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This article presents two cases of anastomosis of hypoglossal nerves in the suprahyoid region in human embryos of CR length 10.75 and 17.5 mm. This variation was studied in two human specimens at this stage of development and compared with the normal arrangement of the hypoglossal nerves in embryos at the same stage. The anastomotic branches were of similar caliber to the main trunks. In both cases the anastomosis was located dorsal to the origin of the geniohyoid muscles and caudal to the genioglossus muscles, lying transversally over the cranial face of the body of the hyoid bone anlage. The anastomosis formed a suprahyoid nerve chiasm on the midline in the embryo of 10.75 mm CR length., Depto. de Anatomía y Embriología, Fac. de Medicina, TRUE, pub

To revisit many theories on fetal development of the manubrium of the sternum, we examined 25 mid-term fetuses at 6-9 weeks of gestation. The initial developmental stage of the manubrium was characterized by a distinct interclavicular mesenchyme that was continuous with the developing clavicles. Because parts of the clavicle in which endochondral ossification occurs originate from the neural crest, the interclavicular mesenchyme seems to be of the same origin. The sternal bands, possibly of the lateral plate origin, were restricted at the anterior ends of the ribs in the paired thoracic walls. The interclavicular mesenchyme extended caudally and laterally to reach the anterior ends of the first ribs, and thus the interclavicular mesenchyme expanded into the intercostoclavicular mesenchyme. Then, the primitive manubrium was delimited by the sternoclavicular joint and its related ligaments, all of which developed from the interclavicular and intercostoclavicular mesenchymes. Although the first ribs were attached to the intercostoclavicular mesenchyme, the former was vimentin-negative in contrast to the latter, positive mesenchyme. Soon afterwards, the small upper end of the sternal bands was integrated into the intercostoclavicular mesenchyme to form the primitive manubrium. The infrahyoid muscles and their supplying nerves maintained a close topographical relation to the interclavicular or intercostoclavicular mesenchyme, whereas the pectoralis major muscle kept attachments to the sternal bands. Consequently, the manubrium of sternum appeared to develop in a complex way at a junction area between derivatives of the neural crest, lateral plate, and somite., Depto. de Anatomía y Embriología, Fac. de Medicina, TRUE, pub

Closure of the middle ear is believed to be closely related to the evolutionary development of the mammalian jaw. However, few comprehensive descriptions are available on fetal development. We examined paraffin-embedded specimens of 20 mid-term human fetuses at 8-25 weeks of ovulation age (crown-rump length or CRL, 38-220 mm). After 9 weeks, the tympanic bone and the squamous part of the temporal bone, each of which was cranial or caudal to Meckel's cartilage, grew to close the lateral part of the tympanosquamosal fissure. At the same time, the cartilaginous tegmen tympani appeared independently of the petrous part of the temporal bone and resulted in the petrosquamosal fissure. Subsequently, the medial part of the tympanosquamosal fissure was closed by the descent of a cartilaginous inferior process of the tegmen tympani. When Meckel's cartilage changed into the sphenomandibular ligament and the anterior ligament of the malleus, the inferior process of the tegmen tympani interposed between the tympanic bone and the squamous part of the temporal bone, forming the petrotympanic fissure for the chorda tympani nerve and the discomalleolar ligament. Therefore, we hypothesize that, in accordance with the regression of Meckel's cartilage, the rapidly growing temporomandibular joint provided mechanical stress that accelerated the growth and descent of the inferior process of the tegmen tympani via the discomalleolar ligament. The usual diagram showing bony fissures around the tegmen tympani may overestimate the role of the tympanic bone in the fetal middle-ear closure., Depto. de Anatomía y Embriología, Fac. de Medicina, TRUE, pub

