# How the Human Heart Works



Model credits \(Sketchfab\):
“Human Heart 3D Model \| Anatomy \| Medical Project” by Mesh\-Magnet, via Sketchfab \(https://sketchfab\.com/3d\-models/5da08bb137014f0392c69f9997f777cd\)\. CC\-BY\-4\.0: https://creativecommons\.org/licenses/by/4\.0/ Prepared for Jig; static geometry/material conversion\.

By Numa

Topic: Human Body & Medicine

[Open the interactive Jig](https://ask.jig.com/j/o0tzTtXBATvo)

## Guide

### 1. A pump the size of your fist

This is a model of a human heart\. It is a muscle about the size of your fist and weighs around 300 grams\. Watch it squeeze, relax and squeeze again\.

Drag anywhere to turn the heart and look around it\.

### 2. Two pumps in one

Your heart is really two pumps joined side by side\. The right side sends blood to your lungs\. The left side sends it to the rest of your body\.

The heart's right side appears on your left, as if it were inside you, facing out\.

### 3. Four rooms inside

Let's open it up\. Inside are four rooms called chambers\. The two on top, the atria, collect blood\. The two below, the ventricles, push it out, and a thick wall called the septum keeps the sides apart\.

### 4. The right side: off to the lungs

Blood that has given away its oxygen returns from the body into the right atrium\. It drops into the right ventricle, which pumps it up to the lungs\. There it picks up fresh oxygen\.

Blue and red are teaching colours\. Real blood is always red, just darker when it carries less oxygen\.

### 5. The left side: out to the body

Fresh blood from the lungs fills the left atrium, then the left ventricle\. This is the strongest chamber, with the thickest wall\. Each squeeze sends blood into the aorta, the body's largest artery\.

### 6. One\-way doors

Four valves work like one\-way doors, so blood only moves forward\. Watch the pale flaps swing open and snap shut\. Their closing makes the lub\-dub sound a doctor hears\.

Each squeeze, each ventricle pushes out about 70 millilitres, roughly five tablespoons\.

### 7. The spark behind every beat

A small patch of cells in the right atrium, the heart's natural pacemaker, sends an electrical signal\. It spreads over the atria, pauses, then races to the bottom of the ventricles, which squeeze from the bottom up\.

Shown in slow motion\. In real life this whole journey takes only about a quarter of a second\.

### 8. Faster or slower

Your heart speeds up when you run and slows down when you rest\. Move the slider to change the beat\. A resting adult's heart beats about 60 to 100 times a minute\.

During hard exercise it can beat more than 150 times a minute\.

### 9. About 100,000 beats a day

Your heart beats around 100,000 times a day and about 3 billion times in a long life\. It never takes a break\. Put a hand on your chest and feel it working for you right now\.