All cells in the body receive food and oxygen through the circulatory system. In addition to being a delivery service, it's also a waste collection service for carrying waste products like carbon dioxide and urea to where they can be removed from the body. A circulatory system is made up of the heart, blood vessels, and blood itself.

The double circulatory system

The human body consists of two circulatory systems that are joined together:

1️⃣
To take in oxygen, the right ventricle pumps deoxygenated blood to the lungs in the first circuit. The blood is then pumped back to the heart.
2️⃣
The left ventricle pumps oxygenated blood around all the rest of the body's organs in the second circuit. Oxygen is given up by the blood in the cells and the deoxygenated blood is pumped out again into the lungs.
The heart and lungs blood flow
The heart and lungs blood flow
The double circulatory system
The double circulatory system



The heart pumps blood around the body

Throughout the body, blood is pumped by the heart. Most of the heart's wall is muscle, which contracts to pump blood. In the heart, blood flows between four chambers: the right atrium, the right ventricle, the left atrium, and the left ventricle. There are four major blood vessels that flow into and out of these chambers: the vena cava, pulmonary artery, aorta, and pulmonary vein.

The heart right atruim and left atruim
The heart right atruim and left atruim

In order to prevent blood from flowing backward, the heart has valves that ensure blood flows in the right direction. The heart also needs oxygenated blood to function. The coronary arteries branch off the aorta and surround the heart, ensuring that it receives plenty of oxygenated blood.



The blood flow in the human heart

1️⃣
The heart is a remarkable organ that constantly pumps blood around the body. It has walls mostly composed of muscle tissue, essential for its functioning.
2️⃣
The heart is equipped with valves that ensure the bloodstream operates in the correct direction. These valves stop the backward flow of blood.
3️⃣
The four chambers (right atrium, right ventricle, left atrium and left ventricle) of the heart work together to push blood throughout your body; this is how the heart pumps blood around.

To understand how the heart pumps blood around the body, you must understand how its four chambers work.

Blood flow in the human heart
Blood flow in the human heart
1️⃣
The vena cava and the pulmonary vein supply blood to the two atria of the heart.
2️⃣
The atria act as a pump, forcing the blood into the ventricles where it can be circulated throughout the body.
3️⃣
The ventricles contract, sending the blood into the pulmonary artery and the aorta, then outward from the heart.
4️⃣
After the heart pumps oxygenated blood, it is then transported to every organ in the body via arteries. The same blood then flows back to the heart through veins.
5️⃣
The atria fill up and the sequence begins again from the start.

The heart is a vital organ that needs a steady supply of oxygen-rich blood. For this purpose, special arteries named coronary arteries branch out from the aorta and encircle the heart, guaranteeing it receives all the oxygen-filled blood it requires.



Pacemakers and the heart

The cells in the right atrium wall that control your resting heart rate are known as pacemakers. A small electric impulse is sent from these cells to the surrounding muscle cells, resulting in their contraction.

If a patient's natural pacemaker cells don't work correctly or if their heartbeat is irregular, then an artificial pacemaker is often used. It consists of a device that is implanted under the skin and has a wire going to the heart. This device keeps the heart beating regularly with an electric current.



Revision Quiz on the Heart

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