A delivery network for the body
Every cell in your body — in your brain, your muscles, your kidneys — needs a constant supply of oxygen and fuel, and a way to carry waste away. Cells cannot store much oxygen, so the supply has to keep arriving second by second. The cardiovascular system is the delivery service that makes this happen. It is sometimes also called the circulatory system, because the blood travels in a loop and comes back.
Think of it as three things working together: a pump (the heart) to push the blood, a set of pipes (the blood vessels) to carry it, and the blood itself as the cargo truck. Cardiology mostly concerns the pump and the pipes; the blood is more the territory of hematology.
Three kinds of pipe
The vessels are not all the same. They come in three main kinds, each shaped for its job.
- An artery carries blood away from the heart under high pressure. Arteries have thick, muscular, springy walls to handle the push.
- A capillary is where the actual delivery happens. These are so thin — one cell wide — that oxygen and nutrients slip straight through the wall into the tissue.
- A vein carries the now oxygen-poor blood back to the heart at low pressure, often helped by valves and your moving muscles.
Delivery in a word: perfusion
Doctors have a single word for “blood actually arriving at a tissue and supplying it”: perfusion. Good perfusion means an organ is getting the oxygen delivery it needs. Poor perfusion is the common thread behind a surprising number of heart problems — a blocked artery, a weak pump, or a sudden drop in pressure all end the same way: somewhere downstream, cells are starved.
So when you read about blood circulation in the guides ahead, remember the point of all of it is perfusion: keeping every part of the body fed, breath by breath, beat by beat.