Adult Anatomy Research Articles

Vitreoretinal Surgery in Pediatric Patients with the Disease of Vitreoretinal Interface

Comparing the ocular anatomy of children and adults, there are certain dimensions and structural differences. A safer surgical method is made possible by an understanding of the major distinctions between the eyes of children and adults,and specific evaluations are required. The primary distinctions are in the locations of sclerotomies, the requirement for posterior hyaloid separation and total vitrectomy, endo-tamponade, and the surgical technique according to the vitreoretinal disease. We tried to summarize the main differences in pediatric patients with the disease of the vitreoretinal interface compared to adult vitreoretinal surgery and some critical points for this surgery.

See-Star: a versatile hydrogel-based protocol for clearing large, opaque and calcified marine invertebrates

Studies of morphology and developmental patterning in adult stages of many invertebrates are hindered by opaque structures, such as shells, skeletal elements, and pigment granules that block or refract light and necessitate sectioning for observation of internal features. An inherent challenge in studies relying on surgical approaches is that cutting tissue is semi-destructive, and delicate structures, such as axonal processes within neural networks, are computationally challenging to reconstruct once disrupted. To address this problem, we developed See-Star, a hydrogel-based tissue clearing protocol to render the bodies of opaque and calcified invertebrates optically transparent while preserving their anatomy in an unperturbed state, facilitating molecular labeling and observation of intact organ systems. The resulting protocol can clear large (> 1 cm3) specimens to enable deep-tissue imaging, and is compatible with molecular techniques, such as immunohistochemistry and in situ hybridization to visualize protein and mRNA localization. To test the utility of this method, we performed a whole-mount imaging study of intact nervous systems in juvenile echinoderms and molluscs and demonstrate that See-Star allows for comparative studies to be extended far into development, facilitating insights into the anatomy of juveniles and adults that are usually not amenable to whole-mount imaging.

Variable gearing at the ankle during walking in adults and young children: implications for foot development and evolution

Introduction: The human foot has evolved over the past seven million years from a relatively mobile, grasping appendage to a highly derived structure with a heel pad and longitudinal arch that can absorb shock at heel strike and weight-bearing yet also function as a powerful lever at toe-off. It has been proposed that the modern human foot evolved to allow our species to use “variable gearing” during walking and running. In this model, the gears of the human foot are defined relative to the ankle center of rotation as R, the distance from the ground reaction resultant vector, and r, the distance from the calf muscle vector. The gear ratio defines the torque generated to propel the body or stretch the triceps surae muscles. We test the hypothesis that variable gearing is associated with modern human pedal anatomy and a heel-to-toe rollover that allows a shift from “low gear” to “high gear” during stance.Methods: Using force plate and video analysis, we examined variable gearing in adults and children engaging in adult heel strike (AHS = 35), flat foot contact (FFC = 39), or initial heel contact (IHC = 26).Results and Discussion: Our hypothesis was partly supported. Although variable gearing was observed in IHC steps and was greater than in FFC steps, it was not as developed as in AHS steps. This may be related to anatomical and motor control differences between juvenile and adult feet, suggesting that adult anatomy, including a high arch, and neural control are critical for full use of variable gearing and that this feature would have evolved in later hominins around two million years ago with the appearance of a fully modern foot.

Morphological Diversity of Turtle Hyoid Apparatus is Linked to Feeding Behavior.

The hyoid apparatus of tetrapods is highly diverse in its morphology. It plays an important role in feeding, breathing, sound production, and various other behaviors. Among turtles, the diversity of the hyoid apparatus has been recurrently linked to their habitat. The ossification of the hyoid corpus is often the main trait used in correlations with "niche" occupancy, an ossified corpus being associated with aquatic environments and a cartilaginous corpus with terrestrial life. Most studies conducted so far have focused on species belonging to Testudinoidea, the clade that occupies the biggest diversity of habitats (i.e., terrestrial, semi-terrestrial, and aquatic animals), while other turtle lineages have been largely understudied. We assessed the adult anatomy of the hyoid apparatus of 92 turtle species from all "families", together with ossification sequences from embryological series of 11 species, some described for the first time here. Using nearly 40 different discrete anatomical characters, we discuss the evolutionary patterns and the biological significance of morphological transformations in the turtle hyoid elements. Morphological changes are strongly associated to feeding modes, with several instances of convergent evolution within and outside the Testudines clade, and are not as strongly connected to habitat as previously thought. Some of the hyoid character states we describe are diagnostic of specific turtle clades, thus providing phylogenetically relevant information.

