食管胃连接处的肌纤维排列形式

观察３０例成人尸体食管胃连接处的肌纤维排列形式，该处肌肉分为浅，深两层。浅层肌为纵简装排；虺支肌为环斜排列。在“食管前庭”上端的浅层，可见两条肌束，其肌纤维为管状食管纵肌的延续，斜行向下移行为胃纵肌。深层的环形肌纤维在管状食管与前庭连接处增厚，位于贲门切迹上方２７。０６±２。１１ｍｍ外。在“食管前庭”中段，其深层环形肌纤维移行为螺旋形和扣状排列形式。在“食管前庭”末端，两条半环形肌束分别位于胃底测     

A light microscope study of the distribution of muscle in the frog esophagus and stomach.

The present study reports light microscopical observations of the distribution of muscle in the esophagus and stomach of both the bull frog (Rana catesbeiana) and the African clawed frog (Xenopus laevis). The external muscle coat of the upper half of the esophagus in both species had several collagen coated bundles of striated muscle fibres around the circumference. These striated muscle bundles ran longitudinally from the pharynx to around the vicinity of the center of the esophagus. Beneath these striated muscle bundles was an inner circular layer of smooth muscle. In both species, the inner circular layer of smooth muscle was particularly thick in the region close to the pharynx. In the bull frog, the lower half of the esophagus lacked striated muscle. However, the circular smooth muscle layer, extending from the upper half of the esophagus, was also observed throughout the lower half of the esophagus. An outer longitudinal layer of smooth muscle developed towards the terminal portion of the esophagus such that in this region, both outer longitudinal and inner circular layers of smooth muscle were observed. Similarly in the African clawed frog, the inner circular layer of smooth muscle was continuous along the full length of the esophagus. Again, no striated muscle bundles were observed in the lower half of the esophagus. However, the outer longitudinal layer of smooth muscle was seen to develop in the middle region of the esophagus. Its muscle layer extended to the terminal portion of the esophagus. Thus, both outer longitudinal and inner circular layers of smooth muscle were observed throughout the lower half of the esophagus. In both frogs, the thickness of the outer longitudinal and inner circular layers of smooth muscle changed before and after the esophago-gastric junction. In both frogs, no muscularis mucosa was observed in the esophageal wall. However, in the lower half of the esophagus of the African clawed frog, small bundles of smooth muscle were observed here and there in the submucosa. A fully developed muscularis mucosa with both outer longitudinal and inner circular layers was observed in the upper stomach of both frogs.     

Distribution of vagal CGRP-immunoreactive fibers in the lower esophagus and the cardia of the stomach of the rat

We have examined whether the smooth muscle fibers in the lower esophagus and the cardia of the stomach of the rat are innervated by calcitonin gene-related peptide-immunoreactive (CGRP-ir) fibers coming from the nucleus ambiguus. Immunohistochemical observations revealed that there were many CGRP-ir fibers and free endings in all external muscular layers of the lower esophagus and the cardia. Occasionally, bundles of CGRP-ir fibers were found in the inner oblique muscle layer of the cardia. There were also many CGRP-ir fibers in the mucous membrane in the lower esophagus and the cardia. When Fluorogold was injected into the junction of the lower esophagus and the cardia, many retrogradely labeled neurons were found in the compact formation of the nucleus ambiguus and the dorsal motor nucleus of the vagus nerve. Double labeling with immunohistochemistry for CGRP and the retrograde tracer Fluorogold showed that almost all of neurons (more than 90%) in the nucleus ambiguus that project to the lower esophagus or the cardia contained CGRP, while no CGRP-ir neurons were found in the dorsal motor nucleus of the vagus nerve. These results indicate that the vagal motor neurons of the nucleus ambiguus that contain CGRP project not only to the striated muscle fibers of the esophagus but also to the smooth muscle fibers of the external muscle layers of the lower esophagus and the cardia.     

