Yuichi Tamatsu

Communication between the buccal nerve (V) and facial nerve (VII) in the human face

Terminal arrangements of communicating branches between the buccal nerve (V) and the facial nerve (VII) have yet to be precisely determined. To clarify distributions and relationships to facial muscles, detailed morphological examination of the two nerves was performed in the buccal region. The facial skin and underlying tissues of three cadavers were removed en bloc from the surface of the skulls and dissected from outside and inside. Arrangements of the facial muscles, nerves, and associated structures were observed. In all specimens, the communicating buccal nerve (CBN) was detected, largely covering the buccal region. The CBN gave off multidirectional twigs around the facial vein, some of which reached the anterior part of the zygomaticus major muscle. Several twigs of the CBN joined proximally with the zygomatic and buccal branches of the facial nerve. Ramified junctions that interconnected the lower zygomatic and upper buccal branches of the facial nerve were observed near sites where the CBN joined. Anterior twigs of the CBN supplied the longitudinal area lateral to the mouth, where many muscles converged. This study presents a precise morphological pattern of the CBN, suggesting functional contribution of the CBN to control of orofacial movements.

The Relationship Between Wrinkle Depth and Dermal Thickness in the Forehead and Lateral Canthal Region

OBJECTIVE To identify a relationship between dermal thinning and wrinkle formation. DESIGN We assessed the wrinkle depth of the forehead and lateral canthus of 58 male and female human cadavers (range of age at death, 29-93 years) using image analysis and measured the dermal thicknesses in Azan-Mallory-stained skin sections obtained around the wrinkles. SETTING Gross Anatomy Section, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan. MAIN OUTCOME MEASURES The maximum depth of the wrinkle was obtained from the forehead and lateral canthus. The dermal thickness was measured at the deepest point of the wrinkle (wrinkle point) and at a location where no wrinkle existed within 1 mm of its surface (nonwrinkle point). The ratio of the dermal thickness at the wrinkle point to the dermal thickness at the nonwrinkle point was calculated. RESULTS The dermal thickness underneath a wrinkle decreased as the depth of the wrinkle increased (P < .001). When the dermis became thinner than one-half of its original thickness, the dermis stopped thinning. Microscopic observations revealed that the junction between the dermis and subcutaneous layers under advanced wrinkles curved downward with invaginations of the dermis into the subcutaneous layer. CONCLUSIONS The dermis under a wrinkle becomes thinner in association with the progression of wrinkles until the dermis becomes thinner than one-half of its original thickness. When the dermis stops thinning, wrinkles develop further by dermal invagination into the subcutaneous layer.

Morphological study of the human chondroglossus muscle in Japanese

The chondroglossus muscle was macroscopically studied to clarify its fundamental morphology. This muscle was present in all of the 100 tongue halves examined in Japanese cadavers. In 14% of the specimens, however, the muscular fibers were sparse and vestigial. Originating mainly from the medial side of the lesser cornu of the hyoid bone, the chondroglossus muscle passed upward to penetrate the inferior longitudinal muscle of the tongue, and immediately entered the genioglossus muscle. Ascending inside the genioglossus muscle, its bundles spread, taking a broom head or a fan-like shape. Thereafter it reached the submucosal layer in the root of the tongue, changed the direction from upward to forward, and terminated diffusely, never going past the sulcus terminalis. The origin, course, and spreading manner of the chondroglossus muscle were quite different from those of the hyoglossus muscle. The nerve fiber supplying the chondroglossus muscle was a ramus from the first lateral branch of the hypoglossal nerve. It should be considered a separate extrinsic lingual muscle independent of the hyoglossus muscle, although they have a phylogenetically close relationship.

Relationship between the depth of facial wrinkles and the density of the retinacula cutis.

OBJECTIVE To identify whether there is a relationship between the depth of facial wrinkles and the density of the retinacula cutis in the subcutaneous tissue of the skin. DESIGN Wrinkle depth was assessed with image analysis on the forehead and the lateral canthus of human cadavers. The density of the retinacula cutis was measured in Azan-Mallory-stained skin sections obtained around the wrinkles. SETTING Gross Anatomy Section, Kagoshima University Graduate School of Medical and Dental Sciences. PARTICIPANTS Fifty-five male and female cadavers (35-93 years old). MAIN OUTCOME MEASURES The maximum depth of each wrinkle was used to represent the wrinkles degree. In the skin sections, the density of the retinacula cutis was measured around the deepest point of each wrinkle in a 1-mm-wide area (the wrinkle-specific area) and a 10-mm-wide area that included the wrinkle (the wrinkle-inclusive area). RESULTS In both the wrinkle-specific and wrinkle-inclusive areas, the retinacula cutis densities became lower in the forehead and in the lateral canthus areas. When a wrinkle was shallow, the density was lower in the wrinkle-specific area than in the wrinkle-inclusive area. With wrinkle progression, the density difference between the wrinkle-specific and the wrinkle-inclusive areas gradually decreased until there was no apparent difference. CONCLUSIONS Facial wrinkles seem to develop above sites of reduced lower retinacula cutis density. As a wrinkle develops, the density decreases in both the wrinkle-specific and the wrinkle-inclusive areas, whereas the density difference between those areas vanishes.

The Influence of Bite Force on the Internal Structure of the Mandible through Implant—Three-dimensional and Mechanical Analysis Using Micro-CT and Finite Element Method—

Applying appropriate stress through the teeth is considered essential for maintaining the homeostasis of the jaw. The aim of this study was to clarify the effects of pressure applied via endosseous implants on internal structures of the jaw. A mandible with dental implants for 15 years was analyzed by micro-CT to prepare a finite element model of the mandible, including implants and the surrounding internal microstructures. Based on this model, mechanical analysis was conducted by the three-dimensional finite element method. The results showed that stress distribution was seen in the trabecular bone around the implants. It became clear that pressure is transmitted to mandibular internal structures via implants, and stress is dispersed along internal trabecular alignment.

