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nutrition in humans - Coggle Diagram
nutrition in humans
name and functions
small intestine
-consists of duodenum(where most digestion occurs) and ileum(mainly involved in absorption of food)
-once chyme enters the duodenum, it stimulates the pancreas to secrete pancreatic juice, the glands in the lining of the small intestine to secrete intestinal juices, the gall bladder to release bile containing bile salts
-pancreatic juice contains pancreatic amylase, protease and pancreatic lipase
-intestinal juice contains maltase, protease and lipase
-water and nutrient are absorbed in the small intestine
-fats are broken into tiny fat droplets which is helped by the bile
-pancreatic amylase digests any remaining starch into malose
-pancreatic lipase digests fats into fatty acids+glycerol
-pancreatic protease digests proteans into polypeptides
-maltase digests maltose into glucose
-protease from the intestinal juice digests polypeptides into amino acids
large intestine
-absorbs water and mineral salts from undigested food
-undigested food+unabsorbed materials=faeces
-faces are stored temporarily in the rectum and is expelled through the anus
-faeces is NOT a metabolic waste product
stomach
-gastric glands secrete gastric juice containing HCL, mucus and pepsin
-HCL provides an acidic environment in the stomach which is the optimum ph for pepsin. Kills harmful microorganisms. Stops action of salivary amylase by denaturing it
-pepsin digests proteins into polypeptides
oessophagus
-peristalsis occurs in the oesophagus
-rhythmic wave-like contractions of the wall of the alimentary canal
-push bolus forward: at one end, circular muscles contract while longitudinal muscles relax. causes wall to constrict and become longer and narrower to squeeze the bolus forward. at the other end, the circular muscles relax while the longitudinal muscles contract. the wall of the alimentary canal dilates and becomes shorter and wider. this allows the bolus to move to a new position
mouth
-salivary glands produce saliva which contains salivary amylase and mucus
-physical digestion: teeth chews the food into smaller pieces
-chemical digestion: starch is digested into maltose by salivary amylase
liver
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detoxification
-enzymes in the liver break down or transform harmful substances like metabolic waste, drugs, alcohol and chemicals into harmless substances so they can be excreted
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types of digestion
chemical
-large and complex food subsances are broken down into smaller and soluble simple substances
-new products are formed
-done to allow food substances to enter bloodstream through intestinal wall
-mouth:starch
-stomach:proteins
-small intestines: carbohydrates, fats, proteins
physical
-mechanical breakdown of large pieces of food into smaller pieces
-no new products formed
-done to increase SA/V ratio
-mouth:chewing
-stomach:churning action
-small intestine:emulsification
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