An atypical inferior gluteal artery passing through the piriformis muscle.

PURPOSE: In this article, we report a case of an atypical inferior gluteal artery that passed through the piriformis muscle when it emerged from the pelvic cavity in an elderly Japanese female cadaver. We speculate that this atypical artery could be entrapped and compressed by the piriformis muscle and may therefore be associated with piriformis syndrome; however, the anatomical characteristics of such an atypical artery have not been previously reported. To assess this potential association, the atypical inferior gluteal artery was anatomically examined. METHODS: The cadaver examined in this report was a 97-year-old Japanese female who was donated to The Nippon Dental University for use in medical education and research. The atypical inferior gluteal artery and surrounding structures in half of the pelvis were examined macroscopically. RESULTS: The atypical inferior gluteal artery arose from the common arterial trunk, formed by itself and the superior gluteal artery, passed through the superior proximal part of the piriformis muscle, and left the pelvic cavity. It supplies branches to the lower half of the gluteus maximus and proximal part of the long head of the biceps femoris muscle. The piriformis muscle originates from the 2nd to 4th sacral vertebrae and attaches to the greater trochanter via a single short tendon. CONCLUSION: According to our findings, when the atypical inferior gluteal artery is entrapped and compressed, ischemic signs and symptoms may emerge in the lower buttocks and proximal posterior thigh. These results provide a new perspective for the diagnosis and treatment of piriformis syndrome.

Morphological significance of the medial brachial cutaneous nerve: An anatomical study of the brachial plexus in primates.

The medial brachial cutaneous nerve (MBC) originates from the medial cord of the brachial plexus and innervates the skin sensory in the medial posterior surface of the upper arm. Considering previous reports of the primate brachial plexus, the MBC appeared to be the sole branch in the brachial plexus that only some primates possess. However, the detailed descriptions and records regarding the morphology of the MBC and related nerves, their origins and distributions (dermatomes) in particular, were frequently lacked in the previous reports, and it remains unclear why the difference in the MBC appearance exists among primates. In this study, the brachial plexus and its branches were first re-evaluated and certainly identified in several primates, humans, chimpanzee, macaque monkey, lutung, tamarin, squirrel monkey, and spider monkey. The MBC was identified in humans, chimpanzee, spider monkey, and squirrel monkey. In the other species, the intercostobrachial nerve (ICB) originating from some of 1st to 3rd intercostal nerves developed and distributed instead of the MBC. According to the kinesiological and behavioral studies, the former species possessing MBC show high shoulder joint mobility associated with their locomotive patterns. We speculate that the MBC corresponds to transformed ICB; specifically, where it originates presumably transfers from the 1st and/or 2nd intercostal nerves to the brachial plexus, which allows it to reach the upper arm by coursing the shortest distance even if the forelimb is raised high. Therefore, MBC may embody phylogenetic morphogenesis of the nerve associated with the locomotive evolution and adaptation in primate forelimb.

Anatomical study of the cardiac conduction system in swine hearts.

The cardiac conduction system (CCS) is crucial for regulating heartbeats; therefore, clinicians and comedicals involved in cardiovascular medicine treatment must have a thorough understanding of the CCS structure and function. However, anatomical education of the CCS based on actual dissection and observation is uncommon, although such educational methodology promotes three-dimensional structural understanding of the observed object. Based on previous studies, we examined the CCS structure in the heart of a swine (pig, Sus scrofa domestica) which has been used in the biological, medical and anatomical curricula as science teaching materials, by using macroscopic dissection procedures. Most CCS structures in a young pig heart were successfully identified and illustrated on a macroscopic scale. The atrioventricular bundle (His bundle) was located on the lower edge of the membranous interventricular septum and was clearly distinguished from the general myocardial fibres by its colour and fibre arrangement direction. Following the atrioventricular bundle towards the atrium or ventricle with properly removing the endocardium and myocardium, the atrioventricular node or the right and left bundles appeared respectively. In contrast, the sinoatrial node was not identified. The anatomy of the CCS in young pig hearts was essentially similar to that previously reported in humans and several domestic animals. Our findings of the CCS in young pig hearts are expected to be useful for medical and anatomical education for medical and comedical students, young clinicians and comedical workers.

Gross anatomy of the gluteal and posterior thigh muscles in koalas based on their innervations.

