Many authors have studied variation in the maxillary artery but there have been inconsistencies between reported observations. The present research aimed to examine the courses and branching patterns of the trunk and branches of the maxillary artery in a large sample of Japanese adult cadavers. The course of the maxillary artery should be reclassified into seven groups as a clear relationship was found between the origin of the middle meningeal artery and the course of the maxillary artery. This indicates that conventional theory about the formation of the maxillary artery, which was considered to be a direct derivative of the stapedial artery, might be inaccurate. Many variations in the origin of the inferior alveolar artery were found. Notably, the inferior alveolar artery origin from the external carotid artery and a double origin of the inferior alveolar artery was also observed. Thus, the maxillary artery might be derived from a combination of both the external carotid and stapedial arteries.

Coronary arteries are frequently covered by cardiac muscles. This arrangement is termed a myocardial bridge. Previous studies have shown that myocardial bridges can cause myocardial ischemic diseases or cardiac arrhythmia, but the relevant pathogenic mechanisms remain unknown. We examined 60 hearts from Japanese cadavers macroscopically to clarify the spatial relationships among coronary arteries, cardiac veins and autonomic nerves. We found 86 myocardial bridges in 47 hearts from the 60 cadavers examined (78.3%). Next, we dissected out nine hearts with myocardial bridges in detail under the operating microscope. We found no additional branches of coronary arteries on the myocardial bridge surfaces. However, the cardiac veins, which usually accompany the coronary arteries, ran independently on the myocardial bridge surfaces in the same region. Cardiac autonomic nerves comprised two rami: one was associated with the coronary artery under the myocardial bridge and the other ran on the surface of the bridge. Such spatial relationships among the coronary arteries, cardiac veins and cardiac autonomic nerves at the myocardial bridges are quite similar to those in mouse embryo hearts.

The arrangement of the nerve bundles at the branching point of the femoral nerve (F), the interrelations of the branches each other and toward other nerves in the anterior region of the thigh, and the patterns and the anatomical features of both the running courses and the distributions of the branches were macroscopically studied, whereby some special findings were observed and the following results were obtained: 1) The periphery of the femoral nerve was fundamentally divided into superficial-deeply arranged three-layered divisions. Including the femoral branch of the genitofemoral nerve (Rf) and the femoral lateral cutaneous nerve (Cfl), the nerve branches at the anterior region of the thigh were totally divided into five-layered divisions. 2) The cutaneous branches of each division including Rf or Cfl could be classified in three groups: the medial cutaneous branches (m), the anterior cutaneous branches (a), and the lateral cutaneous branches (l). Based on the above results, the branches could be described systematically. Parallelly, several accessory bundles of F penetrating the psoas major muscle were observed, and two types of accessory femoral nerves (F') could be distinguished: One was higher on the segmentation and mainly flew into the 1st division of F. While the other distributed only to the medial region of the thigh. To clarify the segmental or stratifical natures of the branches of each division, F', and the interrelations among them, analyses of the nerve fibers were undertaken under the operational microscope. Consequently, the segmental differences between the divisions were distinct, and the medial branches or F'm obviously contained ventral components. Thus, when a component originated from the higher segments, it distributed to the proximal region generally taking a superficial course; when it originated from the lower ones, it distributed to the distal region of the thigh forming the deeper division; when it belonged to the ventral stratum, it distributed to the medial region; and when it belonged to the dorsal stratum, it distributed to the lateral region. On the occasion of the fiber analysis, it was found that each root of the lumbar nerve was generally divided into two or three subsegmentally-arranged subroots that divided themselves into some fasciculi arranged micro-segmentally. A minute analysis of the segmentations of the nerves became possible because of the above characteristics.

