The Human Heart
The human heart is an amazing organ of the human body. The heart is an organ which pumps life-giving blood throughout the body. It works together with blood and blood vessels to supply all of the needs of the cells.
The circulatory system of the body makes up the heart, blood and blood vessels. Blood vessels are tubes which carry the blood. Blood carries oxygen and food to the cells of the body. The blood then returns to the heart.
The heart is located in the middle of the chest and slightly to the left. It is divided into two halves and has two hollow spaces or chambers. The blood enters the atria, which is the upper chamber and is then pumped to the ventricles, two lower chambers. Blood from the ventricles goes to the lungs and to every cell in the body. A valve in each ventricle stops the blood from flowing backwards.
An artery is a blood vessel which carries blood away from the heart. A main artery may be as thick as a thumb.
Blood is made up of red cells, white cells and platelets floating in a fluid called plasma. Plasma is a liquid and can easily pass through small blood vessels into cells and makes up over one-half of the blood. The plasma carries nutrients (food) from the stomach to be used as fuel for energy. Plasma also helps keep the body warm.
The blood then returns to the heart through blood vessels called veins. The veins on the skin, may look blue, especially on the hands and arms. The walls of a vein are much thinner than those of an artery. Two large veins bring the blood back to the heart. One comes from the brain and the chest. The other comes from the stomach and lower body.
Blood doesn't flow at the same speed through all of the body. As it gets farther away from the heart, it slows down. It goes slowly when the red blood cells carrying the food and oxygen squeeze through into the cells.
The heart beats or pumps every second of the day or night. It beats or pumps 100,000 times a day, every day of a person's life. Every time a heart beats or pumps out a stream of blood, this beat, called a pulse, can be felt on the inside of the wrist. The pulse rate in an adult is between sixty and one hundred beats per minute. Children's pulse rates range from ninety to one hundred twenty beats per minute.
In summary, the circulatory system which includes the heart, blood vessels and blood, work together to supply the cells with all the food and oxygen a body needs to maintain life. Blood is made up of red cells, white cells and platelets floating in a fluid called plasma. Arteries carry blood away from the heart, and veins carry the blood back to the heart. The heart beats thousands of times a day, every day. It beats much faster in children. The human heart is an amazing organ which is part of a system of many veins, arteries, and vessels which moves blood throughout the body keeping humans alive.
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