Morphology of the Upper Esophageal Sphincter or Cricopharyngeus Muscle Revisited

Histological examination of specimens from 22 donated elderly cadavers and 15 human fetuses revealed that the cricopharyngeus muscle (CPM) provided (1) posterior circular muscle fibers adjacent to the external aspect of the uppermost esophageal circular muscle and (2) a thin anterior sling connecting to that same muscle. Another thick lateral bundle of longitudinal muscle originated independently from a fascia covering the posterior cricoarytenoideus muscle, extended laterally and posteriorly, and occupied a space after the CPM had disappeared at the anterolateral angle of the esophagus below the cricoid. The thick fascia contained abundant elastic fibers along the internal surface of the pharyngeal constrictors (posteromedial elastic lamina), but was interrupted or discontinued near the cricoid origin of the CPM. As no submucosal smooth muscles or elastic fibers were connected to it, the CPM did not accompany a specific elastic structure at the interface between the pharyngeal and esophageal muscles. In fetuses, the medial half of the CPM was inserted into the cricoid while the lateral half continued to the sternothyroideus muscle or ended at a fascia covering the cricothyroideus. These anterolateral ends provided a mechanical load for longitudinal growth of the pharyngeal constrictors. Consequently, the CPM was unlikely to develop and grow to form the upper esophageal sphincter, and the muscle bundle crossing the lateral aspect of the pharyngo-esophageal junction appeared to have a secondary passive role as a sphincter. This situation contrasts with that of another sphincter in the human body formed from striated muscle. Clin. Anat., 33:782–794, 2020. © 2019 Wiley Periodicals, Inc.     

Unique structure of the esophago-gastric junction of the house musk shrew (Suncus murinus)

The house musk shrew (Suncus murinus) belongs to the Order Insectivora, and has been used for the research in comparative anatomy as one of the most primitive placental mammals. Another feature of this shrew is its ability to easily vomit which mimics the human emesis or motion sickness response. The house musk shrew has thus been utilized as a rare small experimental animal for studies on the neurophysiological mechanism of vomiting. However, there is no report investigating the morphological background of vomiting in this species. The purpose of this study is to provide detailed morphological and histological features of the house musk shrew stomach as they possibly correlate to vomiting. The stomachs of ten female house musk shrews were used. Six of them were the wild type (Jic: SUN), two were the high-emesis strain (Jic: SUN-Her) and the rest of them were the low-emesis strain (Jic: Sun-Ler). In addition to the macroscopic anatomy, the region of esophago-gastric (EG) junction and the gastric groove were observed using the light and transmission electron microscopy. Although evident differences in structure of stomach were not found among the three strains, some interesting findings in comparative anatomy were noted. The circular valve-like thick fold was seen at the cardiac portion, which protruded into the esophageal lumen forming a deep groove between its frilled edge and the esophagus. The second frilled ridge was often found as inner ridge of this valve-like thick fold. The esophago-gastric junction between the stratified squamous and the simple columnar epithelium was found at the edge of the second frilled ridge. The lamina propria of the frilled edge was occupied by loose connective tissue and many large lumens of lymphatic vessels. The lamina muscularis mucosae, which developed in the esophageal region, was not in the main frilled edge. A well-developed inner muscle layer was found around the base of the fold, which seemed to correspond to the human lower esophageal sphincter. Cardiac glands occupied most of the thick cardiac wall, forming complicated crypts lined by simple columnar epithelium, and ducts of cardiac gland opened to these crypts. Since the house musk shrew has no esophageal gland, these cardiac glands may actively protect the lower part of the esophagus. In the cardiac wall, the inner circular and outer longitudinal muscle layer largely crossed each other obliquely as same as other reports. The transition area from the striated to the smooth muscle was observed in the sphincter surrounding the distal end of the cardiac wall. The gastric groove, lined by simple columnar epithelium in the lesser curvature, which has been reported to play a role as a shortcut from the cardia to the pylorus in other species including rodents, was also confirmed in the house musk shrew. The mucosal fold in the boundary between the esophageal and the gastric epithelium of house musk shrew may correspond to the structure called the limiting ridge (in mouse, rat and hamster), the teeth-like fimbria or Grenzfalten (in vole), and the gastric teeth (in crustacean and mollusk). The valve-like mucosal fold protruding into the esophageal cavity, the well developed huge cardiac glands, and the cardiac sphincter localized distally to the cardiac gland appear to facilitate the regurgitation of the stomach content, that is, vomiting. These findings suggest that this structure might have developed to support the feeding habit of house musk shrew, and that the differences of strains in vomiting may be determined by neurophysiological mechanisms.     

