1. Structure and Function of the Heart Pathophysiology October 11, 2004

2. Heart Facts Put your hand on your heart. Did you place your hand on the left side of your chest? Many people do, but the heart is actually located almost in the center of the chest, between the lungs. It's tipped slightly so that a part of it sticks out and taps against the left side of the chest, which is what makes it seem as though it is located there. Put your hand on your heart. Did you place your hand on the left side of your chest? Many people do, but the heart is actually located almost in the center of the chest, between the lungs. It's tipped slightly so that a part of it sticks out and taps against the left side of the chest, which is what makes it seem as though it is located there.

3. Your heart beats about 100,000 times in one day and about 35 million times in a year. During an average lifetime, the human heart will beat more than 2.5 billion times. Your heart beats about 100,000 times in one day and about 35 million times in a year. During an average lifetime, the human heart will beat more than 2.5 billion times. The aorta, the largest artery in the body, is almost the diameter of a garden hose. Capillaries, on the other hand, are so small that it takes ten of them to equal the thickness of a human hair. The aorta, the largest artery in the body, is almost the diameter of a garden hose. Capillaries, on the other hand, are so small that it takes ten of them to equal the thickness of a human hair.

4. Your body has about 5.6 liters (6 quarts) of blood. This 5.6 liters of blood circulates through the body three times every minute. In one day, the blood travels a total of 19,000 km (12,000 miles)--that's four times the distance across the US from coast to coast. Your body has about 5.6 liters (6 quarts) of blood. This 5.6 liters of blood circulates through the body three times every minute. In one day, the blood travels a total of 19,000 km (12,000 miles)--that's four times the distance across the US from coast to coast. lub-DUB, lub-DUB, lub-DUB. Sound familiar? If you listen to your heart beat, you'll hear two sounds. These "lub" and "DUB" sounds are made by the heart valves as they open and close. lub-DUB, lub-DUB, lub-DUB. Sound familiar? If you listen to your heart beat, you'll hear two sounds. These "lub" and "DUB" sounds are made by the heart valves as they open and close.

5. Heart Anatomy Location: mediastinum Location: mediastinum Surrounded by: pericardial sac Surrounded by: pericardial sac Composed of: cardiac muscle Composed of: cardiac muscle Epicardium contains lubricating fluid to faciliate heart movement Epicardium contains lubricating fluid to faciliate heart movement Mycardium is the cardiac muscle Mycardium is the cardiac muscle Endocardium is the inner layer that forms heart valves Endocardium is the inner layer that forms heart valves

6. External Structure Four chambers: Four chambers: 2 Upper: Atria 2 Upper: Atria Blood enters the heart Blood enters the heart 2 Lower: Ventricles 2 Lower: Ventricles Blood leaves the heart Blood leaves the heart Two halves separated by the septum Two halves separated by the septum

7. Internal Structure Atrioventricular (AV) valves separate the atria and ventricles Atrioventricular (AV) valves separate the atria and ventricles Right: tricuspid Right: tricuspid Left: mitral (bicuspid) Left: mitral (bicuspid) Semilunar valves at the exits of the aorta and pulmonary artery Semilunar valves at the exits of the aorta and pulmonary artery

8. Blood Flow (Right side) Deoxygenated blood enters through the VENA CAVAE Deoxygenated blood enters through the VENA CAVAE Passes through the RIGHT ATRIUM Passes through the RIGHT ATRIUM It then passes through the TRICUSPID VALVE and enters the RIGHT VENTRICLE It then passes through the TRICUSPID VALVE and enters the RIGHT VENTRICLE It leaves the heart through the PULUMONARY ARTERIES where it goes to the lungs to pick up OXYGEN It leaves the heart through the PULUMONARY ARTERIES where it goes to the lungs to pick up OXYGEN

9. Blood Flow (Left side) Oxygen rich blood enters the heart through the PULMONARY VEINS Oxygen rich blood enters the heart through the PULMONARY VEINS It passes through the LEFT ATRIUM It passes through the LEFT ATRIUM It moves through the MITRAL VALVE and enters the LEFT VENTRICLE It moves through the MITRAL VALVE and enters the LEFT VENTRICLE It will leave the heart through the AORTA to deliver oxygen rich blood to the body It will leave the heart through the AORTA to deliver oxygen rich blood to the body

11. Conduction System Electrical impulses from your heart muscle cause it to beat (contract). Electrical impulses from your heart muscle cause it to beat (contract). This electrical signal begins in the sinoatrial (SA) node, located at the top of the right atrium. The SA node is sometimes called the heart's "natural pacemaker." This electrical signal begins in the sinoatrial (SA) node, located at the top of the right atrium. The SA node is sometimes called the heart's "natural pacemaker." When an electrical impulse is released from this natural pacemaker, it causes the atria to contract. When an electrical impulse is released from this natural pacemaker, it causes the atria to contract. The signal then passes through the atrioventricular (AV) node. The AV node checks the signal and sends it through the muscle fibers of the ventricles, causing them to contract. The signal then passes through the atrioventricular (AV) node. The AV node checks the signal and sends it through the muscle fibers of the ventricles, causing them to contract.

12. The Heartbeat – Two pumping Action When the SA Node causes the atria to contract, blood is pushed through the tricuspid and mitral valves into the resting ventricles. When the SA Node causes the atria to contract, blood is pushed through the tricuspid and mitral valves into the resting ventricles. This part of the two-part pumping phase (the longer of the two) is called the diastole. This part of the two-part pumping phase (the longer of the two) is called the diastole.

13. The second part of the pumping phase begins when the ventricles are full of blood. The electrical signals from the SA node travel along a pathway of cells to the ventricles, causing them to contract. This is called systole. The second part of the pumping phase begins when the ventricles are full of blood. The electrical signals from the SA node travel along a pathway of cells to the ventricles, causing them to contract. This is called systole.