Sphenomandibular ligament and degenerating Meckel's cartilage revisited: Sequential variations with temporal bone deformity for ligament attachment in near-term human fetuses.

BACKGROUND: The sphenomandibular ligament (SML) is considered to originate from Meckel's cartilage (MC). However, no study has examined how the os goniale contributes to SML development. METHODS: Semiserial histological sections of heads from 18 near-term fetuses at 27-40 weeks of gestation were examined. OBSERVATIONS: The os goniale and the anterior process of the malleus (AP) provided a long, bar-like membranous bone complex that passed through the petrotympanic and tympanosquamosal fissures. Notably, the AP-goniale complex is sometimes elongated inferiorly to join the SML (n = 4 specimens). Along the complex in the bone fissures, a degenerating MC was often present (n = 12). With (n = 6) or without (n = 3) the MC remnant, the tympanic bone (TYB) protruded inferomedially near the tympanosquamosal fissure, and it sometimes continued to a cartilaginous SML (n = 3). The temporal bone squamosa or petrosa provided a similar bony process approaching the SML. The middle meningeal artery often ran between the sphenoid and petrosa. CONCLUSIONS: Most of the specimens (n = 15) exhibited a sequential change from a cartilaginous SML as a continuation of the MC remnant to the ligament after the disappearance of the cartilage. The degenerating MC appeared to cause transformation from the AP-goniale complex and/or TYB to "another ligament" that replaced the usual SML at the upper part. Near the MC remnant, a similar transformation was also suggested on the squamosa or petrosa. The sphenoid spine appeared to originate often from the sphenoid ala major but sometimes from the TYB.

Localization of macrophages and dendritic cells in human thoracic lymph nodes: An immunohistochemical study using surgically obtained specimens.

Both dendritic cells (DCs) and macrophages are bone marrow-derived cells that perform antigen presentation. The distribution of DCs and CD68-positive macrophages were immunohistochemically examined in 103 thoracic nodes obtained from 23 lung cancer patients (50-84 years old) without metastasis. Among three antibodies tested initially-CD209/DCsign, fascin, and CD83-DCsign was chosen as the DC marker. For comparison, 137 nodes from 12 patients with cancer metastasis were also examined histologically. In patients without metastasis, DCs were found as (1) clusters along the subcapsular sinus and in a border area between the medullary sinus and cortex (mean sectional area of multiple nodes at one site, 8.4%) and, (2) rosette-like structures in the cortex (mean number in multiple nodes at one site, 20.5). Notably, DC clusters and rosettes contained no or few macrophages and were surrounded by smooth muscle actin (SMA)-positive, endothelium-like cells. The subcapsular linear cluster corresponded to 5%-85% (mean, 34.0%) of the nodal circumferential length and was shorter in older patients (p = 0.009). DC rosettes, solitary, or communicating with a cluster, were usually connected to a paracortical lymph sinus. Few differences were found between nodes with or without metastasis, but DC cluster sometimes contained abundant macrophages in cancer metastasis patients. The subcapsular DC cluster is not known in the rodent model, in which the subcapsular sinus is filled with macrophages. This quite different, even complementary, distribution suggests no, or less, cooperation between DCs and macrophages in humans.

Development and growth of the human fetal sacroiliac joint revisited: a comparison with the temporomandibular joint.

The human fetal sacroiliac joint (SIJ) is characterized by unequal development of the paired bones and delayed cavitation. Thus, during the long in utero period, the bony ilium becomes adjacent to the cartilaginous sacrum. This mor-phology may be analogous to that of the temporomandibular joint (TMJ). We examined horizontal histological sections of 24 fetuses at 10-30 weeks and compared the timing and sequences of joint cartilage development, cavitation, and ossification of the ilium. We also examined histological sections of the TMJ and humeroradial joint, because these also contain a disk or disk-like structure. In the ilium, endochondral ossification started in the anterior side of the SIJ, extended posteriorly and reached the joint at 12 weeks GA, and then extended over the joint at 15 weeks GA. Likewise, the joint cartilage appeared at the anterior end of the future SIJ at 12 weeks GA, and extended along the bony ilium posteriorly to cover the entire SIJ at 26 weeks GA. The cavitation started at 15 weeks GA. Therefore, joint cartilage development seemed to follow the ossification of the ilium by extending along the SIJ, and cavitation then occurred. This sequence "ossification, followed by joint cartilage formation, and then cavitation" did not occur in the TMJ or humeroradial joint. The TMJ had a periosteum-like membrane that covered the joint surface, but the humeroradial joint did not. After muscle contraction starts, it is likely that the mechanical stress from the bony ilium induces development of joint cartilage.