Ultrastructure of the female pedal gonad in Phoxichilidium femoratum (Chelicerata, Pycnogonida)

Phoxichilidium femoratum is a common species of sea spiders – a small and unique group of chelicerates with unusual adult anatomy. In particular, substantial parts of the reproductive system in pycnogonids (unlike euchelicerates) are located in the appendages. Existing studies of pycnogonid gonads are often limited to light-microscopic level, cover a small range of species, and focus on the contents of the gonad diverticula. Ultrastructural data are rare and contradictory, and the organisation of the gonad wall and the gonoducts is unknown. Here we present a detailed light and transmission electron microscopy-based examination of the pedal portion of the adult female reproductive system in Phoxichilidium femoratum Rathke, 1799. We describe its gross anatomy and the ultrastructure of the gonad diverticulum, oviduct and gonopore, as well as development of the oocytes. Each gonad diverticulum is enclosed in the extracellular matrix of the horizontal septum and bears some internal cellular lining. However, neither the gonad lining, nor the septum sheath cells, ever form a continuous epithelial layer. Oocytes, which undergo maturation in the diverticulum, remain, until very late in the process, attached to the gonad wall though specialised stalk cells. Interestingly, stalk cells do not participate in egg envelope or yolk formation: both are synthesized endogenously in the oocytes. The oviduct is supplied with musculature, which assists in egg transport to the gonopore, whereas the gonopore itself is surrounded by specialised glands.

Region- and age-specific effects of perinatal phthalate exposure on developmental cell death and adult anatomy of dorsal and ventral hippocampus and associated cognitive behaviors

Humans are exposed to phthalates, a class of endocrine-disrupting chemicals used in food packaging/processing, PVC plastics, and personal care products. Gestational exposure may lead to adverse neurodevelopmental outcomes. In a rat model, perinatal exposure to an environmentally relevant mixture and dose of phthalates leads to increased developmental apoptosis in the medial prefrontal cortex (mPFC) and a subsequent reduction in neurons and in cognitive flexibility measured in adults of both sexes (Sellinger et al., 2021b; Kougias et al., 2018b). However, whether these effects generalize to other cognitive regions, like the hippocampus, is less well understood as existing studies used single phthalates at large doses, unrepresentative of human exposure. In the current study, patterns of naturally occurring cell death were first established in the dorsal and ventral hippocampal subfields (CA3 and CA1). Both dorsal and ventral CA3 reached high levels of cell death on P2 while levels in dorsal and ventral CA1 peaked on P5 in both sexes. Exposure to a phthalate mixture (0.2 and 1 mg/kg/day) throughout gestation through postnatal day 10 resulted in subtle age- and region-specific decreases in developmental cell death, however there were no significant changes in adult neuron number or associated behaviors: the Morris water maze and social recognition. Therefore, perinatal exposure to a low dose mixture of phthalates does not result in the dramatic structural and behavioral changes seen with high doses of single phthalates. This study also adds to our understanding of the distinct neurodevelopmental effects of phthalates on different brain regions.

