In this experiment, we obtained a fresh heart and dissected it to examine and observe the different parts of the heart, as well as studying how they function and work Problem: How can we study the heart through dissection? The most basic function of the circulatory system is to move the blood. The organ that provides the force to push the blood through the vessels is the heart. The mammalian heart is composed of four chambers to which large blood vessels are connected. The walls of these chambers are made of cardiac muscle tissue.
It is the ontraction of these muscular walls in a synchronized manner that moves the blood through this pump and its connected vessels. Valves are present in several locations, where they function to maintain a indirectional flow of blood. By doing this experiment, we will gain an understanding of the complexity of a heart, by learning and doing how to probe the chambers and observe it carefully, and inspecting the valves. We will also learn about our own hearts, because besides the size, mammalian hearts are all very similar.
Materials: mammalian heart, glass probe, dissecting pan, single-edged razor blade, issecting needle, scalpel, absorbent paper towel Procedure & Results: Refer to lab sheets! 1) Describe the function of each of the four heart chambers. Blood first enters the right atrium while the atria are relaxing. This blood is coming back from the body tissues. The blood that is returning from the lungs enters the left atrium. The atria contracts, and causes the ventricles to fill with blood.
This contracts also and makes the blood flow out of the left ventricle, into the aorta, while blood flows into the pulmonary artery from the right ventricle. How are these chambers adapted for their specific functions? The four heart chambers contract and relax because of the function of the cardiac muscles. This controls the blood flow in and out of the heart. 3) Why is the mammalian heart often described as two hearts that beat as one? This is because the right side pumps blood to the lungs, while the other side pumps blood to the rest of the body, except for the lungs, thus creating a double beat. 4) Why is it necessary for there to be lag between the simultaneous contraction of the tria and the simultaneous contraction of the ventricles?
The blood must be able to flow from the atria and to the ventricles. The lag allows the closing and opening of the valves. 5) How is timing discussed in question 4 achieved? It is achieved by the rhythmical on-going process of contraction and relaxation. 6) How is the pulse related to ventricular contraction (systole)? The pulse is caused by the constant flexing. 7) Why is it essential to the function of the cuspid valves that the muscles attached to These valves must prevent back-flow of blood in the heart.
Describe the position of the atria-ventricular valves and the semi-lunar valves during ventricular contraction (systole) and during ventricular relaxation (diastole). During systole, the atrioventricular valves are closed as a result of the contraction of the ventricles, while the semilunar valves are open. During diastole, 9) What causes the heart sounds that can be heard with a stethoscope? What is meant The sounds are caused by the opening and closing of the heart valves. 10) What actually occurs in the heart that results in a myocardial infarction (heart
A large deposit of fatty material in the artery largely reduces the size of the space where blood flows through, and so blood cannot flow naturally through. 11) Trace the path of a blood cell from the time it enters the heart from the vena cava until it leaves through the aorta. Mention each chamber, valve, major vessel and organ As the blood cell enters the vena cava, it also enters the atria during diastole. Going through the cuspid valves, it flows to the ventricles. The cuspid valves close, and the semilunar valves open, when systole begins.