The Digestive System
3.5 & 3.6
Stages of Food Processing
• ingestion
• digestion
• absorption
• egestion
Ingestion
• teeth: physical breakdown of food• salivary glands: amylase in saliva
breaks down starch (chemical digestion)
• tongue: forms bolus, pushes it back to pharynx
• esophagus: peristalsis moves bolus down http://www.youtube.com/watch?v=h0E9ITyRlh0
Digestion (Stomach)
Digestion (Stomach)
• gastric juices: hydrochloric acid + enzymes (e.g., pepsin)
• mucus: protects lining of stomach from damage
• chyme = partly digested food, water, and gastric juice that enters the small intestine
Digestion (Duodenum)
Digestion (Duodenum)
• bile (produced in liver, stored in gall bladder): emulsifies fat
• lipase, amylase, trypsin (produced in pancreas): digest fat, starch, protein
• maltase, peptidases (produced in duodenum): digest maltose, polypeptides
Absorption (Small Intestine)
Small Intestine
• up to 7 metres in length (25 cm of which is duodenum), 2.5 cm wide
• villi & microvilli increase surface area for absorption
Large Intestine
• 1.5 metres long, 5 cm in diameter
• absorbs water• helpful bacteria
produces vitamins K and B
Egestion
Animations
• Process of digestion:• http://www.youtube.com/watch?v=Z7xK
YNz9AS0• Animation & Quiz:• http://highered.mcgraw-hill.com/sites/00
72495855/student_view0/chapter26/animation__organs_of_digestion.html
Is it Art?
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