Publications by authors named "Gen Murakami"

362 Publications

Superior labial artery and vein anastomosis configuration to be considered in lip augmentation.

Ann Anat 2021 Jul 26:151808. Epub 2021 Jul 26.

Department of Anatomy, Tokyo Dental College, 2-9-18 Misaki-cho, Chiyoda-ku, 101-0061 Tokyo, Japan; Tokyo Dental College Research Branding Project, 2-9-18 Kanda-misakicho, Tokyo, 101-0061, Japan.

The treatment of cleft lip and palate is performed over a long period, starting immediately after birth. However, esthetic problems remain after lip augmentation. Endothelial cells of new capillaries are important for wound healing. Thus, the reconstruction of vascular networks is key to postoperative wound healing during lip augmentation. However, studies describing the superior labial artery (SLA) and superior labial vein (SLV) are rare, and their mutual positional relationship thus remains unclear. We procured 29 adult cadavers and ten fetuses. Macroscopic and histological examinations were performed on adult cadavers. We extracted soft tissues and blood vessels after micro-computed tomography (CT) and 3D tissue reconstruction. We performed histological investigations of vascular networks within the cleft lip in fetal samples. In adults, the SLV was distributed throughout the cutaneous side of the orbicularis oris muscle and the SLA, throughout the mucosal side. The SLV and SLA were separated by this muscle. Micro-CT images revealed that the SLA on the mucosal side transversed the orbicularis oris muscle to the SLV (55%). Histological analysis of fetuses revealed that the SLA was on the mucosal side, similar to that in adults, and traversed the orbicularis oris muscle in continuity with the SLV of the cutaneous side (100%). In lip augmentation, the reconstruction of the vascular structure, which involves the anastomosis of SLA and SLV passing through the orbicularis oris muscle, is an important factor when considering esthetic repair.
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http://dx.doi.org/10.1016/j.aanat.2021.151808DOI Listing
July 2021

Association between the developing sphenoid and adult morphology: A study using sagittal sections of the skull base from human embryos and fetuses.

J Anat 2021 Jul 15. Epub 2021 Jul 15.

Department of Anatomy, Tokyo Dental College, Tokyo, Japan.

The developing sphenoid is regarded as a median cartilage mass (basisphenoid [BS]) with three cartilaginous processes (orbitosphenoid [OS], ala temporalis [AT], and alar process [AP]). The relationships of this initial configuration with the adult morphology are difficult to determine because of extensive membranous ossification along the cartilaginous elements. The purpose of this study was therefore to evaluate the anatomical connections between each element of the fetal sphenoid and adult morphology. Sagittal sections from 25 embryos and fetuses of gestational age 6-34 weeks and crown-rump length 12-295 mm were therefore examined and compared with horizontal and frontal sections from the other 25 late-term fetuses (217-340 mm). The OS was identified as a set of three mutually attached cartilage bars in early fetuses. At all stages, the OS-post was continuous with the anterolateral part of the BS. The BS included the notochord and Rathke's pouch remnant in embryos and early fetuses. The dorsum sellae was absent from embryos, but it protruded from the BS in early fetuses before a fossa for the hypophysis became evident. Although not higher than the hypophysis at midterm, the dorsum sellae elongated superiorly after gestational age 25 weeks. In early fetuses, the AP was located on the side immediately anterior to the otic capsule. The AT developed on the side immediately posterior to the extraocular rectus muscles. At late term, the greater wing was formed by membranous bones from the AT and AP. The AT and AP formed a complex bridge between the BS and the greater wing. A small cartilage, future medial pterygoid process (PTmed) was located inferior to the AT in early fetuses. At midterm, one endochondral bone and multiple membranous bones formed the PTmed. The lateral pterygoid process (PTlat) was formed by a single membranous bone plate. Therefore, we connected fetal elements and the adult morphology as follows. (1) Derivative of the OS makes not only the lesser wing but also the anterior margin of the body of the sphenoid. (2) Derivatives of the BS are the body of the sphenoid including the sella turcica and the dorsum sellae. (3) Most of the greater wing including the foramen rotundum and the foramen oval originate from the AT and AP and multiple membranous bones. (4) The PTmed originate from endochondral bones and multiple membranous bones, while the PTlat derive from a single membranous bone.
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http://dx.doi.org/10.1111/joa.13515DOI Listing
July 2021

Development of the cartilaginous connecting apparatuses in the fetal sphenoid, with a focus on the alar process.

PLoS One 2021 12;16(7):e0251068. Epub 2021 Jul 12.

Department of Anatomy, Tokyo Dental College, Chiyoda-ku, Tokyo, Japan.

The human fetal sphenoid is reported to have a cartilaginous connecting apparatus known as the alar process (AP), which connects the ala temporalis (AT) (angle of the greater wing of the sphenoid) to the basisphenoid (anlage of the sphenoid body). However, how the AP develops in humans is unclear. In addition, although the AP is a common structure of the mammalian chondrocranium, little is known about whether it is really a fundamental feature in mammals. This study examined the histological sections of 20 human embryos and fetuses from 6 to 14 weeks of development, of 20 mouse embryos from embryonic days 12-18, and of 4 rats embryos form embryonic days 17 and 20. In addition, we reconsidered the definition of the AP by comparing humans and rats with mice. In humans, the AP was continuous with the basisphenoid but was separated from the AT by a thick perichondrium. Then, the AP-AT connection had a key-and-keyhole structure. Unlike a joint, no cavitation developed in this connection. In mice, there was no boundary between the AT and the basisphenoid, indicating the absence of the AP in the mouse chondrocranium. In rats, the AP was, however, separated from the AT by a thick perichondrium. Therefore, the AP can be defined as follows: the AP is temporally separated from the AT by a thick perichondrium or a key-and-keyhole structure during the fetal period. This is the first study that confirms the absence of the alar process in the mice skull, and its presence in other mammals skull should be further investigated.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0251068PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8274926PMC
July 2021

Fetal development and growth of the fissula ante fenestram in the human ear.

Anat Rec (Hoboken) 2021 Jul 9. Epub 2021 Jul 9.

Department of Otolaryngology-Head and Neck Surgery, Tohoku University Graduate School of Medicine, Sendai, Japan.