Genetic models for lineage tracing in musculoskeletal development, injury, and healing

Musculoskeletal development and later post-natal homeostasis are highly dynamic processes, marked by rapid structural and functional changes across very short periods of time. Adult anatomy and physiology are derived from pre-existing cellular and biochemical states. Consequently, these early developmental states guide and predict the future of the system as a whole. Tools have been developed to mark, trace, and follow specific cells and their progeny either from one developmental state to the next or between circumstances of health and disease. There are now many such technologies alongside a library of molecular markers which may be utilized in conjunction to allow for precise development of unique cell ‘lineages’. In this review, we first describe the development of the musculoskeletal system beginning as an embryonic germ layer and at each of the key developmental stages that follow. We then discuss these structures in the context of adult tissues during homeostasis, injury, and repair. Special focus is given in each of these sections to the key genes involved which may serve as markers of lineage or later in post-natal tissues. We then finish with a technical assessment of lineage tracing and the techniques and technologies currently used to mark cells, tissues, and structures within the musculoskeletal system.

The Inside Out of Flies

There can be absolutely no doubt that author and researcher Erica McAlister finds flies fascinating. The enthusiasm and joy with which she discusses her Diptera subjects is infectious; although readers might not end up truly loving flies, as McAlister does, they will certainly come away with appreciation for the evolutionary wonder of this ubiquitous group of insects. McAlister’s previous book, The Secret Life of Flies, examined fly behavior. This companion volume, The Inside Out of Flies, examines fly anatomical adaptations. The first chapter describes “pre-adulthood” (development of flies, from egg through adulthood); the following eight chapters focus on adult anatomy, working their way from the head (with separate chapters on the antennae and the mouthparts) to the end of the abdomen (the terminalia). In each chapter the anatomical aspects and evolutionary adaptations shown in each body part are carefully presented with many unique examples. The book itself is physically lovely: great attention has been paid to layout, and visuals are clear and informative.Open this book to any page, and you will find something astounding about flies. Flies being flies, this could be somewhat revolting (maggot extra-oral digestion and tissue debridement) or amazing (“mag-bot” robots that mimic maggot motion to deliver pharmaceuticals to specifically targeted locations in the body). Did you know that some flies don’t even have functional mouthparts as adults? Or that flies have sensory hairs that literally “taste” bitter and sweet molecules in the atmosphere? Or that some female flies have eversible sacs (McAlister describes them as “resembling car air bags”) that emit pheromones and make the female’s body look bigger to entice males to mate? The almost unending examples are fascinating, though they are in a way the source of the book’s biggest fault. Although McAlister undoubtedly felt she omitted many examples important to dipterists (such as the global attendees at “fly school” described in the end chapter), the more general student of biology would have benefitted from a more selective presentation. Example after example with scientific names, classifications, and adaptations lead at times to reader fatigue. Overall, however, this is a wonderful volume, of potential interest and use to a wide variety of readers interested in biology, entomology, behavior, and evolution.

A three-component model of the spinal nerve ramification: Bringing together the human gross anatomy and modern Embryology.

Due to its long history, the study of human gross anatomy has not adequately incorporated modern embryological findings; consequently, the current understanding has often been incompatible with recent discoveries from molecular studies. Notably, the traditional epaxial and hypaxial muscle distinction, and their corresponding innervation by the dorsal and ventral rami of the spinal nerve, do not correspond to the primaxial and abaxial muscle distinction, defined by the mesodermal lineages of target tissues. To resolve the disagreement between adult anatomy and embryology, we here propose a novel hypothetical model of spinal nerve ramification. Our model is based on the previously unknown developmental process of the intercostal nerves. Observations of these nerves in the mouse embryos revealed that the intercostal nerves initially had superficial and deep ventral branches, which is contrary to the general perception of a single ventral branch. The initial dual innervation pattern later changes into an adult-like single branch pattern following the retraction of the superficial branch. The modified intercostal nerves consist of the canonical ventral branches and novel branches that run on the muscular surface of the thorax, which sprout from the lateral cutaneous branches. We formulated the embryonic branching pattern into the hypothetical ramification model of the human spinal nerve so that the branching pattern is compatible with the developmental context of the target muscles. In our model, every spinal nerve consists of three components: (1) segmental branches that innervate the primaxial muscles, including the dorsal rami, and short branches and long superficial anterior branches from the ventral rami; (2) plexus-forming intramural branches, the serial homolog of the canonical intercostal nerves, which innervate the abaxial portion of the body wall; and (3) plexus-forming extramural branches, the series of novel branches located outside of the body wall, which innervate the girdle and limb muscles. The selective elaboration or deletion of each component successfully explains the reasoning for the standard morphology and variability of the spinal nerve. Therefore, our model brings a novel understanding of spinal nerve development and valuable information for basic and clinical sciences regarding the diverse branching patterns of the spinal nerve.

