著者

都築 茂

出版者

日本医科大学医学会

雑誌

日本医科大学雑誌 (ISSN:00480444)

巻号頁・発行日

vol.24, no.3, pp.183-205, 1957-03-15 (Released:2009-07-10)

参考文献数

22

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After Streeter begins the human arm in his horizon XIII to develop. The author's investigation begins from the. Streeter's horizon XIV upward. The author's to the youngest horizon belonging human embryo is 7 mm long which arm is only the mass of simple homogenous mesenchymal tissue, the nerve plate consisting of from the 4 th to the 8th cervical and the first thoracal nerves is protruding in the basic part of this appendage (plate 1). This nerve plate is the anlage of the brachial plexus and is beginning to divide into ventral and dorsal parts. This condition is almost the same in the next to the horizon XV belonging 6 mm long embryo, in which the central tissue of the arm is a little different from the surrounding more condensed tissue (plate 1). This central tissue may be called the beginning of the praecartilageous. The praecartilageous tissue is observed in the next to the horizon XVI belonging 9 mm long embryo, the cartilageous in the 9.5 mm long, which belongs to the Streeter's horizon XVII.The brachial plexus, which divides into ventrocranial and dorsocaudal portions without any prolongation of the branches in the 6 mm long embryo, is in the next 9 mm long well developed so that all the branches of the plexus are distinguished.In the next stage are all branches of the plexus brachialis prolonged and distinct, the precartilageous tissue of the axis of the arm is becoming cartilageous. The chondrification of the skeleton is observable in the scapula, humerus, radius, ulna and in a few carpal bones, the others yet precartilageous.A. axillaris of the 6 mm long embryo divides into A. brachialis and profunda brachii, in the 9 min long thus divided A. brachialis is prolonged to become A. interossea. The distal branch of the interossea reaches the hand plate, where it terminates as the dorsal and volar interossea. This form of the arterial branches is also in the next 9.5 mm long embryo observed, in which A. mediana from the brachialis communicates with the volar interossea.As for the venous system of the arm of these human embryos, there is no distinct change of form. The socalled Randvene or primary ulnae vein of the early stages is observed through three horizons XV, XVI, XVII, almost the same. The cranial end of the vein terminates as a venous net at the root of the arm, the caudel prolongation continues to the lateral side of the brachial plexus where it ascends and bends medialward to pour into the anterior cardinal vein.