Denonvilliers' fascia as a potential nerve-course marker for the female urinary bladder.

OBJECTIVES: This study investigated the relationship between Denonvilliers' fascia (DF) and the pelvic plexus branches in women and explored the possibility of using the DF as a positional marker in nerve-sparing radical hysterectomy (RH). METHODS: This study included eight female cadavers. The DF, its lateral border, and the pelvic autonomic nerves running lateral to the DF were dissected and examined. The pelvis was cut into two along the mid-sagittal line. The uterine artery, deep uterine veins, vesical veins, and nerve branches to the pelvic organs were carefully dissected. RESULTS: The nerves ran sagitally, while the DF ran perpendicularly to them. The rectovaginal ligament was continuous with the DF, forming a single structure. The DF attached perpendicularly and seamlessly to the pelvic plexus. The pelvic plexus branches were classified into a ventral part branching to the bladder, uterus, and upper vagina and a dorsal part branching to the lower vagina and rectum as well as into four courses. Nerves were attached to the rectovaginal ligament and ran on its surface to the bladder ventral to the DF. The uterine branches split from the common trunk of these nerves. The most dorsal branch to the bladder primarily had a common trunk with the uterine branch, which is the most important and should be preserved in nerve-sparing Okabayashi RH. CONCLUSION: The DF can be used as a marker for nerve course, particularly in one of the bladder branches running directly superior to the DF, which can be preserved in nerve-sparing Okabayashi RH.

Association between the social network of medical students and their academic performance on the anatomy written examination.

Although medical students learn human anatomy within a social network of friends/classmates, limited research has examined how social network structure is related to student's performance in human anatomy examinations. This study aimed to examine the association between centrality (i.e., the degree to which a student is connected to other students in class) before the start of the anatomy laboratory and changes in centrality owing to the start of the laboratory and failing the written examination taken on the last day of the course. Data included all 211 medical students at Tokyo Medical and Dental University who took anatomy classes in 2018 and 2019. The in-class social network before the laboratory was defined as "connected" if the student had more than one connection to the same individual in terms of the type of club activity, high school, and affiliation with an extracurricular program. The laboratory group adds the connection to the prelaboratory network, resulting in a postlaboratory network. Logistic regression models were used to estimate the association of degree and eigenvector centrality and changes in centrality after the laboratory with failing the written examination. Of the 211 students, 38 failed the examination. A one standard deviation increase in eigenvector centrality before the laboratory was significantly associated with a 44% decrease in odds of failing the examination (OR: 0.56, 95% CI: 0.34, 0.92). Changes in centrality measures were not associated with the performance of students in the examination. Higher in-class network centrality was associated with lower odds of failing the written examination.

Guidelines for cadaver dissection in education and research of clinical medicine (The Japan Surgical Society and The Japanese Association of Anatomists).

This article translates the guidelines for cadaver surgical training (CST) published in 2012 by Japan Surgical Society (JSS) and Japanese Association of Anatomists from Japanese to English. These guidelines are based on Japanese laws and enable the usage of donated cadavers for CST and clinical research. The following are the conditions to implement the activities outlined in the guidelines. The aim is to improve medicine and to contribute to social welfare. Activities should only be carried out at medical or dental universities under the centralized control by the department of anatomy under the regulation of Japanese law. Upon the usage of cadavers, registered donors must provide a written informed-consent for their body to be used for CST and other activities of clinical medicine. Commercial use of cadavers and profit-based CST is strongly prohibited. Moreover, all the cadaver-related activities except for the commercial-based ones require the approval of the University's Institutional Review Board (IRB) before implementation. The expert committee organized at each university for the implementation of CST should summarize the implementation of the program and report the details of the training program, operating costs, and conflicts of interest to the CST Promotion Committee of JSS.

Guidelines for cadaver dissection in education and research of clinical medicine (The Japan Surgical Society and The Japanese Association of Anatomists).