Fourth thoracic vertebra as landmark for depth of right internal jugular vein catheterization in infants

The carina is considered a reliable marker for the depth of right internal jugular vein catheterization in infants on chest radiograph. In adult anatomy, the carina is typically located at the level of the fifth thoracic vertebra. We are not aware of a positional relationship between infant carina and thoracic vertebrae. Thus, we evaluated that a vertebral body may be at the same level as carina and can be as radiographic landmarks for the depth of right internal jugular vein catheterization in infants. In this retrospective analysis, 108 infants (aged 1–12 months) who underwent congenital heart surgery between January 1, 2019 and June 30, 2019 were included. We analyzed the post-operative chest radiographs of those who underwent right internal jugular vein catheterization and assessed the positional relationship of the carina and vertebral bodies. We measured the vertical distance of the central venous catheter (CVC) catheter tip from the carina (below the carina 22 mm, it may be close to or into the right atrium). In total, 95 children were enrolled; The carina was located at the third thoracic vertebra in two cases (2%) and at the fourth thoracic vertebra in 93 cases (98%). The distance between the tip of CVC and the carina was 10 (4, 15) mm, and 6.3% (6 cases) had the catheter tip at more than 22 mm below the carina. Most fourth thoracic vertebrae were at the same level as the carina on chest radiographs. Therefore, it has potential as a radiographic landmark for the depth of right internal jugular vein catheterization in infants on chest radiograph.

Discrete embryonic character variation uncovers hidden ecological adaptations in lacertid lizards.

Embryogenesis is the first step in the ontogenetic life journey of any individual, and is thus a starting point for natural selection to cause evolutionary change. There are slight variations in the timing of embryonic development, known as heterochrony, which may eventually lead to major differences in adult anatomy. To test this hypothesis, the embryonic development of three closely related lizard species, Darevskia armeniaca, Lacerta agilis, and L. viridis, which are adapted to different habitats, was compared by analyzing discrete timing characters. Both intra- and interspecific variation was detected. The latter may be interpreted as embryonic pre-adaptions to later adult lifestyles, demonstrating that developmental penetrance manifests within a few million years. Traits with large intraspecific temporal variation, such as limb-related features, were susceptible to natural selection. In particular, the mountain-dwelling, climbing species D. armeniaca showed embryonic preadaptions by an early developing limb anlagen. This observation demonstrated interspecific variation, which was elusive in a previous comparative study based on purely metric data of developing limb lengths, and highlighted the importance of multiple data sources to draw robust conclusions about evolutionary change. Timing differences indicated unexplored ecological adaptations of the poorly understood lifestyle of these lizards. Thus, embryonic research provides a platform to explore superficially hidden evolutionary adaptations of all organisms on Earth.

Anatomic Characteristics of the Adolescent Cricothyroid Membrane on Computed Tomography Scans.