The glandular odontogenic cyst is a rare jawbone cyst that is considered to be an independent entity, although its histopathological characteristics may lead to an incorrect diagnosis as a low-grade mucoepidermoid carcinoma. The treatment of glandular odontogenic cysts is controversial. Case report: We present two high-risk cases treated with conservative approaches, one by enucleation and curettage and the other by marsupialisation. This report also presents a review of the clinical and pathological aspects of glandular odontogenic cysts, and considers their development. No evidence of disease was observed after 3 years of follow-up in the two cases presented. Conclusions: When possible, treatment plans for these lesions should be customised for each case, taking into account the data available in the literature and patient preferences. For high-risk cases, that are treated with conservative approaches, such as the two cases presented here, strict and regular controls and rigorous radiological follow-up evaluations are mandatory., Depto. de Especialidades Clínicas Odontológicas, Fac. de Odontología, TRUE, pub

This study was performed on 50 human embryos and fetuses between 7 and 17 weeks of development. Reichert's cartilage is formed in the second pharyngeal arch in two segments. The longer cranial or styloid segment is continuous with the otic capsule; its inferior end is angulated and is situated very close to the oropharynx. The smaller caudal segment is in contact with the body and greater horn of the hyoid cartilaginous structure. No cartilage forms between these segments. The persistent angulation of the inferior end of the cranial or styloid segment of Reichert's cartilage and its important neurovascular relationships may help explain the symptomatology of Eagle's syndrome., Depto. de Anatomía y Embriología, Fac. de Medicina, TRUE, pub

The hyoid body is traditionally believed to have a dual origin from second and third arch mesenchyme, but this theory remains controversial. We examined paraffin-embedded sections from the hyoid region of 12 embryos and fetuses at 5-7 weeks of gestation (11-22 mm cranio-rump length). We found that the second (Reichert's cartilage) and third arch mesenchymal condensations did not reach the median area at the base of the tongue. Rather, a midline mesenchymal condensation was seen, and it separated from these arches at an early stage. This condensation was triangular and plate-like, and the cranial part was narrow between the bilateral Reichert's cartilages, while the caudal part was wide along the mediolateral axis between the bilateral primitive greater horns. We considered the midline mesenchymal condensation as the hyoid body anlage. At 7 weeks, a cartilaginous mass appeared in the midline condensation. The hypoglossal nerve changed its direction at the superolateral ends of the midline condensation. We propose that: (i) the hyoid body originates from the hypobranchial eminence via the midline condensation; (ii) the lesser horn originates from the caudal end of Reichert's cartilage; and (iii) the greater horn of the hyoid and the superior cornu of the thyroid cartilage originate from the third arch cartilage. The second and third arches may not regulate early hyoid body morphology., Depto. de Anatomía y Embriología, Fac. de Medicina, TRUE, pub

Pleuroperitoneal canal (PP canal) closure is generally considered to result from an increase in the height, and subsequent fusion, of the bilateral pleuroperitoneal folds (PP folds). However, the folds develop in the area ventral to the adrenal, in contrast to the final position of the diaphragm, which extends to the dorsal side of the adrenal (the "retro-adrenal" diaphragm). We examined the semiserial histology of 20 human embryos and fetuses (crown-rump length 11-40 mm). We started observations of the canal at the stage through which the lung bud extends far caudally along the dorsal body wall to the level of the future adrenal, and the phrenic nerve has already reached the PP fold. Subsequently, the developing adrenal causes narrowing of the dorsocaudal parts of the canal, and provides the bilateral midsagittal recesses or "false" bottoms of the pleural cavity. However, at this stage, the PP fold mesenchymal cells are still restricted to the ventral side of the adrenal, especially along the liver and esophagus. Thereafter, in accordance with ascent of the lung, possibly due to anchoring of the liver to the adrenal, the PP fold mesenchymal cells seem to migrate laterally along the coelomic mesothelium covering some sheet-like loose mesenchymal tissue behind the adrenal. Final closure of the PP canal by lateral migration to provide the "retro-adrenal" diaphragm is a process quite different from the common dogma. It is likely that the sheet-like loose mesenchymal tissue becomes the caudal part of the pleural cavity through a process involving cell death., Depto. de Anatomía y Embriología, Fac. de Medicina, TRUE, pub