Muscular Architecture of the Abdominal Part of the Esophagus and the Stomach

The aim of this study was to clarify the muscular architecture of the abdominal part of the esophagus and the stomach. This study investigated 60 embalmed Korean adult cadavers. The circular and oblique fibers of the stomach that originated from the abdominal part of the esophagus crossed each other in the cardia. The arrangement of the circular fibers of the stomach differed between its anterior and posterior surfaces in all specimens (100%). On the posterior surface of the stomach, the circular and longitudinal fibers on the greater curvature merged and ran parallel toward the fundus. The three layers of the musculature of the stomach have different arrangements in different regions of the stomach and are connected to each other. Understanding the muscular architecture of the stomach and the abdominal part of the esophagus can be helpful when evaluating stomach motility and performing various types of gastrectomy. Clin. Anat. 33:530–537, 2020. © 2019 Wiley Periodicals, Inc.     

Acetylcholinesterase and choline acetyltransferase staining of neurons in the opossum esophagus

The purpose of the present investigation was to identify and compare cholinergic intramural neurons in the lower esophageal sphincter and esophageal body by histochemical staining for acetylcholinesterase and the enzyme that synthesizes acetylcholine, choline acetyltransferase. Opossums were anesthetized and their abdominal cavity was opened by a midline incision to expose the esophagogastric junction. The lower esophageal sphincter was identified manometerically and localized in situ with markers. Tissues were removed, rapidly frozen in freon cooled with liquid nitrogen and serial cryostat sections were obtained from the lower esophageal sphincter and esophageal body. Sections were stained with one of the above histochemical procedures and adjacent sections were stained with Solachrome cyanin , which differentially stains nerve elements from muscle fibers. The muscle of the lower esophageal sphincter and esophageal body was stained with nonspecific cholinesterase with some selectivity of intensity of reaction in the various smooth muscle layers. All identifiable plexus neurons in the esophagus stained for nonspecific cholinesterase and acetylcholinesterase. Nerve fiber tracts were also stained for acetylcholinesterase within the longitudinal and circular layers of the tunica muscularis. Reaction for choline acetyltransferase showed no staining in the muscle layers or nerve fiber tracts of either part of the esophagus studied; however, selected neurons within the myenteric plexus of both regions (approximately 38%) were reactive. There was no significant difference in the number of positive choline acetyltransferase neurons in the lower esophageal sphincter or esophageal body.     

The atrioventricular valves of the guinea-pig. I. A light microscopic study

The atrioventricular valves contain dense plexuses of adrenergic nerve fibers, derived from atrial and ventricular sources. Most of the adrenergic terminals are located in the lower third of the cusps. This region, which contains adrenergic terminals and acetylcholinesterase-positive nerve endings is devoid of muscle fibers and blood vessels. The acetylcholinesterase-positive endings may be sensory; and norepinephrine released from the adrenergic terminals may influence their performance. In the mitral valve, the atrial adrenergic plexus is separated from the ventricular plexus by a narrow zone that is free of adrenergic nerves. In most other respects the innervation, musculature and vascular supply of the mitral valve is similar to that of the tricuspid valve. Each valve has an intrinsic skeleton. This is made up of collagenous “ribs” that pass up from the chordae tendineae and fan out in the cusps. “Ribs” from adjacent chordae overlap and interweave, forming a complex support system. The musculature of the valves is complex and seems to have several functions. The annular muscle around the valve orifice may act as an atrioventricular sphincter, while offshoots that insert into the collagenous “ribs” of the cusp may assist the papillary muscles in maintaining tension on the cusps. The meshwork of muscle fibers between “ribs” may prevent ballooning of the cusps during systole. We found no consistent association between valvar muscles and nerves. Blood vessels are restricted mainly to the upper muscular part of the cusps, although a few capillary loops descend into the midzone of the cusps.     

