So there are actually four chambers (spaces) inside the heart.Each top chamber is called an atrium (plural: atria). The atria are often referred to as holding chambers, while the ventricles are called pumping chambers.
Blood can flow from the atria down into the ventricles because there are openings in the walls that separate them.
These openings are called valves because they open in one direction like trapdoors to let the blood pass through.
The blood does not spill all over the place when it leaves the heart. But the arteries soon branch again and again to form smaller and smaller tubes.
Instead, it flows smoothly in tubes called blood vessels. The smallest blood vessels, called capillaries, form a fine network of tiny vessels throughout the body.
All of the blood from the body is eventually collected into the two largest veins: the superior vena cava, which receives blood from the upper body, and the inferior vena cava, which receives blood from the lower body region.
Both venae cavae empty the blood into the right atrium of the heart.
The heart is a pump whose walls are made of thick muscle.
They can squeeze (contract) to send blood rushing out.
Every time the heart beats it goes thump against the chest wall.
The pointed tip at the bottom of the heart touches the front wall of the chest.