The so-called absorption process of the pulmonary vein into the left atrium of the heart: a histological study using human embryos and fetuses.

BACKGROUND: Embryonic pulmonary veins (PVs) are believed to be absorbed into the left atrium (LA) to provide an adult morphology in which "four" veins drain separately into the atrium. MATERIALS AND METHODS: Serial histological sections were obtained from 27 human embryos and fetuses. RESULTS: Between 5 and 6 weeks, the four PVs joined together to form a trunk-like structure (initial spatium pulmonalis) that was larger than the initial LA (two-ostia pattern). The cardiac nerves ran inferiorly along the posterior aspect of the four veins, as well as the spatium. At and until 7 weeks, the cardiac nerves were concentrated to elongate the nerve fold, and the latter separated the left PV trunk from the expanding LA (left spatium). Similarly, the right PV opened to a thick and deep LA recess (right spatium). At 8-12 weeks, depending on the growth of the LA, the opening of the left and right PVs became distant, and the spatium was elongated transversely. The left spatium was enlarged to open widely to the proper left atrium in contrast to the right spatium pushed anteriorly by the right atrium. The three-ostia pattern was transiently observed because of the lost delimitation between the left spatium and proper atrium. The myocardium was thin in the left spatium behind the left atrial nerve fold, whereas the right spatium was tube-like with a thick myocardium. CONCLUSIONS: The four-ostia pattern seemed to be established at birth due to a drastically increased venous return from the lung, resulting in a flat smooth left atrial posterior wall.

Development and growth of the calcaneal tendon sheath with special reference to its topographical relationship with the tendon of the plantaris muscle: a histological study of human fetuses.

BACKGROUND AND PURPOSE: The calcaneal tendon sheath has several vascular routes and is a common site of inflammation. In adults, it is associated with the plantaris muscle tendon, but there are individual variations in the architecture and insertion site. We describe changes of the tendon sheath during fetal development. MATERIALS AND METHODS: Histological sections of the unilateral ankles of 20 fetuses were examined, ten at 8-12 weeks gestational age (GA) and twelve at 26-39 weeks GA. RESULTS: At 8-12 weeks GA, the tendon sheath simply consisted of a multilaminar layer that involved the plantaris tendon. At 26-39 weeks, each calcaneal tendon had a multilaminar sheath that could be roughly divided into three layers. The innermost layer was attached to the tendon and sometimes contained the plantaris tendon; the multilaminar intermediate layer contained vessels and often contained the plantaris tendon; and the outermost layer was thick and joined other fascial structures, such as a tibial nerve sheath and subcutaneous plantar fascia. The intermediate layer merged with the outermost layer near the insertion to the calcaneus. CONCLUSION: In spite of significant variations among adults, the fetal plantar tendon was always contained in an innermost or intermediate layer of the calcaneal tendon sheath in near-term fetuses. After birth, mechanical stresses such as walking might lead to fusion or separation of the multilaminar sheath in various manners. When reconstruction occurs postnatally, there may be individual variations in blood supply routes and morphology of the distal end of the plantaris tendon.

Distally-extending muscle fibers across involved joints: study of long muscles and tendons of wrist and ankle in late-term fetuses and adult cadavers.

