How your Heart beats.

The heart is a muscular organ found in humans and other animals. This organ pumps blood through the blood vessels.[1] Heart and blood vessels together make the circulatory system.[2] The pumped blood carries oxygen and nutrients to the tissue, while carrying metabolic waste such as carbon dioxide to the lungs.[3] In humans, the heart is approximately the size of a closed fist and is located between the lungs, in the middle compartment of the chest, called the mediastinum.[4]

In humans, the heart is divided into four chambers: upper left and right atria and lower left and right ventricles.[5][6] Commonly, the right atrium and ventricle are referred together as the right heart and their left counterparts as the left heart.[7] In a healthy heart, blood flows one way through the heart due to heart valves, which prevent backflow.[4] The heart is enclosed in a protective sac, the pericardium, which also contains a small amount of fluid. The wall of the heart is made up of three layers: epicardium, myocardium, and endocardium.[8]

Видео How your Heart beats. канала Science Nerd