Topographical relationship between the accessory hepatic duct and the hepatic artery system.

Hepatic biliary injury is one of the most common complications in cholecystectomy and is frequently accompanied by arterial injuries. Because there are several anatomical variations of the hepatic ducts, including the accessory hepatic ducts (AHDs), it is important to consider not only the anatomical position of the hepatic ducts but also those of the AHDs in cholecystectomy. However, the topographical relationships between the AHDs and the hepatic arteries are still poorly understood. In the present study we show that AHDs were observed in 7 out of 59 (11.9%) of the cadavers. There was a single AHD in the 6 out of the 7 cadavers and double AHDs in one. In these cases, the right AHDs emerged from the anterior medial segment of the liver piercing the parenchyma, while the left AHDs emerged directly from the anterior part of the caudate lobe. The right AHDs ran anterior to the right hepatic artery, while the left AHDs ran posterior to the hepatic arteries. The topographical relationship between the AHD and the hepatic artery system was thus reversed in the cases of the right and the left AHDs.

Anomalous course of the external carotid artery.

The course and the branching patterns of the external carotid artery were investigated macroscopically in a total of 550 bodies or 1100 head sides of Japanese subjects, donated for student dissection at Kumamoto University from 1994 to 2014. With the exception of 14 head sides, the external carotid arteries running between the posterior belly of the digastric and stylohyoid muscles were found in 42 (3.87 %) out of 1086 head sides. Strictly speaking, they passed between the stylohyoid muscle and the stylohyoid branch of the facial nerve in 23 out of these 42 head sides. In the remaining 19 instances, the stylohyoid branch of the facial nerve was cut and its relationship to the external carotid artery was not clear. The external carotid artery running lateral to the intact stylohyoid branch of the facial nerve, medial to the digastric muscle was not found. The external carotid arteries running lateral to the digastric muscle were found in 4 (0.37 %) out of 1086 head sides. As a result, it is proposed that plural, potential courses of the external carotid artery originally exist and that some parts of such potential courses remain as branches of the external carotid artery in the usual instance, while the anomalous courses of the external carotid artery are induced mainly by anastomosis between the muscular branches supplying the wall of the head and neck in contrast to the usual external carotid artery induced mainly by the branches originally supplying the pharynx.

A schematic diagram showing the various components of the embryonic aortic arch complex in the retroesophageal right subclavian artery.

A retroesophageal right subclavian artery, arising from the arch of the aorta as the terminal branch and passing dorsal to the esophagus, was found in five (1.2%) of 428 bodies donated for student dissection at Kumamoto University between 1993 and 2008. The presence of a retroesophageal right subclavian artery has been generally explained to be caused by the persistence of the normally eliminated part of the right dorsal aorta caudal to the seventh intersegmental artery and the disappearance of the normally patent right fourth aortic arch and the part of the right dorsal aorta cranial to the seventh intersegmental artery during the developmental process. However, the parts which remain or disappear are different in each case. With the aim of determining the portions eliminated or persisting and thereby gaining an understanding of the developmental process of the retroesophageal right subclavian artery in each instance, we made schematic diagrams showing the various components of the embryonic aortic arch complex as the prototype just before the anomaly occurred. Based on these diagrams, we conclude that immediately preceding the disappearance of the distal part of the right dorsal aorta and the dorsal part of the right sixth aortic arch, the third intersegmental artery was situated opposite to the fourth aortic arch and the seventh intersegmental artery was situated cranial to the point of junction of the right and left dorsal aortae.

The superficial brachial artery passing superficially to the pectoral ansa, the highest superficial brachial artery (Arteria brachialis superficialis suprema).

The human superficial brachial artery passes superficially to the median nerve and can be classified into three subtypes according to its topographical relationship to the pectoral ansa. When the superficial brachial artery passes superficially to the pectoral ansa, it is defined as the highest superficial artery. We found the highest superficial brachial arteries in both arms of a single cadaver. The right one coexisted with a normal axillary artery, and its identification was not difficult. The left one ran medially to the brachial plexus proximally and became superficial to the brachial plexus after branching off the artery, which gave the subscapular artery, then passed between the radial nerve and its accessory root from deep to superficial and ended as an inferior collateral ulnar artery. We also found a muscular axillary arch in each of the arms, both of which were innervated by the medialmost branch from the pectoral ansa. The right highest superficial brachial artery passed deep to the nerve to the muscular axillary arch. We conjectured that the left axillary artery is where the highest superficial brachial artery, as found on the right, coexists with the axillary artery in the case of Adachi's C-type brachial plexus (AxC). Then, the highest superficial brachial artery develops as a main stem, and the latter remains as a rudimentary AxC. Because the left axillary artery is caught on neither the pectoral ansa nor its branches, the left axillary artery can shift medially to the brachial plexus, and its true form is not obvious.