Morphologic Characteristics of Palatopharyngeal Muscle

In an effort to clarify the morphologic characteristics of the palatopharyngeal muscle, we examined its origin, insertion, and positional relationship with other muscles. We found that the origin of the palatopharyngeal muscle was both the oral and the nasal side of the soft palate; it was also attached to both the palatal aponeurosis and the soft palate median. However, in some cases the muscle originated on the nasal side was lacked. When the palatopharyngeal muscle originated from both the oral and the nasal side, it traveled through its insertion via the levator muscle of the palatine velum. This insertion was seen in a wide area and could be divided into three parts: the pharynx anterior, central, and posterior walls. In the central pharyngeal wall, insertion into the pharyngeal aponeurosis, inferior constrictor pharyngeal muscle, and esophagus were observed. The present results suggest that the palatopharyngeal muscle has a close positional relationship with the levator and tensor muscles of the palatine velum, the pharyngeal constrictor muscles, and the esophagus.

Changes in the Myosin Heavy Chain 2a and 2b Isoforms of the Anterior Belly of the Digastric Muscle Before and After Weaning in Mice

During the process of growth and development, the digastric muscle is subjected to marked functional changes, including the change from suckling to mastication. In particular, because the anterior belly of the digastric muscle, which is one of the suprahyoid muscles, plays an important role in mastication. Therefore, this muscle seems to undergo a marked functional change before and after weaning. However, the details remain unknown. Here, to clarify the changes in the muscle fibre characteristics of the anterior belly of the digastric muscle before and after weaning, we examined myosin heavy chain isoforms at the protein (immunohistochemistry) and mRNA (transcription) levels. As a control, the changes in the muscle fibre characteristics of the sternohyoid muscle, which is anatomically aligned in the same direction as the anterior belly of the digastric muscle, were analyzed. The results showed that, in the anterior belly of the digastric muscle that is involved in mandibular movements in mice, the ratio of a fast‐contraction isoform with strong contractile force increased after weaning. We believe that this occurred in response to a functional change from suckling to mastication. On the other hand, there was little change in the composition of sternohyoid muscle.

CORROSION CASTS OF CONVOLUTED TESTICULAR ARTERIES IN MICE AND RATS

The preparation of vascular corrosion casts enables us to observe the minute feautures of blood vessels. For mice and rats, reports on the macroscopical appearance of testicular arteries with the cast technique have been quite limited. Therefore, in the present study, we tried to prepare corrosion casts of such arteries in order to observe the three-dimensional structures in mice and rats. Vascular casts of testicular arteries were produced by intravenous injection of a polymethylmethacrylate solution, followed by treatment of the whole animal bodies with NaOH. Additionally, the gross appearance of human testicular arteries in cadavers was compared with that of the vascular casts. The results showed that the testicular arteries of humans, mice, and rats run from the abdominal aorta to the testes, with various configurations (straight, meandering, spiral, or coiled forms), and each species exhibits a specific pattern. The specific forms of testicular arteries may play several roles in protection of normal spermatogenesis, such as allowing wide mobility of the testes on physical attack, heat emission with the entwined pampiniform plexus, and reduction of the blood flow rate. The great extension of the testicular arteries during the fetal period from the upper abdomen to the scrotum when the testes descend might be another feature of the specific development of their running configuration.

Findings of unique small muscle fibers at the superficial portion of the orbicularis oculi in the lateral canthal region of Japanese adult cadavers.

This study reports the existence of previously unknown muscle fascicles in Japanese adult cadavers. A bundle of these muscle fascicles diverged from the pretarsal portion of the orbicularis oculi muscle and coursed in a lateral direction superficial to this muscle. When observed with the naked eye, the bundle seemed to originate at the medial canthus and run along or near the edge of the upper eyelid. However, its boundary with the orbicularis oculi muscle was indistinguishable until it crossed superficial to this muscle. Throughout our observations, the thin muscle bundle was identified with high frequency (94%, 49 of 52 individual cadavers), and is thus unlikely to be an artifact. Light microscopy revealed that, in sagittal sections, the thin muscle bundle was located on the superficial side of the lateral portion of the orbicularis oculi muscle, while in horizontal sections, it ran in a superficial plane to the orbicularis oculi muscle in a medial to lateral direction. Despite having some similarity to a muscular raphe, the lateral canthal band, and to one of the previously known inferior muscles of the orbicularis oculi muscle, the results of our anatomical study suggest that the bundle is none of these. Rather, it is a previously unreported muscle that likely contributes to the surface morphology at the lateral canthus. Clin. Anat. 23:637–641, 2010.

Morphological Changes in the Internal Structure of the Articular Eminence of the Temporal Bone during Growth from Deciduous to Early Mixed Dentition

Previously, bio-mechanical studies on the temporomandibular joint have concentrated mainly on the mandibular condyle while the articular eminence has been largely overlooked. Furthermore, research on the mechanical properties of bone using finite element analysis has focused on the cortical bone in preference to cancellous bone. In this study morphorogical changes in the internal structure of the articular eminence as related to child growth were examined using Micro-CT. Morphometric analysis of samples of cancellous bone representing both deciduous and early mixed dentitions showed an increase in the bone volume fraction and trabecular thickness in the early mixed dentition, and finite element analysis indicated directional transmission of stress as well. These results suggest that the morphology of the trabecular bone was altered to adapt to the functional growth progressed from the deciduous to the early mixed dentition.