Morphological and functional comparison of convergently-evolved traits in marsupials and eutherians is an important aspect of studying adaptive divergence in mammals. However, the anatomy of marsupials has been particularly difficult to evaluate for multiple reasons. First, previous studies on marsupial anatomy are often uniformly old and non-exhaustive. Second, muscle identification was historically based on muscle attachment sites, but attachment sites have since been declared insufficient for muscle identification due to extensive interspecific variation. For example, different names have been used for muscles that are now thought to be equivalent among several different species, which causes confusion. Therefore, descriptions of marsupial muscles have been inconsistent among previous studies, and their anatomical knowledge itself needs updating. In this study, the koala was selected as the representative marsupial, in part because koala locomotion may comprise primate (eutherian)-like and marsupial-like mechanics, making it an interesting phylogenetic group for studying adaptive divergence in mammals. Gross dissection of the lower limb muscles (the gluteal and the posterior thigh regions) was performed to permit precise muscle identification. We first resolved discrepancies among previous studies by identifying muscles according to their innervation; this recent, more reliable technique is based on the ontogenetic origin of the muscle, and it allows for comparison with other taxa (i.e., eutherians). We compared our findings with those of other marsupials and arboreal primates and identified traits common to both arboreal primates and marsupials as well as muscle morphological features unique to koalas.

Relationship between the lumbosacral plexus deviation and 12th rib length in Japanese macaques (Macaca fuscata).

The relationship between the lumbosacral plexus (LSP) origin and the 12th rib length was recently determined in humans; cranial and caudal deviations of the plexus origin are related to shortening and elongation of the 12th rib, respectively. However, it remains unclear whether such anatomical correlations are also observed in non-human mammals. To address this issue, in the present study, we evaluated the LSP origin and the 12th rib length in Japanese macaques (Macaca fuscata). In typical cases, the femoral and obturator nerves were derived from both the 4th and 5th lumbar nerves, and the lumbosacral trunk was from the 5th to 7th lumbar nerves. Some of the LSPs exhibited a caudal deviation of their origins; the femoral and obturator nerves were also derived from the 6th lumbar nerve, in addition to the 4th and 5th lumbar nerves; the lumbosacral trunk lost the 5th lumbar nerve origin and arose from the 6th and 7th lumbar nerves. Individuals with the caudal deviation of LSP origin exhibited significant elongation of the 12th ribs, in comparison with individuals with the typical plexus. The present findings indicate that the caudal deviation of LSP origin was correlated to the 12th rib elongation in Japanese macaques, similar to humans. As a future studies, we need to clarify which mammalian groups exhibit such correlation between the deviation of the LSP origin and the lowest rib length, and further to provide evolutionary implications of this correlation.

Relationship of segmental variations in the human lumbar plexus to the length of the 12th rib.

BACKGROUND: Evaluating segmental variations in the lumbar plexus is crucial for neurological diagnosis. In the present study, we examined the relationship between the segmental composition of the lumbar plexus and length of the 12th rib. PROCEDURES: To evaluate segmental variations in the lumbar plexus, the furcal nerve (Nf) which forms the boundary between the lumbar and sacral plexus, was used as an index of plexus arrangement. MAIN FINDINGS: Segmental variations in the Nf were classified into four groups on the basis of whether the Nf originated from the ventral rami of L3 and L4 (Nf L3 + L4 group), L4 (Nf L4 group), L4 and L5 (Nf L4 + L5 group), or L5 (Nf L5 group). The Nf L3 + L4 group was associated with short 12th rib, and groups Nf L4 + L5 and Nf L5 were associated with long 12th rib. These findings suggest that the segmental variations in the lumbar plexus are related to the length of the 12th rib. CONCLUSIONS: Therefore, the segmental variations in the lumbar plexus can be evaluated non-invasively and easily by measuring the length of the 12th rib. This may contribute to the diagnosis and treatment of various lumbar radiculopathies.

Variations in the course of the superior gluteal artery in relation to the lumbosacral plexus.

