--- title: "Bicuspid Valve | Anatomy and Physiology I" description: "Bicuspid valve is the left atrioventricular valve between the left atrium and left ventricle, stopping backflow as blood enters systemic circulation." canonical: "https://fiveable.me/anatomy-physiology/key-terms/bicuspid-valve" type: "key-term" subject: "Anatomy and Physiology I" unit: "Unit 19" --- # Bicuspid Valve | Anatomy and Physiology I ## Definition The bicuspid valve, also called the mitral valve, is the left atrioventricular valve between the left atrium and left ventricle. It lets blood move forward into the ventricle and closes to prevent backflow. ## What It Is In Anatomy and Physiology I, the bicuspid valve is the left atrioventricular valve of the heart. It sits between the left atrium and the left ventricle and has two cusps, or leaflets, that open and close with each heartbeat. Its job is simple but essential. When the left atrium contracts, the valve opens so oxygen-rich blood can flow into the left ventricle. When the left ventricle starts to contract, the pressure inside that chamber rises fast and the valve shuts, keeping blood from moving backward into the atrium. That one-way movement matters because the left ventricle is the chamber that pumps blood out to the entire body. If the bicuspid valve did not close tightly, some of the blood would leak backward instead of being sent into the aorta. That leakage would make the heart work harder and reduce how much blood reaches the body each beat. You may also see this valve called the mitral valve. That name comes from its shape, which resembles a bishop’s mitre, and it is the standard term in many lab models, diagrams, and anatomy atlases. In a heart diagram, it is usually drawn between the upper left chamber and the lower left chamber, often paired with the chordae tendineae and papillary muscles that help keep it from flipping backward. A useful way to think about the bicuspid valve is as a pressure gate. It opens when pressure is higher behind it and closes when pressure rises in front of it. That timing is what lets the heart fill efficiently and then pump efficiently without blood sloshing the wrong way. ## Why It Matters The bicuspid valve matters because it connects heart anatomy to the pumping action you trace in cardiovascular physiology. If you know where it sits and what it does, you can follow blood flow through the left side of the heart without getting lost in the chamber names. It also helps you explain why the left side of the heart is built the way it is. The left ventricle needs to generate enough pressure to send blood through the systemic circuit, so the valve has to seal well under strong contraction. That is why the valve works together with the chordae tendineae and papillary muscles instead of floating on its own. This term also shows up when you compare normal heart function with valvular problems. A leaky bicuspid valve means regurgitation, which changes the sound of the heartbeat and can reduce cardiac efficiency. So when you see a heart murmur, a valve diagram, or a case study about shortness of breath and fatigue, this valve may be part of the explanation. ## Connections ### [atrioventricular valves](/anatomy-physiology/key-terms/atrioventricular-valves) The bicuspid valve is one of the two atrioventricular valves. The other is the tricuspid valve on the right side of the heart. Together, these valves separate atria from ventricles and open during filling, then close during ventricular contraction so blood moves in the right direction. ### [Chordae Tendineae](/anatomy-physiology/key-terms/chordae-tendineae) The chordae tendineae anchor the bicuspid valve leaflets to the papillary muscles. They do not open or close the valve by themselves, but they keep the cusps from inverting into the left atrium when the left ventricle contracts. On a heart model, this trio often gets labeled together. ### [Aortic Valve](/anatomy-physiology/key-terms/aortic-valve) The bicuspid valve works just before the aortic valve in the left side of the heart. Blood passes from the left atrium to the left ventricle through the bicuspid valve, then leaves the heart through the aortic valve. If you trace flow in order, these two valves show the path through the left heart. ### Valvular Heart Disease Problems with the bicuspid valve are a type of valvular heart disease. In class, this may show up as regurgitation, stenosis, or