Human Anatomy in Full Color by Unknown

Author:Unknown
Language: eng
Format: epub
ISBN: 0000000000000
Published: 2021-11-02T07:30:03+00:00

THE HEART

The heart is a hollow muscular organ situated just to the left of the breastbone and enclosed in a sac—the pericardium. The heart functions as a pump, circulating the blood through the body. It is separated into right and left halves by the interventricular septum. Each half has a backward-facing receiving chamber (atrium) and forward-facing ejection chamber (ventricle). An orifice controlled by a valve allows blood to pass one way from atrium to ventricle. Deoxygenated blood, high in carbon dioxide, is collected from the body through the two venae cavae (superior vena cava and inferior vena cava) into the right atrium and through the tricuspid valve to the right ventricle, where it is pumped via the pulmonic valve and right and left pulmonary arteries to the lungs, where the blood receives fresh oxygen. The blood then reaches the left atrium through the pulmonary veins. Contraction of the atrium sends the blood through the mitral valve to the left ventricle, whose powerful contractions force blood past the aortic valve into the arch of the aorta and to the rest of the body. The left ventricle has a thicker muscular wall than the right and each contraction corresponds to a pulse felt at the wrist or neck. The heart has its own blood supply—the coronary arteries, arising from the ascending aorta, supply the heart muscle. In a heart attack, these become blocked by a blood clot, with resultant tissue death.

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