Search

We observed an arterial ring communicating the superior and inferior gluteal arteries in the left half of the pelvis of an 88-year-old male. Although many previous studies have shown variations in the internal iliac artery, there has been no literature describing the fenestration. Therapeutic embolization is commonly performed for intractable bleeding in pelvic region. Surgeons should be aware of the arterial ring formation because of possible danger in the intravascular treatments. In patients with similar arterial rings, embolization of the anterior trunk of the internal iliac artery could be insufficient when blood runs through the circle of the arterial ring.

We observed a rare case of the middle suprarenal artery branching out from the superior mesenteric artery in a 78-year-old male. This atypical artery enters the right suprarenal gland that was also supplied by the superior and the inferior suprarenal arteries as usual. In embryonic stages, vasculature of the vitelline system and the gonadal system is differentially organized. The superior mesenteric artery has been generally thought to be pure vitelline, since there has been no evidence that the superior mesenteric artery supplies other organs than digestive. We then speculate that the present middle suprarenal artery is a remnant of the embryonic gonadal artery from the superior mesenteric artery, whereas a stem artery to the testis disappeared. Surgeons should take notice of the middle suprarenal artery when operations are conducted around the superior mesenteric 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.

Summary 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.

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.

Summary 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.

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, they 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.

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.

Summary An aberrant axillary artery that penetrated the radial nerve from deep to superficial during its course, was observed. The brachial plexus in the present case was classified as the Adachi's C-type brachial plexus. Further, an accessory radial root existed, which was a nerve bundle branching from the deep aspect of the inferior trunk and communicating with the radial root from the posterior cord to form the radial nerve. The axillary artery went on along the lower border of the brachial plexus and passed between the radial root and the accessory radial root from deep to superficial at its third section. As the axillary artery penetrated the origin of the radial nerve from deep to superficial, it was judged to reach deep under the posterior cord, hence deeper than the brachial plexus.

The attachment and innervation of the scalenus muscles in both sides of two Japanese monkeys and a rhesus monkey were observed to discuss their morphological significance while comparing their findings in humans. The scalenus ventralis muscle in macaques had almost the same attachments as the scalenus anterior muscle in humans and was innervated by the cervical nerve branches, which were lower in spinal segment than in humans and had a close relationship with the branches to the intertransversus ventralis muscles. Furthermore, the scalenus ventralis muscle was penetrated by the phrenic nerve in all cases observed. The posterior part of the scalenus muscle in macaques (the scalenus dorsalis muscle) was divided into short (the scalenus dorsalis brevis) and long (the scalenus dorsalis longus) parts according to their attachments. The former was attached to the transverse processes of the lowest two cervical vertebrae and the first rib, whereas the latter was attached to the 3rd-5th ribs. It is notable that the scalenus dorsalis muscles in macaques were innervated by branches from the long thoracic nerve in addition to direct branches from the cervical nerve roots. In addition, the scalenus dorsalis longus was supplied by twigs from the lateral cutaneous branches of the 2nd and 3rd intercostal nerves. This indicates that the scalenus dorsalis muscles contain a muscular component derived from the upper limb girdle musculature, unlike the human scalenus muscles, which have been considered to belong to the cervical trunk muscles.

The anterior belly of the digastric muscle is usually supplied by the mylohyoid nerve, and in general anatomy textbooks, the anterior belly is invariably described as receiving no other nerve except the mylohyoid nerve. In fact, however, it is sometimes supplied by a branch of the facial nerve in addition to the mylohyoid nerve. Such cases were found in 8 bodies or 9 head sides among 539 bodies or 1078 head sides of Japanese subjects. Those nine cases were investigated in detail and it was clarified that they had the following three characteristics in common: (1) the twig originating from the facial nerve appears as the twig of the stylohyoid branch in most cases, (2) the twig from the facial nerve enters the anterior belly on its lower (shallow) surface and the twig of the mylohyoid nerve on its upper (deep) surface, (3) the twig of the mylohyoid nerve is distributed to the deep region and the twig of the stylohyoid branch is distributed to the shallow region of the anterior belly. From these results, it was concluded that the anterior belly, receiving the twigs of the mylohyoid and facial nerves, had been formed by secondarily combining the most ventral and rostral part of the primordium of the stylohyoid muscle in the second branchial arch with the caudal part of the primordium of the anterior belly in the first branchial arch.

In 1997, an anomalous small mass of soft tissue was found in the left thoracic cavity of a Japanese male cadaver during student dissection practice. It was linked only by branches from the thoracic aorta, hemiazygos vein and greater splanchnic nerve, with no connection to the normal lung by vessels or airway. Examination of cut sections clarified that this anomalous small tissue mass was an extralobar pulmonary sequestration (EPS). Many cases of pulmonary sequestration have been reported from the clinical aspect, but there are few from a purely anatomical viewpoint. In the present case, detailed gross anatomical and histologic observations clarified that the anomalous artery supplying the sequestration resembled an elastic artery. In view of the findings of other reports, the anomalous arteries are divided into two types, the elastic type such as the pulmonary artery and the muscular type such as the bronchial artery. So it is thought that the histologic observation of an anomalous artery in comparison with normal pulmonary and bronchial arteries may offer an important clue to consider in elucidating the origin and development of pulmonary sequestration.

Seasonal changes in litter components were measured in a closedLeucaena leucocephala forest stand in Chichijima, Ogasawara (Bonin) Islands, situated in a wet subtropical climate. The phytomass of the stand was estimated as 5.62, 1.47 and 0.448 kg d.w. m−2 for stems, branches and leaves, respectively.

The progress of growth of a subalpine youngAbies veitchii andA. mariesii forest during 25 years was analyzed on the basis of measurements of the processes of height growth of about 230 trees in a quadrat where the old canopy had been completely destroyed by a typhoon in 1959. The original forest floor sapling population had consisted of trees shorter than 2 m. Saplings grew faster after the breakage of the canopy than before,A. veitchii growing faster thanA. mariesii. During the 25 years of growth, a few well developed trees exceeded 6 m in height, while others remained around only 1 m or less. Some small trees, mostlyA. veitchii died at sites of high density. A bimodality in the distribution of tree height had developed with a trough at about 2.5 m, differentiating the trees into canopy and suppressed populations. Canopy trees grew with wide variation of rates, while most of the suppressed trees showed little recent growth. No difference was found in recent growth rates between the two canopyAbies species. Differences in height growth rates among individual canopy trees were analyzed on the basis of their horizontal crown overlapping. Competition models evaluating the difference in height between trees with overlapping crowns were shown to be effective. The height growth rate of a canopy tree appeared to be controlled by both the closely grown taller trees and the local density of trees including those shorter than the subject tree.