This article translates the guidelines for cadaver surgical training (CST) published in 2012 by Japan Surgical Society (JSS) and Japanese Association of Anatomists from Japanese to English. These guidelines are based on Japanese laws and enable the usage of donated cadavers for CST and clinical research. The following are the conditions to implement the activities outlined in the guidelines. The aim is to improve medicine and to contribute to social welfare. Activities should only be carried out at medical or dental universities under the centralized control by the department of anatomy under the regulation of Japanese law. Upon the usage of cadavers, registered donors must provide a written informed-consent for their body to be used for CST and other activities of clinical medicine. Commercial use of cadavers and profit-based CST is strongly prohibited. Moreover, all the cadaver-related activities except for the commercial-based ones require the approval of the University's Institutional Review Board (IRB) before implementation. The expert committee organized at each university for the implementation of CST should summarize the implementation of the program and report the details of the training program, operating costs, and conflicts of interest to the CST Promotion Committee of JSS.

Usage of cadavers in surgical training and research in Japan over the past decade.

The "Guidelines for Cadaver Dissection in Education and Research of Clinical Medicine" drafted by the Japan Surgical Society (JSS) and the Japanese Association of Anatomists in 2012 helped dispel legal concerns over cadaver surgical training (CST) and the usage of donated human bodies for research and development (R&D) in the country. Subsequently, in the fiscal year 2018, the Ministry of Health, Labour and Welfare increased the funding for CST, prompting its wider implementation. This study analyzed data obtained in 2012-2021 through the reporting system of the JSS-CST Promotion Committee to map the usage of cadavers for clinical purposes, specifically education and R&D, in Japan. We found that the number of medical universities using cadavers for CST and R&D programs was just 5 in 2012, and it reached 38 for the decade. Thus, about half of Japan's medical universities implemented such programs over the period. Meanwhile, the total number of programs was 1,173. In the clinical field, the highest number of programs were implemented in orthopedics (27%), followed by surgery (21%), and neurosurgery (12%). Based on the purpose, the most common objective of the programs (approximately 70%) was acquiring advanced surgical techniques. Further, the highest number of programs and participants were recorded in 2019 (295 programs, 6,537 participants). Thus, the guidelines helped expand cadaver usage for clinical purposes in Japan. To further promote the clinical usage of cadavers in medical and dental universities throughout Japan, sharing know-how on operating cadaver laboratories and building understanding among the general public is recommended.

A mixed methods study on the readiness of dental, medical, and nursing students for interprofessional learning.

BACKGROUND: Interprofessional education (IPE) is crucial in dentistry, medicine, and nursing. However, scant mixed methods studies have compared the IPE outcomes across these disciplines to develop evidence-based IPE. This study explored the differences in the readiness of dental, medical, and nursing students for interprofessional learning before and after IPE workshops and elucidated reasons for this disparity. METHODS: Data were obtained from dental, medical, and nursing students who participated in IPE workshops conducted at Tokyo Medical and Dental University in Japan in 2019 and 2020. The participants filled the validated Japanese version of the Readiness for Interprofessional Learning Scale (RIPLS) before and after attending the workshops (n = 378). Paired t-tests were performed to assess differences between the pre- and post- workshop RIPLS scores. Welch's t-tests were deployed to evaluate interdisciplinary differences in their scores. Qualitative analyses were conducted using an explanatory sequential design with focus group discussions (FGDs) held with 17 dental students to explain the quantitative results. RESULTS: Total RIPLS scores increased significantly for every discipline after the workshops (p < 0.001). Dental students scored significantly lower pre- and post- workshop aggregates than medical and nursing students, respectively (p < 0.001). The FGDs yielded three principal themes in the explanations tendered by dental students on their lower scores: 1) dental students rarely felt the need for interprofessional collaborations, 2) dentists often worked without the need for interprofessional collaborations, and 3) dental students believed their contribution to the workshop was insufficient. CONCLUSIONS: The results revealed divergences in the readiness of dental, medical, and nursing students for interprofessional learning, and the study illuminated possible reasons for these disparities. These outcomes will help develop evidence-based IPE by indicating approaches to place a higher value on interprofessional collaborations in educational environments, ameliorate the awareness of educators, and enhance the workshop facilitation style.

