Congenital heart disease in newborns exhibits a spectrum of defects, one of which is the occlusion of the vascular conduits of the arteries. For students first learning about cardiovascular lesions, the tortuous path of blood vessels can be visually overwhelming to the untrained eye, and useful models are needed to help deconstruct the morphological complexity of heart chambers and vessel location during heart development and disease. Here, I present two hands-on activities to explore how pulmonary artery stenosis may have dire consequences, such as cardiac muscle cell hypertrophy. These activities will not only help students explore genetic aberrations associated with congenital heart diseases, but will also encourage them to think about how to develop molecular and cellular strategies that fix primary obstruction in other branched organs such as the gut, kidney, and pancreas.

One of the pressing challenges in teaching concepts of developmental biology is enabling students to gain an integrated molecular and cellular understanding of important biological processes during tissue development and disease progression. Retracing the stepwise progression of disease requires engaging and gauging (engauging) student learning (Handelsman et al., 2007) through a multifaceted approach: laboratory inquiry (Buskohl et al., 2012; Dorrell et al., 2012; Liang et al., 2014), teaching methods used to clarify students’ misconceptions about physiological processes (Michael et al., 2002; Modell et al., 2005), and hands-on activities (Goodman et al., 2006; Hudson, 2012, 2013, 2014; Bailey, 2013; Kao, 2014). In particular, Howard Hughes Medical Institute (HHMI) offers a virtual cardiology lab (Wallace, 2009) and articles on cardiac hypertrophy (Diwan & Dorn, 2007) and renal artery stenosis (Eirin & Lerman, 2013) (see Life Science Teaching Resource Community, LifeSciTRC.org). There are also teaching methods that provide students an opportunity to probe heart valve formation in the cardiovascular system (Hudson, 2013, 2014), as well as models that provide exploration of cellular strategies to repair lumen pathologies, or lumopathies (Kao, 2014). However, one open question remains: How do we integrate these heart valve models to develop inexpensive, hands-on models that engage students to explore how a primary defect influences secondary defects during hole-in-heart diseases? In organ development, such as the formation of heart and coronary vessels (Majesky, 2004; Dong et al., 2008; Tomanek, 2012), newborns with congenital heart defects display a spectrum of defects: holes between heart chambers, hypertrophy of cardiac muscle cells, mixing of oxygenated and deoxygenated blood, and narrowing of arteries (Tomanek, 2012). Just as detectives need to piece together the facts underlying a complicated multicar accident on a major highway, scientists and physicians use experimental tools to probe for the molecular and cellular basis of congenital heart defects. As a Fellow at the Pacific Science Center, I developed two related hands-on activities (step-by-step assembly is presented below) for students to explore how an obstruction in a particular region of the heart can lead to dire consequences for cardiac muscle cells. These two activities aim to address two questions: (1) Where is the obstruction present in the heart? (2) What happens to the cardiac muscle cells when there is a roadblock in the pulmonary artery?

The first activity allows students to identify where the obstruction is in one of the modified heart chambers (Figures 1 and 2). The steps for constructing the model of pulmonary artery stenosis defect are outlined in Figure 1. As shown in Table 1, the Bloom's taxonomy (Bloom et al., 1956, 1971) questions to be done in class or as homework will depend on students’ background levels with regard to heart development and mammalian heart anatomy. Inspired by coffee-maker machines, I designed the heart chamber model to highlight a region where stenosis of the pulmonary artery occurs (Figure 2B), as well as a second activity (described below) that enables students to explore one of the right ventricular cardiac muscle's cellular responses to a pulmonary artery stenosis. Here are the step-by-step instructions for constructing the heart-chamber roadblock activity (Figure 1):

  1. Take small and medium-sized shoeboxes and two empty coffee cups (Figure 1A) and an empty rectangular cardboard box (Figure 1B).

  2. Make a slit in one of the colored boxes to ensure that it bisects both the small and the medium-sized shoeboxes (Figure 1C; cyan dotted lines). One half will be the right ventricle and pulmonary artery for either the unobstructed or the obstructed model.

  3. Arrange the halved, gold-colored medium shoebox on top of the smaller red shoebox (Figure 1D) and make a small rectangular opening for three of the four halved shoeboxes (Figure 1D; magenta arrowheads and dotted lines). The obstructed red box representing the pulmonary artery will not be cut (Figure 1D; cyan arrow and dotted square). Fasten the right ventricle and pulmonary artery with fast-bonding glue or transparent masking tape (Figure 1A, E; arrowheads mark glued or taped locations).

