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The Human Digestive System
Transcript of The Human Digestive System
begin breakdown of smaller food pieces into food molecules
triple muscle layers churns food up to produce 'chyme'.
can break down food for about 45 minutes to 2 hours.
Chyme enters the small intestine but is still very acidic
neutralised by bile (produced in the liver) and sodium bicarbonate.
The Human Digestive System
A graphical view
Processes - a review
Break large pieces of food into small pieces
increases surface area
called 'mechanical digestion'
Optimal pH for enzyme
also good for killing bacteria
Begin breakdown of proteins
called 'chemical digestion'
Protect stomach from acid attack
Break small food pieces down into dissolved food molecules (more 'chemical digestion')
bile breaks up fats and lipids
enzymes break down
carbohydrates to glucose (and other simple sugars)
proteins to amino acids
lipids to fatty acids and glycerol
Extract water back into the blood stream
Make some vitamins (bacteria)
Storage of faeces
Elimination of faeces
Absorption of small food molecules into blood stream
Glucose and simple sugars
Fatty acids and glycerol
Vitamins and minerals
Vitamins e.g. Vitamin K
Small food pieces continue to be broken down into small food molecules.
main process is digestion by enzymes from the pancreas and lining of the small intestine.
Only when food is broken down to small food molecules (e.g. glucose, amino acids, fatty acids, vitamins) can it be absorbed into the blood stream.
the shape of the villi increase the surface area for absorption.
Time spent in the small intestine - 2.5 to 4 hours depending on the food and the person.
Any undigested or indigestible material enters the large intestine.
Bacteria in the gut help breakdown some of this material particularly anything high in fibre.
Bacteria also make some vitamins (e.g. K)
As much water as possible is extracted from the waste - well, most of the time.
Waste is stored in the rectum until it can be eliminated