The cricothyroid membrane (CTM) is the most important anatomic structure when performing emergency front-of-neck access (FONA) procedures. Adolescence is a period of rapid morphologic change in laryngeal structures, including the CTM. We hypothesized that the adolescent CTM would be sufficiently different from pediatric or adult anatomy to merit special consideration in FONA. The aim of the study was to define the procedurally relevant CTM anatomy in an adolescent population. This was a retrospective, multicenter cohort study composed of patients who underwent a diagnostic computed tomography scan during routine clinical care. Inclusion criteria were ages 16 to 19 years and a computed tomography of the neck with or without contrast. The primary outcome was CTM height measured in the midsagittal plane using electronic calipers. One hundred thirty-four imaging studies met inclusion criteria. The average CTM height was strongly associated with age and ranged between 5.4 and 6.2 mm in male adolescents and 4.6 and 5.8 mm in female adolescents. We predicted that standard cuffed endotracheal and tracheostomy tubes recommended for FONA procedures (5.0- and 6.0-mm devices) could potentially fail for most patients in our cohort. The adolescent CTM is smaller than previously recognized. We recommend having a variety of equipment sizes readily available at any site where airway management in adolescents may occur.

Newborn anatomy.

Newborn anatomy, despite being distinctly different than adult anatomy, does not constitute a major component of a typical medical school course in gross anatomy. Accordingly, there is a perception that other than the well-known late 20th-century atlas and small textbook by Edmund Crelin on newborn anatomy, there is almost no information available for anatomists and clinicians to refer to on normal infant anatomy. This perception, as verbalized by Crelin in his books, is not correct. There is an amazing wealth of accurate descriptive and pictorial information on infant anatomy available from late 19th- and early 20th-century sources. One of these sources is a comprehensive 200-page chapter on pediatric anatomy by Richard Scammon that was published in 1923 and that is freely available. Because of some inconsistencies and inaccuracies we have identified in the Crelin works, we suggest that any anatomist or clinician who wishes to learn and teach about infant anatomy refer to Scammon's chapter before using any text or image from the Crelin books.

An Updated Staging System for Cephalochordate Development: One Table Suits Them All.

Chordates are divided into three subphyla: Vertebrata, Tunicata, and Cephalochordata. Phylogenetically, the Cephalochordata, more commonly known as lancelets or amphioxus, constitute the sister group of Vertebrata and Tunicata. Lancelets are small, benthic, marine filter feeders, and their roughly three dozen described species are divided into three genera: Branchiostoma, Epigonichthys, and Asymmetron. Due to their phylogenetic position and their stereotypical chordate morphology and genome architecture, lancelets are key models for understanding the evolutionary history of chordates. Lancelets have thus been studied by generations of scientists, with the first descriptions of adult anatomy and developmental morphology dating back to the 19th century. Today, several different lancelet species are used as laboratory models, predominantly for developmental, molecular and genomic studies. Surprisingly, however, a universal staging system and an unambiguous nomenclature for developing lancelets have not yet been adopted by the scientific community. In this work, we characterized the development of the European lancelet (Branchiostoma lanceolatum) using confocal microscopy and compiled a streamlined developmental staging system, from fertilization through larval life, including an unambiguous stage nomenclature. By tracing growth curves of the European lancelet reared at different temperatures, we were able to show that our staging system permitted an easy conversion of any developmental time into a specific stage name. Furthermore, comparisons of embryos and larvae from the European lancelet (B. lanceolatum), the Florida lancelet (Branchiostoma floridae), two Asian lancelets (Branchiostoma belcheri and Branchiostoma japonicum), and the Bahamas lancelet (Asymmetron lucayanum) demonstrated that our staging system could readily be applied to other lancelet species. Although the detailed staging description was carried out on developing B. lanceolatum, the comparisons with other lancelet species thus strongly suggested that both staging and nomenclature are applicable to all extant lancelets. We conclude that this description of embryonic and larval development will be of great use for the scientific community and that it should be adopted as the new standard for defining and naming developing lancelets. More generally, we anticipate that this work will facilitate future studies comparing representatives from different chordate lineages.