Morphological study, by teasing examination, of the communication from the musculocutaneous to median nerves.

Nine specimens with communications from the musculocutaneous to the median nerves were investigated, by teasing examination, from their origins in the brachial plexus to their final destinations in nerve fibers. The nerve fibers of the communications were derived from the sixth and seventh cervical ventral rami of the spinal nerves. The distributions of the nerve fibers of the communications were divided into four types. In Type A, the nerve fibers reached the thenar muscles and the lateral digital nerves. In Type B, they reached the pronator teres or flexor carpi radialis muscles in addition to Type A. In Type C, they reached the anterior interosseous nerve area in addition to Type B. Finally in Type D, they also reached the distal muscle belly of the index of the flexor digitorum superficialis. It was revealed that there was a definite rule in the distribution of the nerve fibers in the communications from the musculocutaneous to median nerves. The area of the distributions was expanded in order from the thenar muscles to the flexor muscles of the forearm. The results in this study are useful for proper diagnosis and treatment of the peripheral nerve injuries involving the musculocutaneous and median nerves.

Morphological study of the communication between the musculocutaneous and median nerves.

We investigated the incidence of each pattern of the communications between the musculocutaneous and median nerves and discussed its morphological significance. The communications between both nerves were seen in 188 (41.5%) of 453 specimens. They were classified into five regular patterns according to their directions and formations. The incidence of the communication was significantly higher in those with excessive heads of biceps brachii than in those without them (p < 0.05). As a result, we established a classification of the regular pattern of the communications and revealed that the musculocutaneous and median nerves had the possibility of forming plexuses in the humeral area. The musculocutaneous nerves are regarded as the bundles that arise from the median nerve with the lateral cutaneous nerve of forearm and the branches to the biceps brachii and brachialis muscles.

Left inferior vena cava with regressed right inferior vena cava.

A left inferior vena cava was found in the cadaver of an 88-year-old Japanese man during a student dissection course at Kumamoto University School of Medicine. The right common iliac vein ascended obliquely toward the left behind the right common iliac artery and united with the left common iliac vein to form the inferior vena cava in front of the fifth lumbar vertebral body behind the left common iliac artery. The inferior vena cava ascended on the left side to the aorta, and after the left renal vein joined to it at the level of the third lumbar vertebral body, it turned obliquely to the right and crossed superficially to the aorta. At the right side of the aorta, the common stem of the third lumbar vein and the posterior renal vein was joined to the oblique part. The inferior vena cava then ascended, receiving the right renal vein as it would normally. The inferior vena cava is thought to develop symmetrically but this left inferior vena cava shows a persistence of the left channel of the infrarenal part, which normally disappears. Although the common stem of the veins that joined to the oblique part on the right side did not continue to the right common iliac vein, gross anatomical findings suggested it to be the remnant of the right inferior vena cava.

Inferior epigastric artery arising from the obturator artery as a terminal branch of the internal iliac artery and consideration of its rare occurrence.

The origins of the inferior epigastric and obturator arteries and the relationship between these arteries have been determined macroscopically in examinations of 706 body-halves of Japanese subjects. Three very rare inferior epigastric arteries were found to arise from the obturator artery leaving the internal iliac artery. The intimate relationship between these arteries has been documented by the obturator artery arising from the inferior epigastric artery and the anastomosis between them. It is generally interpreted that such anomalies occur as remnant or partial disappearance of the connection between the pubic branches of the inferior epigastric and obturator arteries. The inferior epigastric artery arising from the obturator artery is also thought to be a similar anomaly. Since the obturator artery from the inferior epigastric artery represents one form of extreme anomaly, and the inferior epigastric artery from the obturator artery represents another form, it would seem that these two forms of extreme anomaly should occur at similar frequencies. However, in our research, the incidence of the former was 10.5% while that of the latter was a very low 0.4%. During normal development, the inferior epigastric artery is established at an earlier stage than the obturator artery as a channel for blood supply. We suppose that the difference of blood flow resulting from this time lag is one of the reasons why the inferior epigastric artery from the obturator artery is very rare in comparison to the obturator artery from the inferior epigastric artery.

Right ligamentum teres joining to the right branch of the portal vein.