Background: Which parts of the male urethra correspond to the female urethra? To resolve this question, we need to understand fetal topographical changes in the urethra, its external sphincter and vagina. The vagina joins the mid-course of the primitive urethra and, later "descends" to the vaginal vestibulum. Methods: We examined histological sections of 14 female and 4 male mid-term fetuses. Results: The inferior end of the vagina was consistently embedded in the posterior wall of the urethra at 9-12 weeks. The supero-inferior level of the vaginal merging was lower in larger fetuses. Thus, the sequential variation in levels appeared to reflect the process of vaginal descent. However, in spite of penetration of the vaginal end into the posterior urethral wall, we found no sign of destruction of the urethral wall after vaginal descent in the low-merging types. Before vaginal descent, the female external sphincter extended posterolaterally around the urethra. Conclusion: The vaginal descent is classically regarded as a relative topographical change, but it is likely to be a result of elongation of the proximal urethra in the superior side of the vaginal merging. Conversely, the distal urethra is likely to be incorporated into the vaginal vestibulum by 15 weeks. During these processes, most of the female external sphincter seems to be expelled from the original anterior position into the vestibular wall as the urethrovaginal sphincter. The adult female urethra seems to correspond to the male prostatic urethra superior to the prostatic colliculus., Depto. de Anatomía y Embriología, Fac. de Medicina, TRUE, pub

Fetal development of the cartilage of the pharyngotympanic tube (PTT) is characterized by its late start. We examined semiserial histological sections of 20 human fetuses at 14-18 weeks of gestation. As controls, we also observed sections of 5 large fetuses at around 30 weeks. At and around 14 weeks, the tubal cartilage first appeared in the posterior side of the pharyngeal opening of the PTT. The levator veli palatini muscle used a mucosal fold containing the initial cartilage for its downward path to the palate. Moreover, the cartilage is a limited hard attachment for the muscle. Therefore, the PTT and its cartilage seemed to play a critical role in early development of levator veli muscle. In contrast, the cartilage developed so that it extended laterally, along a fascia-like structure that connected with the tensor tympani muscle. This muscle appeared to exert mechanical stress on the initial cartilage. The internal carotid artery was exposed to a loose tissue facing the tubal cartilage. In large fetuses, this loose tissue was occupied by an inferior extension of the temporal bone to cover the artery. This later-developing anterior wall of the carotid canal provided the final bony origin of the levator veli palatini muscle. The tubal cartilage seemed to determine the anterior and inferior margins of the canal. Consequently, the tubal cartilage development seemed to be accelerated by a surrounding muscle, and conversely, the cartilage was likely to determine the other muscular and bony structures., Depto. de Anatomía y Embriología, Fac. de Medicina, TRUE, pub

The Cardio-vocal Syndrome (Ortner's syndrome) is described as hoarseness due to the left recurrent laryngeal nerve palsy, caused by a specific cardiovascular pathology. In this case, we present a patient with a giant aortic arch aneurysm with an initial clinical presentation of Cardio-vocal Syndrome. The conventional open-surgery, instead of endovascular approach, was useful to control the morbidity from the compressive effect of adjacent structures, also preventing the aortic rupture. We strongly recommend analyzing carefully the individual case and the clinical targets to resolve, because the new technologies are not always the most effective therapeutic response., Depto. de Anatomía y Embriología, Fac. de Medicina, TRUE, pub

