Innervation patterns of the canine masticatory muscles in comparison to human

The aim of this study was to clarify the nerve distribution of the masseter, temporalis, and zygomaticomandibularis (ZM) muscles to elucidate the phylogenetic traits of canine mastication. A detailed dissection was made of 15 hemisectioned heads of adult beagle dogs. The innervations of the masticatory nerve twigs exhibited a characteristic pattern and were classified into seven groups. Twig innervating the anterior portion of the temporalis (aTM) was defined as the anterior temporal nerve (ATN). Anterior twig of ATN branched from the buccal nerve and innervated only the aTM, whereas posterior twig of ATN innervated both of the aTM and deep layer of the tempolaris (dTM). From this and morphological observations, it was proposed that the action of the canine aTM is more independent than that of the human. The middle temporal nerve ran superoposteriorly within the dTM and superficial layer of the temporalis (sTM) innervating both of them, whereas the posterior temporal nerve innervated only the posterior region of the sTM. The masseteric nerve (MSN) innervated the ZM and the three layers of the masseter. Deep twig of MSN was also observed innervating sTM after entering the ZM in all cases. The major role played by the canine ZM might thus underlie the differential arrangement of the distribution of the masticatory nerve bundles in dogs and humans. Although the patterns of innervation to the canine and human masticatory muscles were somewhat similar, there were some differences that might be due to evolutionary adaptation to their respective feeding stylesope

Topographic anatomy of the zygomatic arch and temporal fossa: a cadaveric study

The zygomatic arch (ZA) is a long, slender and laterally protruding structure of the face that is vulnerable to fracture by various types of trauma. Knowledge of the topographic anatomy of the ZA and temporal fossa is important for appropriate management of ZA problems. Thirty-seven male and 33 female cadavers were investigated in this study. Skin, subcutaneous tissue, fascia and periosteum were completely removed from around the ZA. Several depths and distances were measured based on three landmarks on the ZA: the anterior, middle and posterior portions of its superior margin. the thickness of the ZA was relatively constant in the three portions. the distance from the internal surface of the ZA to the surface of the temporalis muscle was similar in the anterior and middle portions, at about 8mm, and slightly lesser in the posterior portion. the distance from the external surface of the ZA to the temporal bone was the greatest at the anterior portion, and there was a large difference between the anterior and middle portions. the temporalis muscle was the thickest in the anterior portion and the thinnest in the posterior portion. This study suggests that the maximum distance from the internal surface of the ZA to the surface of the temporalis muscle is 8mm, and this should be considered when performing reduction malarplasty on the ZA.ope

A Variation of the Musculocutaneous Nerve Absent

A variation of the brachial plexus, characterized by the absence of the musculocutaneous nerve on the left arm, was found during the dissection of a 28-year old male cadaver. The whole lateral cord was joined to the median nerve, which it met in two points. One was a typical junction of both roots of the median nerve at the level of the coracoid process. The other was a junction of the remaining lateral cord and the median nerve, which was 92 mm away from the typical junction. This case provided some evidence about the absence of the musculocutaneous nerve, rather than a complete fusion of the median and musculocutaneous nerves. As the nerves are named due to their course or innervation, and not from their origin, it is reasonable to assume that the combined nerve was actually the median nerve, and that the musculocutaneous nerve did not exist.ope