Ligamentum teres joining to the right branch of the portal vein in a 79-year-old Japanese male cadaver was noted during student dissection at Kumamoto University in 2004. The ligamentum teres entered the liver along the left side of the gallbladder fossa. The quadrate lobe was not distinguished from the left lobe in the visceral surface. When the liver parenchyma was removed by tearing off to expose the branches of the portal and hepatic veins, it was clarified that the ligamentum teres unusually joined to the bifurcation of the upper anterior and lower anterior branches of the right branch of the portal vein. The ligamentum teres is the remnant of the umbilical vein working throughout fetal life. Initially a pair of the umbilical veins entered the sinus venosus. During the fourth and fifth weeks they connect to the hepatic sinusoids, which become the portal and hepatic veins, and the parts entering the sinus venosus of both umbilical veins disappear. By the eighth week, as all remainder of the right umbilical vein disappears, the left umbilical vein is the only one to carry blood from the placenta to the liver. It results in the ligamentum teres joining to the left branch of the portal vein. However, in the present case it is thought that the right umbilical vein remained instead of the left one for some reason, and it then became the right ligamentum teres joining to the right branch of the portal vein.

Nerve fiber analysis on the so-called accessory subscapularis muscle and its morphological significance.

A rare muscular anomaly, so-called accessory subscapularis muscle, was found in the left axillary fossa of a 95-year-old male cadaver during a student dissection practise. The muscle arose near the lateral margin of the scapula from the surface of the subscapularis muscle and ran upward to fuse with the capsule of the shoulder joint via a tendon. It measured 1.0 cm in width, 7.0 cm in length and 1.5 mm in thickness, and was separated from the underlying subscapularis muscle by the axillary and inferior subscapular nerves. Macroscopically, the anomalous muscle received its nerve supply from a branch arising from the lower root of the radial nerve near the origin of the thoracodorsal nerve and entered the muscle from its ventral surface. Nerve fiber analysis showed that the supplying nerve originated from fibers of the dorsal element of C7 immediately cranial to the thoracodorsal nerve. These findings indicate that the present anomalous muscle might be close to the formation of the latissimus dorsi muscle in its derivation rather than the subscapularis muscle.

Radial artery running beneath the biceps tendon and its interrelation between the radial recurrent arteries.

A radial artery running beneath the biceps tendon was found in the cadaver of a Japanese woman during a student dissection course at Kumamoto University School of Medicine in 2006. The brachial artery bifurcated into the radial artery and the ulnar artery in the cubital fossa, and the radial artery twisted laterally running beneath the biceps tendon, and when it was situated laterally to the tendon, twisted distally at the level of the radial tuberosity, and then twisted medially again. After the radial artery passed over the biceps tendon, it turned distally and continued as a normal radial artery. The superficial brachial artery, which coexisted with the brachial artery, was given off from the axillary artery and it continued to the final twist of the radial artery. The course of this radial artery is similar to the arterial rings surrounding the biceps tendon, found during the same dissection course. The arterial rings were formed between the brachial artery and the radial artery, and their proximal origins ran beneath the biceps tendon, while the distal origins were superficial. The present arterial variation is thought to have occurred when the normal part of the radial artery in the cubital fossa was substituted by the arterial ring, coexisting with the superficial brachial artery, which usually disappears during normal development. Furthermore, it is suggested that a part of the arterial ring always remains as a radial recurrent artery.

Two anatomical autopsy cases of direct communication between a persistent primitive trigeminal artery and an anterior inferior cerebellar artery.

The persistent primitive trigeminal artery (PPTA) is the most common persistent carotid-basilar anastomosis. However, morphological findings of the PPTA based on the anatomical autopsy are very scarce. To understand the reason why such a variant artery develops, it is essential to examine the detailed morphology of the PPTA and developmental process of this artery. Here, we present two anatomical autopsy instances of the PPTA (cases 1 and 2). In the first case (78-year-old female; right side), the anterior inferior cerebellar artery (AICA) arose from the internal carotid artery passing medial to the abducens nerve. This artery gave off a small branch communicating to the basilar artery, passed lateral to the trigeminal nerve root, and continued backward to the dorsal surface of the cerebellum. Thus, in this case, the AICA is considered to be branched from the PPTA. In the second case (75-year-old female, left side), the PPTA branched from the internal carotid artery, and passed lateral to the abducens nerve, giving off an artery connecting with the AICA. These communicating arteries between the basilar artery and the AICA, recognized in cases 1 and 2, are considered to be the persistence of the primitive lateral basilovertebral anastomosis during the early embryological period. We propose that the primitive lateral basilovertebral anastomosis forms the arterial network around the trigeminal nerve root, and the AICA develops through this anastomosis.

