Sunday, May 30, 2010

KNOW YOUR HEART. Structure of the heart and blood vessels and how they work.

( Adopted from“Learn about your heart… Made simple” by Nicolas W. Shammas, MS, MD, FACC, FACP)

The heart is a pump that distributes blood to the organs of the body. The heart is made of 4 chambers. The top 2 collecting chambers are called atria; the bottom 2 ejecting chambers are called ventricles.
The right atrium receives blood deficient in oxygen from the body and sends it into the right ventricle. The right ventricle squeezes the blood out to the lungs to pick up fresh oxygen.The oxygenated blood returns from the lungs to the left atrium, which then funnels the blood into the left ventricle. The left ventricle ejects the oxygenated blood into the entire body via the aorta.

What are the major components of the heart?

The heart is made of a contracting muscle that generates the force required to transport blood to all parts of the body. The muscle contracts from the bottom up to eject the blood into the aorta. The aorta branches out into a network of blood vessels that distributes blood to the organs of the body.

In the heart, there are 4 valves that allow the blood to move in 1 direction only. For example, the aortic valve opens when the ventricle contracts and closes immediately when the heart relaxes, preventing the blood from returning back to the left ventricle.

In addition to the muscle and the valves, the heart is made of a complex electrical system that allows the muscle to pump continuously and predictably. Electrical impulses are generated from a site in the right atrium called the sino-atrial node. This serves as the natural pacemaker of the heart, generating electrical impulses at the normal resting rate of 60 to 100 beats per minute. At a rate of 60 beats per minute, the heart contracts approximately 31,536,000 beats per year.

Describe the heart valves and their function

The 4 valves in the heart that allow blood to move only in 1 direction are the aortic, mitral, tricuspid, and pulmonic valves (see Figure 3). The aortic and pulmonic valves, when open, allow the blood to leave the heart and, when closed, prevent the blood from returning to the heart. The mitral and tricuspid valves, when open, allow the blood to move from the atria to the ventricles and, when closed, prevent the blood from moving backward into the atria.

What is the aorta?

The aorta is the major blood vessel that comes out of the heart and distributes oxygenated blood to the rest of the body including the heart itself . Blood vessels coming out of the aorta and supplying blood to the heart are called coronary arteries.The aorta supplies blood to the head via the carotid and vertebral arteries. Major branches coming out of the aorta also include the renal arteries (supplying blood to the kidneys), the mesenteric arteries (supplying blood to the gut), the celiac artery (supplying blood to the liver and spleen), and the iliac arteries (supplying blood to the hip and lower legs).

What are the blood vessels?

Blood vessels are essentially hollow tubes that carry blood to the organs and tissues throughout your body. The four basic types of blood vessels are:

 Arteries. These blood vessels carry blood away from your heart and out to your body, delivering oxygen and nutrients. The aorta is the largest blood vessel of all.

 Veins. These blood vessels carry deoxygenated blood back to your heart. Lacking oxygen, they have a bluish cast on your skin.

 Capillaries. These tiny vessels connect arteries and veins.

 Lymphatics. Fluid leaks out of capillaries to bathe cells. Lymphatics are delicate vessels that carry this fluid back into your body's central circulation.


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