The Cardiovascular system

The heart has two pathways, The Pulmonary, and the systemic. 

The right side of the heart pumps the blood through the Pulmonary so that it can be oxygenated in the lungs. The left side of the heart pumps oxygenated blood throughout the body, then comes back to the heart, and does that cycle again. 

What makes up the heart: 

- A muscular organ 

- 4 hollow chambers: 2 atria (upper chamber) 

2 ventricles (lower chamber) 

- Three layers of tissue: Endocardium (innermost layer) Myocardium  (middle layer) Pericardium (outer layer). 

Blood Vessels: 

Blood vessels carry blood around the body, one of the vessels is called the Arteries, and the other one is the Veins. The heart pumps the blood through the Arteries, and returns back to the heart by from the Veins.