On the arterial supply in the human biceps brachii muscle

The distribution of the arterial supply and innervation of skeletal muscle in the whole human body has been being researched in our laboratory. The results obtained on the biceps brachii from 25 bodies (50 sides) are reported here. Generally, in this muscle, A. coracobrachialis (Cb, SATO, 1980), a branch of A. axillaris (Ax), is distributed at the upper muscle bundles of the short head after running parallel to N. musculocutaneus (Nmc) and supplying M. coracobrachialis. The main artery (Ma), which is a branch of A. brachialis (Br), is distributed at the upper and middle parts of both heads, and the point where Ma enters the muscle bundles almost coincides with the point where R. brachialis (Rb) branches from Nmc. R. biceps brachii (Rbi), which is distributed only at this muscle and Om, the common trunk to other muscles, is distributed at the lower part of the muscle bundles. The arterial supply of this muscle was classified as follows according to the conditions of origin and its distribution. Type I: Ax(Cb) was distributed to the upper part of the muscle bundle. Type II: The absence of Ax(Cb) in the upper part of the muscle bundle. Type A, a and 1: Ma.Br(Om) supplying the long, short and both heads of the biceps brachii. Type B, b and 2: Ma.Br(Rbi) supplying the long, short and both heads of the biceps brachii. In the long head, Type II-A accounted for 62.0%, Type II-B for 30.0%. In the short head, Type I-a was 62.0%, Type I-b 28.0%. In both heads, Type I-1 was 62.0%, Type I-2 28.0%. There were significant differences in the distribution of the nutrient arteries between the long and short heads. A. brachialis superficialis (Bs) was recognized in 3 of these cases (2 cases of Type III and 1 case of Type VII by Adachi's classifications), which were rare cases. In these cases, arterial branches other than Cb branching from A. brachialis profunda are branches of Bs. This means, judging from ontogeny, that Bs, the blood vessels in the superficial layer, supplies this muscle, which belongs to the superficial layer of the brachium.