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Heart Structure and Function

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In my quest to find a suitable diagram for the heart, this is what I found:

 

 

Definitely use your textbook as a guide on this. It only takes a google search to realise the ridiculous number of variations of diagrams for the heart and different annotations.

 

You need to be able to sketch a heart and label the main veins, valves, arteries and aorta, and the ventricles and atria.

 

There are two types of circulation going on via the heart: pulmonary circulation and systemic circulation. Pulmonary circulation is a short-distance route between the heart and the lungs, where deoxygenated blood is taken to be replenished with oxygen. Although normally veins take blood away, and arteries take blood to, in the case of pulmonary circulation things are the opposite way around. The pulmonary vein brings freshly oxygenated blood into the heart – left atrium -, while the pulmonary artery takes deoxygented blood back from the right ventricle into the lungs.

 

Here’s a quick nifty video that shows what happens as the bigger picture…

 

 

The atrioventricular valves and semilunar valves play an important role in ensuring proper heart function. The former ensure no blood flows back into the atria from the ventricles, while the latter ensure no blood flows from the ventricles into the atria.

 

Electrical impulses cause heart muscle contraction which creates an increased pressure of blood, resulting in it being pushed in a certain direction, with the valves opening in its way. The sequence of events in heart contraction is this:

 

1. Both atria contractatrial systole
2. Both ventricles contractventricular systole
3. All chambers relaxdiastole

 

The heart muscle contracts without brain stimulation – the brain only controls the speed. Electrical impulses start in the sino-atrial node in the right atrium, travels down to the atrio-ventricular node, which then spreads it across the bundle of His, which results in the left ventricle contracting.

 

 

Cardiac output = heart rate x stroke volume


Heart rate is measured in beats per minute, while stroke volume is measured in cm3 or ml.

 

Make sure you can interpret graphs showing the sequence of atria and ventricles contracting followed by diastole.

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