El objetivo de este estudio fue el de investigar el efecto que podía tener la aplicación de cargas laterales controladas de forma temprana, en la osteointegración de implantes dentales. Se analizaron los resultados obtenidos mediante análisis de frecuencia de resonancia (RFA), utilizando unos nuevos prototipos de pilares de compresión (patentados por los autores como modelo de utilidad*) y se demostró que dichas cargas controladas eran beneficiosas para mantener e incluso mejorar, la estabilidad de los implantes colocados durante los estadios iniciales de la cicatrización, acelerando el proceso de osteointegración final. *Modelo de Utilidad: “Pilares compresores perimplantarios”. Inventores: Cano J, Campo J, Bascones A. Número solicitud 200701862. Fecha publicación 1066151., Depto. de Especialidades Clínicas Odontológicas, Fac. de Odontología, TRUE, pub

Torus mandibularis, a well-known protuberance in the dental field, has been defined as a hyperostosis in the lingual aspect of the body of the mandible above the mylohyoid line. However, the origin of the torus mandibularis has not yet been clarified. The aim of this study was to provide a better understanding on the origin of the torus in view of the specific development of Meckel's cartilage at the site corresponding to the adult torus. A total of 40 mid-term human fetuses at 7-16 weeks of gestation were examined. The 10-13 weeks stage corresponded to the critical period in which Meckel's cartilage with endochondral ossification underwent a bending at the beginning of the intramandibular course. At the level of mental foramen, which was located between the deciduous canine and the first deciduous molar germs, the medial lamina of the mandible protruded medially to reach Meckel's cartilage. Thus, the medial lamina covered the posterior and superior aspect of the bending Meckel's cartilage just above the attachment of the developing mylohyoid muscle (i.e., in the oral cavity). We considered a bony prominence, which composed the protruding medial lamina and the bending Meckel's cartilage as the fetal origin of the torus mandibularis. A new theory is proposed for the origin of the torus mandibularis based on the existence of an anlage formed during the development of the mandible, variable in morphology and size, but always constant., Depto. de Anatomía y Embriología, Fac. de Medicina, TRUE, pub

Currently, theories based on acquired calcification of the stylohyoid ligament are believed to be a pathogenesis of syndromes associated with the hyoid apparatus (HA) and its variations. We studied the development of the HA from Reichert´s cartilage using serial sections of 25 human embryos and 45 fetuses. We ensured a fact that, at the initial stage, the HA appeared as two independent cartilage segments, that is, the cranial or styloid segment and the caudal or hyoid segment of Reichert's cartilage, those are connected by a mesenchymal structure. However, between 8 and 10 weeks of development, the mesenchymal connection was lost. We hypothesize that this disconnection is likely to be one of the major factors to make a descent of the hyoid bone in evolution. The stylohyoid ligament was not observed. The variations of the HA, should be considered variations of the development of Reicherts cartilage. If these variations are maintained in the adult, are likely to explain a major symptom associated with Eagle's syndrome., Depto. de Anatomía y Embriología, Fac. de Medicina, TRUE, pub

The objective was to analyze the development of the stapedius muscle to understand an isolated unilateral absence of the tendon of the stapedius muscle in a human fetus. The study was made on 50 human embryos and fetuses aged 38 days to 17 weeks post-conception. The stapedius muscle was formed by two anlagen, one for the tendon, which derives from the internal segment of the interhyale and another for the belly, located in the second pharyngeal arch, medially to the facial nerve and near the interhyale. In the interhyale, two segments were observed forming an angle and delimited by the attachment of the belly of the stapedius muscle. The internal segment will form the tendon. The lateral segment of the interhyale was attached to the cranial end of the Reichert's cartilage (laterohyale), and normally it disappears at the beginning of the fetal period. The right unilateral agenesia of the tendon of the stapedius muscle, observed for the first time in a human fetus of 14 weeks post-conception development (PCd), was brought about by the lack of formation or the regression of the internal segment of the interhyale. It presented a belly of the stapedius muscle with an anomalous arrangement, and with a pseudo tendon originated by the persistence of the external segment of the interhyale., Depto. de Anatomía y Embriología, Fac. de Medicina, TRUE, pub