Congenital leiomyomatous epulis: a case report with immunohistochemical study

The histologic and immunohistochemical findings of an extremely rare case of congenital soft tissue mass on the alveolar ridge in an infant are reported. The lesion clinically mimicked an ordinary congenital epulis (congenital granular cell epulis, granular cell tumor of the newborn); however, histologically it consisted of a conglomerate of spindle-shaped cells, akin to smooth muscle cells, which formed interlacing and whorled fasciculi. Nerve fibers with myxoid degeneration, capillaries and muscle walled small vessels intermingled with fasciculi of spindle-shaped cells. The border between the conglomerate of spindle-shaped cells and the surrounding connective tissue was not evident. Immunohistochemically, most of the spindle-shaped cells were intensely positive for antibodies to alpha-smooth muscle actin, HHF-35 and desmin. These findings suggest that the lesion was composed of mature smooth muscle cells that were of hamartomatous or choristomatous nature. The term 'congenital leiomyomatous epulis' is proposed.     

Pancreatic acinar cells—a normal finding at the gastroesophageal junction? Data from a prospective Central European multicenter study

Pancreatic acinar cells are a well-recognized finding at the gastroesophageal junction, but their histogenesis and biological significance are unclear. From the prospective Central European multicenter histoGERD trial, we recruited 1,071 individuals undergoing gastroscopy for various non-selected reasons. Biopsy material was systematically sampled from the gastroesophageal junction and from the stomach. The study aimed to assess the prevalence of pancreatic acinar cells and to relate their presence to various histologic and clinical features. Overall, pancreatic acinar cells were observed in 184 (17.2 %) participants. Individuals diagnosed with pancreatic acinar cells were slightly younger than those without (median 50 vs. 53 years; p?=?0.009). There was no association with patients’ symptoms and/or complaints or with an endoscopic diagnosis of esophagitis or Barrett’s esophagus. Regarding histology, pancreatic acinar cells were not associated with features of the squamous epithelium indicating reflux disease, such as basal cell hyperplasia, papillary elongation, dilation of intercellular spaces, and inflammatory cell number, but were associated with the presence of cardiac mucosa (p?<?0.001), oxyntocardiac mucosa (p?<?0.001), and intestinal metaplasia (p?=?0.038), respectively. No association with Helicobacter pylori infection or diagnosis of gastritis was noted. In conclusion, pancreatic acinar cells are a common finding at the gastroesophageal junction, and no association with either reflux disease (histologically or endoscopically) or diagnosis of gastritis was observed. These data suggest a congenital rather than an acquired (metaplastic) origin of pancreatic acinar cells at the gastroesophageal junction. This questions the term “pancreatic acinar metaplasia” which is currently widely used for their diagnosis.     

新生大鼠脊神经节与心肌细胞联合培养的光镜观察

将新生大鼠的脊神经节与心肌细胞进行联合培养，用相差显微镜和Ｈｏｌｍｅｓ还原银染色观察了神经元的生长以及神经纤维与心肌细胞之间的关系。脊神经节与心肌细胞联合培养７２￣９６小时可观察到神经纤维终止于搏动的心肌细胞表面。神经节组织块周围有许多神经纤维在心肌细胞表面相互交织成网状。交叉的神经纤维相互粘连在一起，终止于搏动的心肌细胞表面的一条神经纤维移动将会牵动邻近的交叉神经纤维网。Ｈｏｌｍｅｓ还原银染色结     

