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Precise clinical knowledge of liver anatomy is required to safely perform a hepatectomy, for both open and laparoscopic surgery. At the 19th meeting of the Japanese Research Society of Clinical Anatomy (JRSCA), we conducted special symposia on essential issues of liver surgery, such as the history of hepatic segmentation, the glissonean pedicle approach, application of 3-D imaging simulation and fluorescent imaging using indocyanine green solution, a variety of segmentectomies including caudate lobectomy, the associating liver partition and portal vein embolization for stage hepatectomy and harvesting liver grafts for living donor liver transplantation. The present review article provides useful information for liver surgeons and anatomic researchers.

Minute dissection was performed in one male adult cadaver in order to elucidate the detailed distribution of muscular branches of intercostal nerves within the lateral abdominal muscles as well as the segmental relationships. In the obliquus internus and transversus abdominis, as well as in the upper half of the obliquus externus, each muscle fascicle receives the nerve of the corresponding segmental attachment to the rib. On the other hand, in the lower half, the obliquus externus abdominis receives a twig from the lower adjacent segmental nerve, because within the muscle the corresponding segmental nerve first runs horizontally and enters the upper adjacent fascicle before descending obliquely, parallel to the fiber direction.

Minute dissection was performed on the ventral primary rami of the first thoracic to first lumbar nerves in two halves of an adult male cadaver in order to determine points of origins of muscular branches from the intercostal nerves. Generally, the muscular branches originated independently, but the branches supplying the intercostalis intimus and internus tended to originate as a common trunk. The muscular branching patterns were compiled in an illustration, and based on these patterns the serial homology of the thoracic and abdominal muscles was proposed. Although the obliquus externus abdominis has been thought to correspond to the intercostales externi, from these innervation findings it appears to correspond to the intercostales interni. Further, the quadratus lumborum seems homologous to the intercostales externi.

Detailed dissection was performed on the ventral primary rami from the first thoracic to the second lumbar nerves in order to obtain more comprehensive data of the ramification of the intercostal nerves in the rhesus monkey. The nerves to the intercostalis intimus and internus and the obliquus externus abdominis tended to arise as a common trunk from the main intercostal nerve. A comparison of the intercostal nerve ramification with that in man is included.