Morphology of the Undersurface of the Anterolateral Acromion and Its Relationship to Surrounding Structures.

BACKGROUND: A better understanding of the morphology underneath the acromion is needed to prevent complications after arthroscopic subacromial decompression. The precise correlations between the morphologic features underneath the acromion and the surrounding structures including the attachment of the coracoacromial ligament (CAL) and the origin of the deltoid middle head have not yet been determined in the absence of artifacts on the bony surface caused by dissection techniques. Moreover, anatomic findings in previous studies using only older-aged cadavers or dried bones may not reflect the morphologic features of younger and healthy specimens. PURPOSE: To characterize the anterolateral structures morphologically in the inferior aspect of the acromion, assess the relationships of these structures with surrounding structures without dissection artifacts on the bony surface, and verify the cadaveric data in the asymptomatic shoulders of living middle-aged patients. STUDY DESIGN: Descriptive laboratory study. METHODS: We initially analyzed the relationship between the morphology of the anterolateral structures and surrounding structures in 18 cadaveric shoulders (mean age, 81.8 years), 15 of which were subjected to macroscopic investigation of the CAL attachment and 3-dimensional micro-computed tomography investigation with radiopaque markers and 3 of which were subjected to histologic examination. We also analyzed the morphology underneath the anterolateral acromion in 24 asymptomatic shoulders of middle-aged patients (mean age, 54.8 years) to verify the cadaveric data. In both the cadaveric shoulders and the asymptomatic shoulders of live patients, the long axis, width, and height of the anterolateral prominence were measured by use of 3-dimensional CT imaging. RESULTS: In cadavers, the anterolateral prominence underneath the acromion corresponded to the attachment of the CAL. Histologic evaluation revealed that the CAL was continuous to the deep layer of the deltoid middle head in the lateral acromion. The study in asymptomatic shoulders of middle-aged patients revealed bony prominences similar to those observed in cadavers. CONCLUSION: The anterolateral prominence, which corresponds to the attachment of the CAL below the acromion, may be a native structure below the acromion. Moreover, the CAL is continuous to the deep layer of the deltoid middle head in the lateral acromion.

Intra-mural distribution of the blood vessels in the stomach demonstrated by contrast medium injection: a cadaver study.

PURPOSE: With advances in diagnostic imaging techniques of gastric cancer screening with X-ray fluoroscopy, it has been suggested that mucosal projections induced by the vessels distributed in the submucosal layer of the stomach may be mistaken for abnormal mucosal folds. In this study, we aimed to describe the distribution of blood vessels in the submucosal layer of the stomach to improve the diagnostic accuracy of screening of gastric cancer. METHODS: Twenty-four stomachs from Japanese cadavers were used in this study. Uncolored or colored contrast agents were injected into arteries and/or veins for macroscopic analyses, X-ray imaging, and methyl salicylate clearing. In addition, histological analysis was performed to examine blood vessels distributed inside the stomach wall. RESULTS: Following contrast agent injection, thick blood vessels were distributed perpendicular to both curvature sides, and branches parallel to both curvature sides flowed from these thick blood vessels, and a vascular network was formed throughout the stomach wall. This vascular network had intra-mural anastomoses connecting both curvature sides. Moreover, in histological analyses, blood vessels depicted by injection were mainly distributed in the submucosal layer. CONCLUSION: This study strongly suggests that the mucosal projections induced by arteries and veins in the submucosal layer could be mistaken for abnormal mucosal folds. Therefore, a better understanding of the vascular distribution in the submucosal layer is important to improve diagnostic accuracy from imaging studies of the stomach. The information provided by this research may facilitate better accuracy in diagnosis and reduce the number of unnecessary invasive procedures.

Morphology of the anterolateral ligament: a complex of fibrous tissues spread to the anterolateral aspect of the knee joint.