Female-to-male proportions of the head and face in Koreans

It is well known that the head and face are smaller in female subjects than in male subjects. However, almost all previous studies have quantified the size difference between female and male subjects as simple numerical values, which might not clarify the difference. the present study evaluated the female-to-male proportions of the head and face so as to clarify the sex-related differences. A total of 1939 female subjects and 1398 male subjects were divided into 3 age groups: young (20-39 y), middle-aged (40-59 y), and elderly (60-79 y). the dimensions were classified into 3 categories: 5 cephalic, 3 frontal facial, and 6 lateral facial. the female-to-male proportions of individual dimensions were compared in the 3 age groups using the following formula: female measurement value x 100/(mean of male measurement value). the female-to-male proportions of the cephalic dimension increased with age, with the female cephalic dimensions overall being about 96% of the male cephalic dimensions. the female-to-male proportions of the frontal facial dimension were constant across the age groups, with the female frontal facial dimensions overall being 95% of the male frontal facial dimensions. the female lateral facial dimension increased markedly from the young to middle-aged group and was constant or decreased slightly from the middle-aged to the elderly group. Overall, the female lateral facial dimensions were approximately 97% of the male lateral facial dimensions. the present study will suggest a new approach to elucidate those sex-related dimensional differences that are characteristic of female and male subjects.ope

The buccofacial wall of maxillary sinus: an anatomical consideration for sinus augmentation

PURPOSE: This study aimed to quantify the thickness of the buccofacial wall of the maxillary sinus where sinus augmentations are often performed. MATERIALS AND METHODS: Fourteen sites located 15 and 20 mm superior to the anatomical cervical line (named as groups H15 and H20, respectively) and along the long axes of the mid and the interproximal of two premolars and two molars were measured from 74 Korean hemiface cadavers. RESULTS: The buccofacial wall of the maxillary sinus was thinnest at the area between the maxillary second premolar and first molar in groups H15 and H20. The lowest mean thickness was 1.2 mm in both groups. The walls were thicker in males than in females, with statistically significant gender differences found at four and two sites on the anterior horizontal reference in groups H15 and H20, respectively. However, the thickness did not differ significantly with age or laterality. Incomplete septa were found in seven of the 74 specimens, and they were present in the area between the first and second molars in six (86%) of these cases. CONCLUSIONS: These observations indicate that anatomical characteristics of the buccofacial wall thickness of the maxillary sinus need to be considered when performing a window opening procedure for sinus augmentation.ope

New anatomic considerations on the levator labii superioris related with the nasal ala

The levator labii superioris (LLS) muscle is well known as one of the upper-lip elevators; however, there have been few reports about the anatomic description of the LLS. Especially, the shape of the LLS and its relationship with the nasal ala were not clearly shown in the literature. The aim of this study was to clarify and describe the morphology and topography of the LLS and the anatomic variations to understand the function of the LLS related with the nasal ala. The LLS was examined in 102 specimens of embalmed Korean and French adult cadavers. The LLS was classified into 3 categories according to its shape and attachment: rectangular (83%), fan (10%), or trapezoid (7%) type. The medial fibers of the LLS were attached to the deep surface of the alar facial crease and were mainly intermingled with the alar part of the nasalis. Some of the deeper muscle fibers of the LLS extended to the vestibular skin of the nasal lobule. These new anatomic findings in the current study could be useful information for understanding the function of the LLS and the various surgical procedures of the perinasal region.ope

Formation of spacing pattern and morphogenesis of chick feather buds is regulated by cytoskeletal structures

Chick feather buds develop sequentially in a hexagonal array. Each feather bud develops with anterior posterior polarity, which is thought to develop in response to signals derived from specialized regions of mesenchymal condensation and epithelial thickening. These developmental processes are performed by cellular mechanisms, such as cell proliferation and migration, which occur during chick feather bud development. In order to understand the mechanisms regulating the formation of mesenchymal condensation and their role in feather bud development, we explanted chick dorsal skin at stage HH29+ with cytochalasin D, which inhibits cytoskeletal formation. We show that the aggregation of mesenchymal cells can be prevented by cytochalasin D treatment in a concentration-dependent manner. Subsequently, cytochalasin D disrupts the spacing pattern and inhibits feather bud axis formation as well. In addition, expression patterns of Bmp-4 and Msx-2, key molecules for early feather bud development, were disturbed by cytochalasin D treatment. Our results fully indicate that both the cytoskeletal structure and cell activity via gene regulation are of fundamental importance in mesenchymal condensation leading to proper morphogenesis of feather bud and spacing pattern formation.restrictio