It has been suggested that in addition to motor axons, which extend directly into the spinal accessory nerve (SAN), ventral rami-associated motor fibers of cervical nerves also innervate the trapezius muscle. Using fluorescent dye labeling and 3D reconstruction in adult rats, this study clarifies the localization of motoneurons, which extend axons either directly through the SAN or through the ventral rami of cervical nerves to innervate the trapezius. DiI or DiI and DiO were used to label the ventral rami of cervical nerves entering the SAN, as well as branches of the SAN. We show that motoneurons whose axons pass through the ventral rami of cervical nerves and then enter the SAN, and those extending axons directly through the SAN are distributed within the same area. The neurons that extend axons through the SAN had a greater diameter than those axons that pass through the cervical nerves en route to the trapezius muscle. In addition, the axons that ultimately extend through the SAN exit the spinal cord dorsolaterally, while those that pass through the cervical nerves extend out the spinal cord through the ventral roots. We presume that the neurons that extend axons through the SAN are mainly alpha-motoneurons and that those projecting axons through the cervical nerves to the trapezius are mainly gamma-motoneurons. Taken together, these results could explain why patients in whom the SAN was used to treat brachial plexus injury retain some control of the trapezius muscle.

It has been believed that the primary arterial trunk of the mammalian forelimb is derived from the 7th intersegmental artery. Here we examined the early morphogenesis of the arteries and nerves in the forelimb region by adopting a method that combined intravascular dye-injection with nerve staining to whole mounted rat embryos. The study was carried out on greater numbers of specimens at smaller intervals of embryonic stages and from earlier stages than those in previous reports. We report that: (1) The multiple primary arterial trunks in the forelimb region (primary subclavians) originate directly from the lateral surface of the dorsal aorta independently of the intersegmental arteries, previous to the formation of limb buds. (2) The tips of the 8th (and the 9th) primary subclavians that originate from the aorta near the origin of the 8th (or the 9th) intersegmental artery bend cranially and/or caudally. With the formation of limb bud, they extend to form the longitudinal trunks in the presumptive axillary region. The primary arteries in the free arm region branch off from this longitudinal trunk, and one of them develops into the axial artery. (3) The origins of the primary subclavians shift their positions on the surface of the dorsal aorta and approach the origins of the neighboring intersegmental arteries to join them, and then replace the latter. Consequently, the primary subclavians appear to be "the lateral branches of the in tersegmental arteries." (4) The 8th primary subclavian is dominant at first, but is replaced by the 7th primary subclavian, which develops into the definitive subclavian artery. (5) With the brachial nerve plexus formation, the axillary arterial plexus derived from the longitudinal trunk develops to form two stems of the axillary artery.

The dorsal pancreatic artery (DP), characterized by a course that crosses behind the proximal part of the splenic vein. It is regarded as clinically important, providing essential distribution to the pancreas. However, the origin of the DP is extremely variable and therefore cannot provide a sufficient basis for identifying it. The DPs of 11 cadavers were investigated in terms of origin, course and distribution. A total of 45 branches of the DP are classified into seven types on the basis of course and distribution. One of these seven types was consistently observed among the specimens: it ran to the right, passed behind the superior mesenteric vein and anterior surface of the posterior part of the head of the pancreas, and then distributed to the uncinate process and the posterior part of the head of the pancreas. Variations in the branching pattern of the DP can be explained from the following perspective: the consistent branch (#5) is the stem of the DP, and other branches originate from it. It is advisable for surgeons to pay attention to this consistent branch of the dorsal pancreatic artery when performing a pancreaticoduodenectomy.

For the sake of clarifying which division of the brachial plexus, anterior or posterior, does the human suprascapular nerve belong to, the suprascapular nerve and cervical nerves concerned were teased into bundles of fibers by the fiber analysis method in six adult human arms of cadavers. The suprascapular nerve received fibers from C4, C5 and C6 in two cases which have a communicating branch between C4 and C5, from C6 and C6 in three cases and only from C5 in one case. In contrast with the posterior root fibers, the anterior root fibers of C5 and C6 could easily be divided into anterior and posterior groups of bundles which entered the anterior and the posterior divisions of the brachial plexus and were called anterior motor and posterior motor elements respectively. The suprascapular nerve received fibers from the anterior and the posterior motor elements of C5 in all cases. In addition to the C5, the nerve received fibers from both elements of C6 in three cases or from the anterior element of C6 in two cases. From this result the suprascapular nerve is judged to be a nerve which belongs to both anterior and posterior divisions of the brachial plexus.

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