Human Heart


Image Caption : Heart within Chest : The heart is located slightly to the left of the center of the chest, between the two lungs. This image shows the location of the heart within a person's ribcage and the network of arteries nearby in the thorax and neck. The subclavian arteries can be seen bringing blood from the heart to the arms. The common carotid arteries run from the heart up into the neck where they will branch to supply the head and neck with blood.

Anatomy of the Heart

Your heart is located under your ribcage in the center of your chest between your right and left lungs. Its muscular walls beat, or contract, pumping blood to all parts of your body.

The size of your heart can vary depending on your age, size, and the condition of your heart. A normal, healthy, adult heart usually is the size of an average clenched adult fist. Some diseases can cause the heart to enlarge.

The Exterior of the Heart

Below is a picture of the outside of a normal, healthy, human heart.

HEART EXTERIOR


Figure A shows the location of the heart in the body. Figure B shows the front surface of the heart, including the coronary arteries and major blood vessels.
Figure A shows the location of the heart in the body. Figure B shows the front surface of the heart, including the coronary arteries and major blood vessels.

In figure B, the heart is the muscle in the lower half of the picture. The heart has four chambers. The heart's upper chambers, the right and left atria (AY-tree-uh), are shown in purple. The heart's lower chambers, the right and left ventricles (VEN-trih-kuls), are shown in red.

Some of the main blood vessels (arteries and veins) that make up your circulatory system are directly connected to the heart.

THE RIGHT SIDE OF YOUR HEART

In figure B above, the superior and inferior vena cavae are shown in blue to the left of the heart muscle as you look at the picture. These veins are the largest veins in your body.

After your body's organs and tissues have used the oxygen in your blood, the vena cavae carry the oxygen-poor blood back to the right atrium of your heart.

The superior vena cava carries oxygen-poor blood from the upper parts of your body, including your head, chest, arms, and neck. The inferior vena cava carries oxygen-poor blood from the lower parts of your body.

The oxygen-poor blood from the vena cavae flows into your heart's right atrium and then to the right ventricle. From the right ventricle, the blood is pumped through the pulmonary (PULL-mun-ary) arteries (shown in blue in the center of figure B) to your lungs.

Once in the lungs, the blood travels through many small, thin blood vessels called capillaries. There, the blood picks up more oxygen and transfers carbon dioxide to the lungs—a process called gas exchange. To learn more about gas exchange, go to the Health TopicsHow the Lungs Workarticle.

The oxygen-rich blood passes from your lungs back to your heart through the pulmonary veins (shown in red to the left of the right atrium in figure B).

THE LEFT SIDE OF YOUR HEART

Oxygen-rich blood from your lungs passes through the pulmonary veins (shown in red to the right of the left atrium in figure B above). The blood enters the left atrium and is pumped into the left ventricle.

From the left ventricle, the oxygen-rich blood is pumped to the rest of your body through the aorta. The aorta is the main artery that carries oxygen-rich blood to your body.

Like all of your organs, your heart needs oxygen-rich blood. As blood is pumped out of your heart's left ventricle, some of it flows into the coronary arteries (shown in red in figure B).

Your coronary arteries are located on your heart's surface at the beginning of the aorta. They carry oxygen-rich blood to all parts of your heart.

The Interior of the Heart

Below is a picture of the inside of a normal, healthy, human heart.

HEART INTERIOR


Figure A shows the location of the heart in the body. Figure B shows a cross-section of a healthy heart and its inside structures. The blue arrow shows the direction in which oxygen-poor blood flows through the heart to the lungs. The red arrow shows the direction in which oxygen-rich blood flows from the lungs into the heart and then out to the body.
Figure A shows the location of the heart in the body. Figure B shows a cross-section of a healthy heart and its inside structures. The blue arrow shows the direction in which oxygen-poor blood flows through the heart to the lungs. The red arrow shows the direction in which oxygen-rich blood flows from the lungs into the heart and then out to the body.

HEART CHAMBERS

Figure B shows the inside of your heart and how it's divided into four chambers. The two upper chambers of your heart are called the atria. They receive and collect blood.

The two lower chambers of your heart are called ventricles. The ventricles pump blood out of your heart to other parts of your body.

THE SEPTUM

An internal wall of tissue divides the right and left sides of your heart. This wall is called the septum.

The area of the septum that divides the atria is called the atrial or interatrial septum. The area of the septum that divides the ventricles is called the ventricular or interventricular septum.

