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Biology of the Heart

heart in bodyThe heart is a very powerful muscle that pushes blood through the arteries and veins. The blood needs to reach each organ, including the heart, in order to feed every tissue with oxygen and nutrients!..

Each beat of your pulse is caused by the contraction of the heart muscles. Unlike the muscles in your arms, legs, and other parts of the body, the heart muscles contract involuntarily, meaning that there is no way to consciously control when the heart beats. The muscular power of the heart circulates blood through the body and to organs such as the brain, bones, and even the heart.

How does the heart beat?

cardiomyocites
This is the surface of the heart, it is made of long muscle cells, cadiomyocites, and it is covered in small blood vessel, capillaries, which feed the cells.

The heart beats due to the synchronized beating of millions of cells across the cardiac muscle.

The cardiac muscle is a special muscle, it is extra strong and extra irrigated with oxygen. Its cells, called cardiomyocites, like all muscle cells, are able to contract and extend themselves, and therefore the muscle they belong to contracts or expands. In the case of the cardiomyocites, when they work together, they make the heart beat!

But a lot of muscles that you are more familiar with, like the skeletal muscles in your arms and legs that allow you to move, are voluntary. That means that they respond directly to a conscious command from the brain, that arrives in the form of an electrical impulse delivered by a nerve. But, the average heart rate of a person of about 20 years old is between 100-170 beats a minute, can you imagine if you had to instruct your heart to beat every time?
Your heart muscle cells, on the other hand,can actually self-stimulate! Even alone, a heart cell would tell itself to beat (contract and relax) rhythmically. The heart muscle cells are connected to their neighbors by special joints (called gap junctions) through which an electrical signal can be passed very easily that allows them to synchronized their beating, so the first one to beat, will lets its neighbor know and so the signal spreads!

This a bit similar to what happens between the cells of the nervous system!

This signal travels across the heart, allowing larger sections of tissue to react in a coordinated way. When all sections of heart tissue do this with the correct timing, it makes the heart beat!

Heart anatomy

Roll your mouse over the heart below to see the names of the structures!

There are four cavities, or open spaces, inside the heart that the blood flows in and out of. Two of these cavities are called atria. The two atria form the curved top of the heart. The ventricles meet at the bottom of the heart to form a pointed base which points toward the left side of your chest.

The left side of the heart houses one atrium and one ventricle. The right side of the heart houses the others. A wall, called the septum, separates the right and left sides of the heart. Valves connect the various cavities to one another.

How does blood circulate through the heart?
The blood does a lot of traveling throughout the body. Each trip begins in the heart. Blood that carries oxygen is pumped towards the aorta, and from there it is distributed through the whole body, bringing oxygen and nutrients to the cells and picking up their waste, such as carbon dioxide.

Blood that has given up all its oxygen is called de-oxygenated blood , and must return to the heart. To enter the heart, deoxygenated blood flows into the right atrium and travels down to the right ventricle. From the right ventricle, blood leaves the heart and enters the lungs through the pulmonary arteries. Within the lungs, the blood is exposed to fresh oxygen that breathing brings in!

The blood releases its carbon dioxide and absorbs oxygen. Now the blood is oxygenated and returns to the heart through the pulmonary veins. In the heart, the blood flows from the left atrium down to the left ventricle. Finally, the blood is pushed out of the left ventricle, through the aorta, and out to the rest of the body. Because the left ventricle must supply enough force to push blood all the way down to the toes, it contracts more forcefully than the right ventricle and is a bigger, stronger muscle. When you feel your pulse in your neck, you are feeling the contraction of your left ventricle!


Remember!

The heart is a muscle made up of millions of cardiomyocyte cells that cause the heart to beat. The beats carry oxygen and nutrients all over the body.



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