and rhomboid) or the thoracic wall (serratus anterior, pectoralis minor... 

The axillary artery continues the subclavian artery beyond the outer border of the first rib. It traverses deep to the pectoralis minor muscle and is accompanied by the cords and distal branches of the bra-... 

Fig. 6.28a,b. Short head of the biceps tendon, coracobrachialis and pectoralis minor. a,b Transverse 12-5 MHz US images obtained a at the level of the coracoid process of the scapula and b approximately 2 cm caudal to it. In a, the relationship of the coracoid (Co) with the humeral head (HH), the subscapularis tendon (SubS) and the deltoid muscle are illustrated. The coracoid is easily identified with US owing to its medial position relative to the humeral head and the curvilinear hyperechoic appearance of its bony surface. In b, three individual structures are seen arising from the coracoid. From lateral to medial, they are the hyperechoic tendon of the short head of the biceps (curved arrow), the hypoechoic myotendinous junction of the coracobrachialis (straight arrow) and that of the pectoralis minor (arrowheads)... 

Fig. 6.61a,b.Normal brachial plexus infraclavicular region. Oblique transverse 12-5 MHz US images obtained under the clavicle a over the major axis of the axillary artery (AA) and b immediately behind it. The cords of the brachial plexus (open and white arrowheads) are visualized as elongated fascicular structures coursing around the axillary artery and deep to the pectoralis minor muscle (Pm). PMj, pectoralis major muscle. The insert at the upper left side of the figure indicates transducer positioning... 

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