Anomaly with no right ventral root at the seventh cervical segment in humans: gross anatomical and neuroanatomical study.

The cadaver of an 89-year-old woman who had died of cerebral apoplexy and which was dedicated to anatomy practice for medical students at Kumamoto University, was found to have complete lack of the right ventral root of the seventh cervical segment (C7). Observation of the peripheral spinal nerve indicated that the branch, which appeared to be a descending collateral of the ventral root of C6, became confluent with the dorsal root of C7 at the point just distal to the dorsal root ganglion. Following this confluence, new fiber elements ran out of the intervertebral foramen as the seventh cervical nerve. More peripherally, this fiber bundle joined the brachial plexus, its outward appearance was normal in the manner of ramification and each nerve's supply to muscles. Additionally, the inside view of the spinal cord of C6, C7 and C8 was examined neuroanatomically. Nissl staining of transverse sections at C7 (block 2) showed that motor neurons existed in the right anterior horn and their histological features were normal. Subsequently, horizontal sections were made from the two blocks, each of which contained C6/C7 (block 1) or C7/C8 (block 3), and were treated dually with Nissl and myelin staining. These sections also had a normal picture of cells and myelinated fibers on the right side as compared with those on the left side. The results suggested that motor neurons of the right C7 had a normal supply to the targets, although the trajectory of their axons in the spinal cord was obscure.

Preureteric inferior vena cava with possible rudiment of the proper inferior vena cava.

A right single preureteric inferior vena cava (IVC) was found in the cadaver of a 77-year-old Japanese male during a student dissection course at Kumamoto University School of Medicine in 2003. The ureter emerged from the lower end of the hilum of the right kidney at the second lumbar vertebral level. It ran inferomedially to pass behind the IVC, and turned inferolaterally to cross the vein superficially at the level of the third to the fourth lumbar vertebrae. Then, the ureter was situated to the right of the IVC, and descended ordinarily. The second lumbar vein of each side united bilaterally, as did the third lumbar veins. The common stem of the second lumbar veins drained into the left side of the IVC posterolaterally at the level of the second intervertebral disc, and the third common stem opened into the left border of the IVC at the fourth lumbar vertebral level. The ureter hooked around the IVC between the openings of those common stems. There was a small continuation (0.2 mm in diameter) between the left second lumbar and the right third lumbar veins along the vertebral column slightly right of the midline. It passed superficial to the right third lumbar artery, as did the IVC. The right testicular vein opened into the IVC at the level of the lower end of the third lumbar vertebral body. Generally, the level of the opening of the gonadal vein corresponds to the level of the caudal end of the remaining subcardinal vein, but it is lower than usual in this case. Furthermore, the segment from the confluence of the common iliac veins to the common trunk of the third lumbar veins, and to the small continuation can be regarded as the proper IVC, and the part where the ureter hooks around it may have derived from the anastomosis between the common trunk of the third lumbar veins and the subcardinal vein.

Double innervation of the anterior belly of the digastric muscle.

We came across a very rare case in which the anterior belly of the digastric muscle was innervated by the twigs of the facial nerve in addition to those of the mylohyoid nerve. The anomaly was discovered in the cadaver of an 84-year-old Japanese male bequeathed for a training seminar in gross anatomy at Kumamoto University in 2003. One twig issued from the marginal mandibular branch of the facial nerve and entered the central region of the anterior belly of the digastric muscle on the lower surface. The other twig issued from the stylohyoid branch of the facial nerve, descended along the lateral margin of the stylohyoid muscle and entered the anterior belly of the digastric muscle on the lower surface near the intermediate tendon. The twig from the marginal mandibular branch was distributed to the shallow (lower) and central region near the medial margin of the anterior belly. The twig from the stylohyoid branch was distributed to the shallow and lateral region of the anterior belly. These two twigs communicated with the mylohyoid nerve at several peripheral parts. Textbooks on general anatomy make mention of only one nerve, the mylohyoid, supplying the anterior belly of the digastric muscle. However, the present case manifests that the anterior belly receiving twigs from the mylohyoid and facial nerves is formed with the second brachial component as well as the first.

The deep axillary artery.

An aberrant axillary artery running deep to the brachial plexus during its course was observed. The brachial plexus in this case was formed by the fourth cervical nerve to the first thoracic nerve and the radial nerve received a small nerve bundle (accessory radial nerve root) from the posterior aspect of the lower trunk. The axillary artery passed between the lateral and the medial cords of the brachial plexus, the same as for an ordinary axillary artery. In addition, it passed between their posterior divisions, forming the posterior cord, and further ran between the radial nerve root and the accessory radial nerve root from deep to superficial. This axillary artery was recognized as the deep axillary artery, the same as the axillary artery we have reported previously. It was thought that the branches to the subscapularis and serratus anterior muscles, nutrient branch to the radial nerve root and the subscapular artery played important roles in its formation.

