Arterial supply in the human pectoralis minor muscle.

In the following, we report our findings obtained as a result of injecting an acrylic pigment in the arteries supplying the pectoralis minor muscle in 50 lateral chests of 26 Japanese adults (15 males and 11 females). In the pectoralis minor muscle, the muscular bundle near the terminal is supplied by A. processus coracoideris (Pc, Sato-Takafuji, '85) or A. coracobrachialis (Cb, Sato, '80) of A. axillaris (Ax), while its middle upper and lower peripherals are supplied by A. thoracoacromialis (Ta) and A. partis abdominalis (Pab, Sato, '76), respectively. Further, the upper and lower peripherals at its origin are supplied by A. thoracica suprema (Ts) and A. thoracica lateralis (Tl), respectively. Pc, Cb, Pab and Ts may occasionally be absent. Arteries supplying this muscle are classified according to their origins and routes of distribution, as follows. Type I-a: Pc or Cb, Ta, Pab, Ts and Tl are present, 32%; Type II-a: Ts is absent from Type I-a, 14%; Type III-a: Pb and Pc are absent from Type I-a, 20%; Type IV-a: Cb, Pc and Ts are absent from Type I-a, 10%. Type b is Type a without Pab. The rates of appearance of Type I-b, II-b, III-b and IV-b were all 6%. The ratios of distribution in area a were as follows, in order of decreasing ratio: 37.6% for Pab (37 cases), 32.4% for Tl (49 cases), 30.2% for Ta (49 cases), 10.8% for Ts (32 cases), 7% for Cb (9 cases), and 6.37% for Pc. In the pectoralis minor muscle, the major supplying arteries are Pab, Tl and Ta, and where Pab was absent, this was compensated for by a branch of Ta. The total number of supplying arteries in this muscle was two to five, with the majority, or 36%, having four arteries. As for sex differences in the incidence of each type, Type I-a appeared more often in males (40%) than in females (20%). The rates according to the ribs of origin were 46%, 36%, 16%, and 2% for types 2.3.4.5, 3.4.5, 2.3.4, and 2.3.4.5.6, respectively. It was interesting that all Type II and Type IV cases without Ts corresponded to Type 3.4.5 without the muscular bundle arising from the second rib, as it suggests the process of degeneration of the pectoralis minor muscle in Homo.(ABSTRACT TRUNCATED AT 400 WORDS)