It is unclear whether forearm and crural muscle fibers extend distally across the wrist and ankle joints, respectively. We hypothesized, in late-term fetuses, an over-production of muscle bellies extending over the joint. Muscle fibers in histological sections from unilateral wrists and ankles of 16 late-term fetuses (30-40 weeks) were examined and compared with 15 adult cadavers. Muscle fibers of the flexor digitorum profundus (FDP) and flexor digitorum superficialis (FDS) in fetuses, especially muscle bellies to the third and fourth fingers, were found to extend far distally beyond the radiocarpal joint. The extensor digitorum and extensor pollicis longus on the extensor side of the wrist were found to carry distally-extending muscle fibers, but these fibers did not extend beyond the distal end of the radius. In the ankle, most muscle bundles in the flexor hallucis longus (FHL), fibularis brevis (FB) and extensor digitorum longus extended distally beyond the talocrural joint, with most FB muscle fibers reaching the level of the talocalcaneal joint. In adult cadavers, muscle fibers of the FDP and FHL did not reach the levels of the radiocarpal and talocrural joints, respectively, whereas the FB muscle belly always reached the talocalcaneal joint. Similarly, some of the FDS reached the level of the radiocarpal joint. Generally, infants' movements at the wrist and ankle could result in friction injury to over-extended muscle. However, the calcaneal and FDP tendons might protect the FB and FDS tendons, respectively, from friction stress.

Temporal and spatial development of intestinal smooth muscle layers of human embryos and fetuses.

The sequential occurrence of three layers of smooth muscle layers (SML) in human embryos and fetus is not known. Here, we investigated the process of gut SML development in human embryos and fetuses and compared the morphology of SML in fetuses and neonates. The H&E, Masson trichrome staining, and Immunohistochemistry were conducted on 6-12 gestation week human embryos and fetuses and on normal neonatal intestine. We showed that no lumen was seen in 6-7th gestation week embryonic gut, neither gut wall nor SML was developed in this period. In 8-9th gestation week embryonic and fetal gut, primitive inner circular SML (IC-SML) was identified in a narrow and discontinuous gut lumen with some vacuoles. In 10th gestation week fetal gut, the outer longitudinal SML (OL-SML) in gut wall was clearly identifiable, both the inner and outer SML expressed α-SMA. In 11-12th gestation week fetal gut, in addition to the IC-SML and OL-SML, the muscularis mucosae started to develop as revealed by α-SMA immune-reactivity beneath the developing mucosal epithelial layer. Comparing with the gut of fetuses of 11-12th week of gestation, the muscularis mucosae, IC-SML, and OL-SML of neonatal intestine displayed different morphology, including branching into glands of lamina propria in mucosa and increased thickness. In conclusions, in the human developing gut between week-8 to week-12 of gestation, the IC-SML develops and forms at week-8, followed by the formation of OL-SML at week-10, and the muscularis mucosae develops and forms last at week-12.

Human lymph node degeneration in the thoracic region: A morphometric and immunohistochemical analysis using surgically obtained specimens.

Lymph node degeneration was examined in 539 mediastinal and intrapulmonary nodes removed from 78 patients, aged 49-82 years, without cancer metastasis. Medullary sinus hyalinization observed in 36.2% of the hilar and 38.5% of the interlobar nodes. Early and smaller lesions were eosinophilic and factor VIII-positive, whereas advanced and large lesions contained a bulky mass of collagenous fiber bundles with few slender cells positive for smooth muscle actin (SMA) and factor VIII, as well as anthracotic macrophages. Subcapsular sinus hyalinization, observed in 4.3% of hilar nodes, was detected as a thick fibrous layer (over 0.2 mm) between the surface cortex and the thickened capsule. The fibrous layer contained SMA-positive slender cells, whereas the thickened capsule contained fibers positive for elastin and factor VIII. These hyalinization lesions occupied 3.6% and 0.8% of the sectional areas of hilar and lower paratracheal nodes, respectively. Areas of early and small cortical degeneration, surrounded by fibers positive for SMA and vimentin, did not contain lymphocytes and macrophages, but contained abundant small stromal cells. Silver staining suggested that advanced cortical degeneration was composed of collagen fibrils other than type I. Fatty tissues, seen in 47.8% of hilar nodes, often extended into and replaced medullary sinus tissue. Island-like remnants of medullary sinuses in areas of fatty degeneration contained various stromal cells positive for SMA, elastin, factor VIII and/or CD34. These degenerative morphologies, however, did not correlate with either age or smoking index. The present cortical degeneration usually seemed to follow hyalinization, but both were likely to occur independently.

Umbilical cord vessels other than the umbilical arteries and vein: a histological study of midterm human fetuses.

