Lab 12. Heart dissection online lab handout-1-1

Fall 2019 BIO160 Name: ___Evelyn Alvarado__________Date: _______________ Class days/times _______________ Lab 12: Heart Dissection Online Lab This lab is a modification of the heart dissection lab we do in Bio 160 lab classes Directions: For this lab you need to watch the you tube video Sheep Heart Structures External and Internal . Look carefully at the external anatomy of the heart in the video. Identify the structures in bold in the following steps. Put a check mark in the box after you have watched a step. Next identify the structures after the heart is cut open. 1. Determine the orientation of the heart. Determine which side is anterior, which side is posterior, which side is superior, and which side is inferior. To help you get oriented, note that the blood vessels of the heart exit out of the superior side of the heart, and they connect to the posterior side of the heart. If you are having a hard time determining the orientation of the heart, watch that part of the video again. 2. The base of the heart is the wide edge on the superior portion of the heart. The apex of the heart is the narrow, pointed, inferior portion of the heart. 3. Attached to the base of the heart are the left auricle and the right auricle . The auricles are flaps that may look like ears (that’s how they got their name). The auricles are connected to the atria. They fill will blood during a heartbeat to increase the amount of blood the atria can hold. 4. The ventricles are the inferior chambers of the heart. On the anterior surface of the heart, you can see a shallow ravine. This ravine is called the anterior interventricular sulcus . This ravine provides an external landmark of the wall that separates the ventricles internally. On the posterior surface of the heart, you will see the posterior interventricular sulcus . 5. There are several large blood vessels that enter and leave the heart. The aorta is a large artery that carries oxygenated blood from the left ventricle to the systemic circulation (the tissues of the body). The superior vena cava and inferior vena cava are large veins that carry deoxygenated blood from the systemic circulation to the right atrium of the heart. The pulmonary trunk is a large artery that carries deoxygenated blood from the right ventricle. 6. Now in the video please to take a look at the internal anatomy of the heart. 7. Look at the walls of the heart. You will notice three layers. The most superficial layer is the visceral pericardium , which is part of the serous membrane of the heart (pericardium). 1

Fall 2019 BIO160 The thick middle layer is the myocardium , which is the cardiac muscle tissue. The deepest layer, lining the inner walls of the chambers is the endocardium . 8. You can differentiate between the right and left sides of the heart by looking at the thickness of the myocardium. The left side of the heart is responsible for pumping blood to all parts of the body, so the myocardium is thicker to be able to produce a stronger contraction. The right side of the heart only has to pump blood to the lungs and back, so the myocardium on the right side of the heart of thinner. 9. There are two chambers on the right side of the heart. The right atrium is the superior chamber and the right ventricle is the inferior chamber. The two chambers are separated by the right atrioventricular valve (also called the tricuspid valve). The right atrioventricular valve has three flaps of tissue called cusps that are anchored to the internal ventricular wall by strings of tissue called the chordae tendineae . When the right ventricle contracts, the cusps snap closed, preventing blood from flowing back into the right atrium. The chordae tendineae prevent the cusps from inverting due to the pressure in the ventricles. 10. Between the right ventricle and the base of the pulmonary trunk, you will find some cup- shaped cusps. These cusps make up the pulmonary semilunar valve . When the right ventricle contracts, the cusps of the pulmonary semilunar valve open, allowing blood to flow into the pulmonary trunk. When the ventricle stops contracting, the cusps close as blood drops back towards the valve due to the gravity. The cusps prevent the blood from going back into the ventricle. 11. The right atrium receives deoxygenated blood from the superior and inferior vena cavae. This blood passes through the right atrioventricular valve into the right ventricle. From the right ventricle, the blood is pumped through the pulmonary semilunar valve into the pulmonary trunk. The pulmonary trunk branches into the left and right pulmonary arteries, which carry the blood to the lungs to drop off carbon dioxide and take up oxygen. 12. The left side of the heart has two chambers – a left atrium and a left ventricle . The left atrium and left ventricle are separated by the left atrioventricular valve (also called the bicuspid or mitral valve). The left atrioventricular valve has two cusps and like the right atrioventricular valve, it is connected to the interior ventricular wall by chordae tendineae . 13. The aortic semilunar valve is located between the left ventricle and the base of the aorta. It has cup-shaped cusps like the pulmonary semilunar valve. 2

Fall 2019 BIO160 2. What causes the atrioventricular valves to close? When the ventricles contract, ventricular pressure exceeds atrial pressure which makes it close. 3. What causes the semilunar valves to open? The semilunar valves opens when the ventricular muscule contracts and creates blood pressure in the ventricle 4. What causes the semilunar valves to close? When the blood pressure in the arteries is greater than the ventricles it pushes them to close. 5. What is the overall function of the heart valves? The overall function of the heart valves is to provide a healthy blood circulation. 4

Fall 2019 BIO160 6. Which artery carries deoxygenated blood out of the heart? Pulmonary arteries carries deoxygenated blood out of the heart. 5