a heart murmur in a case example. Knowing the normal valve function makes it easier to explain what changes when the valve does not open or close correctly. ## On the AP Exam A quiz or lab practical may ask you to point out the bicuspid valve on a heart diagram, identify which chambers it separates, or explain what happens if it fails to close. You may also see it in a blood-flow sequence question, where you have to trace oxygenated blood from the lungs through the left atrium, bicuspid valve, left ventricle, and out to the body. If your instructor uses heart models or cross-section images, this valve is often a label you need to know fast. On written questions, be ready to connect it to backflow prevention and left ventricular pumping pressure rather than just naming it. ## bicuspid valve vs tricuspid valve The bicuspid valve is on the left side of the heart and has two cusps, while the tricuspid valve is on the right side and has three cusps. Both are atrioventricular valves, but they serve different chambers and different circulation routes. ## Key Takeaways - The bicuspid valve is the left atrioventricular valve between the left atrium and left ventricle. - It opens to let blood move into the left ventricle and closes to stop backflow during ventricular contraction. - Its two cusps work with the chordae tendineae and papillary muscles to keep the valve from inverting. - This valve is the same structure often called the mitral valve in anatomy classes and textbooks. - If the bicuspid valve does not close properly, blood can leak backward and reduce pumping efficiency. ## FAQs ### What is the bicuspid valve in Anatomy and Physiology I? It is the valve between the left atrium and left ventricle. It lets oxygen-rich blood move forward into the left ventricle and then shuts so blood cannot flow backward when the ventricle contracts. ### Is the bicuspid valve the same as the mitral valve? Yes. Bicuspid valve and mitral valve are two names for the same left atrioventricular valve. "Bicuspid" refers to the two leaflets, while "mitral" refers to the shape of a bishop’s mitre. ### What happens if the bicuspid valve is damaged? If it does not close tightly, blood can leak back into the left atrium, which is called regurgitation. If the opening becomes too narrow, it can limit filling of the left ventricle, which makes the heart work harder. ### How do you identify the bicuspid valve on a heart diagram? Look on the left side of the heart between the upper chamber and the lower chamber. If the diagram shows the left atrium, left ventricle, and a valve with two cusps, that is the bicuspid valve. ## Related Study Guides - [19.1 Heart Anatomy ](/anatomy-physiology/unit-19/1-heart-anatomy/study-guide/rkGmPKJ0SjTIT3Kf) ## About This Document Canonical Fiveable pages are available as Markdown at the same path plus `.md`. - [llms.txt](https://fiveable.me/llms.txt): index of Fiveable's sections and URL patterns - [llms-full.txt](https://fiveable.me/llms-full.txt): complete subject and unit listing - [MCP server](https://fiveable.me/mcp): call Fiveable as tools instead of fetching pages (`https://fiveable.me/api/mcp`) - [MCP server for AP teachers](https://fiveable.me/mcp/teachers): a teacher's classes, assignments and AP-rubric grading (`https://fiveable.me/api/mcp/teacher`) ## Structured Data ```json {"@context":"https://schema.org","@graph":[{"@type":"LearningResource","@id":"https://fiveable.me/anatomy-physiology/key-terms/bicuspid-valve#resource","name":"Bicuspid Valve | Anatomy and Physiology I","url":"https://fiveable.me/anatomy-physiology/key-terms/bicuspid-valve","learningResourceType":"Concept explainer","educationalLevel":"AP® / High School","about":{"@id":"https://fiveable.me/anatomy-physiology/key-terms/bicuspid-valve#term"},"audience":{"@type":"EducationalAudience","educationalRole":"student"},"dateModified":"2026-07-03T02:20:36.800Z","isPartOf":{"@type":"Collection","name":"Anatomy and Physiology I Key Terms","url":"https://fiveable.me/anatomy-physiology/key-terms"},"publisher":{"@type":"Organization","name":"Fiveable","url":"https://fiveable.me"}},{"@type":"DefinedTerm","@id":"https://fiveable.me/anatomy-physiology/key-terms/bicuspid-valve#term","name":"bicuspid valve","description":"The bicuspid valve, also called the mitral valve, is the left atrioventricular valve between the left atrium and left ventricle. 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