From Simple to Complex: An Incremental Approach to Help Teach Students. the Complex Anatomy of Midgut Rotation in the Human Embryo

Transcription

1 1 From Simple to Complex: An Incremental Approach to Help Teach Students the Complex Anatomy of Midgut Rotation in the Human Embryo Using Animations and an Interactive Website Takami Iijima June 24, 2008

2 2 Abstract Morphogenesis in the human embryo is complex and involves changes that occur in 3-dimensions. An example is the formation of the gut as it changes from a straight tube to the extensive convolution that is present in the adult human. In its primitive stage, the gut has three divisions, the foregut, midgut, and hindgut, which undergo distinct morphogenesis. Of these, the midgut undergoes the most remarkable changes. The 270-degree rotation of the so-called midgut loop is a key event in the normal formation of the midgut. The midgut continues to grow in different directions as it rotates in a 3-dimensional space so it becomes a notably difficult phenomenon to visualize. Students, however, need to understand such complex morphological events in normal human embryological development because they provide an explanation for the complex anatomy seen in the child and adult. Moreover, understanding the normal development of structure is critical to understanding and explaining the origins of common congenital disorders. Thus, a visualization tool that could effectively be used as a teaching tool for students studying human embryology becomes essential. In order to address this problem, I propose to create a teaching tool designed specifically for teaching the complex anatomy of midgut rotation in the human embryo. In the following, I describe how I plan to use an incremental approach from a simple 2D animation to complex 3D animations of the developing midgut using advanced computer software. I will then incorporate the animations into a Flash website to add user-interactivity and for easy accessibility. I also plan to test the website on a relevant student population to assess its usefulness. Introduction

3 3 Methods for visualizing human embryology have evolved tremendously through the years. This is owed largely to the level of complexity of the morphological events that occur naturally in human embryos (Schleich and Almange 2002, Yamada et al. 2005). As human embryos grow, they undergo dynamic changes that involve 3- dimensional morphogenesis. In order to fully appreciate these changes there is a need to develop an appropriate visualization method with which to illustrate complex movements that occur in 3-dimensional space. Traditionally, the preferred visualization methods are 2D illustrations in embryology textbooks and sculptural reconstructions of embryological anatomy using wax or plastic materials (Hopwood 1999, Yamada et al. 2005). With the introduction of computer technology, the methodology for visualizing complex events has shifted to 3D imaging techniques. Magnetic resonance imaging (MRI) (Matsuda et al. 2007, Puerta-Fonolla et al. 2004, Smith et al. 1996) and episcopic fluorescence image capture (EFIC) (Rosenthal et al. 2004, Weninger et al. 1998) are techniques used to obtain detailed 3D images by directly scanning specimens. Many collections of preserved human embryos have been scanned in this way. These 3D images have been incorporated into websites and are available for public access on the internet (Mizuta et al. 2002, Smith et al. 1999, Watt et al. 1996, Yamada et al. 2005). Advanced computer software such as SoftImage (Mizuta et al. 2002, Yamada et al. 2005) and Lightwave (Schleich and Almange 2002) can be used to make detailed 3D models. 3D modeling techniques are particularly interesting in that they can be used to create high quality animations which can also be brought into a website (Schleich and Almange 2002). One of the more challenging morphological events in human embryology to visualize is midgut rotation. The midgut begins organogenesis from a straight tube, as do

4 4 the foregut and hindgut (Blechschmidt 2004). As the midgut develops, it elongates and forms a ventral U-shaped loop called the midgut loop (Moore et al. 2000). The midgut continues to elongate; however, due to the small abdominal space and relatively large liver and kidneys, the midgut loop is forced to project into the proximal part of the umbilical cord. This key event is called the physiological umbilical herniation (Blechschmidt 2004, Moore et al. 2000). As the midgut loop enters the umbilical cord, it undergoes a counterclockwise 90-degree rotation. This is the first of about 270-degrees which the midgut will have completed by the end of its development (Moore et al. 2000). The superior mesenteric artery, which lies within the dorsal mesentery and supplies the midgut and its derivatives, serves as the axis of rotation (Jirasek 2004, Larsen 2001, Moore et al. 2000). Within the umbilical cord, the midgut grows rapidly and forms the intestinal loops (Blechschmidt 2004). At the beginning of the fetal period, the midgut returns to the abdomen, which by that time is large enough to accommodate the extensive convolutions of the small intestine. The final counterclockwise 180-degree rotation also begins at this time (Larsen 2001, Sweeney 1998). Clearly, midgut development in the human embryo is complex. The components of the midgut undergo a multitude of morphogenetic changes including elongation, herniation, rotation, and growth at different rates and in different directions. Students need to understand the importance of learning complex morphological events such as midgut rotation in human embryology. For example, to understand the causes for common congenital disorders of midgut rotation such as malrotation and omphalocele, there is a need to understand normal development of the structures affected by the disorder (Kim et al. 2003). Moreover, umbilical hernias, which can be observed via

