The heart is the hardest working muscle in the human body that functions as a pump. To understand this function you must first understand that every cell in our body -
Your heart, shaped more like an upside-
The atria receive blood coming back to the heart.
The ventricles pump the blood out of the heart.
The right atrium receives de-
The right ventricle receives de-
The left atrium receives oxygenated blood from the lungs through the pulmonary vein. As the contraction triggered by the sinoatrial node progresses through the atria, the blood passes through the mitral valve into the left ventricle.
The left ventricle receives oxygenated blood as the left atrium contracts. The blood passes through the mitral valve into the right ventricle. The aortic valve leading into the aorta is closed, allowing the ventricle to fill with blood. Once the ventricles are full, they contract. As the left ventricle contracts, the mitral valve closes and the aortic valve opens. The closure of the mitral valve prevents blood from backing into the left atrium and the opening of the aortic valve allows the blood to flow into the aorta and flow throughout the body.
• Blood Vessels
compose a network of arteries and veins that carry blood throughout the body.
Arteries transport blood from the heart to the body tissues.
Veins carry blood back to the heart.
Superior Vena Cava
The superior vena cava is one of the two main veins bringing de-
The inferior vena cava is one of the two main veins bringing de-
The aorta is the largest single blood vessel in the body. It is approximately the diameter of your thumb. This vessel carries oxygen-
The pulmonary artery is the vessel transporting de-
The pulmonary vein is the vessel transporting oxygen-
The four heart valves include the following:
tricuspid valve: located between the right atrium and the right ventricle
pulmonary valve: located between the right ventricle and the pulmonary artery
mitral valve: located between the left atrium and the left ventricle
aortic valve: located between the left ventricle and the aorta
Each valve has flaps, called leaflets, that allow the forward flow of blood and prevent the backward flow.
A valve lets something in and keeps it there by closing -
Two of the heart valves are the mitral valve and the tricuspid valve. They let blood flow from the atria to the ventricles. The other two are called the aortic valve and pulmonary valve, and they're in charge of controlling the flow as the blood leaves the heart. These valves all work to keep the blood flowing forward. They open up to let the blood move ahead, then they close quickly to keep the blood from flowing backward.
• Anatomy and Function of the Heart Valves
Four types of valves regulate blood flow through your heart:
The tricuspid valve regulates blood flow between the right atrium and right ventricle.
The pulmonary valve controls blood flow from the right ventricle into the pulmonary arteries, which carry blood to your lungs to pick up oxygen.
The mitral valve lets oxygen-
The aortic valve opens the way for oxygen-
The tricuspid valve separates the right atrium from the right ventricle. It opens to allow the de-
The mitral valve separates the left atrium from the left ventricle. It opens to allow the oxygenated blood collected in the left atrium to flow into the left ventricle. It closes as the left ventricle contracts, preventing blood from returning to the left atrium; thereby, forcing it to exit through the aortic valve into the aorta.
The pulmonary valve separates the right ventricle from the pulmonary artery. As the ventricles contract, it opens to allow the de-
The aortic valve separates the left ventricle from the aorta. As the ventricles contract, it opens to allow the oxygenated blood collected in the left ventricle to flow throughout the body. It closes as the ventricles relax, preventing blood from returning to the heart.
• An Electrical System
Controls how fast the heartbeats
An electrical stimulus is generated by the sinus node (also called the sinoatrial node, or SA node), which is a small mass of specialized tissue located in the right atrium (right upper chamber) of the heart. The sinus node generates an electrical stimulus periodically (60-
Your heart does not work alone, though. Your brain tracks the conditions around you—climate, stress, and your level of physical activity—and adjusts your cardiovascular system to meet those needs. The younger you are, the faster your heart beats. A baby's heart beats about 90 times a minute. A twelve year old heart beats about 78 times a minute and an adult heart beats about 70 times a minute. Of course the more active you are, the more your heart beats, since the cells need oxygen faster to keep you moving. The human heart is a muscle designed to remain strong and reliable for a hundred years or longer. By reducing your risk factors for cardiovascular disease, you may help your heart stay healthy longer.
Electrical impulses from your heart muscle (the myocardium) cause your heart 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." 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 SA node sends electrical impulses at a certain rate, but your heart rate may still change depending on physical demands, stress, or hormonal factors
A heartbeat is a two-
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. As the tricuspid and mitral valves shut tight to prevent a back flow of blood, the pulmonary and aortic valves are pushed open. While blood is pushed from the right ventricle into the lungs to pick up oxygen, oxygen-
After blood moves into the pulmonary artery and the aorta, the ventricles relax, and the pulmonary and aortic valves close. The lower pressure in the ventricles causes the tricuspid and mitral valves to open, and the cycle begins again. This series of contractions is repeated over and over again, increasing during times of exertion and decreasing while you are at rest.
ANATOMY OF THE HEART
The human heart is primarily a shell. There are four cavities, or open spaces, inside the heart that fill with blood. Two of these cavities are called atria. The other two are called ventricles. The two atria form the curved top of the heart. The ventricles meet at the bottom of the heart to form a pointed base which points toward the left side of your chest. The left ventricle contracts most forcefully, so you can best feel your heart pumping on the left side of your chest.
The left side of the heart houses one atrium and one ventricle. The right side of the heart houses the others. A wall, called the septum, separates the right and left sides of the heart. A valve connects each atrium to the ventricle below it. The mitral valve connects the left atrium with the left ventricle. The tricuspid valve connects the right atrium with the right ventricle.
The top of the heart connects to a few large blood vessels. The largest of these is the aorta, or main artery, which carries nutrient-
The heart's structure makes it an efficient, never-
Considering how much work it has to do, the heart is surprisingly small. The average adult heart is about the size of a clenched fist and weighs about 11 ounces (310 grams). Located in the middle of the chest behind the breastbone, between the lungs, the heart rests in a moistened chamber called the pericardial cavity which is surrounded by the ribcage. The diaphragm, a tough layer of muscle, lies below. As a result, the heart is well protected.