Bundle of His heart – Definition

Definition The bundle of nerve fibers that conveys the heart’s electrical pacing impulse from the ATRIOVENTRICULAR (AV) NODE to the ventricles, also called the bundle branches. The short trunk portion of the bundle before it splits into the right branch and left branch is the main bundle of His. The German physician Wilhelm His (1863–1934) discovered the […]

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Aorta artery – definition and function

What is an Aorta artery and definition The Aorta is ARTERY that carries BLOOD from the HEART to the body. The largest blood vessel in the body, the aorta arises from the left ventricle. At its widest point the aorta is about one and a half inches in diameter. As the aorta leaves the heart it ascends to curve behind the right […]

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Capillary Beds – definition and function

Definition The meshlike network of arterioles and venules, the body’s tiniest BLOOD vessels, where OXYGEN–CARBON DIOXIDE EXCHANGE takes place – are present throughout the body. Arterial pressure forces blood into the capillary beds. Erythrocytes (red blood cells) carry oxygen and other NUTRIENTS to the capillary beds, where these molecules pass through to cells. Correspondingly, the cells pass […]

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Cardiac Enzymes – definition

What are Cardiac Enzymes and definition Cardiac Enzymes – proteins the HEART releases into the bloodstream when HEART ATTACK or other circumstances cause damage to the heart MUSCLE (MYOCARDIUM). BLOOD tests that measure the levels of these enzymes help doctors determine whether, and how long ago, a heart attack has taken place. All muscle tissue releases certain enzymes when injured, so the combination […]

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Circle of Willis – what is and function

What is Circle of Willis and definition Circle of Willis is a looped network (anastamosis) of arteries at the base of the BRAIN. Branches of the internal carotid arteries form the front of the circle and branches of the posterior cerebral arteries form the back of the circle, with smaller arteries, collectively called the communicating arteries, branching […]

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Coronary Arteries – definition and function

What are Coronary Arteries and function Coronary Arteries are the network of arteries that encircles the HEART to provide its BLOOD supply. The two primary coronary arteries, the right coronary ARTERY and the left coronary artery, branch from the AORTA as it arises from the left ventricle. The left coronary artery is significantly larger and supplies the left heart. […]

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Endocardium – definition and function

Definition and Function Endocardium is the membrane that lines the inner HEART, made up of epithelial cells. It also covers the heart valves, providing a smooth surface that offers no opportunity for BLOOD cells (particularly platelets) to stick to it as they pass through the heart. The endocardium contains Purkinje fibers, specialized MUSCLE cells that convey the electrical impulses that cause […]

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Heart Rate

What is Heart Rate and Definition Heart Rate is the number of times in a minute that the HEART completes a CARDIAC CYCLE, commonly measured as the PULSE. At rest, the healthy adult heart beats between 60 and 80 times per minute. The heart rate of a person who is aerobically fit is slower because the […]

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Heart – health, disease and definition

What is Heart and Definition Heart is the organ that pumps BLOOD and maintains circulation. About the size of a closed fist, the heart resides in the chest between the LUNGS, slightly offset to the left behind the protective STERNUM (breastbone). It begins beating at about 3 weeks gestational age and during a typical life time contracts about 2.5 […]

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Myocardium (muscle tissue heart) – Definition and Function

Myocardium and definition The muscle tissue that forms the walls of the HEART. Myocardial cells are unique in their structure, blending muscle and nerve structures so they can both contract and conduct electrical impulses. Myocardial cells thus can contract independent of external stimulation. The myocardial fibers of the atria have a different configuration from those […]

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