Illustrated Encyclopedia of Human Anatomic Variation: Opus I: Muscular System: Alphabetical Listing of Muscles: C
Ronald A. Bergman, PhD
Adel K. Afifi, MD, MS
Ryosuke Miyauchi, MD
Peer Review Status: Internally Peer Reviewed
The muscle actually consists of three parts:
In humans the middle part is the most constant, but it is generally accompanied by a part of the distal portion, with the musculocutaneus nerve passing between them. In 3.5-6.5% of arms the muscle is not traversed by the musculocutaneus nerve. The distal part is occasionally found quite separate from the other parts. The proximal part is represented occasionally by a proximal extension of insertion onto the surgical neck of the humerus or capsule of the shoulder joint, or by an accessory head (coracobrachialis superior or brevis) . The distal portion is sometimes present in the form of the coracobrachialis inferior or longus (Wood), and may be attached to the humerus, to a fibrous band of the medial intermuscular septum (ligament of Struthers), or even to the medial epicondyle.
Mori reported the separation of the belly into superficial and deep layers as follows:
In three (6%) instances, Mori found a deviant slip arising from the distal (deep) portion of coracobrachialis that ran medialward to fuse with the medial surface of the terminal portion of pectoralis major.
The muscle is sometimes connected to the brachialis muscle (Hyrtl, Wood) and a fasciculus has been observed joining the medial head of the triceps.
Coracobrachialis minor s. secundus (Gruber), coracobrachialis brevis s. rotator humeri (Wood), le court coracobrachialis (Cruveilhier) is an accessory muscle originating from the coracoid process; it crosses the radial nerve in the axilla and inserts into the tendinous part of latissimus dorsi.
Coracocapsularis (Wood) arises from the coracoid process and inserts into the shoulder capsule. Coracobrachialis may be absent.
Syn. : m. perforatus Casserii s. coracoideus, levator humeri internus (Arnold), Haken-arm muskel, Raben-Armmuskel (Hyrtl), Hakenmuskel.
Redrawn and modified from Beattie
Beattie, P.H. (1947) Description of bilateral coracobrachialis muscle. Anat. Rec. 97:123-126.
Becker, A.E. (1963) Variation of the M. coracobrachialis. Acta Morphol. Neer. Scand. 5:217-220.
Bianchi, S. (1886) Varietà muscolari. Sperimentale (Firenze). 57:113-125.
Curnow, J. (1873) Notes of some irregularities in muscles and nerves. J. Anat. Physiol. 7:304-309.
Macalister, A. (1875) Additional observations on muscular anomalies in human anatomy (third series), with a catalogue of the principal muscular variations hitherto published. Trans. Roy. Irish Acad. Sci. 25:1-134.
Mori, M. (1964) Statistics on the musculature of the Japanese. Okajimas Fol. Anat. Jap. 40:195-300.
Odin, -. (1869) Faisceau supplémentaire du long chef du biceps et coraco-brachial surnuméraire sur le méme bras. Lyon Mêd. 2:1869.
Reid, R.W. and S. Taylor. (1879) Anatomical variations. Reports. St. Thomas's Hospital 9:46.
Wood, J. (1864) On some varieties in human myology. Proc. Roy. Soc. Lond. B 13: 299-303.
Wood, J. (1867) On human muscular variations and their relation to comparative anatomy. J. Anat. Physiol. 1:44-59.
Wood, J. (1868) Variations in human myology observed during the winter session of 1867-68 at King' College, London. Proc. Roy. Soc. Lond. B 17: 483-525.
Zagorsky, P. (1809) Observationés anatomicae de musculorum quorundam corporis humani varietate minus frequente. Mem. d. L'Acad. Imp. d. Sci. d. St. Petersbourg T.1:355-359.
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