The Digestive System Flashcards
What has to happen to these large insoluble molecules?
Must be broken down (digested) into small soluble molecules before they can be absorbed into blood stream
What are the 5 main stages in the digestive system?
- Indigestion
- digestion
- absorption
- assimilation
- egestion
What is indigestion?
When food is taken in through the mouth
What is digestion?
When the food is broken down into soluble substances
What is absorption?
When the molecules are absorbed into blood stream and transported around the body.
What is assimilation?
When the soluble products are taken into cells where they are used
What is egestion?
Removal of waste food
Most of the food we eat is made up of…
Large insoluble molecules
What is mechanical digestion?
Food is broken up teeth and tongue in mouth and churned in stomach by muscular movements
What is chemical digestion?
When food is broken down by enzymes
What is an enzyme?
A special molecule that speeds up breakdown of food
What are the three main enzymes?
- Amylase
- protease
- lipase
What does an amylase enzyme do?
Breaks down carbohydrates into simple sugars
What does an protease enzyme do?
Breaks down proteins into amino acids
What does an lipase enzyme do?
Breaks down fats into fatty acids and glycerol
How many parts is there in the digestive system?
6
What are the parts of the digestive system?
- mouth
- Oesophagus
- stomach
- digestion into the small intestine, liver and pancreas
- absorption in the small intestine
- large intestine
What happens in to first part of the digestive system (mouth)?
- food mechanically digested by teeth
- food mixes with saliva which lubricates food for swallowing
- saliva contains amylase
- chewing makes food easier to swallow and increases surface area of food
What happens in the second part of the digestive system (Oesophagus)?
- food is pushed along this tube from mouth to stomach by waves of muscular movements (peristalsis)
- muscles above bolus have to contract
- muscles below bolus have to relax to allow food to pass down to stomach
What happens in the third part of the digestive system (Stomach)?
- Swallowed food enters stomach
- stomach is a large muscular bag able to expand when large amount of food has been eaten
- food stays I stomach for about 4 hours
- food is digested by constant muscle contraction
- glands in stomach release hydrauchloric acid which kills germs
- rings of muscle at exit of stomach help acidic food move through duodenum bit by bit
What happens in the fourth part of the digestive system (Digestion in the small intestine, liver and pancreas)?
- First part of small intestine is duodenum
- bile is released into duodenum and helps neutralise stomach acid
- pancreas produces juice containing enzymes
- enzymes are released into the ileum where digestion is completed
- soluble products are then absorbed through intestinal wall into blood
What happens in the fifth part of the digestive system (Absorption in the small intestine)?
- small intestine is 7m long
- this is to help food be passed into bloodstream
- on folds are thousands of fingerlike projections called villi
- villus is made up of microvilli
- lining is very thin, usually one cell thick. this allows easy passage of digested food
- well supplied with blood vessels close to surface to carry away food
What happens in the sixth part of the digestive system (The large intestine)?
- all that’s left of passed through food is a wet mixture of indigestible fibre, bacteria and dead cells
- most remaining water is absorbed into bloodstream
- fibre helps food move smoothly along
- faeces is stored in rectum before passed through anus
What is the faeces?
Remaining material after food has been digested in the large intestine
What are the villi?
Finger like projections that increase surface area for absorption
What are the microvilli?
Microscopic folds of ileum that increase surface area even more than villi
What is the ileum?
The third and end part of the small intestine
What is a bolus?
A swallowed chunk of food
What is the anus?
An opening in which solid waste matter leaves body
What is egestion?
Waste matter (I think)
What is excretion?
Getting rid of waste materials