5 5 ultrasound, have been mistaken for omphalocele or gastroschisis (Cyr et al. 1986). Thus, proper knowledge in normal midgut development is important in preventing a misdiagnosis. Literature Review The developing midgut was first described by Meckel in 1817 (Kim et al. 2003) while O Rahilly and Muller described the staging of human embryos in 1987 (O Rahilly and Muller 1986). Today, succeeding textbooks have adopted Meckel s description for the developing midgut and O Rahilly and Muller s staging nomenclature is important when noting the timing of key events in the human embryonic period. In general, these textbooks differ from each other only slightly mainly with respect to the exact timing of the key events that are highlighted in the developing midgut (Blechschmidt 2004, Jirasek 2004, Larsen 2001, Moore et al. 2000, Sweeney 1998). Traditional 2D illustrations in many of these textbooks have attempted to show the developing midgut using sequential drawings. Artists have experimented with various illustration techniques from pen and inks to computer renderings. Yet, whatever the artist s choice of style and approach, it is a difficult task to illustrate on a 2-dimensional surface the complex changes that 3- dimensional structures undergo in a 3-dimensional space. This problem can be solved by using sculptural reconstructions since the models are tangible and can be physically examined. However, anatomical models are costly and time-consuming to make, as they require special materials such as wax or plastic and specially trained artists to produce them (Hopwood 1999, Yamada et al. 2005). Anatomical models also may lack anatomical accuracy and detail due to limitations of the material and of the artisan who may not be trained in anatomy. Recently, with the advancement of computer technology,

6 6 detailed 3D images can now be obtained from scans using magnetic resonance imaging (MRI) (Matsuda et al. 2007, Puerta-Fonolla et al. 2004, Smith et al. 1996) and episcopic fluorescence image capture (EFIC) (Rosenthal et al. 2004, Weninger et al. 1998). Both methods are highly effective in capturing information from actual specimens and detailed scans of the midgut have been obtained in this way. However, the technology is not yet sensitive enough to scan the youngest embryos because of their small size. The earliest stages of the developing midgut are therefore much too small to be captured using MRI or EFIC (Yamada et al. 2005). Methods more effective for visualizing midgut rotation have been developed with the advancement of computer software. Animations have become a method of choice because they have the power to make static images come to life (Guttmann 2000). Animations also can make the learning experience more dynamic and interesting for the learner. Studies have shown that test subjects were better able to remember information learned from dynamic visuals over static visuals (Lewalter 2003). High quality animations can be made using advanced computer software, which can now be obtained at a low cost and are not difficult to learn how to use (Guttmann 2000). Both flat 2- dimensional illustrations and complex 3-dimensional models can be animated, but midgut rotation requires a visualization method ideal for visualizing complex movements in 3- dimensions. High quality 3D models of complex structures can be built using advanced computer software. Schleich and Almange built 3D models of the developing heart and animated them using Lightwave. The animation was tested in classrooms and the results have been favorable (Schleich and Almange 2002). Furthermore, animations can be incorporated into a website. This makes the learning experience not only user-interactive

7 7 but also easily accessible to students (Guttmann 2000, Sinav and Ambron 2002). Some 3D models and animations that show midgut rotation are available on the internet, many of which are linked to university websites. Most of these, however, are rudimentary in quality and presented with poor rendering technique, which is important in clearly communicating the midgut anatomy. There is no evidence that a combined method of animation and website has been used for visualizing midgut rotation, however, this method is perhaps the most effective. Students have difficulty learning midgut rotation for various reasons. One reason is lack of spatial cognition. Spatial cognition refers to the understanding of the spatial arrangement of objects in space. This skill is required in visualizing complex movements such as midgut rotation. Another reason is based on the assumption that the learner will try to use all of the information presented to them at once (Lewalter 2003). This could cause problems if there is too much information for the learner to process, for example, using realistic 3D models rather than simplified 2D illustrations. It can be argued that a more simplistic approach may be more appropriate in showing the complex anatomy of the midgut in order to prevent possible cognitive overload (Weiss et al. 2002). However, because dynamic visual aids such as animations seem to enhance learning by helping the learner make connections between visual material and their prior knowledge, a proper balance between simplistic and complex visuals should be considered (Lewalter 2003). My hypothesis is that students will learn midgut rotation incrementally from simplistic to realistic animations. By doing so, I intend to reduce cognitive overload by first showing a simplistic 2D version of an animation of the developing midgut and then show a realistically rendered 3D version of the same animation. Finally, I also intend to show

