4 Cardiac Mechanics copy

4 Cardiac Mechanics copy - CARDIAC MECHANICS THE CARDIAC...

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Unformatted text preview: CARDIAC MECHANICS THE CARDIAC CYCLE SYSTOLE AND DIASTOLE MINDSET The heart is a mechanical pump . This is an advantage in studying the heart because its function is easily accessible and intuitive . We can see it!! Valves open and close; walls contract and relax; blood Fows through the chambers and into the arteries. That’s it! The ultrasound image below visualizes everything seen on the gross anatomical image of the previous slide. A 4 Chamber View of the heart by Ultrasound The diagram below is the mechanical function of the heart as imaged by a 1-D echocardiogram. It shows valves opening and walls contracting CARDIAC CYCLE A continual cyclic series of SYSTOLES (ventricular contractions) and DIASTOLES (ventricular Fllings) VALVES Tough fbrous connective tissue attached to valve rings. Two types : 1. Atrioventricular ( A - V ) valves ( Between A tria and V entricles) Open during ventricular flling ( Diastole ) Closed during ventricular emptying ( Systole ) 2. Semi - lunar ( Arterial ) valves ( Between ventricles and arteries) Open during ventricular emptying ( Systole ) Closed during ventricular flling ( Diastole ) Purpose of valve action They are one way valves in order to keep the blood Fowing in the right direction. The chordae tendineae hold the valve from everting into the L.A. during systole. The classic mechanism of A-V valve opening is said to be passive due to the Fow of blood from the L.A. to the L.V. But recent work of Steffens has challenged this idea with echocardiographic evidence that indicates that the A-V valves are opened actively by traction of the chordae tendinae....
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This note was uploaded on 04/30/2011 for the course ANATOMY 3504 taught by Professor Steffens during the Spring '11 term at St. John's.

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4 Cardiac Mechanics copy - CARDIAC MECHANICS THE CARDIAC...

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