Digestive system Flashcards
What is the digestive system?
A group of organs that work together to break down and absorb food.
What happens during the digestive system?
During digestion, large, insoluble molecules are broken down into smaller soluble molecules by enzymes. The small molecules can then be absorbed into the bloodstream and used by the body’s cells.
Name the different parts of the digestive system
Mouth
Salivary glands
Oesophagus
Liver
Gall bladder
Stomach
Pancreas
Large intestine
Small intestine
Rectum
Anus
Label the digestive system
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State the function of mouth
The mouth physically breaks down food into smaller pieces
State the function of the salivary glands
The salivary glands produce saliva that contains enzymes
State the function of the Gullet (Oesophagus)
Oesophagus is the tube the food travels down to the stomach
What does the stomach do?
The stomach churns food with enzymes and acid
What does the liver do?
The liver releases bile into the stomach to break down fats
What does the Pancreas do?
The Pancreas produces digestive juices containing enzymes
What does the small intestine do
In the small intestine, small molecules pass through the wall of the small intestine into the blood stream
What does the Large intestine do
In the large intestine, water gets reabsorbed
What does the rectum do
The rectum stores the faeces until it leaves the body
What does the Anus do
The Anus is a muscular ring through which food passes from the body
How is the small intestine adapted for absorbing the products of digestion
The wall of the small intestine is covered in tiny structures called villi.
These villi stick out of the wall and increase the surface area so large amounts of nutrients can pass through.
Microvilli (found on the surface of villi) increase the surface area even further.
The wall of the small intestine has a thin membrane.
The thin membrane ensures a short diffusion path.
The villi have a very good blood supply. The blood capillaries rapidly remove the products of digestion. This increases the concentration gradient.
The small intestine is very long (the human small intestine has a length of around 5m). This provides a very large surface area for absorption of the products of digestion.
All these features mean that there is a rapid rate of diffusion.
Any molecules which cannot be absorbed by diffusion are absorbed by active transport.
Why does the stomach produce hydrochloric acid
The stomach produces hydrochloric acid,
to kill bacteria
To give the right pH for the protease enzyme (pespin) to work (which is pH 2 - acidic)
Where is the bile made and stored
The bile is made in the liver and it is stored in the gall bladder
Why is bile alkaline
The HCl in the stomach makes the pH too acidic for enzymes in the small intestine to work properly.
The Bile is alkaline to neutralises the acid and makes conditions in the small intestine alkaline.
The enzymes in the small intestine work best in these conditions
How does the bile help with the digestion of fats
Bile is alkaline to neutralise the hydrochloric acid from the stomach.
The bile emulsifies fats to form small droplets. This increases the surface area of fat for the lipase enzyme to work on.
The alkaline conditions and large surface area increase the rate of fat breakdown by lipase.
Describe the process of digestion
1) The mouth physically breaks down food into smaller pieces. Enzymes (Amylase) in the saliva begin to digest the starch into smaller sugar molecules
2) The food travels down the oesophagus into the stomach
3) In the stomach, the food is churned with enzymes and acids. Protease enzymes (pepsin) begin the digestion of proteins in the stomach. The churning action of the stomach muscles turns the food into a fluid increasing the surface area for enzymes to digest, this makes the digestion of proteins faster.
4) The food passes into the small intestine. At this point chemicals are released into the small intestine from the liver and the pancreas.
The pancreas releases protease and amylase enzymes which continue the digestion of starch and protein. The pancreas also releases lipase, to start the digestion of lipids.
The liver releases bile which helps to speed up the digestion of lipids by the process of emulsification - breaking the fat into tiny droplets. The bile also neutralises the hydrochloric acid released from the stomach and makes conditions alkaline.
The enzymes in the small intestine work best in these alkaline conditions.
The walls of the small intestine release protease, amylase and lipase to continue the complete digestion of protein, lipids and carbohydrates.
5) In the small intestine, the small food molecules produced by digestion are absorbed into the bloodstream either by diffusion or active transport.
6) The digested food travels through the large intestine, where water is excess water is absorbed into the blood stream.
7) The faeces (undigested food), stored in the rectum, is released from the body by the anus.
What are the products of digestion used for by the body
The products of digestion are used by the body, to build new carbohydrates, lipids and proteins. Some of the glucose produced is used in respiration
Why are large food molecules digested into smaller soluble ones
Large food, insoluble molecules are too big to pass through the walls of the digestive system, so they have to be broken down into smaller soluble molecules.
Name the enzymes that break down proteins
Proteins are broken down by enzymes called proteases
Name the enzymes that break down carbohydrates (specifically starch)
Starch (a type of carbohydrate) is broken down by enzymes called amylase.
Name the enzymes that break down lipids
Lipid molecules are broken down by enzymes called lipase
Where in the digestive system is protease produced
Proteases are produced by the stomach, pancreas and small intestine
Where in the digestive system is amylase produced
Amylase is produced by the salivary glands, the pancreas and the small intestine
Where in the digestive system is lipase produced
Lipase molecules are produced in the pancreas and the small intestine.
What do the protease enzymes convert the protein into.
The protease enzymes convert the protein back to individual amino acids, which are absorbed into the bloodstream
What do the amylase enzymes convert the carbohydrate/starch into.
The amylase enzymes convert the starch into simple sugars
What do the lipase enzymes convert the lipids into.
The lipase enzymes convert the lipids into fatty acids and glycerol
