Blood movement and Capillaries

Blood movement and Capillaries

Blood movement

BloodBlood enters the heart through the atria. When the atria contract the blood is forced through valves into the ventricles. The ventricles then contract pushing the blood out of the heart. Both sides of the heart pump together but the blood moves in different directions.

Valves are very important in ensuring that the blood flows in the right direction. In a human heart there are four valves:

  • two between the atria and the ventricles
  • two between the ventricles and the body

All four valves act as one-way valves. They control the blood flow by opening and closing when the heart contracts.

NOTE: You don’t need to know the names of the valves.



The third type of blood vessel in the blood is the capillaries. The function of a capillary is to let food and oxygen reach the cells. It also takes away waste products like carbon dioxide. In order for this diffusion to happen faster the walls of capillaries are very thin: only one cell thick in fact.


If an artery has started to narrow, the blood flow is restricted. A stent is then inserted to hold open the artery thereby allowing blood to flow through more easily. It’s essentially a small wire mesh tube. Once it has been surgically inserted into an artery it expands, opening the blood vessel. In general they’re used to support coronary arteries and can take a lot of stress off the heart and help with chest pains. If a blocked artery is left untreated it can lead to a heart attack or heart failure because not enough oxygen can reach the heart.