  4. Take the unobstructed and obstructed heart-chamber models and arrange them so that a cardboard panel touches the opening ends of the attached shoeboxes (Figure 1F). Glue or use clear masking tape to secure the cardboard panel to the unobstructed or obstructed heart-chamber models (Figure 1G; arrowheads mark glued or taped portions).

  5. Use scissors to create two holes with an approximate diameter of 3 cm, wide enough for bell entry (Figure 1H; cyan dotted lines and arrowheads). Use transparent masking tape to secure the two heart-chamber models to the large cardboard box (from Figure 1B) at the top and bottom (Figure 1H; white arrows and dotted lines mark attachment sites). Finally, place two empty coffee cups, which will collect the marble blood cells (Figure 1H, magenta arrows). Use superglue and tape to secure the small straw pieces in the holes.

Figure 1.

Construction of model for the pulmonary stenosis defect activity. (A) Small and medium-sized shoeboxes and two empty coffee cups. (B) Large rectangular cardboard box for normal and obstructed heart chambers. (C) Dotted lines and arrows showing where to bisect the shoeboxes. (D) Placement of upper right ventricle (gold-colored, halved medium shoebox) and lower pulmonary artery (red-hatched small shoebox). Magenta dotted lines depict openings for lumen (magenta arrowheads) and obstructed pulmonary artery (uncut cardboard surface, cyan dotted lines, arrow). (E) Tape secures the shoeboxes (arrowheads, dotted lines). (F) Placement of heart chambers that sandwich the middle (12 × 6 inches) piece of cardboard. (G) Tape secures the two heart chambers to the middle cardboard. (H) Placement of heart chambers into large cardboard box. Holes for straws (cyan dotted lines, arrows) marked above right ventricle (gold shoeboxes). Tape secures the middle cardboard to the top and bottom ends of the large cardboard box (white dotted lines, arrowheads). Empty coffee cups are placed below normal and obstructed boxes (magenta arrows).

Figure 1.

Construction of model for the pulmonary stenosis defect activity. (A) Small and medium-sized shoeboxes and two empty coffee cups. (B) Large rectangular cardboard box for normal and obstructed heart chambers. (C) Dotted lines and arrows showing where to bisect the shoeboxes. (D) Placement of upper right ventricle (gold-colored, halved medium shoebox) and lower pulmonary artery (red-hatched small shoebox). Magenta dotted lines depict openings for lumen (magenta arrowheads) and obstructed pulmonary artery (uncut cardboard surface, cyan dotted lines, arrow). (E) Tape secures the shoeboxes (arrowheads, dotted lines). (F) Placement of heart chambers that sandwich the middle (12 × 6 inches) piece of cardboard. (G) Tape secures the two heart chambers to the middle cardboard. (H) Placement of heart chambers into large cardboard box. Holes for straws (cyan dotted lines, arrows) marked above right ventricle (gold shoeboxes). Tape secures the middle cardboard to the top and bottom ends of the large cardboard box (white dotted lines, arrowheads). Empty coffee cups are placed below normal and obstructed boxes (magenta arrows).

Figure 2.

(A) Demonstration to identify pulmonary stenosis defect. (B) Close-up view of right atrium (blue straw), right ventricle (red and gold cardboard box), and pulmonary artery (tea-bag wrapper). (C) Bells (0.39 inches or 10 mm in diameter) represent test red blood cells. (D) Pipette cleaners as an alternative to bell-drop test to check where stenosis is present (black arrow at entry into right atrium; white arrow marks pulmonary artery).

Figure 2.

(A) Demonstration to identify pulmonary stenosis defect. (B) Close-up view of right atrium (blue straw), right ventricle (red and gold cardboard box), and pulmonary artery (tea-bag wrapper). (C) Bells (0.39 inches or 10 mm in diameter) represent test red blood cells. (D) Pipette cleaners as an alternative to bell-drop test to check where stenosis is present (black arrow at entry into right atrium; white arrow marks pulmonary artery).