A standardized terminology of spines in the order Siluriformes (Actinopterygii: Ostariophysi)

AbstractA standardized terminology for the anatomy of pectoral- and dorsal-fin spines in the order Siluriformes is proposed based on an extensive literature review and direct examination of representatives of the order. The adult anatomy of the spines is described in detail. Terminology of various spine parts are reviewed and standardized, each term provided with a synonymic list organizing previous usage. Most of the structures treated have been recorded and named in the literature, but some are herein named for the first time. A quantitative approach is proposed for orienting decisions on name usage, aiming at minimizing differences between the terminology proposed and the vast amount of pre-existing literature, herein called the cost function. It is expected that this system will aid efforts in organizing the chaotic anatomical nomenclature of the appendicular skeleton in Siluriformes, and provide a solid basis for advances in comparative anatomy and nomenclature. The proposed terminology system has potential application on a number of fields that utilize information from catfish spines, ranging from taxonomy to phylogenetic systematics to paleontology and archaeology.

The fibers of the circular junction of the linea alba in normal adult anatomy.

The linea alba (LA) is known to be useful to surgeons for making surgical incisions. Laparoscopic entry into the peritoneal cavity using the open technique may involve identification of a point just above or below the umbilicus where the peritoneum is fused to the LA. This anatomical site is found through superficial dissection to expose the junction between the umbilical stalk (US) and the LA, where distinct fibers seem to form a unique ligament-like structure in normal adult anatomy. This point, in fact, is part of a circular fibrous structure that exists almost like a ring around the remnant US. It is formed by the fusion of oblique and transverse fibers of the LA with circular fibers from proliferation of an encircling band of compact mesoderm to close a patent umbilical ring. We describe and name this anatomical landmark as junctio circularis alba or the "circular junction of the LA" as encountered in normal adult human anatomy. We believe this is crucial for describing key surgical procedures at this site to aid effective surgical training and reduce iatrogenic complications from laparoscopic port site entries.

Anatomical changes in postembryonic development of Pycnogonum litorale.

Sea spiders (Pycnogonida) are a small group of arthropods, sister to other chelicerates. They have an unusual adult bauplan, oligosegmented larvae, and a protracted postembryonic development. Pycnogonum litorale (Strøm, 1762) is an uncommonly long-lived sea spider with a distinctive protonymphon and adult anatomy. Although it was described ~250 years ago, little is known about its internal organization and development. We examined the anamorphic and early epimorphic development of this species using histology, light microscopy, and SEM, and provide the first comprehensive anatomical study of its many instars. Postembryonic development of P. litorale includes transformations typical of pycnogonids: reorganization of the larval organs (digestive, nervous, secretory), formation of the abdomen, trunk segments (+ appendages), primary body cavity and reproductive system. Specific traits include the accelerated articulation of the walking legs, formation of the subesophageal and posterior synganglia, and the system of twin midgut diverticula. In addition, P. litorale simultaneously lose the spinning apparatus and all larval appendages. We found that developmental changes occur in synchrony with changes in ecology and food sources. The transition from the anamorphic to the epimorphic period in particular is marked by considerable anatomical and lifestyle shifts. HIGHLIGHTS: Postembryonic development of P. litorale includes numerous anamorphic and epimorphic stages. The instars acquire abdomen, trunk segments, body cavity, and gonads, while losing all larval appendages. Developmental changes are synchronized with changes in lifestyle and food sources.

Tissue engineering of the gastroesophageal junction.

The gastroesophageal junction has been of clinical interest for some time due to its important role in preventing reflux of caustic stomach contents upward into the esophagus. Failure of this role has been identified as a key driver in gastroesophageal reflux disease, cancer of the lower esophagus, and aspiration-induced lung complications. Due to the large population burden and significant morbidity and mortality related to reflux barrier dysfunction, there is a pressing need to develop tissue engineering solutions which can replace diseased junctions. While good progress has been made in engineering the bodies of the esophagus and stomach, little has been done for the junction between the two. In this review, we discuss pertinent topics which should be considered as tissue engineers begin to address this anatomical region. The embryological development and adult anatomy and histology are discussed to provide context about the native structures which must be replicated. The roles of smooth muscle structures in the esophagus and stomach, as well as the contribution of the diaphragm to normal anti-reflux function are then examined. Finally, engineering considerations including mechanics and current progress in the field of tissue engineering are presented.

