Yamamoto Masahito, Kojyo Urara, Yanagisawa Nobuaki, Mitomo Keisuke, Takayama Takeshi, Sakiyama Koji, Abe Shinichi
Department of Anatomy, Tokyo Dental College, 2-9-18 Misaki-cho, Chiyoda-ku, Tokyo, 101-0061, Japan.
Language Laboratory, Tokyo Dental College, 2-9-18 Misaki-cho, Chiyoda-ku, Tokyo, 101-0061, Japan.
Surg Radiol Anat. 2018 Mar;40(3):303-311. doi: 10.1007/s00276-017-1919-7. Epub 2017 Sep 11.
Major anatomical textbooks generally state that the biceps brachii muscle (BB) is composed of long and short heads, whereas the brachialis muscle (BR) consists of a single head. However, the numbers of heads comprising the BB and the BR are very variable. The purpose of this study was to investigate how the branching patterns of the musculocutaneous nerve (MC) influence the number of heads of the BB and the BR.
Morphological examinations of the BB and MC were conducted using cadavers of 22 Japanese individuals, and morphological examinations of the BR and the MC were conducted in 9 of those 22 individuals.
A three-headed BB was observed in 7 of the 22 specimens (31.8%). Most of these specimens showed a Type III branch pattern (after penetrating the long head or the short head, the MC innervated the supernumerary head or communicated with the main root again). The number of BR heads was categorized into three types: Type A, two heads (superficial and deep heads, 22.2%); Type B, three or four heads (two or three superficial heads and one deep head, 44.4%); and Type C, multiple heads (33.3%). Among these categories, branches of the MC in Type A specimens were most simple.
A supernumerary head of the BB seemed to be present if the MC penetrates it. The BR basically consists of superficial and deep heads, and the number of superficial heads is affected by branches of the MC.
主要的解剖学教科书通常指出，肱二头肌（BB）由长头和短头组成，而肱肌（BR）由单一头组成。然而，构成BB和BR的头数差异很大。本研究的目的是探讨肌皮神经（MC）的分支模式如何影响BB和BR的头数。
对22例日本个体的尸体进行BB和MC的形态学检查，对其中9例个体进行BR和MC的形态学检查。
22个标本中有7个（31.8%）观察到三头BB。这些标本大多表现为III型分支模式（MC在穿透长头或短头后，支配额外的头或再次与主根相连）。BR的头数分为三种类型：A型，两个头（浅头和深头，22.2%）；B型，三个或四个头（两个或三个浅头和一个深头，44.4%）；C型，多个头（33.3%）。在这些类型中，A型标本中MC的分支最简单。
如果MC穿透BB，似乎会出现额外的头。BR基本上由浅头和深头组成，浅头的数量受MC分支的影响。