Since the fissula ante fenestram (FAF) is considered as a focus of otosclerotic lesion and a route of perilymph leakage, there are few description of prenatal development of the cartilaginous canal passing though the cochlear wall. We examined the sagittal and frontal histological sections of the ear from 32 human fetuses at 8-37 weeks of gestational age. At 8-12 weeks, in the immediately anterior side of a connection between the cochlear and canalicular parts of the otic capsule cartilage, the FAF appeared as a tear of a cartilage between the basal and second turns of the cochlea. The tear became a slit opening to the scala vestibuli. At 13-15 weeks, the FAF, less than 1.2 mm in length, had the anterosuperior and postero-inferior apertures: the former was near the geniculate ganglion and became closed after 15 weeks, while the latter approached the oval window. Third trimester fetuses, the FAF, 1.5-2.0 mm in length, consistently carried a single, postero-inferior aperture extending along the anterior margin of the oval window and it contained no definite epithelium and vessel. Although it was endochondral ossification, there was no clear zonation in cartilage cells of the FAF. A mechanical stress during three-dimensional coiling of the cochlear ducts seemed to provide the FAF. After the FAF was established, the stapes footplate might use a part of the inferior aperture for the syndesmosis. A specific ossification was seen in the FAF, but it might rarely cause the pathological syndesmosis.
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http://dx.doi.org/10.1002/ar.24711DOI Listing
July 2021

Fetal development and growth of the human erector spinae with special reference to attachments on the surface aponeurosis.

Surg Radiol Anat 2021 May 31. Epub 2021 May 31.

Division of Internal Medicine, Cupid Clinic, Iwamizawa, Hokkaido, Japan.

Purpose: The longissimus (LO) and iliocostalis (IC) of adults consist of myofibers extending from the superolateral to the inferomedial side of the back and, because of the same course, they are fused in the thoracolumbar region. The LO also has a medial attachment to the long myofibers of the transversospinalis (TS) showing a course from the superomedial to the inferolateral side. However, there is apparently no information regarding when and how these similar longitudinal muscles differentiate from a cluster of dorsomedial myotome cells.

Methods: We examined sagittal and horizontal sections of the trunks of 39 human embryos and fetuses (18-330 mm crown-rump length).

Results: At 6-7 weeks gestational age (GA), the surface aponeurosis appeared prior to and independent of the thoracolumbar fascia. At 6-9 weeks GA, the LO myofibers had a postero-inferior course, from the transverse process to the initial aponeurosis, whereas the TS myofibers had a postero-superior course, from a lateral extension of the intertransverse ligament to the aponeurosis. However, the IC consisted of supracostal longitudinal myofibers and was distant from the LO until 12 weeks GA. Because of the lack of ligamentous attachments and ribs, myofibers of the TS, LO, and IC took a similar inferior course in the lumbar region. When the early TS was represented by the transverso-aponeurotic muscle, consequently, the LO corresponded to the aponeuro-transversal muscle and was independent from the IC.

Conclusion: The classical model of TS and LO development does not recognize the essential role of the aponeurosis identified here.
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http://dx.doi.org/10.1007/s00276-021-02759-wDOI Listing
May 2021

Functional MHCI deficiency induces ADHD-like symptoms with increased dopamine D1 receptor expression.

Brain Behav Immun 2021 May 20. Epub 2021 May 20.

Division of Psychology, Department of Integrated Human Sciences, Hamamatsu University School of Medicine, Hamamatsu 431-3192, Japan; Department of Liberal Arts, Faculty of Medicine, Saitama Medical University, Saitama 350-0495, Japan. Electronic address:

Inappropriate synaptic development has been proposed as a potential mechanism of neurodevelopmental disorders, including attention-deficit hyperactivity disorder (ADHD). Major histocompatibility complex class I (MHCI), an immunity-associated molecule expressed by neurons in the brain, regulates synaptic development; however, the involvement of MHCI in these disorders remains elusive. We evaluated whether functional MHCI deficiency induced by β2mTap1 double-knockout in mice leads to abnormalities akin to those seen in neurodevelopmental disorders. We found that functional MHCI deficiency induced locomotor hyperactivity, motor impulsivity, and attention deficits, three major symptoms of ADHD. In contrast, these mice showed normal spatial learning, behavioral flexibility, social behavior, and sensorimotor integration. In the analysis of the dopamine system, upregulation of dopamine D1 receptor (D1R) expression in the nucleus accumbens and a greater locomotor response to D1R agonist SKF 81297 were found in the functional MHCI-deficient mice. Low-dose methylphenidate, used for the treatment of ADHD patients, alleviated the three behavioral symptoms and suppressed c-Fos expression in the D1R-expressing medium spiny neurons of the mice. These findings reveal an unexpected role of MHCI in three major symptoms of ADHD and may provide a novel landmark in the pathogenesis of ADHD.
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http://dx.doi.org/10.1016/j.bbi.2021.05.015DOI Listing
May 2021

Arteriovenous Anastomosis in Human Hand Digital Skin.

Bull Tokyo Dent Coll 2021 Jun 14;62(2):63-70. Epub 2021 May 14.

Department of Anatomy, Tokyo Dental College.

While a digital arteriovenous anastomosis (Hoyer-Grosser's organ, Masson's glomus) is a well-known structure, photographic evidence of communication between arterial and venous lumens might not be demonstrated in routine histological or immunohistochemical analysis. Abundant clusters of so-called glomera were found in semi-serial sections of the distal aspect of 14 fingers obtained from 7 donated elderly cadavers. Two to six round or oval clusters were observed in each longitudinal section (over 0.3-0.6 mm in maximum diameter) in subcutaneous tissue 0.5-1.5 mm below the basal layer of the skin, whereas none were often observed in transverse sections. Lumen-to-lumen communication between arteriole and venule at 8 sites in 2 cadavers was identified in these clusters of glomera. The opening in the arteriole was large (50 μm in diameter) at 3 sites in specimens from an 80-year-old man, whereas it was small (10-30 μm) at 5 sites in those from a 91-year-old man. The arterial aspect was tightly surrounded by abundant nerve fibers expressing tyrosine hydroxylase immunoreactivity, whereas the venous part was not. No or little expression of S100 protein immunoreactivity suggested that these nerve fibers were unmyelinated. The morphology at the lumen-to-lumen communication was simple - possibly an end-to-end anastomosis - rather than a sinuous curve of arteriole opening on to a short funnel-shaped venule as seen in the standard textbooks.
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http://dx.doi.org/10.2209/tdcpublication.2020-0036DOI Listing
June 2021

Relationship of the fabella with the origins of the plantaris and gastrocnemius lateral head muscles in late-term fetuses: a histological study.

Anat Cell Biol 2021 Jun;54(2):270-279

Department of Anatomy and Embryology, School of Medicine, Complutense University, Madrid, Spain.

