Wikijunior:Human Body/Heart

What does a heart look like?
The heart is about the size of a person's clenched fist. It is made of muscle. It is a muscular organ.

What are the parts of the heart?
The heart has two sides: the left side and the right side. Each side of the heart is divided into two parts, called the atrium and the ventricle. The atrium is the top part. The ventricle is on the bottom.

Both sides of the heart have a blood vessel (a vein) through which blood flows into the atrium. Valves are like doors that control where blood goes. Valves separate the atrium from the ventricle. Another set of valves controls the flow of blood from the ventricle to the artery that sends blood back into the body.

The heart is a big muscle that builds up blood pressure by contracting. When the heart contracts, it squeezes or pumps blood throughout the entire body. This is the "beating" of your heart.

Right heart
The vein leading to the right atrium is called vena cava'. It has the blood returning from all parts of the body (without oxygen). The right ventricle pumps the blood through the pulmonary artery to the lungs to get oxygen. Veins bring blood to the heart.

Left heart
Blood with fresh oxygen returns from the lungs through the pulmonary vein and flows into the left atrium. The left ventricle pumps the blood into the artery called the aorta. It supplies the whole body except the lungs with blood.

What is the function of the heart?
The heart is the strongest muscle in the body. The heart is a pump that pumps blood to different organs of the body.

Blood is the medium that carries gases, liquids, nutrients, and waste all over the body. It is red in color because of the red blood cells. Blood also contains white blood cells which defends the body against diseases and makes repairs to damaged tissues.

The heart moves the blood (with the oxygen, nutrients, water, and waste) to and from all parts of the body.

How does the heart beat?
Before each beat, your heart fills with blood. Then its muscle contracts to squirt the blood along. When the heart contracts, it squeezes — try squeezing your hand into a fist. That is like what your heart does so it can squirt out the blood. Your heart does this all day and all night, all the time.

What organ system(s) is the heart connected with?
The heart is part of the circulatory system. Its main job is to move blood from the lungs to all other parts of the body and back. In the lungs, the blood gets oxygen from the air you breathe and leaves waste to be breathed out.

How does the heart interact with other parts of the body?
Blood with fresh oxygen is pumped through the body through tubes called arteries. Arteries divide up into smaller and smaller blood vessels. Finally, tiny blood vessels called capillaries deliver oxygen and nutrients to the body's cells. Then carbon dioxide and waste products are absorbed in the blood. The blood then returns to the right heart through blood vessels called veins. From the right heart, blood is pumped through the lungs where carbon dioxide is released and oxygen is absorbed to re-oxygenate the blood. From the lungs, the blood returns to the left heart where the cycle begins all over.

Note:
 * Blood vessels leaving the heart are called arteries. (You can remember this by thinking of "a" for "away" from the heart.)
 * Blood vessels entering the heart are called veins.
 * All arteries contain oxygenated blood except the pulmonary artery which sends blood to the lungs.
 * All veins contain de-oxygenated blood except the pulmonary vein which moves blood from the lungs to the left heart.

How can you keep your heart healthy?
You can have a healthy heart by:
 * getting appropriate exercise
 * eating healthy food (a balanced diet)
 * controlling high blood pressure
 * controlling how much you smoke