Heart valve
HEART VALVE PROJECT
In this project, we started to learn about calculating the young modulus of a product, as well as the functions of an aortic heart valve. To showcase what we learned, we built a prototype of an aortic heart valve and calculated its young modulus. For more information about this project, check out my teacher Mr. Tronconi's website:
sites.google.com/students.nusd.org/stemse/u5-part-1-design-a-heart-valve
sites.google.com/students.nusd.org/stemse/u5-part-2-design-a-heart-valve
sites.google.com/students.nusd.org/stemse/u5-part-3-design-a-heart-valve
Background- Our Research
In this project, we started to learn about calculating the young modulus of a product, as well as the functions of an aortic heart valve. To showcase what we learned, we built a prototype of an aortic heart valve and calculated its young modulus. For more information about this project, check out my teacher Mr. Tronconi's website:
sites.google.com/students.nusd.org/stemse/u5-part-1-design-a-heart-valve
sites.google.com/students.nusd.org/stemse/u5-part-2-design-a-heart-valve
sites.google.com/students.nusd.org/stemse/u5-part-3-design-a-heart-valve
Background- Our Research
- Young's modulus is a 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. In physics, a force is any interaction that, when unopposed, will change the motion of an object. A force can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a push or a pull. A force has both magnitude and direction, making it a vector quantity. It is measured in the SI unit of newtons and represented by the symbol F. The original form of Newton's second law states that the net force acting upon an object is equal to the rate at which its momentum changes with time. If the mass of the object is constant, this law implies that the acceleration of an object is directly proportional to the net force acting on the object, is in the direction of the net force, and is inversely proportional to the mass of the object. Concepts related to force include: thrust, which increases the velocity of an object; drag, which decreases the velocity of an object; and torque, which produces changes in rotational speed of an object. In an extended body, each part usually applies forces on the adjacent parts; the distribution of such forces through the body is the internal mechanical stress. Such internal mechanical stresses cause no acceleration of that body as the forces balance one another. Pressure, the distribution of many small forces applied over an area of a body, is a simple type of stress that if unbalanced can cause the body to accelerate. Stress usually causes deformation of solid materials, or flow in fluids. In physics, elasticity is the ability of a body to resist a distorting influence and to return to its original size and shape when that influence or force is removed. Solid objects will deform when adequate forces are applied on them. In continuum mechanics, stress is a physical quantity that expresses the internal forces that neighboring particles of a continuous material exert on each other, while strain is the measure of the deformation of the material.
- The heart is a muscular organ about the size of a closed fist that functions as the body’s circulatory pump. It takes in deoxygenated blood through the veins and delivers it to the lungs for oxygenation before pumping it into the various arteries (which provide oxygen and nutrients to body tissues by transporting the blood throughout the body). The heart is located in the thoracic cavity medial to the lungs and posterior to the sternum. The heart sits within a fluid-filled cavity called the pericardial cavity. The walls and lining of the pericardial cavity are a special membrane known as the pericardium. Pericardium is a type of serous membrane that produces serous fluid to lubricate the heart and prevent friction between the ever beating heart and its surrounding organs. Besides serving as lubrication, the pericardium helps to hold the heart in position and maintain a hollow space for the heart to expand into when it is full. The pericardium has 2 layers—a visceral layer that covers the outside of the heart and a parietal layer that forms a sac around the outside of the pericardial cavity. The heart wall is made of 3 layers: epicardium, myocardium and endocardium. The epicardium is the outermost layer of the heart wall and is just another name for the visceral layer of the pericardium. Thus, the epicardium is a thin layer of serous membrane that helps to lubricate and protect the outside of the heart. Below the epicardium is the second, thicker layer of the heart wall: the myocardium. The myocardium is the muscular middle layer of the heart wall that contains the cardiac muscle tissue. Myocardium makes up the majority of the thickness and mass of the heart wall and is the part of the heart responsible for pumping blood. Below the myocardium is the thin endocardium layer. Endocardium is the simple squamous endothelium layer that lines the inside of the heart. The endocardium is very smooth and is responsible for keeping blood from sticking to the inside of the heart and forming potentially deadly blood clots. The thickness of the heart wall varies in different parts of the heart. The atria