Histo-topographic study of the longitudinal anal muscle

The longitudinal anal muscle (LAM) has been described as a vertical layer of muscular tissue interposed between the circular layers of the internal (IAS) and external (EAS) anal sphincters. There is, however, no general agreement in the literature on its composition and attachments. The aim of this study was to investigate the histological structure, attachments, and topography of the LAM in order to evaluate its role in continence and defecation, thus enhancing knowledge of the surgical anatomy of this region. After in situ formalin fixation, the pelvic viscera were removed from eight male and eight female cadavers (age range: 52-72 years). Serial macrosections of the bladder base, lower rectum and anal canal, cervix and pelvic floor complex, cut in the transverse (six specimens) and coronal (six specimens) planes, underwent histological and immunohistochemical studies. Four specimens were studied using the E12 sheet plastination technique. The LAM was identified in 10/12 specimens (83%). Transverse and coronal sections made clear that it is a longitudinal layer of muscular tissue, marking the boundary between the internal and external anal sphincters. From the anorectal junction it extends along the anal canal, receives fibers from the innermost part of the puborectalis and the puboanalis muscles, and terminates with seven to nine fibro-elastic septa, which traverse the subcutaneous part of the external anal sphincter, reaching the perianal dermis. In the transverse plane, the mean thickness of the LAM was 1.68 +/- 0.27 mm. Immunohistochemical staining showed that the LAM consists of predominantly outer striated muscle fibers and smaller numbers of inner smooth muscle fibers, respectively coming from the levator ani muscle and from the longitudinal muscular layer of the rectum. The oblique fibers suggest that the LAM may represent the intermediate longitudinal course of small bridging muscle bundles going reciprocally from the striated EAS to the smooth IAS and vice versa. The spatial result is the helical course of striated and smooth muscle fibers between the EAS and IAS, which contribute not only to the narrowing but also to some shortening of the anal canal during sphincter contraction. Thus, rather than being a boundary, the LAM gives anatomical evidence of a functional connection between two muscle systems with different structures and topography.     

Idiopathic hydronephrosis. Light microscopic features and pathogenesis

A histological study of surgical specimens of idiopathic hydronephrosis demonstrated an abnormal muscle arrangement at the ureteropelvic junction in 18 of 26 cases. We believe this abnormality to be the cause in these cases. At this junction, the muscle bundles, instead of displaying the normal interwoven (braided) pattern, are arranged into an outer circular and an inner longitudinal layer. This abnormal muscle arrangement can be attributed to local failure of the physiological uncoiling during growth and development.     

The neural regulation of the mammalian esophageal motility and its implication for esophageal diseases

In contrast to the tunica muscularis of the stomach, small intestine and large intestine, the external muscle layer of the mammalian esophagus contains not only smooth muscle but also striated muscle fibers. Although the swallowing pattern generator initiates the peristaltic movement via vagal preganglionic neurons that project to the myenteric ganglia in the smooth muscle esophagus, the progressing front of contraction is organized by a local reflex circuit composed by intrinsic neurons similarly to other gastrointestinal tracts. On the other hand, the peristalsis of the striated muscle esophagus is both initiated and organized by the swallowing pattern generator via vagal motor neurons that directly innervate the muscle fibers. The presence of a distinct ganglionated myenteric plexus in the striated muscle portion of the esophagus had been enigmatic and neglected in terms of peristaltic control for a long time. Recently, the regulatory roles of intrinsic neurons in the esophageal striated muscle have been clarified. It was reported that esophageal striated muscle receives dual innervation from both vagal motor fibers originating in the brainstem and varicose intrinsic nerve fibers originating in the myenteric plexus, which is called ‘enteric co-innervation’ of esophageal motor endplates. Moreover, a putative local neural reflex pathway that can control the motility of the striated muscle was identified in the rodent esophagus. This reflex circuit consists of primary afferent neurons and myenteric neurons, which can modulate the release of neurotransmitters from vagal motor neurons in the striated muscle esophagus. The pathogenesis of some esophageal disorders such as achalasia and gastroesophageal reflux disease might be involved in dysfunction of the neural networks including alterations of the myenteric neurons. These evidences indicate the physiological and pathological significance of intrinsic nervous system in the regulation of the esophageal motility. In addition, it is assumed that the components of intrinsic neurons might be therapeutic targets for several esophageal diseases.     