The course of the superior gluteal artery (SGA) as it passes through the lumbosacral plexus is variable. The variations of the arterial course in relation to the lumbosacral plexus have focused on statistical analysis, and it is limited arterial diversity. In this study, we investigated the positional relation between the SGA and the furcal nerve (FN): guide to segmentation of the lumbosacral plexus, arising from the L4, ie, the contribution to the femoral nerve, obturator nerve, and lumbosacral trunk. We could classify the pathway of the SGA into three types based on its positional relation to the FN. The SGA courses under the ramus from which the FN originates (Type A), under the ramus one segment below the origin of the FN (Type B), or between the obturator nerve and the lumbosacral trunk (Type C). The SGA pathway in Types A and B showed a cranial or caudal shift along with cranial or caudal deviation of the FN. In summary, the variation in the SGA pathway was correlated with cranial or caudal shift of the FN. Our findings indicate that variations of the SGA pathway are associated not only with arterial transformation, but also with diversity of the lumbosacral plexus.

Middle thymothyroid artery arising from the common carotid artery: case report of a rare variation.

A middle thymothyroid artery, arising from the anterior aspect of the right common carotid as an anomalous branch was observed in a 71-year-old Japanese male cadaver. It soon divided into a thyroidea ima artery, a branch supplying the sternoclavicular joints, and a thymic branch. In addition, twigs from these three main branches supplied the sternohyoid and sternothyroid muscles, right inferior parathyroid gland and also some deep cervical lymph nodes. Anatomical features, clinical implications and a brief account of the developmental aspects of this rare variation are included in this report.

Nerve fiber analysis of ansa cervicalis-vagus communications.

Communications between the ansa cervicalis and the vagus nerve, although described only as variations in many textbooks, can be observed frequently in the dissection room. Following macroscopic observation, some of such cases were subsequently dissected under surgical microscope to determine the nature of such communications. As a result, two broad categories of communications between the ansa cervicalis complex and the vagus nerve could be recognized: (i) false (pseudo) communications, where the two nerves were attached only by the connective tissue with no fiber exchange; and (ii) true communications, with nerve fiber involvement. Fiber analysis showed that the majority of the ansa-vagal communications observed during gross dissection were of the first category. True communications, when present, were only scanty contributions and always directed towards the side of the vagus. In addition, the vagus (region of the inferior ganglion) and hypoglossal nerves were found to be in close contact at the base of the skull and usually could not be separated by gross dissection. But such attachments, too, were shown to be almost entirely of false nature except for the possible presence of a few fine nerve filaments. It seems that the ansa-vagal communications are merely a result of the close physical relationship between the two structures and serve no significant functional purpose, but at the same time may hinder the prospects of using ansa cervicalis in surgical procedures such as re-innervation of laryngeal and facial muscles, following damage to recurrent laryngeal and facial nerves, respectively.

Nerve communication between the glossopharyngeal nerve, external carotid plexus and the superficial cervical ansa: human autopsy case.

The authors encountered a very rare human autopsy case in which the supernumerary branch of the glossopharyngeal nerve and a nerve branch arising from the external carotid plexus communicated with the superficial cervical ansa. This anomaly was observed on the left side of a 71-year-old male cadaver during the gross anatomical seminar at Niigata University in 2004. The nerve fascicle and fiber analyses indicated that the supernumerary branch of the glossopharyngeal nerve separated cranial to the branches to the pharyngeal constrictor muscles, carotid sinus and stylopharyngeal muscle and sent the nerve fibers to the muscular branches to the platysma and the cutaneous branches to the cervical region. Additionally, it was shown that the branch arising from the external carotid plexus sent the nerve fibers to the cutaneous branch to the cervical region. Although the external carotid plexus is primarily postganglionic sympathetic fibers originating from the superior cervical ganglion, the vagus and glossopharyngeal nerves gave off branches connecting to the plexus, and therefore it was not possible to determine the origins of this branch of the external carotid plexus. The present nerve fascicle analysis demonstrates that the supernumerary branch of the glossopharyngeal nerve, which innervated the platysma, did not share any nerve components with the branches to the pharyngeal constrictor muscles, carotid sinus and stylopharyngeal muscle, suggesting that this supernumerary branch may be categorized into the different group from these well-known branches.

Anatomical significance of the nerve to the pyramidalis muscle: a morphological study.