At birth, the umbilical cord contains various types of thin vessels that are near and outside the umbilicus and separate from the umbilical arteries and vein. These vessels are regarded as the remnant "vitelline vessels" and are often called "umbilical vessels", although this terminology could lead to confusion with the true umbilical arteries and vein. No study has yet comprehensively examined these vessels using histological sections. Our examination of these vessels in 25 midterm fetuses (gestational age: 10-16 weeks) led to five major findings: (i) all specimens had umbilical branches of the inferior epigastric artery; (ii) 5 specimens had vitelline vein remnants; (iii) 4 specimens had a thin artery originating from the left hepatic artery that ran along the umbilical vein; (iv) 2 specimens had a so-called "para-umbilical vein" that was along the umbilical vein and reached the umbilicus; and (v) all specimens had lymphatic vessels originating from the umbilicus that ran caudally along the umbilical artery. The pelvic vein tributaries were well developed along the intra-abdominal umbilical artery, but did not reach the umbilicus. The lymphatic vessel was distinguished from the veins by an intraluminar cluster of lymphocytes attaching to the endothelium. The arterial branch in the umbilical cord did not accompany veins and lymphatic vessels, in contrast to the mother artery in the rectus abdominis. All these thin vessels seemed to be obliterated when the fibrous umbilical ring grew during late-term. The para-umbilical collateral vein in adults might develop outside the fibrous umbilical ring after birth.

Distal vaginal atresia: a report of a rare type found a late-term fetus and its histological comparison with the normal pelvis.

Solitary distal vaginal atresia is generally caused by a transverse septum or an imperforate hymen. We found a novel type of distal vaginal atresia in a late-term fetus (gestational age approximately 28 weeks) in our histology collection. This fetus had a vaginal vestibule that was closed and covered by a thick subcutaneous tissue beneath the perineal skin in the immediately inferior or superficial side of the imperforate hymen. The uterus, uterine tube, anus, and anal canal had normal development. The urethral rhabdosphincters were well-developed and had a normal topographical relationship with the vagina, but the urethrovaginal sphincter was absent. Thus, vaginal descent seemed to occur normally and form the vestibule. However, the external orifice of the urethra consisted of a highly folded duct with hypertrophied squamous epithelium. Notably, the corpus cavernosum and crus of the clitoris had poor development and were embedded in the subcutaneous tissue, distant from the vestibule. Normally, the cloacal membrane shifts from the bottom of the urogenital sinus to the inferior aspect of the thick and elongated genital tubercle after establishment of the urorectal septum. Therefore, we speculate there was a failure in the transposition of the cloacal membrane caused by decreased elongation of the genital tubercle. The histology of this anomaly strongly suggested that the hymen does not represent a part of the cloacal membrane, but is instead a product that appears during the late recanalization of the distal vagina after vaginal descent. The transverse septum was also likely to form during this recanalization.

Topographical relationships of the yolk sac remnant and vitelline vessels with the midgut loop in the extra-embryonic coelom of human embryos.

The yolk sac is supplied by the vitelline artery and vein (VA, VV), which run through the yolk stalk in combination with the omphaloenteric duct. Moreover, the VV takes a free posterior course outside the midgut mesentery containing the secondarily-developed superior mesenteric vein (SMV). However, the regression process of these structures has not been demonstrated photographically. The present study evaluated serial histological sections from 20 embryos of stages 15-19 or crown-rump length (CRL) 7.5-20 mm. All specimens carried the SMV as sequential tissue slits. However, an omphaloenteric duct with epithelia continuous with the midgut loop was not observed. In smaller embryos (CRL <13 mm) the VA extended distally or anteriorly from the midgut apex in the extra-embryonic coelom, whereas in larger embryos (CRL 16-20 mm) the artery was absent from the distal side of the apex. The entire course or part of the VV outside the mesentery was always seen, but four larger embryos lacked the venous terminal near the duodenum. A vacuole-like remnant of the yolk sac was present in all smaller embryos (CRL <10 mm), but was absent from 7 of the 11 larger embryos. The size of the remnant was equal to the thickness of the VA or VV, with the remnant being sandwiched between the VA and VV. Moreover, the regressing yolk sac often communicated with or opened to the VV. Consequently, the yolk sac regressed first, followed by the regression of the VA until 6 weeks. The yolk stalk was clearly observed until 5 weeks.

