Left atrioventricular valve
The left atrioventricular valve is the valve between the left atrium and left ventricle. It opens to let blood into the left ventricle and closes during contraction to prevent backflow.
What is the left atrioventricular valve?
The left atrioventricular valve is the valve in the left side of the heart that sits between the left atrium and the left ventricle. In Anatomy and Physiology I, you will also hear it called the mitral valve or bicuspid valve, because it has two flaps, or cusps.
Its job is simple but essential: it lets oxygen-rich blood move from the left atrium into the left ventricle, then shuts when the left ventricle contracts. That closure keeps blood from slipping backward into the atrium during ventricular systole.
The valve works as part of the heart's one-way flow system. The atrium fills with blood returning from the lungs, then pushes that blood into the ventricle. When the ventricle contracts, pressure rises fast, and the valve responds by closing so the blood is driven forward toward the aorta instead of reversing direction.
This valve does not work alone. It is supported by chordae tendineae, which are strong string-like cords attached to the valve cusps, and by papillary muscles in the ventricle. When the ventricle squeezes, those structures help keep the cusps from flipping backward into the atrium.
A useful way to picture it is as a door between two chambers that opens only one way. If that door leaks, the heart has to work harder because some blood moves the wrong direction. In a lab model, diagram, or heart dissection, you can identify the left atrioventricular valve by finding the opening between the left atrium and left ventricle, on the side that leads toward the aorta.
In heart anatomy, this valve sits in the pathway of pulmonary return to systemic circulation, so it is one of the main checkpoints that makes the double pump work efficiently. If you know where blood comes from, where it goes next, and when the valve opens or closes, the structure makes a lot more sense than memorizing the name by itself.
Why the left atrioventricular valve matters in Anatomy and Physiology I
The left atrioventricular valve matters because it shows how heart structure matches heart function. Anatomy and Physiology I is full of these structure-plus-function connections, and this valve is one of the clearest examples. You are not just naming a part of the heart, you are tracing how blood stays moving in the correct direction through the left side of the circulatory system.
It also helps you understand pressure changes inside the heart. The valve opens when atrial pressure is higher and closes when ventricular pressure rises. That pattern explains why valves are passive structures that respond to pressure differences rather than active pumps.
This term also comes up when you study heart sounds, valve disorders, and blood flow diagrams. If a quiz asks why blood does not return to the left atrium during ventricular contraction, the left atrioventricular valve is part of the answer. If a lab image shows the left side of the heart, recognizing this valve helps you orient the chambers and follow the route to the aorta.
Once you know this valve, the rest of the left-side circulation makes more sense, including how oxygenated blood leaves the heart and why valve damage can affect the whole cardiovascular system.
Keep studying Anatomy and Physiology I Unit 19
Official unit cheatsheet
open one-pagerHow the left atrioventricular valve connects across the course
Left Atrium
The left atrium is the chamber that sends oxygen-rich blood into the left atrioventricular valve. When you trace the flow of blood through the heart, this is the chamber just before the valve opens. If blood backs up here, that can affect pressure on the pulmonary side and interrupt the smooth path into the left ventricle.
Left Ventricle
The left ventricle sits right below the left atrioventricular valve and is the chamber that receives blood after the valve opens. Its stronger wall matters because it has to pump blood into the aorta and out to the body. The valve closes when this chamber contracts so blood does not move backward into the atrium.
Chordae Tendineae
Chordae tendineae are the tough cords attached to the valve cusps. They do not open or close the valve, but they stop the cusps from turning inside out when the left ventricle contracts. If you are labeling a heart diagram, these cords often help you tell an atrioventricular valve from a semilunar valve.
Aortic Valve
The aortic valve is the next valve blood passes through after leaving the left ventricle. The left atrioventricular valve is on the entrance side of the ventricle, while the aortic valve is on the exit side. Together they make sure blood moves from atrium to ventricle to aorta without backflow.
Is the left atrioventricular valve on the Anatomy and Physiology I exam?
A label question or heart diagram usually asks you to identify the valve between the left atrium and left ventricle, then explain its direction of flow. A short-answer item may describe ventricular contraction and ask why blood does not move back into the atrium. Your job is to connect the structure to the pressure change: the valve opens when the atrium fills the ventricle and closes when ventricular pressure rises. If a question includes chordae tendineae or papillary muscles, use them to explain how the valve stays shut during contraction. In lab images, look for the left side of the heart and the opening just before the left ventricle.
Key things to remember about the left atrioventricular valve
The left atrioventricular valve sits between the left atrium and left ventricle.
It opens to let oxygen-rich blood enter the left ventricle and closes during ventricular contraction.
Its closure prevents backflow into the left atrium, which keeps blood moving forward through the heart.
Chordae tendineae help hold the valve cusps in place when the left ventricle contracts.
In diagrams and lab models, it is the valve on the left side of the heart that leads toward the aorta.
Frequently asked questions about the left atrioventricular valve
What is left atrioventricular valve in Anatomy and Physiology I?
It is the valve between the left atrium and left ventricle. It opens to let blood pass into the ventricle and closes when the ventricle contracts so blood does not flow backward. You may also see it called the mitral valve or bicuspid valve.
Is the left atrioventricular valve the same as the mitral valve?
Yes. Mitral valve is the more common name, and bicuspid valve is another name because the valve has two cusps. In heart anatomy, all three terms refer to the same structure.
What happens if the left atrioventricular valve does not close properly?
Blood can leak back into the left atrium when the left ventricle contracts. That backflow makes the heart work less efficiently and can change blood flow through the lungs and the rest of the body.
How do I identify the left atrioventricular valve on a heart diagram?
Find the left atrium and left ventricle, then locate the valve between them. It is on the side of the heart that sends blood toward the aorta, and chordae tendineae may be shown attaching to it from below.