Previous studies of midterm fetuses indicated that a cartilaginous fabella appeared to be embedded in the plantaris (PL), and was fused with the gastrocnemius lateral head (GL). We re-examined the topographical anatomy of the fabella or its analogue (a tight fibrous mass) originating in the GL and/or PL by evaluating histological sections of the unilateral knees of 15 late-term fetuses. Regardless of whether the cartilaginous fabella was present (6 fetuses) or absent (9 fetuses), the origins of the PL and GL muscles each had three parts. In each fetus, the fabella or its analogue was embedded in a thick common tendinous origin of the GL and PL. PL1 (whose origin is similar to that of the adult PL) originated from the femoral condyle immediately above the common tendon; PL2 originated from the posteromedial aspect of the fabella or its analogue; and PL3 originated from the inferior aspect of the fabella or its analogue. The muscle fibers of PL1, PL2, and PL3 joined to provide a thick plantaris. GL1 (which is adjacent to PL2) originated from the common tendon in the superior side of the fabella or its analogue and GL2 originated from the inferior side of the fabella or its analogue. GL1 and GL2 joined to provide a thick bundle, whereas GL3 (located far below the fabella or its analogue) originated from the posterior surface aponeurosis. Therefore, drastic reconstruction at these muscle origins was necessary during development. Due to the strong mechanical stress from the GL and the space-occupying effect of the muscle, we hypothesize that PL2 and PL3 are degraded or absorbed into the GL1 and GL2 during the postnatal period, so that the remaining PL1 was likely the remaining PL in adults.
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http://dx.doi.org/10.5115/acb.20.326DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8225468PMC
June 2021

Auricular cartilage configuration: A histological study using late-stage human fetuses and adult cadavers.

Anat Rec (Hoboken) 2021 Feb 23. Epub 2021 Feb 23.

Department of Anatomy, Tokyo Dental College, Tokyo, Japan.

The auricular cartilage is considered to develop from a funnel-like arrangement of six embryonic hillocks. However, there is little information as to when and how the initial cartilage plate differentiates into the major three hollows or caves: the concha, the scapha and the triangular fossa. We examined semiserial histological sections from 42 human fetuses as well as from seven cadavers of elderly individuals. Tangential sections from adults suggested that three ring-like cartilages were combined to provide a single auricular cartilage and that the external auditory meatus was attached to the lowest ring or concha. All of the fetuses studied carried the three major hollows delineated by skin folds. These skin folds often contained a cartilage loop as a core in place of a thickening or tubercle. Conversely, some of the skin folds corresponded to a highly wavy cartilage plate without looping. According to whether the cartilage loop was present or absent in horizontal sections from 35 fetuses, we classified the cartilage morphology into four patterns, the most frequent of which was absence of the triangular fossa loop (27 fetuses), followed by absence of the scapha loop (11 fetuses). Each pattern was evenly distributed among small and large fetuses. This suggested that some form of cartilage correction or reconstruction was likely to occur after birth, especially at the triangular fossa and/or scapha. Infants appear to show significant region-specific variation in the postnatal growth of the auricular cartilages, especially at the triangular fossa and/or scapha.
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http://dx.doi.org/10.1002/ar.24608DOI Listing
February 2021

Fetal cervical zygapophysial joint with special reference to the associated synovial tissue: a histological study using near-term human fetuses.

Anat Cell Biol 2021 Mar;54(1):65-73

Department of Histology and Embryology, Tokyo Dental College, Tokyo, Japan.

Human fetal cervical vertebrae are characterized by the large zygapophysial joint (ZJ) extending posteriorly. During our recent studies on regional differences in the shape, extent, and surrounding tissue of the fetal ZJ, we incidentally found a cervical-specific structure of synovial tissues. This study aimed to provide a detailed evaluation of the synovial structure using sagittal and horizontal sections of 20 near-term fetuses. The cervical ZJ consistently had a large cavity with multiple recesses at the margins and, especially at the anterior end, the recess interdigitated with or were located close to tree-like tributaries of the veins of the external vertebral plexus. In contrast to the flat and thin synovial cell lining of the recess, the venous tributary had cuboidal endothelial cells. No or few elastic fibers were identified around the ZJ. The venous-synovial complex seems to be a transient morphology at and around birth, and it may play a role in the stabilization of the growing cervical ZJ against frequent spontaneous dislocation reported radiologically in infants. The venous-synovial complex in the cervical region should be lost and replaced by elastic fibers in childhood or adolescence. However, the delayed development of the ligament flavum is also likely to occur in the lumbar ZJ in spite of no evidence of a transient venous-synovial structure. The cuboidal venous endothelium may simply represent the high proliferation rate for the growing complex.
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http://dx.doi.org/10.5115/acb.20.265DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8017452PMC
March 2021

Distribution of sole Pacinian corpuscles: a histological study using near-term human feet.

Surg Radiol Anat 2021 Jul 20;43(7):1031-1039. Epub 2021 Jan 20.

Department of Foot Surgery, Hitsujigaoka Hospital, Sapporo, Japan.

Introduction: Fast-adapting afferent input from the sole Pacinian corpuscles (PCs) is essential for walking. However, the distribution of PCs in the plantar subcutaneous tissue remains unknown.

Materials And Methods: Using histological sections tangential to the plantar skin of eight near-term fetuses, we counted 528-900 PCs per sole.

Results: Almost half of the sole PCs existed at the level of the proximal phalanx, especially on the superficial side of the long flexor tendons and flexor digitorum brevis. Conversely, the distribution was less evident on the posterior side of the foot. The medial margin of the sole contained fewer PCs than the lateral margin, possibly due to the transverse arch. In contrast to a cluster formation in the anterior foot, posterior PCs were almost always solitary, with a distance greater than 0.5 mm to the nearest PC.

Discussion And Conclusion: Because a receptive field of PCs is larger than that of the other receptors, fewer solitary PCs might cover the posterior sole. In infants, the amount of anterior sole PCs seemed to determine the initial walking pattern using the anterior foot without heel contact. Anterior PCs concentrated along flexor tendons might play a transient role as tendon organs during the initial learning of walking. During a lesson in infants, mechanical stress from the tendon and muscle was likely to degrade the PCs. In the near term, the sole PCs seemed not to be a mini-version of the adult morphology but suggested an infant-specific function.
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http://dx.doi.org/10.1007/s00276-021-02685-xDOI Listing
July 2021

Fetal development of the thoracolumbar fascia with special reference to the fascial connection with the transversus abdominis, latissimus dorsi, and serratus posterior inferior muscles.

Surg Radiol Anat 2021 Jun 12;43(6):917-928. Epub 2021 Jan 12.

Department of Anatomy, Wuxi Medical School, Jiangnan University, Wuxi, Jiangsu Province, China.

Purpose: The three-layered thoracolumbar fascia (TLF) encapsulates the erector spinae and the quadratus lumborum and has been a major concern for physical therapists. However, knowledge of its prenatal development and growth is limited.

