--- title: "Pulmonary Valve | Anatomy and Physiology II" description: "Pulmonary Valve in Anatomy and Physiology II: the right ventricular valve that sends blood to the pulmonary artery and prevents backflow after systole." canonical: "https://fiveable.me/anatomy-physiology-ii/key-terms/pulmonary-valve" type: "key-term" subject: "Anatomy and Physiology II" unit: "Unit 1" --- # Pulmonary Valve | Anatomy and Physiology II ## Definition The pulmonary valve is the semilunar valve between the right ventricle and the pulmonary artery. It opens during ventricular contraction to send blood to the lungs and closes to stop backflow. ## What It Is The pulmonary valve is the outflow valve for the right side of the heart in Anatomy and Physiology II. It sits between the right ventricle and the pulmonary artery, and it lets blood leave the ventricle only when the ventricle contracts. It has three cusps, or flaps, that respond to pressure changes. When the right ventricle builds enough pressure during systole, the valve opens and blood is pushed into the pulmonary artery. That vessel carries deoxygenated blood to the lungs, where carbon dioxide is released and oxygen is picked up. Once the ventricle relaxes, the pressure inside it drops. Pressure in the pulmonary artery is now higher than pressure in the ventricle, so a small amount of blood tries to drift backward. The valve cusps fill and snap shut, stopping that backflow. That closing action is what keeps blood moving in one direction through the right heart. This valve is called a semilunar valve because its cusps are shaped like half moons. The other semilunar valve in the heart is the aortic valve, and both work in the same pressure-driven way. They are different from the atrioventricular valves, which sit between atria and ventricles and use chordae tendineae and papillary muscles to keep from flipping backward. In a heart diagram or lab model, the pulmonary valve is usually identified by its position at the exit of the right ventricle. If you trace blood flow from the right atrium to the right ventricle, the pulmonary valve is the next stop before blood reaches the pulmonary artery and travels to the lungs. ## Why It Matters The pulmonary valve matters because it is one of the checkpoints that makes pulmonary circulation work as a one-way path. Without a valve that opens at the right moment and closes right after, blood would not move efficiently from the right ventricle to the lungs, and the right ventricle would lose pressure with each beat. This term also connects directly to how you read the heart as a pump. A&P II often asks you to follow blood through the chambers and valves in order, so the pulmonary valve marks the transition from the ventricular pump to the lung circuit. If you know where it sits, you can explain what comes before it, what comes after it, and why the right side of the heart has a lower-pressure job than the left side. It also gives you a way to make sense of valve disorders. For example, pulmonary stenosis means the valve opens too narrowly, which makes the right ventricle work harder to push blood through. That can raise pressure in the ventricle and change the way the heart sounds or functions in a case study. In labs, diagrams, and practicals, this is one of the structures you should be able to point to quickly and connect to its function. It is not just a label. It is a mechanical gate that keeps circulation moving in the right direction. ## Connections ### Right Ventricle The right ventricle is the chamber that pushes blood through the pulmonary valve. If you understand the valve, you can trace what the ventricle is doing during systole and why the pressure inside it has to rise high enough to open the valve. ### [Pulmonary Artery](/anatomy-physiology-ii/key-terms/pulmonary-artery) Blood passes from the pulmonary valve into the pulmonary artery after leaving the right ventricle. That relationship matters because the artery is not just a tube, it is the vessel that carries deoxygenated blood to the lungs for gas exchange. ### Semilunar Valve The pulmonary valve is one of the two semilunar valves in the heart. Comparing it with the aortic valve helps you see the shared structure, the shared pressure-based opening and closing pattern, and the different circuits they serve. ### [Aortic Valve](/anatomy-physiology-ii/key-terms/aortic-valve) The aortic valve is the left-side counterpart to the pulmonary valve. They work in parallel on opposite sides of the heart, so when you study one valve, you can often use the same logic to understand the other, then focus on which vessel each one leads into. ## On the AP Exam A quiz or lab practical may show you a heart diagram and ask you to identify the valve between the right ventricle and pulmonary artery. A case question might describe a narrowed semilunar valve and ask what part of the heart is working harder or where blood flow is being restricted. You may also need to trace the sequence of circulation, such as right ventricle to pulmonary valve to pulmonary artery to lungs. In a short-answer response, use the term to explain why blood moves forward during systole and