Heart & Blood Circulation

Blood carries nutrients, oxygen and waste through the circulatory system, a network of routes around your body. Your heart is a muscle that repeatedly contracts to drive blood along blood vessels.

Arteries take blood outward from the heart; veins bring it back. Between them lie narrow capillaries, where red blood cells often pass one behind another. Oxygen and nutrients enter body cells there, while carbon dioxide and other wastes enter the blood.

The heart pumps through two circuits. The lung circuit collects oxygen. The body circuit supplies that oxygen to your cells. Each heartbeat keeps blood moving through both, day and night.

Your heart is a strong muscle that pumps blood. It has four spaces called chambers. The upper pair are atria; the lower pair are ventricles. Valves act as gates that prevent backward flow.

Blood with less oxygen arrives on the right. The heart sends it to the lungs to release carbon dioxide and collect oxygen. Returning blood enters the left, which pumps it around your body.

Arteries lead away from the heart. Their thick, stretchy walls handle high blood pressure. Veins lead back. Tiny capillaries have thin walls that let oxygen and nutrients reach body cells.

Together, the lung and body circuits form a double circulation. Blood passes through the heart twice during one complete journey.

Here are the key words for how blood moves around your body. The circulatory system is the body system that carries blood, nutrients, and waste to where they need to go. Anything to do with the heart is called cardiac, and anything to do with the lungs is called pulmonary. An artery is a blood vessel that moves blood away from the heart. A vein is a blood vessel that moves blood toward the heart. The aorta is the biggest artery of all, and it carries blood out to the whole body. A capillary is a very small blood vessel where nutrients and oxygen are swapped with your cells. Inside the heart, an atrium is an upper chamber and a ventricle is a lower chamber. You have two of each, so four chambers in total. If you remember just one trick, make it this one: arteries go away from the heart, and both words start with A.

Your heart contains an upper pair of atria and a lower pair of ventricles. These four chambers receive blood and pump it onward. Valves keep the flow forward by blocking its return.

The heart muscle has its own blood supply through coronary arteries. Arteries carry blood outward from the heart. Those serving the body deliver oxygen-rich blood, while those leading to the lungs carry less oxygen. Chambers, valves and arteries work together to circulate blood where it is needed.

Blood leaves the heart along arteries. These vessels divide into finer branches called arterioles, which feed groups of capillaries known as capillary beds.

At these tiny vessels, body tissues receive oxygen and nutrients from blood. Wastes move into the blood for removal.

Blood next enters venules, small vessels that merge to form veins. Veins complete the journey back to the heart, ready for another circuit.