Methods: Histological examination of 25 embryos and fetuses at 6-37 weeks (CRLs, 15-310 mm).

Results: At the posterior end, the abdominal muscles continued toward an initial posterior layer of the TLF (pTLF) at 6 weeks, but the connection became narrow and limited to the obliquus externus aponeurosis until near term. The middle layer of the TLF (mTLF) appeared as a posterior continuation of the transversalis fascia at 9 weeks and, depending on a mechanical demand for the vertebral column extension near term, it grew as a thick intermuscular septum between the iliocostalis and quadratus lumborum. Thus, the mTLF lateral end changed from the abdominal wall to the back or pTLF. The serratus posterior inferior originated from the pTLF after 9 weeks, but a connection of the latissimus dorsi with the fascia was established much later. Near term, the gluteus maximus was attached to an aponeurosis covering the multifidus behind the sacrum. Therefore, the pTLF extended to cover the gluteal muscles.

Conclusion: We rejected the hypothesis that the mTLF develops as a marginal tissue between the primitive epaxial and hypaxial muscles. This study seemed to be the first report showing a fact that, within prenatal life, a drastic change is likely to occur in interfascial connections and their topographical relation to muscles; the TLF might be the best sample.
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http://dx.doi.org/10.1007/s00276-020-02668-4DOI Listing
June 2021

Fetal development of the human trapezius and sternocleidomastoid muscles.

Anat Cell Biol 2020 12;53(4):405-410

Department of Anatomy, Tokyo Dental College, Tokyo, Japan.

At present, there is no photographic evidence of splitting of the trapezius and sternocleidomastoid muscles (SCMs), which share a common anlage that extends caudally toward the limb bud in the embryo at a length of 9 mm. Therefore, the aim of the present study was to identify which structures divide the caudal end of the common anlage at the first sign of splitting into two muscles. In 11 mm-long specimens, the SCM and trapezius muscles were identified as a single mesenchymal condensation. In 15 and 18 mm-long specimens, the SCM and trapezius muscles were separated and extended posteriorly and lymphatic tissues appeared in a primitive lateral cervical space surrounded by the SCM (anterior). In 21 mm-long specimens, the lymphatic vessels were dilated and the accompanying afferents were forming connections with the subcutaneous tissue through a space between the SCM and trapezius muscles. In 27 mm-long specimens, cutaneous lymphatic vessels were evident and had entered the deep tissue between the SCM and trapezius muscles. Vascular dilation may be viewed as a result of less mechanical stress or pressure after muscle splitting.
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http://dx.doi.org/10.5115/acb.20.202DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7769109PMC
December 2020

Histologic Investigation of the Female Vesicourethral Junction and Adjacent Tissues for Nerve-sparing Radical Cystectomy.

Urology 2021 Mar 10;149:161-167. Epub 2020 Dec 10.

Department of Urology, Kobe University Graduate School of Medicine, Kobe, Japan.

Objective: To understand the structures around the vesicourethral junction and to improve functional outcomes after nerve-sparing radical cystectomy with orthotopic urinary diversion for female patients, we histologically elucidated the fibromuscular construction and nerve distribution around the vesicourethral junction.

Methods: Pelvic specimens containing all the pelvic viscera were obtained from 33 donated female cadavers. Macroslices that included the urethra, the anterior wall of the vagina, and the inferomedial edge of the levator ani muscle were made and performed elastica Masson and immunohistochemical staining. The intraoperative findings were collected in 3 female patients undergoing nerve-sparing radical cystectomy.

Results: In 18 out of the 33 cadavers, smooth muscle mass occupied a space between the urethra and the inferomedial edge of the levator ani muscle and covered the inferior margin of the bladder detrusor. We termed this mass the hiatal smooth muscle. The detrusor nerves entered the bladder, and the cavernous and sphincter nerves ran between the hiatal smooth muscle and vesicourethral junction. The boundary between hiatal smooth muscle and urethral smooth muscle was easily distinguished intraoperatively during dissection of the vesicourethral junction.

Conclusion: We found that more than half of elderly women have hiatal smooth muscle between the urethra and inferior edge of the levator ani. Autonomic nerve fibers innervating the urethral sphincter, run between the hiatal smooth muscle and vesicourethral junction in female cadavers with hiatal smooth muscle. When performing female radical cystectomy before neobladder reconstruction, nerve sparing can be reliably performed using the hiatal smooth muscle as a landmark.
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http://dx.doi.org/10.1016/j.urology.2020.12.001DOI Listing
March 2021

Variations in Laminar Arrangements of the Mesocolon and Retropancreatic Fascia: a Histological Study Using Human Fetuses Near Term.

Tokai J Exp Clin Med 2020 Dec 20;45(4):214-223. Epub 2020 Dec 20.

Department of Anatomy, Division of Basic Medical Science, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa 259-1193, Japan.

Objective: The embryonic mesentery of the ascending and descending colons as well as the pancreas disappears due to peritoneal fusion, but there might be no or few photographic demonstrations of the intermediate morphologies during the process. The aims of this study were to characterize the morphological relationship of the interface between the renal fascia and peritoneum.

Methods: Fourteen late-stage fetuses with crown rump lengths (CRLs) of 250-325 mm (gestational age: 30-38 weeks) were histologically examined.

Results: The renal fascia, a thick or thin layer consisting of densely-distributed abundant fibers, was consistently separated from the renal capsule by a perirenal space containing fat. The transverse colon carried a typical mesocolon histologically different from the renal fascia. The ascending and descending mesocolons were irregularly divided into multiple laminae and the colic external longitudinal muscle appeared to directly contact the renal fascia. There was a spectrum of variations from multiple laminae to a single thick fascia between the pancreatic body and the left kidney or adrenal.

Conclusions: A fascial development after retroperitoneal fusion of the mesentery showed great individual and site-dependent differences in proportion of 1) a complete fusion with the renal fascia and 2) a multilaminar structure including the remnant peritoneum. These variations masked the likely stage-dependent change.
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December 2020

Abnormal Intestinal Anatomy in Late-stage Human Fetuses: Three Case Series.

Tokai J Exp Clin Med 2020 Dec 20;45(4):162-169. Epub 2020 Dec 20.

Department of Anatomy, Division of Basic Medical Science, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa 259-1193, Japan.

Objective: We reported three cases of fetuses with abnormal intestinal anatomy found during our recent study of the transverse mesocolon using 20 late-stage fetuses.