The anterolateral ligament (ALL) has recently received considerable attention as a key structure maintaining the rotational stability of the tibia. However, the morphology of the ALL, particularly the proximal attachment, is controversial. This study aimed to elucidate the morphological relationship between the ALL and its adjacent structures. A total of 25 knees from 22 cadavers were used in the current study. One knee was set at 30°, 60° and 90° of flexion. Stretched or winkled fibrous tissues were then observed with internal and external rotations of the tibia at each angle. In 22 knees, fibrous tissues that were attached to the lateroposterior area to the Gerdy's tubercle were macroscopically observed. In the other 2 knees, the fibrous tissues were histologically investigated and analyzed using computer-assisted three-dimensional reconstruction. A taut fibrous tissue was observed between the lateroposterior area to the Gerdy's tubercle and the posterosuperior area to the lateral epicondyle during an internal rotation of the tibia. A complex of fibrous tissues that were attached to the lateroposterior area to the Gerdy's tubercle spread to the anterolateral aspect of the knee as a sheet-like structure. This complex tissue was composed of the fascia lata and fibrous tissues continuous from the fabellofibular ligament, intermuscular septum, and tendon of the gastrocnemius. Three-dimensional reconstruction showed that each fibrous tissue formed a sheet. The structure recognized as the ALL could not be detected; therefore, the ALL that has been reported to date is considered to be a complex of fibrous tissues with a sheet-like structure.

Deep cervical fascia as an anatomical landmark of lingual lymph nodes: An anatomic and histologic study.

OBJECTIVES: We aimed to discuss the definition of lingual lymph nodes based on the deep cervical fascia anatomy. METHODS: A total of 11 cadavers were histopathologically evaluated. Specimens were dissected into serial stepwise cross-sections. The deep cervical fascia and lymph nodes were evaluated by staining the cross-sections with Elastica van Gieson and hematoxylin and eosin stains, respectively. The gross anatomy of the deep cervical fascia was evaluated in 1 cadaver after bilateral dissection. RESULTS: A single severely degenerated medial lingual lymph node (MLLN) was identified in the lingual septum of 1 cadaver. A single lateral lingual lymph node (LLLN) was identified in 1 cadaver, between the genioglossus and the hyoglossus. The superficial layer of deep cervical fascia (SLDF) was found to split into two layers encapsulating the submandibular gland. The deeper portion of this fascia was in close contiguity with the hyoglossus and formed the boundary between the mouth and the neck. The SLDF was found to be discontinuous with the area between the sublingual space and the submandibular gland. CONCLUSIONS: The SLDF could serve as an anatomical landmark for lingual lymph nodes, since it is considered to be the demarcating boundary during neck dissection. When lymph nodes that are located deeper than the SLDF were defined as lingual lymph nodes, 1 MLLN and 1 LLLN were identified.

Aortic inflation with agar injection is a useful method of cadaveric preparation which creates a mediastinal anatomy that better mimics the living body for surgical training.

In cadavers, even Thiel-embalmed cadavers, the arteries (especially the thoracic aorta) are extremely collapsed. This is in marked contrast to the state of the arteries in a living body. Aortic inflation is necessary to improve this unfavorable situation for anatomical observation or dissection. To inflate the aorta, we injected 500 ml of hot liquid agar into the aorta using a 18-Fr catheter inserted into the common femoral artery and subclavian artery. The injected agar then rapidly cools to room temperature and solidifies. As a result, the thoracic aorta remains sufficiently and constantly inflated in the mediastinum. This method is not only easy and inexpensive, but also useful and effective for achieving a life-like anatomy in cadavers used in surgical training for operations involving mediastinal organs, with the exception of the heart and great vessels.

Anatomic study of the medial side of the ankle base on the joint capsule: an alternative description of the deltoid and spring ligament.