Anatomy of the vitelline vein remnant in human embryos and fetuses.

PURPOSE: To demonstrate the entire course of the human vitelline vein (VV) in specimens after degeneration of the yolk sac. METHODS: Sagittal and horizontal histological sections from 8 embryos and 19 fetuses (gestational age approximately 6-12 weeks; crown-rump length 11-61 mm) were examined. RESULTS: Two types of VV remnants were observed: a long VV on the right superior side of the mesentery of the jejunum (VV1) and a short VV on the left inferior side of the mesentery (VV2). The VV1, observed in 12 specimens, was 20-30 microns in diameter and ran dorsally between the right liver lobe and the jejunum, subsequently merging with an initial superior mesenteric vein on the pancreatic head immediately below the superior portion of the duodenum. The VV2, observed in four specimens, passed dorsally between loops of the ileum on the left side of the mesentery of the ileum and connected to the mesentery. Many of the VVs did not originate from the umbilical cord but suddenly started in the sack of physiological herniation. At 10-12 weeks, after herniation, the VVs originated from the umbilicus and were involved by the expanding greater omentum. CONCLUSIONS: The right-sided and left-sided VVs seemed to correspond to right and left VV remnants, respectively, and both took an upstream course outside the mesentery of the jejunum and ileum. The right VV upstream portion was likely to disappear later than the left one, but the timing of degeneration varied greatly among individuals, depending on the topographical relationship between the right liver lobe and the jejunum.

Identification of potential predictive biomarkers and biological pathways and the correction with immune infiltration in the activation of Crohn's disease.

Crohn's disease (CD), a subtype of inflammatory bowel disease (IBD), has increasing prevalence in the world. Due to the lack of cure strategy, most patients with CD develop progressive disease companying with a series of serious complications. Therefore, exploring molecular mechanism differences between active and inactive CD will help in the screening of predict markers and therapeutic targets. In this study, we analyzed differentially expressed genes (DEGs) and molecular pathways through between active and inactive CD patients. In addition, the abundance of 22 immune cell types were assessed by using the CIBERSORT. The hub DEGs were screened out by the CytoHubba in Cytoscape, followed by the least absolute shrinkage and selection operator (LASSO) regression. Finally, the clinical predictive model was constructed by binary logistic regression model. The diagnostic efficacy was tested by receiver operating characteristic (ROC) curve and verified in independent datasets. The results showed that there were 137 DEGs between the active and inactive CD. Most of them were involved in regulating the immunity process. In addition, the decreased abundance of CD8 T cells and the increased abundance of M0, M1 macrophages, and neutrophils were closely related to CD activation. CXCL9, C3AR1, IL1B, and TLR4 were the hub gene and can be applied to the prediction of CD activation. Our results provided important targets for the prediction of CD activation and the selection of therapeutic targets.

Major change in morphology of the talofibular ligaments during fetal development and growth.

BACKGROUND AND PURPOSE: Ankle sprain is often attributed to damage of the anterior and posterior talofibular ligaments (ATFL, PTFL). We compared the morphology of these ligaments in fetuses of different gestational ages (GAs) with the horizontal configuration in adults. MATERIALS AND METHODS: Histological sections of unilateral ankles were examined in 22 fetuses, 10 at GA of 9-12 weeks and 12 at GA of 26-39 weeks. RESULTS: At a GA of 9 to 10 weeks, the ATFL and PTFL consisted of horizontally running straight fibers. The initial ATFL appeared as a thickening of the capsule of the talocrural joint, although the initial PTFL was distant from this joint. Until a GA of 12 weeks, the talus and fibula were separated by an expanding joint cavity. Thus, the initial horizontal ligaments were "pulled" in a distal direction. The distal parts of the ligaments consisted of thin collagenous fibers that had an irregular array, whereas the short proximal parts had thick fibers and a horizontal array. In near-term fetuses, the ligaments contained no horizontal fibers. The ATFL had a wavy course around the thick synovial fold, and was exposed to the joint cavity along the entire course; the distal part was thinner than the proximal part. The PTFL was bulky and consisted of fibers with an irregular array. Therefore, the morphology in a near-term fetus was quite different from that in adults. CONCLUSION: The horizontal and straight composite ankle fibers in adults apparently result from postnatal reconstruction, depending on mechanical demand.

