Your heart has tiny doors.
These doors help blood move. They only open one way. This keeps your blood moving right. It helps you stay well.
Can you feel your heart beat?
Your heart has tiny doors called valves.
These doors help blood move. They only open in one direction. This keeps blood from flowing backward.
Pressure pushes the doors open. Then, the doors close to seal the way. This makes a sound. It sounds like a "lub-dub" beat.
Some doors have two flaps. Other doors have three flaps. These flaps act like little seals. They make sure the blood goes the right way.
Your heart uses these doors to stay strong. They work all day and night.
Your heart has special doors called valves.
These valves act like one-way gates. They let blood flow in one direction. They also stop blood from flowing backward.
Valves open and close because of blood pressure. Pressure is the push that blood makes against its surroundings. When pressure on one side is high, the valve opens. When pressure changes, the valve shuts tight. This closing makes the "lub-dub" sound of your heartbeat.
A mammalian heart usually has four valves. Two are called atrioventricular valves. These sit between the top and bottom parts of the heart. The mitral valve has two flaps, called cusps. The tricuspid valve has three cusps.
The other two are semilunar valves. These are at the exits of the heart. They are the aortic valve and the pulmonary valve. Both of these have three cusps.
These flaps work like little seals. They make sure blood moves from the heart to the rest of your body.
Your heart uses special doors to keep blood moving correctly. These doors are called heart valves, or cardiac valves. They are biological one-way valves. Their main job is to let blood flow in only one direction. This keeps blood moving through the different chambers of the heart. Without them, blood might flow backward instead of forward.
A mammalian heart usually has four of these valves. Together, they decide exactly which way the blood travels.
These valves work because of blood pressure. Pressure is the push that blood makes against its surroundings. A valve opens when the pressure on one side is higher. It closes when the pressure changes on the other side. This movement creates the sounds you hear in a heartbeat. The first sound, called "lub," comes from atrioventricular valves closing. The second sound, called "dub," comes from semilunar valves closing.
The valves use flaps called leaflets or cusps to seal. These flaps push open to let blood through. Then, they close together to prevent backflow.
There are two main sets of valves in the heart. The first set is the atrioventricular valves. These sit between the top atria and the bottom ventricles. On the right side, you have the tricuspid valve. It has three cusps to help it work. On the left side, you have the mitral valve. This is also called the bicuspid valve because it has two cusps. It gets its name from a bishop's mitre, which is a type of hat.
The second set is called the semilunar valves. These sit at the exits where blood leaves the heart. The aortic valve is located at the aorta. It has three cusps and sits between the left ventricle and the aorta. The pulmonary valve is at the pulmonary artery. It also has three cusps.
These valves help blood move from the ventricles into the large arteries. They do not have the same strings, called chordae tendineae, that the other valves use.
Sometimes, these valves can have a hard job to do. This is called valvular heart disease. One type is called regurgitation. This happens when a valve does not seal well. It lets some blood leak in the wrong direction. Another type is called stenosis. This is when a valve becomes narrow. This can happen if a valve becomes too thick.
Doctors use tools like echocardiograms to see how these valves move. Understanding these valves helps us see how the whole heart stays healthy.
A heart valve, also known as a cardiac valve, is a biological one-way valve. Its primary purpose is to allow blood to flow in only one direction through the chambers of the heart. In mammals, the heart usually contains four distinct valves. These structures work together to determine the exact direction of blood flow. They ensure that blood moves forward through the heart rather than leaking backward.
The mechanism of a heart valve is driven by blood pressure. Pressure is the force exerted by blood against its surroundings. A valve opens when the pressure on one side is higher than the pressure on the other side. When the pressure changes, the valve closes to create a seal. The valves consist of flaps called leaflets or cusps. These flaps are shaped similarly to a duckbill or a flutter valve. They are pushed open to allow flow and then meet to prevent backflow. To make the seal tighter, there are often nodules at the tips of the cusps.
There are two main groups of valves in the mammalian heart. The first group is the atrioventricular valves. These separate the upper atria from the lower ventricles. On the right side of the heart, the tricuspid valve sits between the right atrium and the right ventricle. It features three cusps: the anterior, posterior, and septal cusps. On the left side, the mitral valve, or bicuspid valve, sits between the left atrium and the left ventricle. It is called bicuspid because it only has two cusps, which are the anterior and posterior ones. The mitral valve gets its name from its resemblance to a bishop's mitre, a type of hat.
The atrioventricular valves use a special support system called the subvalvular apparatus. This system includes chordae tendineae, which are strings that anchor the valves to the ventricle walls. These strings are attached to papillary muscles. The purpose of this apparatus is to prevent the valves from prolapsing, or flipping backward, into the atria. While these structures help hold the valve in place, they do not cause the opening or closing. That action is caused entirely by the pressure gradient across the valve.
The second group is the semilunar valves. These are located at the exits of the heart where blood enters the large arteries. The aortic valve is located at the entrance to the aorta. It sits between the left ventricle and the aorta and has three cusps: left, right, and posterior. The pulmonary valve, or pulmonic valve, is at the entrance to the pulmonary artery. It also has three cusps: left, right, and anterior. Unlike the atrioventricular valves, semilunar valves do not have chordae tendineae. They are more similar to the valves found in arteries.
We can actually hear these valves working through the sounds of a heartbeat. The closure of the atrioventricular valves creates the first heart sound, known as "lub" or S1. The closure of the semilunar valves creates the second heart sound, known as "dub" or S2. The aortic valve contributes to the A2 component of this second sound. The pulmonary valve contributes to the P2 component. Because the right heart is a low-pressure system, the P2 component is usually softer than the A2 component.
During development, these valves form from specific tissues in the embryonic heart. The atrioventricular valves develop from the edges of the atrioventricular canals. The semilunar valves form from four thickenings called endocardial cushions. These cushions are located at the cardiac end of the truncus arteriosus. The truncus arteriosus is a single outflow tract that eventually splits into the aorta and the pulmonary trunk. By the ninth week of development, these valves are visible as unique structures. As the heart grows, the valves rotate and move closer to the heart.
Sometimes, these valves do not function correctly, which is called valvular heart disease. There are two main types of dysfunction. The first is regurgitation, or insufficiency. This happens when a valve fails to seal properly, allowing blood to flow in the wrong direction. The second type is stenosis. This occurs when a valve becomes narrow because it has become too thick. For example, mitral valve stenosis is a common result of rheumatic fever. Doctors often use tools like echocardiograms to study these movements and ensure the heart maintains proper fluid dynamics.
Where will your curiosity go next?
🖼️ Images & Media (6)
More to explore
✨ What else?
Related topics you might enjoy
🔬 Go deeper
More advanced topics to explore
What is Nepedia?
A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.