This is how the heart and blood circulation work

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Last Medical Review: April 1, 2020
Medically Reviewed by Dr. Elisabeth Vincent Hamelin
Circulation of the Heart (April 1, 2020)
Heart and Circulatory System (April 1, 2020)

The heart pumps blood through the body’s blood vessels. The blood is pumped out to the body’s various organs and tissues and then back to the heart again. It’s called the bloodstream.

This is how the heart is built

The heart is about the size of a clenched hand. It is made up of a kind of cross-striated muscle called heart muscle. Other cross-striated muscles in the body can be controlled by the will, but the movements of the heart cannot be affected by the will.

The whole heart is surrounded by double layers of connective tissue, the so-called heartbeat.

Inside the heart are four heart chambers

The heart has two so-called heart spaces on the right side and two on the left side. In each half of the heart there is an atrium and a chamber. The atrium receives blood and the chambers pump the blood further.

Two types of flaps

In the heart are flaps, which open and close while the heart muscles are contracted. The flaps cause the blood to move in the right direction. They close and then the blood cannot flow back.

There are two types of flaps:

  • The sling flaps that exist between the atrium and the chambers in both the right and left half of the heart.
  • The flaps that are located where the pulmonary artery exits from the right ventricle, and where the large body pulmonary vein exits from the left ventricle.

Movie: Blood’s way through the heart

The film shows the way of blood through the heart. The blood enters the heart and is pumped into the body while the flaps in the heart are opened and closed.

The film shows the way of blood through the heart. The blood enters the heart and is pumped into the body while the flaps in the heart are opened and closed.

The coronary vessels provide the heart with nutrition and oxygen

The heart muscle receives nutrition and oxygen from two coronary vessels. The coronary vessels are small blood vessels that form a network around the heart. They supply the heart muscle with blood, oxygen and nutrition. The blood is then led back through the coronary veins.

So the heart works

The heart acts like a pump. It pumps out blood through the body’s blood vessels and organs. The pressure that occurs in the vessels when the heart pumps out blood is called the blood pressure. The heart constantly switches between contracting and relaxing. A contraction and a relaxation together constitute a heartbeat.

The number of heartbeats per minute is called the heart rate

During rest, the number of heartbeats is usually between 60 and 80 beats per minute. Well-trained people often have fewer beats per minute. The number of heartbeats per minute is called the heart rate. Heart rate increases as you exert yourself. With very heavy effort, the number of heartbeats can reach close to 200 beats per minute. This is done to increase blood flow as the need for oxygen to the body’s muscles increases. It is also common for the heart rate to be called the heart rate.

The heartbeat is started by impulses

The heartbeat is controlled by starting an impulse from a small area in the right atrium called the sinus node. The impulse causes the atrium of the heart to contract so that blood flows into the two chambers of the heart. Then the impulse reaches on to the so-called AV node, and then through the so-called His bundle. The His bundle divides into two branches which lead the impulse to both walls of the chambers. This leads to a contraction of the chambers. Before the next heartbeat, a rest occurs.

The sinus node, the AV node, and the His bundle are called the cardiac rectal system.

The bloodstream transports oxygen and nutrition

The heart pumps out the blood into the body’s bloodstream. The blood circulation is a system of blood vessels for the transport of, among other things, oxygen, nutrients and hormones. The blood also removes waste products that the body does not need, such as carbon dioxide.

Three types of blood vessels

There are three types of blood vessels:

  • Arteries are called the blood vessels that direct the blood from the heart to the various parts of the body.
  • Veins are called the blood vessels that direct the blood to the heart from the various parts of the body.
  • Capillaries are called the smallest vessels at the far end that connect the arteries to the veins.

The arteries for the blood into the body

The arteries further direct the blood that is pumped out of the heart. The blood in the arteries from the left ventricle is oxygen rich. This is because the blood has been passed through the blood vessels in the lungs and taken oxygen from there.

You can feel the pulse in the arteries

The large arteries divide into smaller blood vessels that reach throughout the body. Each time the heart pumps blood into the arteries, they dilate a little. You can feel this via the pulse, for example on the wrist or on the side of the neck. When you take the pulse at the wrist, it is the radiation leg artery you feel. The radial artery is also called the radial artery. When you take the pulse on the side of the neck, it is the throat arteries you feel. Another name for the carotid artery is the carotid artery.

Large body pulmonary artery is the largest artery of the body

Large coronary arteries are also called aorta. It is the body’s largest artery. Large coronary arteries have a diameter of about 2.5 centimeters and exit from the left ventricle of the heart. It first goes upwards in an arc, and then proceeds down through the body. At about the lower vertebrae of the spine, the large body pulse vein divides into two branches. One to each side of the lower body half.

Pulmonary artery conducts oxygen-poor blood

The pulmonary artery starts from the right ventricle and divides into two pulmonary arteries, one for each lung. The pulmonary artery contains oxygen-low blood even though it is an artery. All other arteries conduct oxygen-rich blood.

The veins bring the blood back to the heart

The veins collect the blood out into the body’s organs and muscles and return it to the heart. The veins are either deep or superficial. Often two deep veins pass next to each artery.

The superficial veins regulate body temperature

The superficial veins on the arms and legs are just below the skin. These veins help regulate body temperature. It occurs by the blood giving off heat as the blood vessels pass near the skin.

The pulmonary veins conduct oxygen-rich blood

The pulmonary veins carry oxygen-rich blood from the blood vessels of the lungs back to the heart. Two pulmonary veins come from each lung. The pulmonary veins conduct oxygen-rich blood even though they are veins. All other veins carry oxygen-poor blood.

The heart pumps out the blood to the various parts of the body, and then the blood must be able to be brought back to the heart. The muscles around the veins help to push the blood back to the heart. Contractions in the muscles cause the veins to compress and the blood to move in the right direction.

Inside the veins are also small flaps. They close the blood vessels so that the blood cannot flow back.

The capillaries are the smallest blood vessels

The capillaries are a network of very small and thin blood vessels. They are so small that only one red blood cell can penetrate at a time.

Liquid and various substances can pass through the walls of the capillaries

The walls of the capillaries are so thin that liquids, nutrients and waste products can pass through them. The blood, for example, releases oxygen and nutrients to the tissues through the walls of the capillaries. At the same time, the tissues dispose of carbon dioxide and other waste products.

Liquid also leaves the capillaries. The fluid is mixed with the tissue fluid that lies between the cells in the body. Most of the fluid is absorbed again by the capillaries, but some excess fluid remains in the tissues. This excess fluid is absorbed by the lymphatic capillaries of the lymphatic system and then returned to the bloodstream.

Large circulation and small circulation

The bloodstream consists of a coherent system of blood vessels. It is usually divided into two parts, the large cycle and the small cycle.

Large circulation reaches the entire body

The large circulation is the blood circulation that reaches throughout the body. The blood is pumped out of the left ventricle of the heart, through the large coronary artery and other arteries. It then reaches the capillaries out into the body. There, oxygen and nutrients are transported into the tissues, while waste products from the metabolism are taken up by the blood. Then the blood is returned to the right atrium of the heart through the veins.

The small cycle goes to the lungs

The small circulation is also called the pulmonary circulation. The right ventricle of the heart pumps blood to the lungs through the pulmonary arteries. In the lungs the blood takes up oxygen and at the same time gets rid of carbon dioxide. The oxygenated blood is returned to the left atrium of the heart through the pulmonary veins. Thereafter, the blood continues to the left ventricle, which pumps it out into the large circulation again.

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