of the heart have a very thin myocardium because they do not need to pump blood very far—only to the nearby ventricles. The ventricles, on the other hand, have a very thick myocardium to pump blood to the lungs or throughout the entire body. The right side of the heart has less myocardium in its walls than the left side because the left side has to pump blood through the entire body while the right side only has to pump to the lungs. The heart contains 4 chambers: the right atrium, left atrium, right ventricle, and left ventricle. The atria are smaller than the ventricles and have thinner, less muscular walls than the ventricles. The atria act as receiving chambers for blood, so they are connected to the veins that carry blood to the heart. The ventricles are the larger, stronger pumping chambers that send blood out of the heart. The ventricles are connected to the arteries that carry blood away from the heart. The chambers on the right side of the heart are smaller and have less myocardium in their heart wall when compared to the left side of the heart. This difference in size between the sides of the heart is related to their functions and the size of the 2 circulatory loops. The right side of the heart maintains pulmonary circulation to the nearby lungs while the left side of the heart pumps blood all the way to the extremities of the body in the systemic circulatory loop. The heart functions by pumping blood both to the lungs and to the systems of the body. To prevent blood from flowing backwards or “regurgitating” back into the heart, a system of one-way valves are present in the heart. The heart valves can be broken down into two types: atrioventricular and semilunar valves. Atrioventricular valves. The atrioventricular (AV) valves are located in the middle of the heart between the atria and ventricles and only allow blood to flow from the atria into the ventricles. The AV valve on the right side of the heart is called the tricuspid valve because it is made of three cusps (flaps) that separate to allow blood to pass through and connect to block regurgitation of blood. The AV valve on the left side of the heart is called the mitral valve or the bicuspid valve because it has two cusps. The AV valves are attached on the ventricular side to tough strings called chordae tendineae. The chordae tendineae pull on the AV valves to keep them from folding backwards and allowing blood to regurgitate past them. During the contraction of the ventricles, the AV valves look like domed parachutes with the chordae tendineae acting as the ropes holding the parachutes taut. The semilunar valves, so named for the crescent moon shape of their cusps, are located between the ventricles and the arteries that carry blood away from the heart. The semilunar valve on the right side of the heart is the pulmonary valve, so named because it prevents the backflow of blood from the pulmonary trunk into the right ventricle. The semilunar valve on the left side of the heart is the aortic valve, named for the fact that it prevents the aorta from regurgitating blood back into the left ventricle. The semilunar valves are smaller than the AV valves and do not have chordae tendineae to hold them in place. Instead, the cusps of the semilunar valves are cup shaped to catch regurgitating blood and use the blood’s pressure to snap shut.
- Here is a padlet full of research information: padlet.com/olgonzalez/STEM_RESEARCH_HEART_VALVE
Our Design
We took a cardboard tube and cut it up into different sized rings. We then layered the rings and covered them with a nitrile rubber glove. We then covered the whole project in a piece of glove, and created a flap for the water to come out. We made the actual valve with popsicle sticks to prevent the water from coming back up into the valve.
The young modulus ended up being 0.98 x 10^8.
Reflections
This project overall was very informative, though it took a lot of work, stress, and frustration. We weren't really taught how to do many of the calculations; it was all research on our own. Though it seemed like simple math, it took a lot of practice to get it right without direction, especially just being told to look on a website. The building process also was very frustrating, but with teamwork and patience, we were able to get a functioning model. All in all, it was a very interesting project.
We took a cardboard tube and cut it up into different sized rings. We then layered the rings and covered them with a nitrile rubber glove. We then covered the whole project in a piece of glove, and created a flap for the water to come out. We made the actual valve with popsicle sticks to prevent the water from coming back up into the valve.
The young modulus ended up being 0.98 x 10^8.
Reflections
This project overall was very informative, though it took a lot of work, stress, and frustration. We weren't really taught how to do many of the calculations; it was all research on our own. Though it seemed like simple math, it took a lot of practice to get it right without direction, especially just being told to look on a website. The building process also was very frustrating, but with teamwork and patience, we were able to get a functioning model. All in all, it was a very interesting project.