Study smarter with Fiveable
Get study guides, practice questions, and cheatsheets for all your subjects. Join 500,000+ students with a 96% pass rate.
Heart valves control the direction of blood flow through the cardiovascular system. Understanding their locations means understanding pressure gradients, the cardiac cycle, and how valve dysfunction disrupts both pulmonary and systemic circulation. When you know where each valve sits, you can predict what happens when it fails.
The four main valves come in two functional pairs: the atrioventricular (AV) valves separate atria from ventricles, and the semilunar valves guard the exits to major arteries. This pairing reflects the heart's two-pump design: the right side handles pulmonary circulation, the left side handles systemic. Don't just memorize valve names. Know what type each valve is, which circuit it serves, and when in the cardiac cycle it opens and closes.
The AV valves prevent backflow from ventricles into atria during ventricular systole. They're anchored by chordae tendineae and papillary muscles, which prevent the leaflets from everting (prolapsing) when ventricular pressure spikes.
Compare: Tricuspid vs. Mitral: both are AV valves anchored by chordae tendineae, but the tricuspid has three cusps (right side, lower pressure) while the mitral has two cusps (left side, higher pressure). If you're asked about valve structure adaptations to pressure, contrast these two.
The semilunar valves prevent backflow from arteries into ventricles during ventricular diastole. Their crescent-shaped (half-moon) cusps fill with blood and snap shut when arterial pressure exceeds ventricular pressure, producing the "dub" (S2) of heart sounds.
Compare: Pulmonary vs. Aortic: both are semilunar valves with three cusps and no chordae tendineae, but the aortic valve faces much higher pressures and is more commonly affected by stenosis and calcification clinically.
These structures are vestigial remnants of fetal circulation. In utero, they helped direct oxygenated blood from the placenta through the foramen ovale, bypassing the non-functional fetal lungs. In adults, they're typically non-functional.
Compare: Eustachian vs. Thebesian: both are rudimentary right atrial valves with fetal origins, but the Eustachian valve directed systemic blood flow while the Thebesian valve guards coronary venous return. Neither is essential for adult circulation.
Understanding valve categories helps you answer questions about mechanisms rather than individual structures.
Compare: AV valves vs. Semilunar valves: AV valves have chordae tendineae and close during systole (S1), while semilunar valves lack chordae and close during diastole (S2). This structural difference is why valve prolapse is a condition of AV valves specifically: semilunar valves don't have leaflets that can evert into a chamber.
| Concept | Best Examples |
|---|---|
| Right heart valves | Tricuspid, Pulmonary |
| Left heart valves | Mitral (Bicuspid), Aortic |
| AV valves (with chordae tendineae) | Tricuspid, Mitral |
| Semilunar valves (no chordae) | Pulmonary, Aortic |
| Three-cusped valves | Tricuspid, Pulmonary, Aortic |
| Two-cusped valve | Mitral (Bicuspid) |
| Valves producing S1 | Tricuspid, Mitral |
| Valves producing S2 | Pulmonary, Aortic |
| Rudimentary/vestigial valves | Eustachian, Thebesian |
Which two valves close simultaneously to produce the S1 heart sound, and what phase of the cardiac cycle does this mark?
Compare the structural support systems of AV valves versus semilunar valves. Why do only AV valves need chordae tendineae?
A patient has regurgitation (backflow) from the aorta into the left ventricle. Which valve is dysfunctional, and during which phase of the cardiac cycle does this backflow occur?
Both the tricuspid and mitral valves are AV valves, yet the mitral valve has only two cusps while the tricuspid has three. How might this structural difference relate to the pressure differences between the right and left sides of the heart?
Trace the path of a red blood cell from the right atrium to the aorta. Which four valves does it pass through in order, and which are semilunar versus atrioventricular?