Anatomy of the heart

A normal heart is a powerful muscle pump. It can weigh between 200 and 425 g (7 to 15 ounces) and its size is slightly larger than your fist. Over a lifetime, the human heart will beat more than 2.5 billion times. Every day, an average heart beats about 100,000 times and pumps about 7,200 liters (1,900 gallons) of blood.

Your heart is located between your lungs in the middle of your chest behind the sternum, slightly to the left. A double membrane called the pericardium surrounds the heart like an envelope. Blood carrying oxygen reaches the lungs and enters the heart. To function, the heart must supply oxygen and nutrients it receives the blood that is pumped into his coronary arteries.

Role

The circulatory system is composed of the heart and cardiovascular system. The heart pumps blood to the organs, tissues and cells in the body delivering oxygen and nutrients to every cell of the body and remove carbon dioxide and waste products by these cells. The oxygen-rich blood is carried from the heart to the rest of the body through a complex network of arteries, arterioles and capillaries. The oxygen-poor blood returns to the heart through the veins.

How does the heart

The heart is a pump made up of four chambers. The upper chambers are called right atrium and left atrium. The lower chambers are called the right ventricle and left ventricle. A muscular wall called the septum separates the right and left atria and right and left ventricles.

The left ventricle, the largest and most powerful of the chambers of the heart, is able to pump blood throughout the body through the aortic valve.

The two cavities of right heart (right atrium and right ventricle) pump blood from the heart to the lungs so that blood cells can pick fresh oxygen in exchange for the waste they have collected during their visit in the body. The oxygen-rich blood returns to the left chambers of the heart (atrium and left ventricle), which then pump the rest of the body.

When the heart muscle contracts, the two upper chambers (the atria) fill with blood. Then, these chambers contract, squeezing blood into the ventricles. Then the ventricles contract and push blood out of the heart or to the lungs or elsewhere in the body.

What happens during a heart beat?

In a normal heart, the electrical impulse that starts the heartbeat begins in a group of cells called the sinus node (or SA node), in the right atrium. The sinus node is often called control heart rate. He plays a bit the same role as the spark plugs of a car engine, producing the electrical signal that makes the heart pump. The sinus node generates a number of signals every minute, according to the needs of the organization. The resting heart rate is usually between 60 and 80 beats per minute.

After an electrical impulse is generated, it spreads at the top of the heart (the atria), a bit like ripples created by a stone thrown into a pond. This signal is getting the upper chambers (atria). In contracting, they expel the blood they contain to the lower chambers of the heart, the ventricles.

Meanwhile, the electrical impulse that made the atria contract has reached the AV node (or AV node), located at the bottom of the right atrium. The AV node is the electrical connection between the atria and ventricles. It keeps the electrical pulse for a while, like a relay, so that blood can be pumped from the atria into the ventricles. Then, it transmits the signal to the lower chambers of the heart, which contract in turn. The contraction of the ventricles pushes blood with great force. The electrical impulse has now traveled the upper and lower chambers of the heart and has to contract. It's a heartbeat. This electrical activity produces electrical impulses measured using a heart test called an electrocardiogram (ECG or EKG).