Digestion story

An illustrated guide to Digestion.

Chapter 1: We chew food and mix it with saliva, passing it as a bolus through pharynx and the Upper Oesophageal sphincter in to the oesophagus. 

Stimulated by how much you chew, some of the enzyme amylase is produced with the saliva to help break down starches.

Chapter 2: The bolus slides down the oesophagus with the help of muscles in an action known as peristalsis, 

to the Lower Oesophageal Sphincter (LOS / LES) which relaxes to permit the bolus to enter the stomach. 

Chapter 3: In the stomach the bolus is churned with strong acid and some of the enzyme pepsin to break it down to a thick liquid chyme to pass on through the pyloric sphincter to the duodenum and small intestines where the most important processes of digestion, assimilation, take place. 

Food can spend upto 4 hours in the stomach depending on its consistency. 

Chapter 4: In the duodenum, digestive enzymes produced in the pancreas, including amylase to help break down carbohydrates and protease to help break down proteins along with bile from the gallbladder where it is stored, enter via the Sphincter of Oddi to commence the real part of digestion. Bile helps break down fats, acting like a detergent as acid doesn’t dissolve fats, and neutralising any excess remaining acid, with help of sodium bicarbonate also produced by the pancreas. 

It then passes into the intestines which are lined with millions of villi, microscopic hairlike protruberences where nutrients are transferred to the small blood vessels they contain so they may be transported to the kidneys and liver to filter and send to the parts of the body that require them. 

Chyme can take upto 4 hours traversing the small intestines.

Chapter 5: The Ileocecal sphincter markes the end of passing nutrients into the blood to the beginning of receiving waste products from the blood to add to the remaining indigestible material that continues through the intestines.

Chapter 6: Waste builds up and is contained until we are ready to excrete it via the Anal Sphincters.

Updated 3 October 2024