Cases: The first case (CRL: 328 mm) appeared to have a duodenum and transverse colon trapped in Winslow's foramen (foramen epiploicum) and the duodenum superior portion elongated rightward. The second case (CRL: 264 mm) had a transverse colon inserted deeply into a space between the right kidney and duodenum. The third case (CRL: 276 mm) had a descending colon that ran inferiorly through a deep space between the left kidney and duodenum. Each case had a greater omentum that was shifted leftward, but this is usual. These 3 abnormalities were not evident in the anterior view during dissection of the liver, stomach, jejunum, and ileum. With underdeveloped pancreatic ducts due to unknown reason other than the internal hernia, the first case seemed to be fatal after birth. However, the second and third cases could have recovered after birth because there was no evidence of definite malrotation and because of loose attachments of the intestines to surrounding structures.

Conclusions: The intestinal morphologies described here could cause some sort of symptoms, such as abdominal pain, whose cause might be difficult to determine.
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December 2020

A missing distal complex of the external and internal anal sphincters: a macroscopic and histologic study using Japanese and German elderly cadavers.

Surg Radiol Anat 2021 May 2;43(5):775-784. Epub 2020 Nov 2.

Department of Anatomy, Tokyo Dental College, Tokyo, Japan.

The lower margin of the internal anal sphincter (IAS) is considered to lie on a J-shaped, subcutaneous part (SCP) of the external anal sphincter (EAS). The lower IAS is united with the J-shaped SCP to form a smooth-striated muscle complex. In the first part of this study, we ensured the presence of the J-shaped EAS in the lateral wall of the anal canal from 12 near-term fetuses. Second, in the lateral anal wall, the examination of the longitudinal section from 20 male and 24 female Japanese cadavers (72-95 years-old) demonstrated that the J-shaped EAS was lost in 15 (34%) due to the very small SCP. Third, we demonstrated that the J-shaped EAS was restricted in the latera anal wall using longitudinal histological sections of the anal canal from 11 male Japanese cadavers (75-89 years-old). Therefore, a site-dependent difference in the IAS-EAS configuration was evident. Finally, we compared a frequency of the lost J-shape between human populations using 10 mm-thick frontal slices from 36 Japanese and 28 German cadavers. The two groups of cadavers were compatible in age (a 0.2-years' difference in males). The macroscopic observations revealed that the J-shaped EAS was absent from 13 (36%) Japanese and six (20%) German specimens, suggesting that the SCP degeneration occurred more frequent in elderly Japanese than elderly German individuals (p < 0.05). The distal IAS-EAS complex seemed to push residual feces out of the anal canal at a transient phase from evacuation to closure. The absence might be the first sigh of anal dysfunction.
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http://dx.doi.org/10.1007/s00276-020-02606-4DOI Listing
May 2021

Regional differences in zygapophysial joint cavities: A histological study of human fetuses.

Anat Rec (Hoboken) 2021 05 15;304(5):979-990. Epub 2020 Oct 15.

Department of Histology and Embryology, Tokyo Dental College, Tokyo, Japan.

Human zygapophysial joints (ZJ) have regional differences in shape and orientation during prenatal growth. However, there is limited knowledge of the synovial recess during fetal development. We examined sagittal and horizontal histological sections of the vertebral columns of 30 human fetuses at gestational ages of 8-37 weeks. Fetuses of all gestational ages had subaxial cervical articular processes that were thicker than in the thoracolumbar regions, and as large as the corresponding vertebral bodies. A small or large synovial recess extending beyond the articular cartilage was evident at most regions. The cervical ZJ had large or deep recesses that extended inferiorly in midterm fetuses and posteromedially along the vertebral pedicle and lamina in near-term fetuses. Likewise, the thoracic ZJ had small recesses that extended superiorly in midterm fetuses and medially in near-term fetuses. The lumbar recesses extended laterally beyond the medially shifted articular cartilage of the upper adjacent vertebrae in near-term fetuses and the lumbar articular surface was smallest in the three regions at all stages. At any region, a deep recess appeared before an area expansion of the ZJ cartilage. A drastic change in direction and size of the prenatal recess seemed to occur depending on a possible minute dislocation of the ZJ. In particular, a deep posteromedial recess of the cervical ZJ, which extended far beyond the articular cartilage, might be necessary to maintain high flexibility suitable for the strong flexion posture in utero.
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http://dx.doi.org/10.1002/ar.24532DOI Listing
May 2021

Examination of the Annular Tendon (Annulus of Zinn) as a Common Origin of the Extraocular Rectus Muscles: 2. Embryological Basis of Extraocular Muscles Anomalies.

Invest Ophthalmol Vis Sci 2020 10;61(12)

Department of Anatomy and Embryology, School of Medicine, Complutense University, Madrid, Spain.

Purpose: Many reports have described anomalous connections of the superior rectus (SR) with other extraocular rectus muscles, in which additional heads of the other three rectus muscles likely provided the connections. We examined how these connections are established during fetal development.

Methods: We analyzed paraffin-embedded horizontal sections from 25 late-stage fetuses. Horizontal sections are best suited for understanding the mediolateral relationships of muscle origins.

Results: We confirmed a common tendinous origin of the lateral rectus (LR), inferior rectus (IR) and medial rectus (MR) muscles that was separated from the SR origin. Notably, eight fetuses (32%) had tendinous or muscular connections between the SR and other rectus muscles that had one of four morphologies: (a) a thin tendon from the SR to the common tendon of the three rectus muscles (2 fetuses), (b) a thin tendon to the LR (one fetus), (c) a thin tendon to the inferior rectus muscle origin (two fetuses), and (d) SR muscle fibers arising from an additional head of the LR (three fetuses).

Conclusions: The SR seemed to issue a thin tendon that passed along the inferior or lateral side of the oculomotor nerve. Conversely, the LR and inferior rectus muscle were likely to carry a supernumerary bundle that reached the SR. The accessory head of the medial rectus muscle showed a stable morphology in that it seemed to also provide an anomalous double head. However, the presence of an accessory head in the LR was rare. In contrast with our previously published diagram of the orbital apex, the accessory head of the medial rectus muscle passed along the lateral side of the superior oblique.
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http://dx.doi.org/10.1167/iovs.61.12.5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7545067PMC
October 2020

Cervical nerve roots and the dural sheath: a histological study using human fetuses near term.

Anat Cell Biol 2020 Dec;53(4):451-459

Department of Anatomy, Tokyo Dental College, Tokyo, Japan.

