The heart is located in the __. It has four __: two ___ and two___. A partition which is called___ separates the chambers. The wall of the heart consists of three ____: ___ which is the inner layer, __ which is the muscular layer and __ , the outer layer. The heart is surrounded by the ___. The two phases of the heartbeat are termed __ and ___. __ is the phase of relaxation, ___ is the phase of contraction.

The heart is located in the thorax. It has four chambers: two atria and two ventricles. A partition which is called the septum separates the chambers.

The wall of the heart consists of three layers: endocardium, which is the inner layer, myocardium, which is the muscular layer, and epicardium, the outer layer. The heart is surrounded by the pericardium.

The two phases of the heartbeat are termed systole and diastole. Diastole is the phase of relaxation; systole is the phase of contraction.

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