Atavistic and vestigial anatomical structures in the head, neck, and spine: an overview.

Organisms may retain nonfunctional anatomical features as a consequence of evolutionary natural selection. Resultant atavistic and vestigial anatomical structures have long been a source of perplexity. Atavism is when an ancestral trait reappears after loss through an evolutionary change in previous generations, whereas vestigial structures are remnants that are largely or entirely functionless relative to their original roles. While physicians are cognizant of their existence, atavistic and vestigial structures are rarely emphasized in anatomical curricula and can, therefore, be puzzling when discovered incidentally. In addition, the literature is replete with examples of the terms atavistic and vestigial being used interchangeably without careful distinction between them. We provide an overview of important atavistic and vestigial structures in the head, neck, and spine that can serve as a reference for anatomists and clinical neuroscientists. We review the literature on atavistic and vestigial anatomical structures of the head, neck, and spine that may be encountered in clinical practice. We define atavistic and vestigial structures and employ these definitions consistently when classifying anatomical structures. Pertinent anatomical structures are numerous and include human tails, plica semilunaris, the vomeronasal organ, levator claviculae, and external ear muscles, to name a few. Atavistic and vestigial structures are found throughout the head, neck, and spine. Some, such as human tails and branchial cysts may be clinically symptomatic. Literature reports indicate that their prevalence varies across populations. Knowledge of atavistic and vestigial anatomical structures can inform diagnoses, prevent misrecognition of variation for pathology, and guide clinical interventions.

The red ruffed lemur, Varecia rubra (É. Geoffroy Saint-Hilaire, 1812): a comparative morphology investigation of lingual papillae and connective tissue cores.

The morphology of the lingual papillae (filiform, foliate, fungiform, and vallate papillae) and the underlying connective tissue core of the red ruffed lemur (Varecia rubra) of a strepsirrhines species were studied using light and scanning electron microscopy. The filiform papillae distributed at the root of the tongue were larger than the structures distributed at the body and apex. Six to eight vallate papillae were arranged in a Y-shape at the border between the lingual body and the lingual root. Foliate papillae were observed at the posterior lateral border of the tongue. Scanning electron microscopy revealed a primary process and numerous auxiliary processes in the epithelial layer of filiform papillae. After epithelial removal, the connective tissue core of the filiform papilla showed several protrusions surrounding an oval-shaped depression that extended slightly posteriorly, and a large, maple-shaped filiform papilla was seen in the posterior portion of the tongue. The connective tissue cores of the fungiform papillae exhibited a longitudinally ridged cylindrical structure. The connective tissue core of the foliate papillae had numerous tubular projections arranged along a groove with a salivary gland conduit at the base. As a Lemuridae species, the appearance of the fungiform and filiform papillae of the red ruffed lemur is similar to that reported in previous studies of the ring-tailed lemur, with some differences, especially in the filiform papillary connective tissue core at the base and tongue body border. These findings suggest the taxonomic and phylogenetic origins of the lemurs as well as the influence of dietary diversity.

Comparative anatomy of dissected optic lobes, optic ventricles, midbrain tectum, collicular ventricles, and aqueduct: evolutionary modifications as potential explanation for non-tumoral aqueductal anomalies in humans.

PURPOSE: An extensive literature has postulated multiple etiologies for aqueductal stenosis. No publications were found, discussing that evolutionary modifications might explain aqueductal anomalies. This study's objectives were to review the evolutionary modifications of vertebrates' tectum structures that might explain human aqueduct anomalies. Undertaking vertebrate comparative study is currently not feasible in view of limitations in obtaining vertebrate material. Thus, vertebrate material collected, injected, dissected, and radiographed in the early 1970s was analyzed, focusing on the aqueduct and components of the midbrain tectum. METHODS: Photographs of brain dissections and radiographs of the cerebral ventricles and arteries of adult shark, frog, iguana, rabbit, cat, dog, and primate specimens, containing a barium-gelatin radiopaque compound, were analyzed focusing on the aqueduct, the optic ventricles, the quadrigeminal plate, and collicular ventricles. The anatomic information provided by the dissections and radiographs is not reproducible by any other radiopaque contrast currently available. RESULTS: Dissected and radiographed cerebral ventricular and arterial systems of the vertebrates demonstrated midbrain tectum changes, including relative size modifications of the mammalian components of the tectum, simultaneously with the enlargement of the occipital lobe. There is a transformation of pre-mammalian optic ventricles to what appear to be collicular ventricles in mammals, as the aqueduct and collicular ventricle form a continuous cavity. CONCLUSIONS: The mammalian tectum undergoes an evolutionary cephalization process consisting of relative size changes of the midbrain tectum structures. This is associated with enlargement of the occipital lobe, as part of overall neocortical expansion. Potentially, aqueductal anomalies could be explained by evolutionary modifications.