Table 1.
Bloom's taxonomy (Bloom et al., 1956, 1971) questions and suggested activities to be done in class or as homework.
Student LevelStudents’ BackgroundSuggested MethodsQuestions/Follow-up Activities
Elementary/middle school No experience with heart development In-class model building with teacher demonstration.
Emphasize compare-and-contrast between normal and congenital-disease heart models. 
Ask students: Where is the defect located? Allow students to explore HHMI cardiology lab and building heart valves (Hudson, 2014).
Progress to questions such as: What if there is an obstruction? What would happen to cardiac muscle cells along the right ventricle? 
High school/AP Biology Some biology background; little physiology background Include mix of low- and high-level Bloom questions; integrate HHMI cardiology lab with hands-on activities (see Hudson, 2014, and activities presented in this article). Have students investigate and search PubMed for genetic mutants with pulmonary artery and cardiomyocyte hypertrophy. 
Undergraduate biology/developmental biology/physiology course Some developmental and physiology background Use “flipped classroom” strategy: have students build their own models prior to class; in class, ask them to think–pair–share what genetic mutants were involved. How would cardiac injury affect epicardial cells compared to cardiac muscle cells?
Selected primary literature found via PubMed may also be included for instruction (e.g., Figure Facts, Jigsaw, and Gallery Walk). 
How can we test whether the gene of interest is involved in cardiac muscle cell development?
What cellular and molecular interventions can relieve the roadblock in the pulmonary artery? 
Student LevelStudents’ BackgroundSuggested MethodsQuestions/Follow-up Activities
Elementary/middle school No experience with heart development In-class model building with teacher demonstration.
Emphasize compare-and-contrast between normal and congenital-disease heart models. 
Ask students: Where is the defect located? Allow students to explore HHMI cardiology lab and building heart valves (Hudson, 2014).
Progress to questions such as: What if there is an obstruction? What would happen to cardiac muscle cells along the right ventricle? 
High school/AP Biology Some biology background; little physiology background Include mix of low- and high-level Bloom questions; integrate HHMI cardiology lab with hands-on activities (see Hudson, 2014, and activities presented in this article). Have students investigate and search PubMed for genetic mutants with pulmonary artery and cardiomyocyte hypertrophy. 
Undergraduate biology/developmental biology/physiology course Some developmental and physiology background Use “flipped classroom” strategy: have students build their own models prior to class; in class, ask them to think–pair–share what genetic mutants were involved. How would cardiac injury affect epicardial cells compared to cardiac muscle cells?
Selected primary literature found via PubMed may also be included for instruction (e.g., Figure Facts, Jigsaw, and Gallery Walk). 
How can we test whether the gene of interest is involved in cardiac muscle cell development?
What cellular and molecular interventions can relieve the roadblock in the pulmonary artery? 

Allow the students to probe which box (pulmonary artery) is obstructed by letting them drop small bells through the straw and having them check the coffee cups for evidence of which chamber has a roadblock (Figure 2C and Online Supplemental Material: Movie 1). Alternatively, students can use two colored pipe cleaners to deduce this by comparing the length differential to estimate where the roadblock is located (Figure 2D). As shown in Table 1, these activities may be coupled with heart valve models or with HHMI's virtual cardiology lab, depending on the learning goals and the students’ background. Once students have correctly identified that the obstruction is in the end of the pulmonary artery, ask them what would happen to the right ventricular cardiac muscle cells if the pulmonary artery lumen were narrowed. Have them guess what would happen and write it down.

After fielding students’ guesses, ask them how we can use household items to demonstrate and test what would happen to the cardiac muscle cells in response to pulmonary artery stenosis. This model could be made before class, or you may want to use a “flipped classroom” strategy by having students make their model as homework and have them share their models in class the following day (Table 1). In order to help students explore how stenosis of the pulmonary artery leads to hypertrophy (or enlargement) of the right ventricular cardiac muscle cells (cardiomyocytes), I have developed a hands-on “water balloon with a twist” activity. As illustrated in Figures 3 and 4, here are the steps to create this activity:

  1. Make a small, 1-cm slit at the bulb-shaped end of a rubber balloon (Figure 3A). The balloon represents the layer of cardiac muscle cells surrounding the right ventricle. Gather rubber bands and bisect a 7-cm-long straw (Figure 3A)

  2. Place one end of a straw into the punctured balloon (Figure 3B, arrow). The straw represents the pulmonary artery.

  3. Wrap a rubber band around the right ventricle/pulmonary artery junction (Figure 3C, D). Make sure the seal is taut.

  4. Create an obstructed pulmonary artery by stuffing the lumen of the pulmonary artery with a rubber band (Figure 3E, red arrow and dotted line). Push the stuffed rubber band with the blunt end of a ballpoint pen (Figure 3E, magenta arrow). This creates the model of an obstructed pulmonary artery (Figure 3F).