Time taken for a primary tumor to metastasize to the brain and the overall survival of patients with brain metastasis: An analysis of outcomes and factors affecting survival.

BACKGROUND: Brain metastasis (BM) is one of the main causes of high morbidity and mortality in cancer patients. OBJECTIVE: To evaluate the factors that influenced the survival time of patients with primary cancer and survival time after BM. METHODS: Ninety patients with BM diagnosed by magnetic resonance imaging (MRI) were included in the study. We retrospectively analyzed the time to brain metastasis (TTB), overall survival time (OS1) and survival time after BM (OS2). The Kaplan-Meier method and Cox regression analysis were used for survival analyses. RESULTS: The median TTB was 12.0 (95% CI: 9.2-14.8 months), the median OS1 was 31.0 (95% CI: 25.8-35.2 months) and the median OS2 was 14.0 (95% CI: 10.9-17.1 months). Surgical excision of the primary tumor was an independent factor for a prolonged TTB (p< 0.000) and prolonged OS1 (p< 0.000). A single intracranial metastatic lesion was an independent protective factor for prolonged OS1 (p= 0.011) and prolonged OS2 (p= 0.050). TTB, OS1 and OS2 were analyzed with Gender (p< 0.000, < 0.000, and = 0.017, respectively). CONCLUSIONS: It suggests that TTB can be prolonged by primary tumor resection. Furthermore, women with a prolonged TTB and single intracranial metastasis are associated with high OS. These were helpful for the clinical treatment of BM patients before brain metastasis.

Growth in fetuses of the constrictor pharyngis superior with special reference to its meeting with the buccinator: an embryological basis of adult variations in palatopharyngeal anatomy.

PURPOSE: The constrictor pharyngis superior (CPS) initially develops along the posterior wall of the pharyngeal mucosal tube, whereas, during the early phase, the buccinators (BC) are far anterolateral to the CPS. The process and timing of their meeting during fetal growth have not been determined. METHODS: The topographical relationship between the growing BC and CPS was assessed in histological sections from 22 early- and mid-term fetuses of approximate gestational age (GA) 8-16 weeks, and eight late-term fetuses of approximate GA 31-39 weeks. RESULTS: At 8-9 weeks, the palatopharyngeus appeared to pull the CPS up and forward. Until 11 weeks, the CPS was attached to the hamulus of the pterygoid (pterygopharyngeal part). Until 13 weeks, the CPS extended anterolaterally beyond the hamulus to meet the BC. Some BC muscle fibers originated from the oral mucosa. Notably, by 30 weeks, the CPS-BC interface had become covered by or attached to the palatopharyngeus. Muscle fibers of the palatopharyngeus, however, were thinner than those of the CPS and BC. At and near the interface, BC muscle fibers tended to run along the left-right axis, whereas those of the CPS ran anteroposteriorly. A definite fascia (i.e., a future pterygomandibular raphe) was usually absent between these muscles in fetuses. CONCLUSIONS: The excess anterior growth of the CPS with its subsequent degeneration might cause individual anatomical variations in composite muscle bundles of the palatopharyngeus-CPS complex or palatopharyngeal sphincter. A tensile transduction from the BC to the CPS through the raphe seemed unnecessary for cooperative suckling and swallowing after birth.

Gut lumen formation defect can cause intestinal atresia: evidence from histological studies of human embryos and intestinal atresia septum.