BACKGROUND: Adult acquired flatfoot deformity (AAFD) is caused by impaired medial ligamentous structures and posterior tibialis tendon dysfunction (PTTD). Although degeneration and trauma could separately cause AAFD, how these factors interact in the pathomechanism of AAFD is unclear. The joint capsule in the medial ankle is considered an important structure, providing passive stability by limiting joint movement. Previous reports on the joint capsule suggest its involvement in pathological changes of the ankle, but because of the high priority placed on the ligaments, few reports address the ankle joint from the joint capsule standpoint. The current study aimed to anatomically examine the medial ankle joint, focusing on the deltoid and spring ligaments in perspective of the joint capsule. METHODS: We conducted a descriptive anatomical study of 19 embalmed cadavers (mean 82.7 years, range 58 to 99). We included 22 embalmed cadaveric ankles. We detached the joint capsule in 16 ankles from the anterior to posteromedial joint, analyzed the capsular attachments of the ankle and adjacent joints, and measured the widths of the bony attachments. We histologically analyzed the joint capsule using Masson's trichrome staining in 6 ankles. RESULTS: The capsule could be separated as a continuous sheet, including 3 different tissues. The anterior capsule was composed of fatty tissue. Between the medial malleolus and talus, the capsule was strongly connected and was composed of fibrous tissue, normally referred to as the deep deltoid ligament. The tibial attachment formed a steric groove, and the talar side of the attachment formed an elliptical depressed area. On the medial part of the subtalar and talonavicular joints, the capsule covered the joints as cartilaginous tissue, normally referred to as the superomedial ligament of the spring ligament. The outer side of the cartilaginous and fibrous tissue formed the sheath floor of the posterior tibialis tendon. Histological analysis revealed three different tissue types. CONCLUSIONS: The capsules of the ankle, subtalar, and talonavicular joints could be detached as a continuous sheet. The deltoid and the superomedial ligament of the spring ligaments could be interpreted as a part of the continuous capsule, which had different histological features. LEVEL OF EVIDENCE: Descriptive Laboratory Study.

Medial elbow anatomy: A paradigm shift for UCL injury prevention and management.

To improve the management outcomes and diagnostic accuracy of the ulnar collateral ligament (UCL) injury, the anatomy of the medial side of the elbow joint is necessary to be understood in terms of the periarticular surroundings rather than the specific ligaments. The aim of this study was to anatomically clarify the medial side of the elbow joint in terms of the tendinous structures and joint capsule. We conducted a descriptive anatomical study of 23 embalmed cadaveric elbows. We macroscopically analyzed the relationship between the flexor pronator muscles (FPMs) and the joint capsule in 10 elbows, histologically analyzed in 6 elbows, and observed the bone morphology through micro computed tomography in 7 elbows. The two tendinous septa (TS) were found: between the pronator teres (PT) and flexor digitorum superficial (FDS) muscles, and between the FDS and flexor carpi ulnaris (FCU) muscles. These two TS are connected to the medial part of the brachialis tendon, deep aponeurosis of the FDS, and FCU to form the tendinous complex, which linked the humeroulnar joint and could not be histologically separated from each other. Moreover, the capsule of the humeroulnar joint under the tendinous complex had attachment on the ST of 7 mm width. The two TS, the brachialis tendon, the deep FDS and FCU aponeuroses, and the joint capsule linked the humeroulnar joint. These anatomical findings could lead to a paradigm shift in the prevention, diagnosis, and treatment of UCL injuries in baseball players. Clin. Anat. 32:379-389, 2019. © 2018 The Authors. Clinical Anatomy published by Wiley Periodicals, Inc. on behalf of American Association of Clinical Anatomists.

Anatomy of the Tarsal Canal and Sinus in Relation to the Subtalar Joint Capsule.

