# How the Mitral Valve Works

By happy\-badger\-bc110837

Topic: Human Body & Medicine

[Open the interactive Jig](https://ask.jig.com/j/ukEwqfhEJFk6)

## Guide

### 1. A door inside your heart

Your heart has four rooms\. On its left side, a valve called the mitral valve sits between the upper room, the left atrium, and the strong pump below, the left ventricle\. It opens and shuts with every heartbeat\.

At about 70 beats a minute, it opens and closes roughly 100,000 times a day\. Drag to turn the model\.

### 2. Two thin leaflets

Looking down from the atrium, you can see two soft flaps called leaflets\. The broad anterior leaflet faces the aorta, and the wider, shallower posterior leaflet has three scallops\. Each is only about a millimetre thick\.

Its name comes from a bishop's tall two\-pointed hat, the mitre\.

### 3. A ring that tightens

The leaflets hang from a tough ring called the annulus\. It is shaped like a letter D and curved like a saddle, about 3 centimetres across\. When the heart squeezes, the ring tightens too, helping the leaflets meet\.

### 4. Filling: the valve swings open

When the ventricle relaxes, pressure in the atrium is higher, so blood pushes the leaflets apart and pours down\. Most of the filling happens in this first rush\. Then the atrium gives a small squeeze to top it up\.

The early rush brings about 70 to 80 percent of the blood; the atrium's squeeze adds the rest\.

### 5. Squeeze: the valve snaps shut

Now the ventricle squeezes\. Its pressure rises above the atrium's, pushing the leaflets up until their edges press together and seal\. Blood can only leave one way: up through the aorta to the body\.

This closing helps make the first heart sound, the 'lub' of lub\-dub\.

### 6. Strings that stop a flip

Thin white cords called chordae tendineae tie the leaflets to two finger\-like papillary muscles on the ventricle wall\. When the heart squeezes, the muscles tighten too, so the leaflets cannot flip backwards into the atrium\.

The cords do not pull the valve shut\. Blood pressure closes it; the cords hold it in place, like the lines of a parachute\.

### 7. Try the heartbeat

Slide to change the heart rate, now shown at real speed\. Running makes your heart beat faster\. Each beat leaves less time to fill, so the quick first rush through the valve matters even more\.

A normal resting heart rate for most adults is 60 to 100 beats a minute\.

### 8. Why a good seal matters

If the leaflets do not meet well, some blood leaks backwards\. If they stiffen and narrow, blood struggles to get through\. Either way the heart works harder, which is why doctors can repair or replace this small, hard\-working door\.

Healthy leaflets overlap by about 8 millimetres when they close\.