Cardiovascular System Facts

The cardiovascular system in humans, also called the circulatory system, consists of

  • the heart, a pump whose contractions move blood through its vessels
  • the blood vessels, a series of arteries, veins and capillaries that provide passageways to transport the blood throughout the body
  • blood, which carries oxygen and nutrients to and removes waste products from human tissue on a cellular level.

Anatomy of the Cardiovascular System

The heart is made up of three layers: the epicardium, the myocardium, and the endocardium.

The epicardium is the outermost layer of the heart and is made up of epithelial cells and connective tissue. It is part of the visceral pericardium, the innermost portion of the pericardial sac, an empty sac with a tiny amount of lubricating fluid in it which surrounds the heart. The outer most portion of the pericardial sac is the parietal pericardium.

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Cardiovascular System facts

Function of Cardiovascular System

This blood enters the thin-walled right atrium, the first area of the right side of the heart to receive blood. With atrial contraction the blood is pumped through the open tricuspid valve (an atrioventricular valve) into the right ventricle, which has thicker walls than the atrium. The tricuspid valve then closes.

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See an image of capillaries

More Cardiovascular System Facts: Heart Sounds

The physician who listens to the patient’s heart with his or her stethoscope will normally hear two heart sounds:

  • S1 which is due to closure of the mitral and tricuspid valves
  • S2 due to closure of the aortic and pulmonary valves.
The time between S1 and S2 is called systole and the time between S2 and S1 is slightly longer and is called diastole.

Heart Murmurs

Heart Murmurs can be functional (innocent) or organic and are caused by turbulence of flow in the heart or blood vessels, which causes vibrations of the heart or vessel walls, perceived as murmurs by the examiner. The louder the murmur, the more likely it is to be pathologic. Functional, benign, or innocent murmurs are usually soft (grade I or II) and usually occur in systole.

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