does not fall back into the ventricle during diastole. ## Pulmonary Valve vs Aortic Valve These two are easy to mix up because both are semilunar valves with three cusps, but they serve different sides of the heart. The pulmonary valve is on the right side and sends blood to the lungs, while the aortic valve is on the left side and sends blood to the body. ## Key Takeaways - The pulmonary valve is the semilunar valve between the right ventricle and the pulmonary artery. - It opens during ventricular contraction and closes when the ventricle relaxes, which keeps blood moving forward. - Its three cusps stop backflow into the right ventricle after blood is pumped toward the lungs. - In A&P II, you should connect the pulmonary valve to the right side of the heart and the pulmonary circulation pathway. - If the valve is narrowed or damaged, the right ventricle may have to work harder to push blood through. ## FAQs ### What is the pulmonary valve in Anatomy and Physiology II? It is the semilunar valve between the right ventricle and the pulmonary artery. In heart flow, it opens when the right ventricle contracts and closes when pressure drops so blood does not flow backward. ### Is the pulmonary valve the same as the aortic valve? No. They are both semilunar valves, but they serve different circuits. The pulmonary valve sends blood to the lungs from the right ventricle, while the aortic valve sends blood to the body from the left ventricle. ### What happens when the pulmonary valve closes? It shuts as the right ventricle relaxes and the pressure in the ventricle falls below the pressure in the pulmonary artery. That closure prevents backflow into the ventricle and keeps circulation one-way. ### How do you identify the pulmonary valve on a heart diagram? Look for the valve at the exit of the right ventricle that leads into the pulmonary artery. On many diagrams, it sits above the right ventricle and marks the route to the lungs. ## Related Study Guides - [1.2 Cardiac Chambers and Valves](/anatomy-physiology-ii/unit-1/cardiac-chambers-valves/study-guide/t0uLiedG3N8ipQ8R) ## 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-ii/key-terms/pulmonary-valve#resource","name":"Pulmonary Valve | Anatomy and Physiology II","url":"https://fiveable.me/anatomy-physiology-ii/key-terms/pulmonary-valve","learningResourceType":"Concept explainer","educationalLevel":"AP® / High School","about":{"@id":"https://fiveable.me/anatomy-physiology-ii/key-terms/pulmonary-valve#term"},"audience":{"@type":"EducationalAudience","educationalRole":"student"},"dateModified":"2026-07-03T02:21:03.693Z","isPartOf":{"@type":"Collection","name":"Anatomy and Physiology II Key Terms","url":"https://fiveable.me/anatomy-physiology-ii/key-terms"},"publisher":{"@type":"Organization","name":"Fiveable","url":"https://fiveable.me"}},{"@type":"DefinedTerm","@id":"https://fiveable.me/anatomy-physiology-ii/key-terms/pulmonary-valve#term","name":"Pulmonary Valve","description":"The pulmonary valve is the semilunar valve between the right ventricle and the pulmonary artery. It opens during ventricular contraction to send blood to the lungs and closes to stop backflow.","url":"https://fiveable.me/anatomy-physiology-ii/key-terms/pulmonary-valve","inDefinedTermSet":{"@type":"DefinedTermSet","name":"Anatomy and Physiology II Key Terms","url":"https://fiveable.me/anatomy-physiology-ii/key-terms"}},{"@type":"FAQPage","mainEntity":[{"@type":"Question","name":"What is the pulmonary valve in Anatomy and Physiology II?","acceptedAnswer":{"@type":"Answer","text":"It is the semilunar valve between the right ventricle and the pulmonary artery. In heart flow, it opens when the right ventricle contracts and closes when pressure drops so blood does not flow backward."}},{"@type":"Question","name":"Is the pulmonary valve the same as the aortic valve?","acceptedAnswer":{"@type":"Answer","text":"No. They are both semilunar valves, but they serve different circuits. The pulmonary valve sends blood to the lungs from the right ventricle, while the aortic valve sends blood to the body from the left ventricle."}},{"@type":"Question","name":"What happens when the pulmonary valve closes?","acceptedAnswer":{"@type":"Answer","text":"It shuts as the right ventricle relaxes and the pressure in the ventricle falls below the pressure in the pulmonary artery. That closure prevents backflow into the ventricle and keeps circulation one-way."}},{"@type":"Question","name":"How do you identify the pulmonary valve on a heart diagram?","acceptedAnswer":{"@type":"Answer","text":"Look for the valve at the exit of the right ventricle that leads into the pulmonary artery. On many diagrams, it sits above the right ventricle and marks the route to the lungs."}}]},{"@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Anatomy and Physiology II","item":"https://fiveable.me/anatomy-physiology-ii"},{"@type":"ListItem","position":2,"name":"Key Terms","item":"https://fiveable.me/anatomy-physiology-ii/key-terms"},{"@type":"ListItem","position":3,"name":"Unit 1","item":"https://fiveable.me/anatomy-physiology-ii/unit-1"},{"@type":"ListItem","position":4,"name":"Pulmonary Valve"}]}]} ```