Heart Valve

Heart Valve Experiment Overview

In this experiment, we constructed a synthetic model of a human aortic valve. We began by selecting materials using the Young’s Modulus data collected from our prior report to construct the model. Using these materials, we designed a prototype that effectively displays the structure and function of a human aortic valve. The device consisted of a pink balloon, latex glove, funnel, clear plastic tube, paper flaps, and tape. We used the balloon as the interior wall of the heart, and the latex glove as the exterior wall of the heart since, from testing, we found that the balloon was less stretchy. There are parallel openings in the “heart” of our device. These openings act as the aortic valves. The openings are taped to clear, plastic tubes that serve as the arteries coming out of the heart. In these tubes are paper leaflets. The paper is laminated in tape to keep from being destroyed by the flow of water. Similar to human leaflets, the paper leaflets open and close to allow the flow of liquid through the heart. There is a funnel attached to the tube coming out of the top of the heart. This allows us to control the amount of water in the system at any given time. The bottom tube acts as the inferior vena cava, directing liquid out of the heart. The heart is “pumped” by manual force. Squeezing the heart will expel liquid through the inferior vena cava tube which empties back into the funnel to re-enter the heart through the aortic valve. With many modifications and redesigns, our group was able to effectively model an authentic human aortic valve. Possible errors include differences in viscosity, pressure of blood, and pressure of water. By using water to test our model, we did not consider the differences of the properties of these substances. Further experimentation could test these discrepancies.

Inintial Research

Initial Sketches/ Research

Materials Testing

Each group was instructed to choose materials that would later be used to make a heart valve model. In this part of the project, we needed to test each material chosen and compare their properties to the properties of real heart valve tissues. Our group decided to use stretchy material that we had access to at home. We ended up choosing balloons and latex gloves as our materials. The goal of our material testing was to be able to calculate the stress and strain of each material. We did this by testing our materials to acquire all of the variables we needed to insert into the equations of stress and strain. This lab write-up displays all of the components that went into our materials testing; including why we chose the materials we chose, how we tested our materials, and why we tested our materials. Our driving question was: What materials have similar Young’s Modulus to that of the natural valves of the human heart?

Content

Systole - The phase of the heartbeat when the heart muscle contracts and pumps blood from the chambers into the arteries.

Aortic Semilunar Valve - Connect your heart ventricles (lower chambers) and arteries. Semilunar valves get their name from the crescent moon shape of the flaps that make up the valve.

Elastin - Is one of the most abundant proteins in your body. It's a stretchy protein that can extend and shrink back recoil.

Ventricularis Layer - Composed of collagen and elastin fibers, serves as an insertion point for the chordae tendineae that anchor the leaflets to the papillary muscles

Laminar Flow - A type of flow pattern of a fluid in which all the particles are flowing in parallel lines

Fibrosa Layer - Cardiac aortic valve is composed mostly of a dense network of type I collagen fibers oriented in circumferential direction. This main layer bears the tensile load and responds to the high stress on a leaflet.

Aortic Valve - The main outflow valve for the left heart. It is the valve between the heart and the body. The aortic valve opens when the left ventricle squeezes to pump out blood, and closes in between heart beats to keep blood from going backward into the heart.

Aorta - The aorta is the main artery in the heart. It carries blood away from your heart to the rest of your body. The blood leaves the heart through the aortic valve. Blood then travels through the aorta, making a cane-shaped curve that allows other major arteries to deliver oxygen-rich blood to the brain, muscles and other cells.

The cross-sectional area - the area of a two-dimensional shape that is obtained when a three-dimensional object. For example a cylinder is sliced perpendicular to some specified axis at a point. For example, the cross-section of a cylinder - when sliced parallel to its base - is a circle.

Ventricles - A ventricle is one of two large chambers toward the bottom of the heart that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs. The atrium (an adjacent/upper heart chamber that is smaller than a ventricle) primes the pump.

Atriums - The two atria are thin-walled chambers that receive blood from the veins. The two ventricles are thick-walled chambers that forcefully pump blood out of the heart. The right atrium receives de-oxygenated blood from systemic veins; the left atrium receives oxygenated blood from the pulmonary veins.

Young's Modulus - Measure of the ability of a material to withstand changes in length when under lengthwise tension or compression. Sometimes referred to as the modulus of elasticity, Young's modulus is equal to the longitudinal stress divided by the strain.

Stress - Force per unit area within materials that arises from externally applied forces, heating, etc

Strain - The measurement of how much an object can stretch before it is deformed.

Elasticity - The measurement of an object or variable's sensitivity to change.

Leaflet - Each valve has flaps (leaflets) that open and close once during each heartbeat. If a valve doesn't open or close properly, blood flow through the heart to the body can be reduced.

Reflection

The Heart Valve Experiment truly tested our group's resiliance, critical thinking, and communication skills. We were able to rise to the challenge and excel at all of these things. No matter how frusterated we got trying to figure out what materials to use, and how to structure a prototype, we never gave up. It took a lot of time, research, and redesigning, but we eventually developed a prototype that followed the guidelines. Our group also had to display a lot of critical thinking skills. Applying our research about the human heart to our data collected in materials testing took a lot of time and critical thinking. Lastly our group had great communication. Our group decided to split up some tasks by communicating what each person was doing. Then we came back together and discussed what each of us accomplished. This worked very well for our group because it gave everyone more perceived time and helped everyone finish their tasks to better understand the project.

One thing our group struggled with was procrastination. We also had a Capstone project to be working on simultaniously with the Heart Valve project. Instead of working on both projects evenly in our timeframe, we prioritized the Capstone Presentation, leaving the Heart Valve prototype to be completed in two days. This was not strategic. While it all turned out fine in the end, better time management could have saved us from a lot of stress. Overall, our group worked very well together and ended with a final product that we are proud of.