We have previously reported that the thoracolumbar posterior nerve root shows a tortuous epidural course, based on studies of human fetuses near term. For comparison with the cervical nerve, examinations were conducted using frontal, sagittal and horizontal sections of cervical vertebrae from 22 fetuses at 30-38 weeks of gestation. The cervical nerve root showed a short, straight and lateral course near the zygapophysial joint. Multiple rather than single bundles of the cervical posterior root seemed to account for the majority of sensory nerve fibers innervating the upper extremity. Fasciculation of rootlets was evident near the thoracolumbar spinal cord, whereas it was seen in the dural pocket at the nerve exit from the dural sac although both sites were subdural. As in the thoracolumbar region, the nerve sheath was continuous with the dura mater and independently surrounded each of the anterior and posterior roots. Radicular arteries were few in the cervical region. In 2 of the 22 fetuses (31 weeks and 33 weeks), there was a segmental, unilateral abnormality of nerve rootlet fasciculation where the dorsal root ganglion was located lateral or peripheral to the intervertebral region. Long nerve roots running inferiorly are a necessary adaptation to the delayed and marked growth of the thoracolumbar vertebral column. In children, the cervical nerve roots are likely to be affected by movement or dislocation of the vertebrae. The segmental abnormality of the cervical nerve root may be linked to rare variations in the brachial plexus.
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http://dx.doi.org/10.5115/acb.20.081DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7769102PMC
December 2020

Topographical anatomy of the tentorium cerebelli and venous confluences in human midterm fetuses.

Ann Anat 2021 Jan 6;233:151596. Epub 2020 Sep 6.

Department of Anatomy, Tokyo Dental College, Tokyo, Japan.

Early development of veins and sinuses at and around the posterior cranial fossa seemed not to be shown by photographs except for our recent study (Ann Anat, 2020). Examination of histological sections of 38 fetuses at 10-16 weeks gestational age (GA) demonstrated that: (1) the superior petrosal sinus passed posterosuperiorly through the tentorium cerebelli and, distant and lateral to both the cerebellum and internal ear, drained into the transverse sinus; (2) the superior sagittal sinus was underdeveloped, and the inferior sagittal sinus was not yet evident; (3) the straight sinus (STS) originated from a joining of the bilateral pial veins from the lateral ventricular choroid plexus, passed through the inferoposterior part of the falx cerebri, reached the initial confluens sinuum, and then divided into the bilateral transverse sinuses. The STS origin was immediately behind the pineal body, and near the inferoposterior end of the third ventricle. The falx had a thick attachment to the tentorium below the entire course of the STS and was behind other parts of the brain. Therefore, the development and growth of the posterior dural system seemed to be independent from brain growth, and occurred well before the cerebellum grew to fill the posterior cranial fossa. A basic configuration of intracranial veins and sinuses, including embryonic transient veins (such as the vena capitis prima) seemed to be established by venous return from the choroid plexus and cranial wall, without greatly increasing the abundance of neuronal or glial cells in the brain.
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http://dx.doi.org/10.1016/j.aanat.2020.151596DOI Listing
January 2021

The third vascular route of the inner ear or the canal of Cotugno: Its topographical anatomy, fetal development, and contribution to ossification of the otic capsule cartilage.

Anat Rec (Hoboken) 2021 04 10;304(4):872-882. Epub 2020 Sep 10.

Department of Maxillofacial Anatomy, Graduate School of Tokyo Medical and Dental University, Tokyo, Japan.

Three vascular routes to the inner ear are known: (a) through the internal acoustic meatus with the vestibulocochlear nerve; (b) from the endolymphatic duct aperture; and (c) along the canal of Cotugno (CC) inserted into the vestibular part of the ear from the superior or brain side. The third is believed to contain only veins. Examinations of 33 human embryos and fetuses at 6-40 weeks demonstrated that (a) the CC appeared as a recess of epidural mesenchymal tissues at the superior aspect of the otic capsule cartilage in embryos and it was inserted deeply to issue multiple peripheral divisions inferolaterally and posteriorly at midterm; (b) the CC consistently passed through a ring of the superior or anterior semicircular canal and contained both, the arteries from the vestibulocochlear nerve origin at the midbrain and the vein draining into the sigmoid sinus or petrosal sinuses; and (c) the CC appeared not to contribute to ossification of the otic capsule cartilage but, after endochondral ossification of the internal ear, woven bone development occurred along a smooth interface of the CC with the ossified ear. In contrast, another interface between the developing bone and the residual cartilage of the otic capsule was rough and wavy with many short bony columns, called osseous globules. In addition, the endolymphatic duct accompanied veins but no arteries. Our results show that the CC is a major vascular route to the vestibular part of the otic capsule cartilage, but its role appears to be limited after ossification.
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http://dx.doi.org/10.1002/ar.24508DOI Listing
April 2021

Left/right difference in the course and division of the pulmonary arterial branches in the lung upper lobe: A study using human embryos and early fetuses.

J Anat 2020 11 24;237(5):854-860. Epub 2020 Jul 24.

Department of Anatomy, Tokyo Dental College, Tokyo, Japan.

Although left/right differences in a configuration of the pulmonary artery (PA) and its branches are well known, there is little information as to when and how such differences are established. Examination of serial sagittal sections of 25 embryos and fetuses at 6-7 weeks of gestation demonstrated that, at O'Rahilly stages 18-20, the right earliest first branch of PA originated in the anterior side of the upper lobar bronchus and overlay the upper bronchi, in contrast to the left branch which was located posteriorly and constricted medially by the upper posterior bronchus B1 + 2b. The right earliest branch was most likely to correspond to the future superior trunk, while the left branch might be a lingual artery. At stages 21-23, the upper posterior parenchyma was still underdeveloped in the left lung, since the ductus arteriosus and the left common cardinal vein seemed to make the left upper thoracic cavity narrow. Conversely, in the right lung, the thick S2 seemed to require a double arterial supply from both the superior and inferior arterial trunks. On the left, A3 originated at the lung apex and took a long descending course along the lung anterior surface. This high position of A3 might soon be corrected by an increased volume of S3. Overall, in contrast to the lower and middle lobes, early-developed branches of the PA did not accompany upper segmental and subsegmental bronchi. A mechanism "differential growth" seemed to explain how to correct the fetal morphology to provide the adult morphology with variations.
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http://dx.doi.org/10.1111/joa.13264DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7542188PMC
November 2020

Tailored radical hysterectomy for locally advanced cervical cancer.

Int J Gynecol Cancer 2020 08 9;30(8):1136-1142. Epub 2020 Jun 9.

Obstetrics and Gynecology, Hokkaido University Graduate School of Medicine, Sapporo, Japan.

Objective: The survival and prognostic factors for locally advanced cervical cancer treated with nerve-sparing Okabayashi-Kobayashi radical hysterectomy have not been elucidated. We aimed to evaluate the oncological outcomes of those patients after radical hysterectomy with adjuvant chemotherapy.

