Digestion

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DIGESTION
BUCCAL CAVITY
Mechanical digestion mastication (chewing)
Saliva:
o Mucus to bind food together lubricant
o Salivary amylase to digest starch into maltose
o Mineral salts act as a buffer, keeping the pH at 7
OESOPHAGUS
Peristalsis of the circular and longitudinal muscles to move food through the gut
Joins the buccal cavity to the stomach
STOMACH
Mechanical digestion churning to break down food increasing the surface area
Mixed with gastric juices by churning
Gastric juices:
o HCl produced by the oxyntic cells creates acidic conditions of pH2,
activates the pepsinogen, maintains the pH at the optimum for pepsin and
kills bacteria
o Mucus secreted by the goblet cells lubricates the food and protects the
stomach lining from the HCl
o Peptic cells secrete pepsinogen, which is the inactive form of the enzyme
pepsin that hydrolyses proteins into peptides
DUODENUM
First 20cm of the small intestine
Large surface area due to villi and microvilli
Bile produced in the liver contains bile salts and mineral salts neutralizes
stomach acid, lowers surface tension of food molecules
Brunner's glands in the wall of the duodenum secrete alkaline juices and mucus
Pancreatic juices:
o Amylase hydrolyses starch into maltose
o Lipases hydrolyses lipids into glycerol and fatty acids
o Trypsin hydrolyses proteins into peptides
o Produced by pancreas

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ILEUM
Enzymes found in the intestine wall:
o Maltase hydrolyses maltose to glucose
o Sucrase hydrolyses sucrose to glucose and fructose
o Endopeptidase hydrolyses peptides into shorter peptides by breaking the
bonds in the middle
o Exopeptidase hydrolyses peptides into amino acids and dipeptides by
breaking off the amino acids on the end of a peptide chain…read more

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