The cavernous carotid inferolateral trunk and persistent primitive maxillary arteries: analysis of dissected arterially injected fetal specimens and high-resolution micro-CT of the dog's anastomotic arteries.

PURPOSE: The presence of a persistent primitive maxillary artery is described in the literature dealing with the development of the cavernous carotid inferolateral trunk, and the relevant similarities of the cranial circulation of the human and dog. The literature includes no dissection photographs of the above-mentioned two human fetal arteries, only diagrammatic representations. This study's objectives were to analyze photographs of fetal dissections for the presence of these two arteries, and also investigate the possibility of obtaining, in preserved dog specimens, high-resolution micro-CT imaging of arteries homologous with the above-mentioned two human arteries. METHODS: The literature describing the embryologic development of the cavernous carotid inferolateral trunk, the persistent primitive maxillary arteries, and their homologies in the dog was reviewed. Relevant dissections of fetal specimens were analyzed. High-resolution micro-CT images of un-dissected dog arteries were produced and analyzed. RESULTS: Photographs of fetal specimen dissections demonstrate the cavernous carotid inferolateral trunk. A separate persistent primitive maxillary artery was not present in the dissected specimens. High-resolution micro-CT images of the dog demonstrate homologous arteries with segments of the human inferolateral trunk, and other skull base and brain arteries. CONCLUSION: This investigation provides the only photographs in the literature of dissected human fetal cavernous carotid inferolateral trunks. A persistent primitive maxillary artery was not present in the dissected specimens and is a non-existent structure, likely a previously misidentified carotid inferolateral trunk. High-resolution micro-CT images of the dog visualized arteries that are homologous to segments of the human cavernous carotid inferolateral trunk artery.

Comparative angiotomographic study of swine vascular anatomy: contributions to research and training models in vascular and endovascular surgery.

BACKGROUND: Medium and large animal models allow researchers to evaluate the efficacy and safety of cardiovascular procedures in systems that resemble human anatomy and can be used to simulate scenarios for training purposes. Although porcine models have been used extensively, many physiological and anatomical features remain unknown or only superficially described. OBJECTIVES: To describe the normal porcine vascular anatomy on computed tomography scans, compare it to human vascular anatomy, and discuss the application of porcine models for open and endovascular procedures. METHODS: Three male Landrace pigs underwent computed tomography. The vascular anatomy of the neck, thorax, abdomen, and limbs was analyzed and described; relevant similarities and differences between porcine and human vascular anatomies and the implications for vascular procedures in pigs are highlighted. RESULTS: The carotid territory, aortic arch, and terminal aorta branches all show marked differences in pigs compared to their human counterparts. Compressions of both left renal and common iliac veins were detected, analogous to those seen in human Nutcracker and May-Thurner syndromes. Vascular measurements (diameters, lengths, and angles) of several different porcine territories are presented. CONCLUSIONS: The data presented should be useful for planning preclinical trials and basic research and for refining surgical training using porcine models in vascular fields.

Estudo de anatomia comparada suína por angiotomografia: contribuições para modelos de pesquisa e treinamento em cirurgia vascular e endovascular / Comparative angiotomographic study of swine vascular anatomy: contributions to research and training models in vascular and endovascular surgery