HEART VALVES

Figure B shows your heart's four valves. Shown counterclockwise in the picture, the valves include the aortic (ay-OR-tik) valve, the tricuspid (tri-CUSS-pid) valve, the pulmonary valve, and the mitral (MI-trul) valve.

BLOOD FLOW

The arrows in figure B show the direction that blood flows through your heart. The light blue arrow shows that blood enters the right atrium of your heart from the superior and inferior vena cavae.

From the right atrium, blood is pumped into the right ventricle. From the right ventricle, blood is pumped to your lungs through the pulmonary arteries.

The light red arrow shows oxygen-rich blood coming from your lungs through the pulmonary veins into your heart's left atrium. From the left atrium, the blood is pumped into the left ventricle. The left ventricle pumps the blood to the rest of your body through the aorta.

For the heart to work well, your blood must flow in only one direction. Your heart's valves make this possible. Both of your heart's ventricles have an "in" (inlet) valve from the atria and an "out" (outlet) valve leading to your arteries.

Healthy valves open and close in exact coordination with the pumping action of your heart's atria and ventricles. Each valve has a set of flaps called leaflets or cusps that seal or open the valve. This allows blood to pass through the chambers and into your arteries without backing up or flowing backward.

What Is the Heart?

Your heart is a muscular organ that pumps blood to your body. Your heart is at the center of your circulatory system. This system consists of a network of blood vessels, such as arteries, veins, and capillaries. These blood vessels carry blood to and from all areas of your body.

An electrical system controls your heart and uses electrical signals to contract the heart's walls. When the walls contract, blood is pumped into your circulatory system. Inlet and outlet valves in your heart chambers ensure that blood flows in the right direction.

Your heart is vital to your health and nearly everything that goes on in your body. Without the heart's pumping action, blood can't move throughout your body.

Your blood carries the oxygen and nutrients that your organs need to work well. Blood also carries carbon dioxide (a waste product) to your lungs so you can breathe it out.

A healthy heart supplies your body with the right amount of blood at the rate needed to work well. If disease or injury weakens your heart, your body's organs won't receive enough blood to work normally.

National Heart Lung and Blood Institute / NIH

The heart is a muscular organ in humans and other animals, which pumps blood through the blood vessels of the circulatory system. Blood provides the body with oxygen and nutrients, and also assists in the removal of metabolic wastes. The heart is located in the middle compartment of the mediastinum in the chest.

In humans, other mammals and birds the heart is divided into four chambers: upper left and right atria; and lower left and right ventricles. Commonly the right atrium and ventricle are referred together as the right heart and their left counterparts as the left heart. Fish in contrast have two chambers, an atrium and a ventricle, while reptiles have three chambers. In a healthy heart blood flows one way through the heart due to heart valves, which prevent backflow. The heart is enclosed in a protective sac, the pericardium, which also contains a small amount of fluid. The wall of the heart is made up of three layers: epicardium, myocardium, and endocardium.

The heart pumps blood through both circulatory systems. Blood low in oxygen from the systemic circulation enters the right atrium from the superior and inferior vena cavae and passes to the right ventricle. From here it is pumped into the pulmonary circulation, through the lungs where it receives oxygen and gives off carbon dioxide. Oxygenated blood then returns to the left atrium, passes through the left ventricle and is pumped out through the aorta to the systemic circulation−where the oxygen is used and metabolized to carbon dioxide. In addition the blood carries nutrients from the liver and gastrointestinal tract to various organs of the body, while transporting waste to the liver and kidneys. In the healthy organism each heartbeat causes the right ventricle to pump the same amount of blood into the respiratory organ as the left ventricle pumps to the body. Veins transport blood to the heart and carry deoxygenated blood - except for the pulmonary and portal veins. Arteries transport blood away from the heart, and apart from the pulmonary artery hold oxygenated blood. Their increased distance from the heart cause veins to have lower pressures than arteries. The heart contracts at a resting rate close to 72 beats per minute. Exercise temporarily increases the rate, but lowers resting heart rate in the long term, and is good for heart health.

Cardiovascular diseases (CVD) are the most common cause of death globally as of 2008, accounting for 30% of deaths. Of these more than three quarters follow coronary artery disease and stroke. Risk factors include: smoking, being overweight, little exercise, high cholesterol, high blood pressure, and poorly controlled diabetes, among others. Diagnosis of CVD is often done by listening to the heart-sounds with a stethoscope, ECG or by ultrasound. Specialists who focus on diseases of the heart are called cardiologists, although many specialties of medicine may be involved in treatment.



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