Medical Assistant Prep / Unit 4 MAS 076 short lesson, about 20 seconds
The Heart's Chambers and Layers
Captions available
The idea
The heart is a muscular organ with four chambers, about the size of a closed fist.
In practice
The two upper chambers, the atria, receive blood from the veins; the two lower chambers, the ventricles, pump it out; the thick middle layer of the heart wall is the myocardium.
Where people slip
The ventricles do the heavy pumping, so their walls are the thickest.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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