The Digestive System Flashcards
The digestive system has 2 main roles. What are they?
Digestion and Absorption
What is the definition of digestion?
The process by which we break down the large food molecules we eat into much smaller molecules.
What is absorption?
The process by which we absorb small, broken down molecules into the bloodstream.
What happens inside the mouth during digestion?
In the mouth, the teeth are used to physically break down the food by chewing, which therefore increases the surface area of the food which makes it easier for enzymes to break it down. Chewing also makes the food easier to swallow.
The salivary glands release saliva, which is a water mix that contains the enzyme amylase. The water part of the saliva makes the food wet and easier to swallow, while the amylase digests starch into maltose.
What do we call enzymes like amylase that reduce the energy that’s needed for reactions?
Biological Catalyst
Where does the food go after it is swallowed?
The food goes through the oesophagus and down to the stomach.
What happens inside the stomach during digestion?
The stomach contracts its muscular walls which pushes around the food and mixes it all together.
It also produces pepsin (which is a protease enzyme) that breaks proteins down into amino acids.
As well as this, is also produces hydrochloric acid which kills bacteria and provides the right pH for pepsin.
Where does the food go after it is finished inside of the stomach?
The small intestine
What does the pancreas do as the food mixture moves into the stomach?
The pancreas releases pancreatic juices into the small intestine.
Pancreatic juice is a liquid that contains many digestive enzymes, including amylase, protease and lipase.
What does the gallbladder do as the food mixture moves into the stomach?
The gallbladder releases bile into the small intestine.
Bile itself is made in the liver and stored in the gallbladder.
Bile neutralises the acid from the stomach to make the pH ideal for the digestive enzymes to function. It can do this because the bile itself is alkaline.
Bile also emulsifies lipids, which means it breaks down large amounts of lipids down into tiny droplets. This helps because it gives the lipids a larger surface area for digestive enzymes to work on.
Why is the small intestine so important?
It’s where most of the digestion takes place, and it’s where the nutrients are absorbed from the intestines into the bloodstream.
What happens inside the small intestine during digestion?
The small intestine releases digestive enzymes like the pancreas. So, it releases more carbohydrases, lipases, and protease enzymes. At this point in the digestive journey, all of the nutrients are broken down.
After all of the useful nutrients have been absorbed into the bloodstream, there is still a lot of material left in the small intestine, because a lot of the food we eat isn’t actually digestible and is still going to be a bit watery.
What are villi and what are their important features?
Villi (plural) or villus (singular) have a huge surface area over which diffusion can take place.
They also only have a single layer of surface cells, which means there’s only a very short distance for diffusion to take place across.
As well as this, they also have a really good blood supply, which maintains the concentration gradient for the absorption of nutrients.
The cells of the villi also have their own tiny projections called microvilli, which further increases the surface area.
Where does the food go after it is finished in the small intestine?
It passes through to the large intestine.
What happens inside the large intestine during digestion?
The large intestine absorbs most of the excess water that hasn’t been absorbed yet. This leaves behind a relatively dry mixture, that we call faeces. These are stored in the rectum until they are ready to be removed at a convenient time through the anus.
