Question: how many different muscles in a human heart are there

Andrew Scott answered on 17 Jun 2015:

We usually think of the main bit of the heart as one big muscle and don’t really separate it into different muscles. However, you could separate the left ventricle (which is the biggest chamber, pumping oxygenated blood around the body) from the right ventricle (which pumps the deoxygentated blood to the lungs to absorb oxygen). The right ventricle is kind of stuck onto the left ventricle.

The left ventricle is really interesting. The muscle on the outside is aligned so the cells point along the length of the heart. In the middle of the heart wall the muscle cells are aligned parallel to the outside wall (circumferentially) a bit like they are forming a ring in the middle of the heart. On the inside of the heart, the muscle cells point along the length of the heart, as they do on the outside.

Inside the heart there are rope like muscles called papillary muscles that are connected to the valves by tendons. These muscles stop the valves from being forced open and allowing blood to go in the wrong direction.