Methods: This retrospective cohort study was conducted from January 2002 to December 2011. Treatment was conducted at a single tertiary center in northern Japan. We used the Okabayashi-Kobayashi radical hysterectomy with lymphadenectomy. We applied unilateral nerve preservation for stage IIA/IIB cancer if there was a one-sided extension of the disease outside the cervix. Indication for adjuvant therapy was based on Sedlis criteria. High-risk was defined as evidence of lymph node metastasis, pathological parametrial invasion, and a positive/close surgical margin. The choice of adjuvant therapy was chemotherapy which consisted of paclitaxel and cisplatin.

Results: The study included 76 early-stage IB1 (≤4 cm) and IIA1 cervical cancer and 45 locally advanced stage IB2 (>4 cm), IIA2, and IIB disease treated consecutively. The median follow-up was 106 (range: 6-203) months. There were 18 (15%) patients with recurrence, with five of 76 in the early-stage (7%) and 13 of 45 in the locally advanced disease (29%) (P<0.001). For locally advanced cervical cancer, pT classification (P<0.001), lymph node metastasis (P=0.007), and histology (P=0.05) were associated with locoregional recurrence. The five-year locoregional recurrence rate in the locally advanced disease was 20% and 5% in the early-stage disease (P=0.01). The five-year disease-free survival in the locally advanced cervical cancer was 71% and 93% in the early-stage disease (P<0.001). The overall survival in locally advanced disease depended on the adeno-type histology and lymph node metastasis.

Conclusion: The tailored use of nerve-sparing Okabayashi-Kobayashi radical hysterectomy with adjuvant chemotherapy based on tumor histology and lymph node metastasis may be a possible option as a treatment of locally advanced cervical cancer in selected patients.
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http://dx.doi.org/10.1136/ijgc-2020-001387DOI Listing
August 2020

Development and growth of the craniocervical junction with special reference to topographical relationship between the occipital basion, the anterior arch of atlas, and the odontoid process of axis: A study using human fetuses.

Anat Rec (Hoboken) 2021 02 4;304(2):353-365. Epub 2020 Jun 4.

Department of Anatomy, Tokyo Dental College, Tokyo, Japan.

The embryonic occipital bone and odontoid process of the axis are attached and connected by the notochord, but become separated in later development and growth. With special attention to the process of separation, we examined sagittal sections of the craniocervical junction in 18 human fetuses at 8-16 weeks and 22 fetuses at 31-37 weeks. At 8-9 weeks, the anterior arch of atlas was always seen overriding the occipital basal part. The odontoid process was close to the occipital with or without a transient joint cavity until 16 weeks. Near term, the top of the odontoid process was usually higher than the anterior arch, but the former was sometimes (7 of 22) at a level almost equal to or lower than the latter. The apical ligament was evident in a few specimens (5 of 22). A distance between the occipital basion and odontoid process was sometimes less than 1.5 mm (8 of 22) or less than half the thickness of the arch (10 of 22). A transient joint cavity between the basion and odontoid process was often (10 of 22). In three fetuses near term, the atlanto-occipital joint cavity was continuous with the median atlanto-axial joint cavity, and the anterior arch was overriding the occipital basal part. Therefore, rather than stage or age, individual differences were evident in the topographical relationship between the three bony elements at the craniocervical junction. An understanding of the embryology and normal development will aid in the correct interpretation of radiologic images of the pediatric cervical spine.
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http://dx.doi.org/10.1002/ar.24424DOI Listing
February 2021

Oncological Outcomes After Okabayashi-Kobayashi Radical Hysterectomy for Early and Locally Advanced Cervical Cancer.

JAMA Netw Open 2020 05 1;3(5):e204307. Epub 2020 May 1.

Department of Obstetrics and Gynecology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan.

Importance: The role of surgery in early-stage cervical cancer has been established, but it is controversial in locally advanced cervical cancer.

Objective: To determine whether a radical hysterectomy method with extended removal of paracervical tissue for locally advanced cervical cancer is associated with satisfactory oncological outcomes.

Design, Setting, And Participants: This retrospective cohort study was conducted from January 1, 2002, to December 31, 2011, and participants were patients with cervical cancer at a single tertiary center in Northern Japan. The median follow-up period was 106 months, and none of the patients were lost to follow-up at less than 60 months. Data analyses were performed from July 1, 2017, to December 31, 2018.

Exposures: Patients underwent radical hysterectomy using the Okabayashi-Kobayashi method. Bilateral nerve preservation was used for stage IB1/IB2 disease and unilateral nerve preservation for stage IIA/IIB if disease extension outside the uterine cervix was 1-sided. Chemotherapy was used as the choice of adjuvant treatment for patients with an intermediate or high risk of recurrence, while some patients chose or were assigned to radiotherapy.

Main Outcomes And Measures: Primary outcomes were the 5-year local control rate and 5-year overall survival rate along with risk factor analysis.

Results: Of 121 consecutive patients, 76 (62.8%) had early-stage cervical cancer in 2008 International Federation of Gynecology and Obstetrics stages IB1 and IIA1 and 45 (37.2%) had locally advanced cervical cancer in stages IB2, IIA2, and IIB. The median (range) age was 42 (26-68) years. Adjuvant radiotherapy was used in 2 patients (3%) with early-stage cervical cancer and 3 (7%) of those with locally advanced cervical cancer. The 5-year local control rates for early-stage cervical cancer and locally advanced cervical cancer were 99% and 87%, respectively. The 5-year overall survival rates for early-stage cervical cancer and locally advanced cervical cancer were 95% and 82%, respectively. Cox regression analysis showed that lymph node metastasis and histology of adeno(squamous)carcinoma were independent risk factors for the overall survival of patients with cervical cancer treated with radical hysterectomy.

Conclusions And Relevance: The nerve-sparing Okabayashi-Kobayashi radical hysterectomy for locally advanced cervical cancer may provide survival not inferior to radical hysterectomy or radiotherapy in published literature. The applicability of radical hysterectomy with adjuvant chemotherapy for locally advanced cervical cancer needs to be validated by prospective comparative trials.
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http://dx.doi.org/10.1001/jamanetworkopen.2020.4307DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7206506PMC
May 2020

Nerve-sparing radical hysterectomy in the precision surgery for cervical cancer.

J Gynecol Oncol 2020 May 21;31(3):e49. Epub 2020 Jan 21.

Department of Obstetrics and Gynecology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan.