8 8 that students can improve their spatial cognition skill as an added benefit to watching the animations. Methods 2D Component with Adobe Photoshop and Flash CS3 A simplified 2-dimensional animation showing midgut rotation will be created using Adobe Photoshop and Flash CS3 (Adobe 2007). Adobe Photoshop allows the user to maintain a schematic look by keeping the rendering technique simple. Structures of the developing midgut will be rendered in Adobe Photoshop and brought into a Flash website that I will also create. The animation will be programmed using the Actionscript 3.0 language. The content will also be kept as schematic as possible by noting only the most important structures, such as the midgut and superior mesenteric artery, and events, such as rotation, herniation and return. Finally, a simple illustration showing orientation will be created to accompany the animation. 3D Component with Maxon Cinema 4D 3-dimensional models of the developing midgut will be created using the 3D software Cinema 4D version 10.0 (Maxon 2007). This advanced program is versatile in that it allows the user to create objects in 3-dimensions, add color and textures, and also create high quality animations. I will be using Cinema 4D to construct detailed and realistic models of the developing midgut. Appropriate colors and textures will be added to enhance realism. I will also include the superior mesenteric artery and appropriate mesenteric tissue. A 3D model of the embryo will be created to accompany the animation to show orientation. Finally, I will create an animation of the midgut as it rotates, herniates into the umbilical cord, and returns back into the abdomen. Animations

9 9 built in Cinema 4D can be rendered from multiple viewpoints by setting cameras at relevant locations around the 3D models. The original 3D animation of the midgut will be rendered in this way. The result is multiple sub animations showing different views of the developing midgut. All of these animations will be incorporated into the website so that the user has the option to view the changing midgut from different angles. Interactive Website with Adobe Flash CS3 The completed animations will be brought into a website that I will create using Adobe Flash CS3 (Adobe 2007). Programming will be carried out using the Actionscript 3.0 language. The interface will have a simple design so that it will be easy to navigate. Multiple forms of user-interactivity will be added to the website to enhance the user s learning experience. Stop and Play buttons and slider bars will be added to allow the user power to control the animations. Slider bars are particularly useful in that the user can go back to a particular part of the animation they found difficult to understand and play it over as needed. The slider bars can also be used to control the animation s speed. Further user-interactivity will be added to the series of 3D animations including the user s ability to choose which view they want to see the developing midgut. Finally, text and a glossary of terms will be included to further aid the student. Testing on a Student Population The completed website will be tested on a student population. Groups of students relevant for testing are undergraduate students taking an advanced embryology or anatomy course, medical students, or surgical residents. The aim of the test is to measure the user s ability to understand midgut rotation before and after using the website. The test will be in the form of questionnaires asking students relevant questions before (pre-

10 10 test) and after (post-test) using the website. The pre-test will consist of questions concerning how students currently are taught midgut rotation, what kind of tools they use to help them learn midgut rotation, and the level of their knowledge in midgut rotation. After using the website, students will take a post-test that will consist of questions concerning the website and the level of their knowledge in midgut rotation. Students will be allowed to add comments after completing each questionnaire. The entire test will be available electronically. Anticipated Results The website will be designed so that students can use it as a supplement to an embryology or anatomy course. I anticipate that by using the website, students will find it easier to learn the complex anatomy of midgut rotation than it was before using the website. I also hope that by utilizing an incremental approach (i.e. from simple 2D animation to complex 3D animations), students can gradually learn midgut rotation and avoid cognitive overload. This approach together with the benefits offered by websites such as user-interactivity, easy accessibility, and an easy-to-use interface design, students will find a complex subject such as midgut rotation less overwhelming and easier to understand. Discussion Midgut rotation in the human embryo is complex and requires a visualization method that will illustrate it in an effective way. Numerous methods have been described and I have concluded that an incremental approach with animations, the first being schematic and 2-dimensional and the second being complex and 3-dimensional, incorporated into a website would be the ideal. This methodology is important for

11 11 furthering both the field of biomedical communications and medicine. This has never been done for visualizing midgut rotation and if successful, I believe that this methodology can be extrapolated for use as a visualization method for other complex morphological events that occur in 3-dimensional space. This includes complex processes that occur in human embryology as well as in other scientific fields. As long as there is a complex process that needs to be visualized, this methodology may prove to be the most useful means. Furthermore, this method is of value clinically since surgical residents can learn anatomy that can be involved in common congenital disorders. References Blechschmidt E The ontogenetic basis of human anatomy: a biodynamic approach to development from conception to birth. Berkeley: Pacific distributing. Cyr DR, Mack LA, Shoenecker SA, Patten RM, Shepard TH, Shuman WP, Moss AA Bowel migration in the normal fetus: US detection. Radiology 161, Guttmann GD Animating functional anatomy for the web. Anat Rec 261, Hopwood N Giving body to embryos: modeling, mechanism, and the microtome in late nineteenth century anatomy. Isis 90, Jirasek JE An atlas of human prenatal development mechanics: anatomy and staging. London: Taylor and Francis. Kim WK, Kim H, Ahn DH, Kim MH, Park HW Timetable for intestinal rotation in staged human embryos and fetuses. Birth Defects Res Part A 67, Larsen WJ Human embryology 3 rd ed. Philadelphia: Churchill Livingstone.

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