Plexus muscularis profundus and associated interstitial cells. I. Light microscopical studies of mouse small intestine

The zinc iodide/osmic acid (ZIO) method was used in a modification that selectively stained nerves and associated interstitial cells of Cajal (ICC ) of muscularis externa. Due to its selectivity the method allowed a detailed stereoscopical analysis of whole mounts with respect to the topography and morphology of these elements. The method thus assisted and expanded our ultrastructural studies. The ZIO staining allowed a distinction of four morphologically different interstitial cell types (ICC-I-IV) confined to four compartments. The stained components were: (1) A rich plexus of highly ramified intestitial cells (1CC-II) in the subserous laver. (2) Auerbach's plexus with an associated extensive plexus of interstitial cells (ICC-I) in close contact with tertiary fasciculi. (3) Nerve fasciculi of the outer division of the circular muscle layer. These formed a nerve plexus in a well-defined plane in the outermost cell layers (plexus muscularis super-ficialis), with few fasciculi located internal to this plexus. A few bipolar interstitial cells (ICC-IV) were associated with nerve fasciculi of this region. (4) A nerve plexus located in the region between the two subdivisions of the circular muscle, plexus muscularis profundus (PMP). PMP was revealed throughout the small intestine as a continuous network of elongated, circularly oriented meshes. The pattern of connections between PMP and the other enteric plexuses was studied stereoscopically. Ganglion cells intrinsic to PMP occurred widely scattered. Interstitial cells associated with PMP (ICC-III) were arranged in a plexiform manner; their morphology and relations to nerves were investigated in great detail. A selective innervation of ICC-III via axons of PMP was strongly supported.     

The Distribution of Muscles Fibers and Their Types in the Female Rat Urethra: Cytoarchitecture and Three‐Dimensional Reconstruction

An attempt to explore urethral cytoarchitecture including the distribution of smooth muscles and fast and slow striated muscles of adult female Sprague Dawley rat—a popular model in studying lower urinary tract function. Histological and immunohistochemical stainings were carried out to investigate the distribution of urethral muscle fibers and motor end plates. The urethral sphincter was furthermore three‐dimensionally reconstructed from serial histological sections. The mucosa at the distal urethra was significantly thicker than that of other segments. A prominent inner longitudinal and outer circular layer of smooth muscles covered the proximal end of urethra. Thick circular smooth muscles of the bladder neck region (urethral portion) decreased significantly distalward and longitudinal smooth muscles became 2‐ to 3‐fold thicker in the rest of the urethra. An additional layer of striated muscles appeared externally after neck region (urethra) and in association with motor end plates ran throughout the remaining urethra as the striated sphincter layer. Most striated muscles were fast fibers while relatively fewer slow fibers often concentrated at the periphery. A pair of extraneous striated muscles, resembling the human urethrovaginal sphincter muscles, connected both sides of mainly the distal vagina to the dorsal striated muscles in the wall of the middle urethra. The tension provided by this pair of muscles, and in conjunction with the striated sphincter of the urethral wall, was likely to function to suspend the middle urethra and facilitates its closure. Comprehensive morphological data of urethral sphincter offers solid basis for researchers conducting studies on dysfunction of bladder outlet. Anat Rec, 296:1640–1649, 2013. © 2013 Wiley Periodicals, Inc.     

Structure of the esophagus in the adult opossum, Didelphis virginiana.

The structure of the esophagus has been studied in the adult opossum, Didelphis virginiana. A thickening of both layers of the muscularis externa occurs at the origin of the esophagus and may represent the upper esophageal sphincter; a massive expansion of the muscularis mucosae occurs in the region of the lower esophageal sphincter. The distribution of striated, mixed and smooth muscle in the muscularis externa differs in the inner and outer layers and elements of the myenteric plexus are found to occur even in the region of striated muscle; however, the ganglia of this plexus become much more prominent as smooth muscle makes its appearance. Esophageal glands are found in the lamina propria where they are confined to the 2 ends. They are especially prominent at the distal end where they are responsible for the formation of permanent transverse folds. Similar glands are found in the submucosa, scattered throughout the length of the esophagus but distally, in the region of the transverse folds, the submucous glands disappear. In both of these layers, the glands contain mucous, serous and myoepithelial cells.     

