Your heart is a pump. It keeps blood moving around your body. The blood delivers oxygen and nutrients to all parts of your body, and carries away unwanted carbon dioxide and other waste products. The heart has four chambers - two on the left side and two on the right. The two upper chambers are called the atria, and the two lower chambers are called the ventricles. The two sides of the heart are divided by a muscular wall called the septum. Each side of the heart has a ‘one-way valve system’, which means that the blood travels only in one direction through the heart.
The heart and circulatory system With each contraction, or heartbeat, the heart pumps blood forward from the left side of the heart through the aorta (the main artery leaving the heart) and into the arteries. The arteries divide off into smaller and smaller branches to supply a microscopic network of capillaries, taking the blood to every part of your body. The blood then travels back to the heart from the capillaries into the veins, back to the heart. The branches of the veins join to form larger veins, which deliver the blood back to the right side of your heart what tissue repair process causes the blistering .
As the heart relaxes in between each heartbeat or contraction, blood from your veins fills the right side of your heart, and blood from the lungs fills the left side of your heart. The two sides of the heart are separate but they work together. The right side of the heart receives dark, de-oxygenated blood which has circulated around your body. It pumps this to your lungs, where it picks up a fresh supply of oxygen and becomes bright red again. The heart wall is made up of special muscle called myocardium. Like every other living tissue, the myocardium itself needs a continuous supply of fresh blood.
This supply of blood comes from the coronary arteries which start from the main artery (the aorta) as it leaves the left ventricle. The coronary arteries spread across the outside of the myocardium, feeding it with a supply of blood. Circulation is the movement of blood around the body, pumped by the heart. This system is called the cardiovascular system. It contains about 5 litres (8 pints) of blood which your heart is continuously recirculating. Each day, your heart beats about 100,000 times and pumps about 23,000 litres (5,000 gallons) of blood.
The Human Heart [pic]The heart is one of the most important organs in the entire human body. It is really nothing more than a pump, composed of muscle which pumps blood throughout the body, beating approximately 72 times per minute of our lives. The heart pumps the blood, which carries all the vital materials which help our bodies function and removes the waste products that we do not need. For example, the brain requires oxygen and glucose, which, if not received continuously, will cause it to loose consciousness.
Muscles need oxygen, glucose and amino acids, as well as the proper ratio of sodium, calcium and potassium salts in order to contract normally. The glands need sufficient supplies of raw materials from which to manufacture the specific secretions. If the heart ever ceases to pump blood the body begins to shut down and after a very short period of time will die. [pic] The heart is essentially a muscle(a little larger than the fist). Like any other muscle in the human body, it contracts and expands. Unlike skeletal muscles, however, the heart works on the "All -or-Nothing Law".
That is, each time the heart contracts it does so with all its force. In skeletal muscles, the principle of "gradation" is present. The pumping of the heart is called the Cardiac Cycle, which occurs about 72 times per minute. This means that each cycle lasts about eight-tenths of a second. During this cycle the entire heart actually rests for about four-tenths of a second. Make-up of the Heart. [pic]The walls of the heart are made up of three layers, while the cavity is divided into four parts. There are two upper chambers, called the right and left atria, and two lower chambers, called the right and left ventricles.
The Right Atrium, as it is called, receives blood from the upper and lower body through the superior vena cava and the inferior vena cava, respectively, and from the heart muscle itself through the coronary sinus. The right atrium is the larger of the two atria, having very thin walls. The right atrium opens into the right ventricle through the right atrioventicular valve(tricuspid), which only allows the blood to flow from the atria into the ventricle, but not in the reverse direction. The right ventricle pumps the blood to the lungs to be reoxygenated.
The left atrium receives blood from the lungs via the four pulmonary veins. It is smaller than the right atrium, but has thicker walls. The valve between the left atrium and the left ventricle, the left atrioventicular valve(bicuspid), is smaller than the tricuspid. It opens into the left ventricle and again is a one way valve. The left ventricle pumps the blood throughout the body. It is the Aorta, the largest artery in the body, which originates from the left ventricle. [pic] The Heart works as a pump moving blood around in our bodies to nourish every cell.
Used blood, that is blood that has already been to the cells and has given up its nutrients to them, is drawn from the body by the right half of the heart, and then sent to the lungs to be reoxygenated. Blood that has been reoxygenated by the lungs is drawn into the left side of the heart and then pumped into the blood stream. It is the atria that draw the blood from the lungs and body, and the ventricles that pump it to the lungs and body. The output of each ventricle per beat is about 70 ml, or about 2 tablespoons.
In a trained athlete this amount is about double. With the average heart rate of 72 beats per minute the heart will pump about 5 litres per ventricle, or about 10 litres total per minute. This is called the cardiac output. In a trained athlete the total cardiac output is about 20 litres. If we multiply the normal, non-athlete output by the average age of 70 years, we see that the cardiac output of the average human heart over a life time would be about 1 million litres, or about 250,000 gallons(US)!