Characteristics of the nerve to the pyramidalis muscle (NPy), including its origin, course and distribution, were observed (macroscopically) in detail in the present study. The spinal segments that give rise to the nerve vary considerably and involve Th12-L2. The course and distribution of the nerve also vary widely. The NPy is given off from one of the following: (i) the anterior cutaneus branch (Rca) of the intercostals nerve; (ii) the ilioinguinal (li) nerve; or (iii) the genital branch (Rg) of the genitofemoral nerve. The NPy can be classified into nine types according to features of the course and branching pattern of the Rca and li. In three of 67 cases, the pyramidalis muscle had two nerves. Double-innervated pyramidalis muscles received one nerve from a transitional-type Rca (Rcat) and a second nerve derived from one of the superficial Rca (Rcas), li or Rg. The NPy derived from the deep Rca (Rcap; Type 1), Rcat (Type 2) and containing their features as well as the Type 9 (Rcat + li + Rg) reach the muscle from behind. Types 3-8 (not containing features of the Rcap and Rcat) enter the muscle from its surface. The branch that gives off the NPy is determined by the level of segmental origin, with the segmental origin of branches from the Rca (Types 1-4), li (Types 5-6) and Rg (Types 7-9) getting lower in that order. The level of segmental origin of the NPy derived from different Rca becomes lower in the following order: Rcap (Type 1), Rcat (Type 2), Rcas (Type 3), Rcas' (Rcas entering the inguinal canal; Type 4). When the origin of the NPy is from a lower segment, the origin of the boundary nerve (Rcap/Rcas) is also deviated downward. The changes in the NPy are related to the deviation of the entire lumbar plexus.

[Reexamination of the communicating branch between the sural and tibial nerves].

Reexamination of communicating branches between the sural and tibial nerves ventral to the calcanean tendon was carried out on 52 legs of 26 Japanese cadavers which were used for ordinary dissection practices at the Niigata University School of Medicine. Communicating branches were found in 7 out of 52 dissections (13.5% of cases). In three of the 7 specimens, the communicating branch, the sural nerve and the tibial nerve with the deep crural fascia were removed from the legs and demonstrated by a modified Sihler's staining technique. Three types of communicating branches, Y, U and N, were distinguished on the basis of their shapes. In type Y, a medial branch from the sural nerve and a branch from the tibial nerve joined in Y-shape and become one terminal branch. In type U, the both branches formed a loop between the sural and tibial nerves. The type N communicating branch ran obliquely and medially to reach the tibial nerve distally. Only the Y type appeared in 5 specimens. Both the Y and U type and the Y and N types occurred in one specimen each. We assume that the communicating branch of the N type contains motor fibers which are derived from the sural nerve and innervate some plantar muscles, because this type is correspond to the communication type of some animals in which motor fibers have been demonstrated. Therefore, if the sural nerve biopsy is performed to examine a pure sensory nerve, removal of the more distal part of the sural nerve than a diverging point of a communicating branch is recommended. This study also indicated that the modified Sihler's staining technique is useful to examine distributions of cadaveric peripheral nerves after medical students' dissection course.

Anatomical study of human adductor hallucis muscle with respect to its origin and insertion.

The adductor hallucis muscle (ADH) is evolutionally and functionally important, but no detailed morphological data about this muscle in the human body is available. In the present study, we examined the origin and insertion of the oblique and transverse heads of the ADH. Forty-five feet (20 right, 25 left) of 34 cadavers (13 men, 21 women, average age of 80 years old) were used in the present study. The origin, insertion and nerve supplies of the oblique and transverse heads of the ADH were macroscopically examined in detail. Most commonly, the oblique head of the ADH arose from the bases of the 2nd, 3rd and 4th metatarsal bones, the plantar metatarsal ligaments spanned between the bases of the 2nd, 3rd and 4th metatarsal bones, the lateral cuneiform bone, the fibrous sheath of the tendon of the peroneus longus muscle and the long plantar ligament, and inserted into the lateral sesamoid bone of the great toe and the capsule of the 1st metatarsophalangeal joint. Most commonly, the transverse head of the ADH originated from the capsules of the 3rd and 4th (and occasionally 5th) metatarsophalangeal joint and the deep transverse metatarsal ligaments, and inserted into the lateral sesamoid bone of the great toe, the capsule of the 1st metatarsophalangeal joint and lateral surface of the base of the 1st proximal phalanx. This muscle was classified into four types based on the origin of its oblique head and was classified into three types based on the origin of its transverse head. The percent ratio of the weight of the oblique head to the total weight of all the intrinsic muscles of the foot was 9.4% +/- 1.5, and the transverse head was 1.5% +/- 0.6 (n = 14). The transverse head of ADH tends to be reduced in size in the human, but the oblique head is well developed with no sign of reduction.