Nerves in the intersphincteric space of the human anal canal with special reference to their continuation to the enteric nerve plexus of the rectum

In the intersphincteric space of the anal canal, nerves are thought to “change” from autonomic to somatic at the level of the squamous‐columnar epithelial junction of the anal canal. To compare the nerve configuration in the intersphincteric space with the configuration in adjacent areas of the human rectum, we immunohistochemically assessed tissue samples from 12 donated cadavers, using antibodies to S100, neuronal nitric oxide synthase (nNOS), and tyrosine hydroxylase (TH). Antibody to S100 revealed a clear difference in intramuscular nerve distribution patterns between the circular and longitudinal muscle layers of the most inferior part of the rectum, with the former having a plexus‐like configuration, while the latter contained short, longitudinally running nerves. Most of the intramural ganglion cells in the anal canal were restricted to above the epithelial junction, but some were located just below that level. Near or at the level of the epithelial junction, the nerves along the rectal adventitia and Auerbach's nerve plexus joined to form intersphincteric nerves, with all these nerves containing both nNOS‐positive parasympathetic and TH‐positive sympathetic nerve fibers. Thus, it was histologically difficult to distinguish somatic intersphincteric nerves from the autonomic Auerbach's plexus. In the intersphincteric space, the autonomic nerve elements with intrapelvic courses seemed to “borrow” a nerve pathway in the peripheral branches of the pudendal nerve. Injury to the intersphincteric nerve during surgery may result in loss of innervation in the major part of the internal anal sphincter. Clin. Anat. 26:843–854, 2013. © 2013 Wiley Periodicals, Inc.     

Does an anatomical sphincter exist in the distal esophagus?

The presence or absence of a lower esophageal sphincter (LES) has been a matter of debate. The aim of the present study was to revisit the gastro-esophageal region in an attempt to elucidate further the presence or absence of such a structure. The distal part of the esophagus was investigated in 12 fixed and 2 fresh cadavers with the aid of a dissecting microscope. Our findings demonstrated a clear thickening of the circular muscle layer of the gastro-esophageal region in all specimens. The mean length of this muscular thickening was measured to be 3.1 cm. The thickest part of this segment was at its midsection. This midpart had a mean thickness of 5.4 mm. The thickness of the esophagus immediately superior to the sphincter had a mean of 2.7 mm. We believe that the findings of the present study strongly suggest the presence of an internal esophageal sphincter in the distal esophagus. Physiologic experimentation would now be necessary to verify our morphological findings.     

Development and innervation of soleplates in the freely grafted extensor digitorum longus (EDL) muscle in the rat

The ultrastructural events in the establishment of the neuromuscular junction of the freely grafted extensor digitorum longus (EDL) muscle of the rat were studied 1–120 days after grafting. The original axons and muscle fibers, including soleplates, degenerated during the first few days, but Schwann cells and basal laminae persisted. Myofibers regenerated within the original basal laminae. Indentations of the sarcolemma, termed “presumptive synaptic clefts” (PSC), wer found on myotubes from 7-day grafts. Schwann cells and residual acetylcholinesterase were invariably associated with the PSC, suggesting that the PSC developed at the site of the original soleplate. Nerves entered the grafts 10 days postoperatively and contacted the PSC of the regenerating muscle fibers on the 18–20th day. The secondary synaptic clefts of these “reconstructed” soleplates extended far beyond the subaxonal region. A second type of soleplate appeared on the 18–20th day. These soleplates were similar to those found in embryonic muscle and were considered to have been induced to form “de novo” by the presence of the nerves. When grafts were placed in permanently denervated limbs the “reconstructed” soleplates appeared, but the “de novo” type did not. These results shows that information directing the morphogenesis and innervation of the soleplate persists after the original muscle fibers and axons of a graft degenerate and regenerate.