肘関節の屈筋群と伸筋群を支配する神経の実験組織学的研究(<特集>脳と神経の研究V)
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概要
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Innervation of flexor muscles (the Brachialis and the biceps brachii) and an extensor (the triceps brachii) of the elbowjoint was examined in 61 dogs, 25 monkeys and 2 men. 1. Macroscopically the musculocutaneous nerve innervating the flexor muscles is usually formed from C_6 and C_7 (2 roots), and the radial nerve which innervates the extensors is from C_7, C_8 and T, (3 roots). Degeneration experiments show, however, that the ventral nerve fibres innervating the flexors are derived from C_6 to T, (4 segments), and the dorsal root fibres are from C_5 to T_3 (7 segments). Further, the ventral root fibres innervating extensors are derived from C_7 to T, (3 segments), and dorsal root fibres are from C_6 to T_2 (5 segments). Thus, the extensor-muscle nerves originate 1 segment caudal than the flexor-muscle nerves, and the flexor and extensor muscles are innervated by more roots from the dorsal nerve fibres than those from the ventral fibres. 2. The ratios between myelinated nerve fibres to the extensors and those to the flexors are 1:0.41 in dog, 1:0.48 in green monkey (Cercopithecus aethiops), 1:0.64 in crab-eating monkey (Macaca cynomolga) and 1:0.83 in man. It appears therefore that the higher the animals, the more the development of the flexor nerves. 3. Myelinated nerve fibres per gram of flexor and extensor muscles are 96.9 and 48.4 in number from dog, 203.3 and 124.2 from crab-eating monkey, and 152.3 and 123.1 from green monkey, respectively. Thus, the innervation rate of the flexor muscle nerves is always higher than that of the extensor. 4. The most of the myelinated nerve fibres innervating voluntary muscles are maximum-sized in dog, monkey and man. The more decrease in diameter of the myelinated nerve fibres the smaller in number of those fibres. No difference of the nerve fibre diameter is found between the flexor and extensor nerves. 5. The ratio between sensory fibres from dorsal roots and motor fibres from ventral roots is 58.4%: 41.6% in the flexor, and 69.6%: 30.4% in the extensor nerves in dog. Thus, the number of sensory nerve fibres always predominate over motor nerve fibres. There are relatively many motor nerve fibres in the flexor muscles than in the extensors, and, on the contrary, many sensory fibres in the extensors.
- 千葉大学の論文