BACKGROUND: Anatomical knowledge of the tarsal canal and sinus is still unclear owing to the complexity of the ligamentous structures within them, particularly the relationship with the capsules of the subtalar joints. The aim of this study was to examine the anatomical relationship between the fibrous tissues of the tarsal canal and sinus and the articular capsules of the subtalar joint. METHODS: We conducted a descriptive anatomical study of 21 embalmed cadaveric ankles. For a macroscopic overview of the subtalar joint, we removed the talus in 18 ankles and separated the fibrous tissues from the surrounding connective tissues to analyze the layered relationship between the inferior extensor retinaculum (IER) and the subtalar joint capsule. Additionally, we histologically analyzed the tarsal canal and the medial and lateral sides of the tarsal sinus using Masson's trichrome staining in 3 ankles. RESULTS: The medial and intermediate roots of the IER and interosseous talocalcaneal ligament (ITCL) were located in the same layer and were connected to each other, between the capsules of the posterior talocalcaneal and talocalcaneonavicular joints. The intermediate root of the IER and the cervical ligament (CL) had adjacent attachments on the tarsal sinus, and synovial tissues originating from the joint capsules filled the remaining area in the tarsal canal and sinus. CONCLUSION: We determined that the tarsal canal and sinus tarsi contained 3 layered structures: the anterior capsule of the posterior talocalcaneal joint, including the anterior capsule ligament; the layer of ITCL and IER; and the posterior capsule of the talocalcaneonavicular joint, including the CL. CLINICAL RELEVANCE: The results of this study may help with the understanding of the pathomechanism of subtalar instability and sinus tarsi syndrome, resulting in better treatment.

Microanatomy of Sensory Nerves in the Upper Eyelid: A Cadaveric Anatomical Study.

BACKGROUND: Plastic surgery requires detailed knowledge of upper eyelid anatomy, but few authors have sufficiently described the specifics of upper eyelid nerve anatomy. This study aimed to provide a thorough description of sensory nerve anatomy in the upper eyelid and to propose considerations for upper eyelid surgery. METHODS: Sixteen orbits were dissected from 16 fixed, adult human cadavers. Microscopically, the authors identified the main trunks of the infratrochlear, supratrochlear, and supraorbital nerves and all branches that projected toward the upper eyelid. The number, size, and distribution of nerve branches were recorded. RESULTS: The branches of the infratrochlear, supratrochlear, and supraorbital nerves covered a wide range in the upper eyelid. The mean numbers of branches per nerve were 1.6 ± 1.2, 3.2 ± 1.5, and 2.6 ± 1.4, respectively. The branches of the infratrochlear nerve were distributed throughout the medial area of the upper eyelid. Those of the supratrochlear nerve were distributed throughout the medial and central areas, and the palpebral branches of the supraorbital nerve were distributed throughout the central and lateral areas of the upper eyelid. The lateral branches of the supraorbital nerve and the cutaneous branches of the lacrimal nerve were distributed in the lateral region of the orbit. CONCLUSIONS: The authors show that upper eyelid sensation is transmitted mainly by the supratrochlear and supraorbital nerves, and the authors provide a map of the distribution of upper eyelid sensory nerves. This precise anatomical knowledge about upper eyelid sensory nerves will facilitate pain control and help minimize nerve injuries during surgery.

A Cadaver Study to Assess the Feasibility of a Cross-Nerve Transfer of the Infraorbital Nerve for Patients With Peripheral Infraorbital Nerve Injury.

BACKGROUND: Patients with facial fracture or head and neck surgery sometimes suffer from infraorbital nerve injury. This injury results in severe hemilateral numbness in the midfacial area. The infraorbital nerve ends with two major branches; the infra nasal branch (INB) and superior labial branch (SLB). In this study, we assessed the feasibility of cross-nerve transfer of the INB and SLB based on a cadaver study. METHODS: The INB/SLB from a total 20 sides of 10 cadavers (2 men and 8 women; average age, 79.9 years) were dissected. The distribution patterns of the INB and SLB, the distance between the INB/SLB and the piriform aperture, and the shortest distance between the INB/SLB were estimated. RESULTS: Three distribution patterns of the INB and SLB were observed, that is type A (65%); only the INB is thick enough for a nerve transfer, type B (20%); only the SLB is thick enough for a nerve transfer, and a combination of types A and B (15%). The distance between the INB, SLB and the piriform aperture was on average 8.61 and 10.81 mm in each. The shortest distance between the INB and SLB was on average 11.34 ± 3.7 mm. CONCLUSIONS: The INB and SLB existed in all the specimens and could be found approximately 1 cm below the piriform aperture. The average distance between the INB and SLB was approximately 11 mm. These results imply the feasibility of a cross-nerve transfer of the distal part of the infraorbital nerve.