Resumo Contexto Modelos com animais de médio e grande porte permitem que pesquisadores avaliem a eficácia e a segurança de procedimentos cardiovasculares em sistemas que se assemelham à anatomia humana e podem ser usados para simular cenários para fins de treinamento. Embora modelos suínos tenham sido extensivamente utilizados, muitos fatores fisiológicos e anatômicos permanecem desconhecidos ou apenas superficialmente descritos. Objetivos Descrever a anatomia vascular do suíno por tomografia computadorizada, compará-la à anatomia humana e discutir a aplicação dos modelos porcinos em procedimentos abertos e endovasculares. Métodos Três porcos machos da raça Landrace foram submetidos a tomografia computadorizada. A anatomia vascular de pescoço, tórax, abdome e membros foi analisada e descrita; foram destacadas similaridades e divergências relevantes entre a anatomia vascular de suínos e de humanos e as implicações em procedimentos vasculares nos suínos. Resultados O território carotídeo, o arco aórtico e os ramos terminais da aorta em suínos apresentaram diferenças marcantes quando comparados aos de humanos. Foram detectadas compressões de veias renal e ilíaca comum, ambas à esquerda, semelhantes às encontradas nas síndromes humanas de Nutcracker e May-Thurner. Medidas vasculares (diâmetro, comprimento e ângulos) de diferentes topografias de suínos foram fornecidas. Conclusões Os dados fornecidos podem ser úteis para o planejamento de ensaios pré-clínicos e pesquisa básica, bem como para o refinamento do treinamento cirúrgico usando modelos suínos no campo da cirurgia vascular.

Abstract Background Medium and large animal models allow researchers to evaluate the efficacy and safety of cardiovascular procedures in systems that resemble human anatomy and can be used to simulate scenarios for training purposes. Although porcine models have been used extensively, many physiological and anatomical features remain unknown or only superficially described. Objectives To describe the normal porcine vascular anatomy on computed tomography scans, compare it to human vascular anatomy, and discuss the application of porcine models for open and endovascular procedures. Methods Three male Landrace pigs underwent computed tomography. The vascular anatomy of the neck, thorax, abdomen, and limbs was analyzed and described; relevant similarities and differences between porcine and human vascular anatomies and the implications for vascular procedures in pigs are highlighted. Results The carotid territory, aortic arch, and terminal aorta branches all show marked differences in pigs compared to their human counterparts. Compressions of both left renal and common iliac veins were detected, analogous to those seen in human Nutcracker and May-Thurner syndromes. Vascular measurements (diameters, lengths, and angles) of several different porcine territories are presented. Conclusions The data presented should be useful for planning preclinical trials and basic research and for refining surgical training using porcine models in vascular fields.

An alternative method for the comparative study of coronary vessels: repletion and diaphanization experience in seven animal models / Repleción y diafanización como una alternativa para el estudio comparativo de los vasos coronarios: experiencia en siete modelos animales

Coronary arteries establish a complex blood vessel system, right and left coronary arteries commonly originate from the aortic sinuses and divide into multiple branches that supply the heart with several important variations between species. Diaphanization is a preservative technique which allows internal structures visualization, maintaining the three-dimensionality of the specimen. In this study, human (Homo sapiens), goat (Capra aegagrus hircus), bovine (Bos Taurus), equine (Equus caballus), porcine (Sus scrofa domesticus), canine (Canis lupus familiaris) and feline (Felis silvestris catus) coronary arteries were injected with selfcuring methyl-methacrylate and posteriorly diaphanized. The coronary vasculature was adequately observed in all models while keeping the three-dimensional relation with surrounding cardiac structures, except for septal arteries which were not visualized. As incidental findings, anatomical variations in canine and human hearts were observed. Repletion-diaphanization is a useful blended method to visualize the morphology of superficial coronary arteries. It could be a valuable tool in anatomical teaching and research, but further research needs to be done to prove its effectiveness in different vessel systems.

Las arterias coronarias son un complejo de vasos sanguíneos que usualmente se originan en los senos aórticos y que al dividirse en múltiples ramas suplen los requerimientos metabólicos del tejido cardiaco; cabe aclarar que la anatomía de estas estructuras posee variaciones importantes entre especies. La diafanización es una técnica de preservación que permite observar estructuras internas de un espécimen sin dañar su tridimensionalidad. En este estudio las arterias coronarias del corazón humano (Homo sapiens), caprino (Capra aegagrus hircus), bovino (Bos Taurus), equino (Equus caballus), porcino (Sus scrofa domesticus), canino (Canis lupus familiaris) y felino (Felis silvestris catus), fueron repletadas con metil-metacrilato y posteriormente diafanizados. Se observa la irrigación coronaria de cada uno de los corazones y su relación con las demás estructuras cardiacas, exceptuando las arterias septales. Como hallazgos incidentales se observaron variaciones anatómicas en los corazones canino y humano. Finalmente, esta técnica resultó de utilidad para evaluar la anatomía coronaria, lo que puede ser valioso para educación e investigación. Posteriores investigaciones deben ser realizadas para probar su utilidad en otros sistemas vasculares.