Intestinal atresia (IA), a common cause of neonatal intestinal obstruction, is a developmental defect, which disrupts the luminal continuity of the intestine. Here, we investigated (i) the process of lumen formation in human embryos; and (ii) how a defective lumen formation led to IA. We performed histological and histochemical study on 6-10 gestation week human embryos and on IA septal regions. To investigate the topology of embryonic intestine development, we conducted 3D reconstruction. We showed that a 6-7th gestation week embryonic gut has no lumen, but filled with mesenchyme cells and vacuoles of a monolayer of epithelial cells. A narrow gut lumen was formed by gestation week-9, the gut was filled with numerous vacuoles of different sizes, some vacuoles were merging with the developing embryonic gut wall. At gestation week-10, a prominent lumen was developed, only few vacuoles were present and were merging with the intestine wall. At IA septal regions, vacuoles were located in the submucous layer, covered by a single layer of epithelium without glandular structure, and surrounded with fibrous tissue. The mucosal epithelium was developed with lamina propria and basement membrane, but the submucosa and the longitudinal smooth muscle layers were not properly developed. Hence, the vacuoles in IA septum could represent a remnant of vacuoles of embryonic gut. In conclusion, the fusion of vacuoles with the developing intestine wall associates with the disappearance of vacuoles and gut lumen formation in human embryos, and perturbation of these developmental events could lead to IA.

Delayed development of vacuoles and recanalization in the duodenum: a study in human fetuses to understand susceptibility to duodenal atresia/stenosis.

ObjectiveWe compared the cross-sectional areas of the duodenum to the distal small intestine during early gestation to determine if there is a difference in age for recanalization.MethodsSerial sagittal sections of six fetuses of gestational age (GA) 8-10 weeks were examined morphologically to compare the degree of recanalization of the duodenum with to the more distal small intestine.ResultsAt GA 8-9 weeks, the duodenum had more epithelial plugs and vacuoles with no or narrower spaces compared to the distal small bowel. Quantitative assessment at GA 10 weeks showed that the cross-sectional area of the duodenal cavity was significantly less than the distal small bowel.ConclusionThe development and recanalization of vacuoles in the duodenum occurs later than the jejunum and ileum may be involved in the more frequent development of atresia/stenosis of the duodenum compared to more distal gastrointestinal tract.

The Allantois and Urachus: Histological Study Using Human Embryo and Fetuses.

Relatively little is known about allantois and urachal development in early humans.Serial sagittal histological sections from eight human embryos and fetuses were examined to determine allantois development.At gestational age 6-7 weeks, the primitive allantois consists of an enlarged tube located between the umbilical cord and abdominal cavity, whereas the urachus is not yet developed. At 8 weeks, the allantois gradually withdraws from the distal to the proximal end of the umbilical cord, and both the proximal allantois and the rectum (hindgut) start to develop into the cloaca. At 10 weeks, the allantois was located mostly in the abdominal cavity.The urachus forms from the distal end of the allantois and develops into a closed fibrous cord between the base of the urinary bladder and the umbilicus. The urogenital sinus forms from the proximal end of the allantois.

Human orbital muscle in adult cadavers and near-term fetuses: its bony attachments and individual variation identified by immunohistochemistry.

PURPOSE: To compare fetal and adult morphologies of the orbital muscle (OM) and to describe the detailed topographical anatomy in adults. METHODS: Using unilateral orbits from 15 near-term fetuses and 21 elderly cadavers, semiserial horizontal or sagittal paraffin sections were prepared at intervals of 20-100 µm. In addition to routine histology, we performed immunohistochemistry for smooth muscle actin. RESULTS: At near term, the OM consistently extended widely from the zygomatic bone or the greater wing of the sphenoid to the maxilla or ethmoid. Thus, it was a large sheet covering the future inferior orbital fissure. In contrast, the adult OM was a thin and small muscle bundle connecting (1) the greater wing of the sphenoid to the maxilla (11/19 cadavers), (2) the lesser wing of the sphenoid to the maxilla (5/19) or the greater wing (3/19). The small OM was likely to be restricted within the greater wing (5/19 cadavers) or the maxilla (3/19). Two of these five types of OM coexisted in eight orbits. OM attachment to the lesser wing was not seen in fetuses, whereas ethmoid attachment was absent in adults. CONCLUSIONS: The lesser wing attachment of the OM seemed to establish after birth. A growing common origin of the three recti was likely involved in "stealing" the near-term OM attachment from the ethmoid. The strong immunoreactivity of remnant-like OM in the elderly suggests that OM contraction is still likely to occur against the increased flow through a thin vein. However, the contraction might have no clinical significance.