Anatomical study of the left superior mediastinal lymphatics for tracheal branches of left recurrent laryngeal nerve-preserving mediastinoscope-assisted surgery in esophageal cancer.

PURPOSE: Curative treatment of esophageal cancer requires meticulous superior mediastinal lymphadenectomy, in addition to esophagectomy, because superior mediastinal lymph node metastases are common in esophageal cancer. When preserving the tracheal branches of the left recurrent laryngeal nerve (RLN), good anatomical understanding is required for confirmation of the positional relationships between the courses of lymphatic vessels, lymph node distribution, and the left RLN and its tracheal branches. We performed a detailed anatomical examination of these relationships. METHODS: Macroscopic anatomical observation and histological examination was performed on cadavers. In addition to hematoxylin and eosin staining, immunostaining using antipodoplanin antibody D2-40 (podoplanin) was performed to identify the lymphatic vessels. RESULTS: The tracheal branches of the left RLN were clearly observed, but no lymphatic vessels crossing the ventral or dorsal side of the branches were identified either macro-anatomically or histologically. CONCLUSION: No complex lymphatic network structure straddling the plane composed of tracheal branches of the left RLN was found in the left superior mediastinum. This suggests that dissection of the lymph nodes around the left RLN via the pneumomediastinum method using the left cervical approach may allow preservation of the tracheal branches of the left RLN by maintaining dissection accuracy.

The extended bundle of the tensor veli palatini: Anatomic consideration of the dilating mechanism of the Eustachian tube.

OBJECTIVE: The aim of this study was to analyze the topographical structures of the muscles surrounding the Eustachian tube. MATERIALS AND METHODS: We conducted macroscopic and histological studies of 24 halves of 12 heads from Japanese cadavers. RESULTS: The main findings were as follows: 1) the infero-lateral muscle bundles of the tensor veli palatini didn't turn medially at the pterygoid hamulus but were distributed laterally and continuous with the buccinator; 2) the tensor veli palatini attached laterally to the membranous part of the Eustachian tube; 3) the superior pharyngeal constrictor was not only adjacent to the buccinator at the pterygomandibular raphe but also had muscular continuation with it laterally and 4) some bundles of the superior pharyngeal constrictor adhered with the palatine aponeurosis. CONCLUSION: We believe that the cooperation of the muscles contributes to the dilating mechanism of the Eustachian tube, due to the complex topographical structures of the surrounding muscles: the tensor veli palatini, the levator veli palatini, the superior pharyngeal constrictor and the buccinator.

The malaris muscle: its morphological significance for sustaining the intraorbital structures.

The orbicularis oculi muscle, an important mimetic muscle, was investigated to ascertain its anatomical relation to facial aging-especially its orbital part (Oo). Previous studies of the distinct muscle bundles frequently found inferior to the Oo have provided various definitions, including that of the malaris muscle. This study aimed to examine these muscle bundles and clarify their function in facial aging. Twelve heads of Japanese cadavers (average age: 82.5 years old) were dissected to observe the muscles, focusing in particular on those in the periorbital region. Six specimens were further dissected from the inner surfaces to examine the patterns of facial nerve branches under the operating microscope. Histological examinations of two head halves were carried out to investigate the relationship between the muscle bundles and the intraorbital structures. Muscle bundles consisting of lateral, medial, and U-shaped suspending bundles were observed in the region inferior to the Oo. Lateral and suspending bundles were found in all specimens, while the medial bundles were noted in only 9 of 22 specimens. Some branches of the facial nerve penetrated through the lateral, medial, and suspending bundles. The relationship between the suspending bundles and the protruding orbital fat was assessed. The muscle bundles found in this study were regarded as the malaris muscle-a transitional muscle between the superficial and deep facial layers. The suspending bundle may play a role in sustaining the intraorbital structures.