“Build an Embryo”: Educational Efficacy of 3D Printed Embryo Models in Pieces or En Bloc in Enhancing Spatial & Temporal Anatomy Learning

Embryology provides a fundamental context to adult anatomy and congenital anomalies. Due to the rapidly changing embryonic structures in 3 spatial dimensions and the 4th, temporal dimension, teaching and learning embryology is challenging. Compounding the matter, embryology education is further challenged by the scarcity of high‐fidelity visual resources and minimal contact hours in the current North American medical curricula. In our previous studies, 3D printed whole embryo models constructed from serial pig embryo tissue sections led to better learning outcomes compared to 2D figures, 3D virtual embryo models, and instructor‐led embryology discussions using cadavers. However, learners consistently noted desire to disassemble and reassemble the 3D printed embryo models to enhance their spatial learning. Therefore, the first aim of the current study was to develop two versions of the 3D printed embryonic head and neck model from a human embryo dataset in the Carnegie collection. One version of the model was printed en bloc (Figure 1A), while the other was printed in multiple pieces to allow for assembly and disassembly (Figure 1B). The second aim of the study was to assess the educational value of the two versions of the 3D printed embryo models. In an IRB exempt, randomized single blind study (#19‐2220), first‐year medical students enrolled in an integrated gross anatomy course were recruited during an hour‐long active review session. The control group received en bloc models while the experimental group received multi‐piece models. All participants completed prequiz before and postquiz after the assigned resource exposure, followed by survey. The two groups then exchanged rooms to gain exposure to the other version of the 3D printed embryo models. After interacting with both models, students’ resource preference was assessed by an exit poll. Data analyses on quiz and quantitative survey data were completed using Two‐Way ANOVAs and Turkey Post Hoc where appropriate. A total of 148 students completed the study (control: n=72, experimental: n=76). Both groups had significant improvements in the postquiz compared to the prequiz (p<0.05; η2=0.47), but the amount of postquiz improvement between the two groups was not significant (p=0.11). There was no significant difference in the quantitative survey data, with both groups rating the 3D printed embryo models high in educational value and wanting more 3D printed models for other embryonic systems. Thematic analysis of survey comments revealed that students perceived the en bloc and the multi‐piece models as helpful from the tactile and visual perspectives, respectively. Despite the lack of significant difference in the learning outcomes or survey, 94% of all participants indicated a preference for the multi‐piece model after exposure to both models. As 3D printing becomes more accessible, this study has important implications in evidence‐based resource development.Embryology Learning Resources – 3D printed embryo models (A: en bloc model, B: Multi‐piece model).Figure 1

The embryonic development of the bovine stomach revisited.

The adult anatomy and physiology of the bovine (Bos taurus) stomach have been investigated extensively. Despite the many studies, however, the early development of the stomach has not yet been fully elucidated. The goal of the present study, therefore, was to review the available literature, to visualize the embryonic and early foetal development of the bovine stomach and to shed light on unresolved issues. The stomachs of fifteen bovine embryos and eleven foetuses from 26 to 80days of gestation were photographed both in situ and after exenteration and critical point drying. A series of photographs was obtained that yielded a contiguous and comprehensive view of all the developmental changes that occurred until the virtually final configuration of the stomach was attained. In addition, the serosal surface was studied by electron microscopy, thus revealing subtle regional differences in the lining of the peritoneal cavity. Our observations corroborate the contention that all the compartments evolve from the fusiform primordium and that no outgrowth at the level of the oesophagus occurs. The greater curvature as well as the attachment line of the dorsal mesogastrium shift to the left, which is similar to the process in monogastrians. The rumen and reticulum develop from separate protrusions, and further compartmentalization results from constrictions and bulges and not from folding. Between 55 and 60days of gestation, the entire bovine stomach except for the abomasum eventually relocates to its final position. In summary, previously debated key issues were addressed and integrated with current findings.