Evaluación anatómica del paladar blando mediante resonancia magnética: Artículo de revisión / Anatomic evaluation of Soft palate using magnetic resonance imaging: Review article

Objetivos: Revisar las publicaciones sobre la anatomía del paladar blando en imágenes de resonancia magnética (RM), para evaluar esta estructura. Contenido: El paladar blando es una estructura anatómica compuesta por músculos con funciones importantes durante la fonación, deglución y la respiración. La resonancia magnética (RM) es una técnica imagenológica que no utiliza radiación ionizante, obteniendo relevancia en los últimos años, por lo que en la actualidad tiene un rol importante en el diagnostico maxilofacial, específicamente en tejidos blandos como el velo del paladar, razón por la cual el odontólogo debe conocer las estructuras y función mediante imágenes de RM. En secuencias rápidas, se pueden evaluar los movimientos del velo del paladar en la deglución y respiración, así como poder observar cambios en las estructuras de la vía aérea superior tal como se da en el síndrome de apnea obstructiva del sueño. Conclusiones: La revisión muestra la importancia de la RM en el estudio de la anatomía del paladar blando; esto debe promover el uso de esta técnica para analizar tejidos blandos. Está demostrado en los diferentes estudios de imágenes por RM que detallan bien estos tejidos en sus diferentes secuencias y tiene como principal ventaja que no utiliza radiación ionizante.

Objectives: This article aims to review the main research about soft palate anatomy and magnetic resonance imaging to evaluate the soft tissues of this structure. Background: Soft palate is an anatomical structure composed of muscles with important functions during phonation, swallowing and breathing. The magnetic resonance is an imaging technique, which does not use ionizing radiation, getting relevance the last few years, so nowadays it plays an important role in maxillofacial diagnosis, especially in soft tissues such as palate veil, a good reason because of dentist specialist must know all about functional magnetic resonance through images in fast sequences where the movements of the veil of the palate in swallowing and breathing can be evaluated, as well as being able to observe changes in the structures of the upper airway as it occurs in obstructive sleep apnea syndrome. Conclusions: The review shows the importance of MRI in the study of the soft palate anatomy; This should promote the use of this technique to analyze soft tissues, it is demonstrated in the different MR imaging studies that detail these tissues well in their different sequences and its main advantage is that it does not use ionizing radiation.

Computed Tomography Staging of Middle Ear Cholesteatoma.

BACKGROUND: To establish computed tomography (CT) staging of middle ear cholesteatoma and assess its impact on the selection of the surgical procedure. MATERIAL/METHODS: Prospective study was conducted on 61 consecutive patients (mean age 26.8 years) with middle ear cholesteatoma. CT scan of the temporal bone and surgery were performed in all patients. CT staging classified cholesteatoma according to its location in the tympanic cavity (T); extension into the mastoid (M); and associated complications (C). Cholesteatoma was staged as stage I (T1, T2), stage II (T3, M1, M2, C1), and stage III (C2). RESULTS: The overall sensitivity of CT staging of cholesteatoma compared to surgery was 88% with excellent agreement and correlation between CT findings and intra-operative findings (K=0.863, r=0.86, P=0.001). There was excellent agreement and correlation of CT staging with surgical findings for T location (K=0.811, r=0.89, P=0.001), good for M extension (K=0.734, r=0.88, P=0.001), and excellent for associated C complications (K=1.00, r=1.0, P=0.001). Atticotympanotomy was carried out in stage I (n=14), intact canal wall surgery was performed in stage II (n=38), and canal wall down surgery was done in stage III (n=5) and stage II (n=4). CONCLUSIONS: We established CT staging of middle ear cholesteatoma that helps surgeons to select an appropriate surgery.

Snake heart: a case of atavism in a human being.

Atavism is the rare reappearance, in a modern organism, of a trait from a distant evolutionary ancestor. We describe an apparent case of atavism involving a 59-year-old man with chest pain whose coronary circulation and myocardial architecture resembled those of the reptilian heart. The chest pain was attributed to a coronary steal phenomenon. The patient was discharged from the hospital on a heightened regimen of ß-blockers, and his symptoms improved significantly. To our knowledge, this is only the 2nd reported clinical case of a human coronary circulation similar to that of reptiles.