A case of nonrotation of the midgut with a middle mesenteric artery.

In 2002, we came across a very rare case of nonrotation of the midgut with a middle mesenteric artery (MM) (tentative name). It was found in a 73-year-old Japanese female cadaver donated for student dissection at Kumamoto University. In this case, the small intestine occupied the right half of the abdominal cavity and the large intestine occupied the left half. The caecum was situated on the anterior inferior part of the abdominal cavity near the midline. The duodenum (Du) was fused to the posterior abdominal wall. The small intestine except the Du and the ascending colon were suspended from the posterior abdominal wall by the mesentery, but the remainder of the colon was fused to the left posterior abdominal wall. In addition, an anomalous branch arose from the abdominal aorta between the superior and inferior mesenteric arteries (SM and IM) in this case. It chiefly supplied the ascending and the transverse colons and anastomosed with the SM and IM, respectively, through the marginal arteries. It is very rare that these anomalies appear simultaneously in one body. In this case, it is difficult to declare that the existence of the MM directly caused the nonrotation of the midgut, but it is reasonable to suppose some kind of relation between them.

A middle meningeal artery which arises from the internal carotid artery in which the first branchial artery participates.

A middle meningeal artery arising from the internal carotid artery was found in the right half of the head of an 85-year-old male cadaver during student dissection practice. It arose from the lateral aspect of the internal carotid artery in the carotid canal, arrived at the foramen lacerum after running forward. It then ran backward under the trigeminal ganglion and took the usual course after passing its posterior margin. On one hand, the maxillary artery did not issue the middle meningeal artery, gave off only a small twig supplying the lateral pterygoid muscle at the corresponding position. It was corroborated by the fact that the foramen spinosum was absent in this example. During usual development, the middle meningeal artery primarily springs from the supraorbital branch of the stapedial artery that arises from the dorsal part of the second branchial artery. Later, by the formation of the external carotid artery connecting with the common trunk of the infraorbital and mandibular branches (maxillomandibular division) of the stapedial artery and by the atrophy of the proximal part of it, the middle meningeal artery is finally supplied by the external carotid artery. But in this example, it is supposed that the middle meningeal artery arose from a more distal position of the internal carotid artery owing to the persistence of the anastomosis between the dorsal part of the first branchial artery and the supraorbital branch and the interruption of the connection between the supraorbital branch and maxillomandibular division of the stapedial artery.

The inferior supernumerary renal arteries: a classification into three types.

Among cases that had multiple renal arteries on one side, an inferior supernumerary renal artery was found in 24/270 cases (ca. 9%) on the right and in 19/270 cases (ca. 7%) on the left, together with the usual renal artery. We have noticed that there are correlations between their levels of origin from the aorta and their positional relation to the ureter and the inferior vena cava (IVC). An inferior supernumerary renal artery (InfRA) of lower origin passes in front of the IVC and behind the ureter. An InfRA of middle origin passes in front of both the IVC and the ureter. An InfRA of upper origin passes behind the IVC and in front of the ureter or renal pelvis. In addition there was a tendency for the lower origin type to have an ureteric branch, while the middle and upper origin types had a gonadal branch. These findings suggest that different derivations lead to the inferior supernumerary renal arteries.

An anatomical study of the partial anomalous pulmonary venous return with special references to the bronchial vein.

Two examples of partial anomalous drainage of the pulmonary vein were detected at dissection. The first case was found in a 70-year-old female Japanese. An aberrant vein, approximately 6 mm in diameter, that derived from the upper lobe of the right lung was observed to drain into the superior vena cava at a point just below the entrance of the azygos vein. The other veins from the right lung gathered into two pulmonary veins and returned into the left atrium as usual. In the second case, which was found in an 80-year-old female Japanese, a connecting vein, approximately 8 mm in diameter, was found between the left superior pulmonary vein and the left brachiocephalic vein. In this case, although the direction of the blood flow within the connecting vein was not certain, it is probable that the blood passed from the pulmonary vein into the brachiocephalic vein, judging from the increase in the width of the latter vein. No other anomalies were found in the cardiovascular systems. At the occurrence of the anomalous drainage of the pulmonary veins in both cases, we suspected the role of the bronchial vein to be a communicating and boundary vein between the pulmonary and systemic circulations. The developmental background of these anomalies is also considered.