  5. Have students pour water or use a running sink faucet at a constant rate for approximately 1–2 minutes, and have them record changes in balloon size (Figure 4A–C and Online Supplemental Material: Movies 2 and 3).

Figure 3.

Construction of the model of cardiac muscle cell hypertrophy. (A) Balloon with 1-cm cut at bulbed end, rubber bands, and halved straw. (B) Placement of straw into the hole at the bulbed end of the balloon (arrow). (C) Hold balloon and straw with left hand and wrap a rubber band around left end of straw. (D) Example of unobstructed pulmonary artery (straw) attached with rubber band (arrow) to right ventricle (cardiac muscle cells represented by balloon). (E) To create the obstructed pulmonary artery, stuff another rubber band (red arrow, dotted line) into the right side opening of the straw with the blunt end of a pen (magenta arrow). (F) Example of an obstructed pulmonary artery (straw; arrow marking obstruction).

Figure 3.

Construction of the model of cardiac muscle cell hypertrophy. (A) Balloon with 1-cm cut at bulbed end, rubber bands, and halved straw. (B) Placement of straw into the hole at the bulbed end of the balloon (arrow). (C) Hold balloon and straw with left hand and wrap a rubber band around left end of straw. (D) Example of unobstructed pulmonary artery (straw) attached with rubber band (arrow) to right ventricle (cardiac muscle cells represented by balloon). (E) To create the obstructed pulmonary artery, stuff another rubber band (red arrow, dotted line) into the right side opening of the straw with the blunt end of a pen (magenta arrow). (F) Example of an obstructed pulmonary artery (straw; arrow marking obstruction).

Figure 4.

Model depicting cardiac muscle hypertrophy on pulmonary artery stenosis. (A, B) Balloon represents normal, unobstructed pulmonary artery before and after effects of blood (water) flow. (C, D) Swelling of cardiac muscle cells before and after blood flow in obstructed pulmonary artery (black arrows). After blood flow, note the striking enlargement in the obstructed pulmonary artery (D, magenta arrows) compared with the unobstructed pulmonary artery (B).

Figure 4.

Model depicting cardiac muscle hypertrophy on pulmonary artery stenosis. (A, B) Balloon represents normal, unobstructed pulmonary artery before and after effects of blood (water) flow. (C, D) Swelling of cardiac muscle cells before and after blood flow in obstructed pulmonary artery (black arrows). After blood flow, note the striking enlargement in the obstructed pulmonary artery (D, magenta arrows) compared with the unobstructed pulmonary artery (B).

This hands-on activity enables students to explore how a narrowed hole or lumen results in the swelling of the balloon, symbolizing an enlargement of right ventricular cardiac cells (or right ventricle hypertrophy). Creating these activities provides a scaffold for students to further integrate new layers of molecular, biomechanical, and cellular understanding of how a primary narrowing of the pulmonary artery leads to cardiac hypertrophy. For instance, by integrating Bloom in Biology learning goals (Crowe et al., 2008), model building that links artery occlusion to cardiac muscle cell hypertrophy may inspire students to explore and identify genetic heart mutants. This framework would then allow students to piece together the molecular and cellular underpinnings of heart development, and may inspire their curiosity to develop their own experiments to test specific research questions and hypotheses. Finally, these activities may inspire students to think of how they could design ways to fix the narrowing of the pulmonary artery, as well as differentiating between primary and secondary defects in other branched organ systems, such as in the kidneys and pancreas.

Online Supplemental Materials

  • Movie 1: Live footage of red blood cell bells for testing which heart model contains a roadblock (or stenosis of pulmonary artery): https://youtu.be/lGP73n6Xfas

  • Movie 2: Illustration of water flow through water-balloon model of normal pulmonary artery: https://youtu.be/U3B1yzh7QP4

  • Movie 3: Illustration of enlargement or hypertrophy of ventricular cardiomyocytes (cardiac muscle cells lining right ventricle) in response to stenosis of water-balloon model of pulmonary artery: https://youtu.be/12Rnbvm8OJk

I thank Jennifer Pritchard and Stephanie Fitzwater Arduindi for their input when I was a fellow at the Pacific Science Center; Mark Majesky, Lisa Maves, and Xiu Rong Dong for scientific discussions; and anonymous reviewers for their comments. This work was supported by the National Institutes of Health (NIDDK T32007467, “Research Training in Renal Disease”).

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