Precision cancer surgery is a system that integrates the accurate evaluation of tumor extension and aggressiveness, precise surgical maneuvers, prognosis evaluation, and prevention of the deterioration of quality of life (QoL). In this regard, nerve-sparing radical hysterectomy has a pivotal role in the personalized treatment of cervical cancer. Various types of radical hysterectomy can be combined with the nerve-sparing procedure. The extent of parametrium and vagina/paracolpium excision and the nerve-sparing procedure are tailored to the tumor status. Advanced magnetic resonance imaging technology will improve the assessment of the local tumor extension. Validated risk factors for perineural invasion might guide selecting treatment for cervical cancer. Type IV Kobayashi (modified Okabayashi) radical hysterectomy combined with the systematic nerve-sparing procedure aims to both maximize the therapeutic effect and minimize the QoL impairment. Regarding the technical aspect, the preservation of vesical nerve fibers is essential. Selective transection of uterine nerve fibers conserves the vesical nerve fibers as an essential piece of the pelvic nervous system comprising the hypogastric nerve, pelvic splanchnic nerves, and inferior hypogastric plexus. This method is anatomically and surgically valid for adequate removal of the parametrial and vagina/paracolpium tissues while preserving the total pelvic nervous system. Local recurrence after nerve-sparing surgery might occur due to perineural invasion or inadequate separation of pelvic nerves cutting through the wrong tissue plane between the pelvic nerves and parametrium/paracolpium. Postoperative management for long-term maintenance of bladder function is as critical as preserving the pelvic nerves.
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http://dx.doi.org/10.3802/jgo.2020.31.e49DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7189083PMC
May 2020

Development and growth of auricular cartilage and muscles: A study using human fetuses.

Int J Pediatr Otorhinolaryngol 2020 Jun 3;133:109973. Epub 2020 Mar 3.

Department of Otolaryngology-Head and Neck Surgery, Tohoku University Graduate School of Medicine, Sendai, Japan. Electronic address:

Objectives: The auricle is a key target in pediatric plastic surgery and is considered to develop from a ring- or funnel-like arrangement of six hillocks in the embryo. However, there has been no report showing the morphologies of the auricular muscle and cartilage after midterm in humans.

Methods: We examined histological sections of 20 near-term human fetuses (29-40 weeks) and those from 7 midterm fetuses (15-16 weeks).

Results: At midterm, the auricular cartilage was a single wavy plate with the helicis major muscle (HMM). The superior and posterior auricular muscles (SAM, PAM) were inserted into the middle parts, and the anterior auricular muscle (AAM) was inserted into the lowest part of the cartilage plate, while the tragus and antitragus were not clearly identified. In near-term fetuses, the cartilage plate varied in size and shape between specimens. The scapha and antihelix were separated from the cartilage plate with major or minor involvement of the HMM from the initial mass along the helix. The SAM inserted to the crus helix or the developing scapha, while the insertion sites of the AAM and PAM into the helix were stable. The tragus-antitragus cartilages were well-developed and they sandwiched a deep notch of skin below the helix tail. The antitragicus muscle was more evident than the tragicus muscle. An unnamed muscle was evident along the external acoustic meatus. The other intrinsic muscles, including the transverse and oblique muscles, might develop from the HMM after birth.

Conclusions: Development of the auricle was advanced after midterm. However, a single wavy plate-like cartilage was maintained until late-stage. Near term, the antihelix and scapha developed from the plate-like core of the auricle and the tragus and antitragus were added in the antero-inferior side of the cartilage plate. Establishment of muscle arrangements was markedly delayed compared to cartilage development. Altogether, the classical concept of an initial funnel-like arrangement of cartilage anlagen might have been biased by studies of adult morphology.
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http://dx.doi.org/10.1016/j.ijporl.2020.109973DOI Listing
June 2020

The incudopetrosal joint of the human middle ear: a transient morphology in fetuses.

J Anat 2020 07 11;237(1):176-187. Epub 2020 Mar 11.

Division of Internal Medicine, Jikoukai Home Visits Clinic, Sapporo, Japan.

In spite of the amount of research on fetal development of the human middle ear and ear ossicles, there has been no report showing a joint between the short limb of incus and the otic capsule or petrous part of the temporal bone. According to observations of serial histological sections from 65 embryos and fetuses at 7-17 weeks of development, the incudopetrosal joint exhibited a developmental sequence similar to the other joints of ossicles, with an appearance of an interzone followed by a trilaminar configuration at 7-12 weeks, a joint cavitation at 13-15 weeks and development of intraarticular and capsular ligaments at 16-17 weeks. These processes occurred at the same time or slightly later than any other joint. Thus, the joint development might coordinate with vibrating ossicles in utero. The growing short limb of incus appeared to accelerate an expansion of the epitympanic recess of the tympanic cavity. Additional observations of five late-stage fetuses demonstrated the incudopetrosal joint located in the fossa incudis joint changing to syndesmosis. Consequently, a real joint with a cavity existed transiently between the human neurocranium and the first pharyngeal arch derivative (i.e. incus) in contrast to the tympanostapedial joint or syndesmosis between the neurocranium and the second arch derivative. The newly described joint might have an effect on the widely accepted primary jaw concept: the mammalian jaw should thus have been created within the first pharyngeal arch, although the connection with neurocranium by the stapes is of a different origin.
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http://dx.doi.org/10.1111/joa.13181DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7309281PMC
July 2020

Cavernous sinus and abducens nerve in human fetuses near term.

Surg Radiol Anat 2020 Jul 28;42(7):761-770. Epub 2020 Feb 28.

Department of Anatomy, Tokyo Dental College, Tokyo, Japan.

A long tortuous course of the abducens nerve (ABN) crossing a highly curved siphon of the internal carotid artery is of interest to neurosurgeons for cavernous sinus surgery. Although a "straight" intracavernous carotid artery in fetuses can change into an adult-like siphon in infants, there is no information on when or how the unique course of ABN is established. Histological observations of 18 near-term fetuses (12 specimens of frontal sections and 6 specimens of sagittal sections) demonstrated the following: (I) the ABN consistently took a straight course crossing the lateral side of an almost straight intracavernous carotid artery; (II) the straight course was maintained when sympathetic nerves joined; (III) few parasellar veins of the developing cavernous sinus separated the ABN from the ophthalmic nerve; and (IV) immediately before the developing tendinous annulus for a common origin of extraocular recti, the ABN bent laterally to avoid a passage of the thick oculomotor nerve. Since the present observations strongly suggested morphologies at birth and in infants, major angulations of the ABN as well as the well-known course independent of the other nerves in the cavernous sinus seemed to be established during childhood. In the human body, the ABN might be a limited example showing a drastic postnatal change in course. Consequently, it might be important to know the unique course of ABN before performing endovascular interventions and skull base surgery for petroclival and cavernous sinus lesions without causing inadvertent neurovascular injuries to neonates or infants.
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http://dx.doi.org/10.1007/s00276-020-02443-5DOI Listing
July 2020
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