Blood Blood consists of: Red blood cells — to carry oxygen White blood cells — that make up part of the immune system Platelets — needed for clotting Plasma — blood cells, nutrients and wastes float in this liquid. The heart The heart pumps blood around the body. It sits inside the chest, in front of the lungs and slightly to the left side.
The heart is actually a double pump made up of four chambers, with the flow of blood going in one direction due to the presence of the heart valves. The contractions of the chambers make the sound of heartbeats. The right side of the heart The right upper chamber atrium takes in deoxygenated blood that is loaded with carbon dioxide.
The blood is squeezed down into the right lower chamber ventricle and taken by an artery to the lungs where the carbon dioxide is replaced with oxygen. The left side of the heart The oxygenated blood travels back to the heart, this time entering the left upper chamber atrium.
It is pumped into the left lower chamber ventricle and then into the aorta an artery. The blood starts its journey around the body once more. Blood vessels Blood vessels have a range of different sizes and structures, depending on their role in the body. Arteries Oxygenated blood is pumped from the heart along arteries, which are muscular.
Arteries divide like tree branches until they are slender. The largest artery is the aorta, which connects to the heart and picks up oxygenated blood from the left ventricle. The only artery that picks up deoxygenated blood is the pulmonary artery, which runs between the heart and lungs. Capillaries The arteries eventually divide down into the smallest blood vessel, the capillary. Capillaries are so small that blood cells can only move through them one at a time.
Oxygen and food nutrients pass from these capillaries to the cells. Capillaries are also connected to veins, so wastes from the cells can be transferred to the blood.
These valves include the tricuspid, mitral, pulmonary and aortic valves. Each valve has flaps, called leaflets or cusps, that open and close once during each heartbeat. In the beginning of a pumping cycle, oxygen-poor blood, shown here as blue, returns to the heart after circulating through your body. The oxygen-poor blood fills the right atrium and then flows to the right ventricle, where it is pumped to the lungs through the pulmonary arteries.
The lungs refresh the blood with a new supply of oxygen, which comes from the air that you breathe in. The now oxygen-rich blood, shown in red, then returns from the lungs and enters the left atrium. The oxygen-rich blood then flows from the left atrium to the left ventricle. The blood is then pumped through the main artery that supplies blood to the body, called the aorta, to supply tissues throughout your body with oxygen.
Your heart is nourished by blood, too. Oxygen-rich blood is delivered by coronary arteries that extend over the surface of your heart. A beating heart contracts and relaxes. Contraction is called systole, and relaxation is called diastole. During systole, your ventricles contract, forcing blood into the vessels going to your lungs and body. Your ventricles then relax during diastole and are filled with blood coming from the upper chambers, the left and right atria.
Then the cycle starts over again. This cycle is driven by your heart's electrical wiring, called the conduction system. Electrical impulses begin high in the right atrium, in the sinus node, and travel through specialized pathways to the ventricles, delivering the signal for the heart to pump.
The conduction system keeps your heart beating in a coordinated and normal rhythm, which in turn keeps blood circulating. This results in the continuous exchange of oxygen-rich blood with oxygen-poor blood that is necessary to keep you alive.
Your heart is responsible for the majority of the circulatory system's function and is where the process begins. The circulatory system begins in your right atrium, the upper right-hand chamber of your heart. Blood moves from the right side of your heart through your lungs to get rid of carbon dioxide and pick up oxygen, and then returns to the left side of your heart, ending up in the left ventricle.
The left ventricle is the strongest part of the heart, since it must pump blood out to the rest of the body. When it comes to circulating blood throughout your body, the left ventricle is the most important chamber in the heart.
The left ventricle is the largest of the four chambers and is responsible for generating the force necessary to propel your blood out of your aorta, the first artery your blood enters as it leaves your heart. Your blood travels from your aorta through a series of smaller blood vessels until it reaches your capillaries. Before reaching your capillaries, however, blood must travel through the arterioles, where its speed and pressure are constantly adjusted as different segments of the arterioles change diameter in response to pressure and chemical sensors positioned nearby.
These sensors adjust blood flow via the arterioles in response to changing conditions in your body. Because of arteriole action, by the time your blood reaches your capillaries, it is no longer traveling in a pulsing fashion. Blood flows continuously through the capillaries, it does not "squirt" and "pause" as your heart beats. This continuous flow is necessary because there is a constant exchange of oxygen and nutrients happening in the capillary walls.
No cell in the body is far from a capillary. As blood travels through the capillaries, its supply of oxygen is reduced and has picked up waste products as well. From the capillaries, blood enters the venules, the veins, and then travels back to the heart to be refreshed and sent out once again.
In conclusion, your heart works like a pump which provides nutrients to every organ, tissue, and cell throughout your body. In turn, your cells dump waste products, like carbon dioxide, back into your blood to be returned to your heart.
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