TEAS Science study guide · 9 minute read
How blood moves through the heart
Four chambers, four valves and two circuits. Learn the order once, and most TEAS heart questions become a matter of following the path.
What the TEAS asks
Heart questions turn up in the anatomy and physiology part of TEAS Science, the largest group of scored Science questions. Almost all of them test one skill: putting the parts of the heart in the order blood reaches them.
Expect to be asked which chamber or valve blood reaches next, which side of the heart holds oxygen-rich blood, what separates an artery from a vein, and why one chamber has a thicker wall than the others.
Good to know: on the TEAS, pulmonary always points to the lungs. Pulmonary arteries go to them; pulmonary veins come back from them.
The four chambers
The heart has two upper chambers, the atria, and two lower chambers, the ventricles. Atria receive blood. Ventricles pump it out. A wall of muscle called the septum keeps the right side, which handles oxygen-poor blood, apart from the left side, which handles oxygen-rich blood.
| Chamber | Receives blood from | Sends blood to |
|---|---|---|
| Right atrium | The vena cavae, from the body | Right ventricle |
| Right ventricle | Right atrium | Pulmonary arteries, to the lungs |
| Left atrium | Pulmonary veins, from the lungs | Left ventricle |
| Left ventricle | Left atrium | Aorta, to the whole body |
The left ventricle has the thickest wall of the four, because it pushes blood through the whole body. The right ventricle only has to reach the lungs, which sit right next to the heart.
The four valves
Valves are one-way doors. Two sit between each atrium and its ventricle, and two sit where blood leaves the ventricles. In the order blood meets them:
- Tricuspid: right atrium to right ventricle
- Pulmonary: right ventricle to the pulmonary arteries
- Mitral (bicuspid): left atrium to left ventricle
- Aortic: left ventricle to the aorta
Memory aid: Try Pulling My Arm gives you tricuspid, pulmonary, mitral, aortic. The “lub-dub” of a heartbeat is the valves closing: lub is the tricuspid and mitral, dub is the pulmonary and aortic.
The path, step by step
The diagram is drawn as if you are facing the patient, so the heart’s right side appears on your left. Blue marks oxygen-poor blood and red marks oxygen-rich blood.
- Body to right atrium. Oxygen-poor blood returns from the body through the superior and inferior vena cavae and fills the right atrium.
- Tricuspid valve. It passes through the tricuspid valve into the right ventricle.
- Pulmonary valve. The right ventricle contracts and pushes it through the pulmonary valve into the pulmonary arteries, toward the lungs.
- Gas exchange. In the capillaries around the alveoli, carbon dioxide leaves the blood and oxygen enters it.
- Pulmonary veins. Now oxygen-rich, the blood returns through the pulmonary veins to the left atrium.
- Mitral valve. It passes through the mitral (bicuspid) valve into the left ventricle.
- Aortic valve. The left ventricle contracts hardest of all and sends it through the aortic valve into the aorta.
- Out to the body. Arteries carry it to every tissue. Cells take the oxygen, and the blood heads back to the heart oxygen-poor.
Arteries carry blood away
Arteries carry blood away from the heart. Veins carry it back. The names describe direction only, not how much oxygen the blood holds. That is why the pulmonary arteries carry oxygen-poor blood and the pulmonary veins carry oxygen-rich blood, a pairing the TEAS likes to test.
Capillaries connect the two. Their walls are a single cell thick, so oxygen, carbon dioxide, nutrients and wastes can pass between the blood and the tissues.
Memory aid: artery and away both start with A. Ignore the colors in textbook diagrams and follow the direction.
What keeps the beat
Each heartbeat starts in the sinoatrial (SA) node in the wall of the right atrium, the heart’s natural pacemaker. The signal spreads across both atria, which contract, and reaches the atrioventricular (AV) node. The AV node holds the signal for a moment so the ventricles can finish filling, then passes it on, and the ventricles contract.
The order of the signal is: SA node, AV node, bundle of His, bundle branches, Purkinje fibers.
Key takeaways
Remember
- Atria receive, ventricles pump.
- Right side: oxygen-poor blood, to the lungs.
- Left side: oxygen-rich blood, to the body.
- Valve order: tricuspid, pulmonary, mitral, aortic.
- Arteries go away from the heart, veins return to it.
Common mistakes
- Calling every artery oxygen-rich. The pulmonary arteries are not.
- Mixing up left and right on a diagram drawn facing the patient.
- Placing the mitral valve on the right side of the heart.
- Forgetting that blood passes through the lungs between the two ventricles.
Check yourself
Three questions on this guide. Each one explains the answer, whichever choice you pick.
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