Parts of Digestion
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Mechanical - breaking up food into small pieces
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Chemical - breakign down polymers with enzymes into small pieces
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Absorption - taking nutrients up into cells
Alimentary canal
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path of food through the body
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mouth - pharynx - esophagus - stomach small intestine - large intestine - rectum
Mouth
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Mechanical and chemical digestion begins here
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the enzyme salivary amylase in saliva begins starch digestion
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tongue and teeth break down food mechanically
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incisors for cutting, canines for tearing, molars for grinding
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Where does starch digestion begin?
Peristalsis
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wavelike muscular action conducted by smooth msulce
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esophagus, stomach, small intestine, large intestine
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involuntary contractions
salivary amylase
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pytalin
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breaks starch into maltose
Esophagus
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NO digestion occurs here
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transports food from throat to stomach
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peristalsis
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foods is directed away from the windpipe by the epiglottis, a flap of cartilage in the back of the pharynx(throat)
Epiglottis
a flap of carilage in the back of the pharynx(throat)
Pharynx
throat
Stomach
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Mechanical and chemical digestion
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Protein digestion begins here
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thick, muscular wall churns food mechanically
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gastric glands produce hydrochloric acid and the enzyme pepsin
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acidic, low pH(2-3) necessary from pepsin; destroys ingested microoragnisms
Hydrochloric Acid
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begins the breakdown of muscle(meat)
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activates the inactive enzyme pepsinogen to becom pepsin, which digests protein
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Pepsinogen
inactive enzyme activiated by hydrochloric acide to become pepsin, which breaks down protein
Rennin
aids the digestion of the protein in milk
Cardiac Sphincter
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at the top of the stomach
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keeps acidified food in the stomach from backing up into the esophagus and burning it
Pyloric Sphincter
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bottom of stomach
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keeps food inthe stomach long enough to be digested
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Through it, Chyme enters the duodenum
Where does protein digestion begin?
Stomach
What does excessive acid do?
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cause an ulcer to form in the esophagus, stomach, or duodenum
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another common cause of ulcers is Heliobacter pylori, bacterium
Duodenum
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1st 10in of small intestine
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Chyme enters the duodenum through the pyloric sphincter
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All digestion is completed here
Chyme
partially digested food in the stomach
Small Intestine
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All digestion is completed(duodenum) and nutrients are absorbed here
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pH - 8
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intestinal enzymes are amylases, proteases, lipases, nucleases
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Pancreatic amylases are secreted in here
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glands produce aminopeptidases for polypeptide digestion and disaccharidases
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Peptidases(ex/ trypsin, chymotrypsin) continue to break down proteins
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Millions of villi line the small intestine and absorb all the nutrients from digested food
Villus(pl. Villi)
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fingerlike projections that line the small intestine and absorb all nutrients from digested food
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each contains:
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Capillaires - absorbs amino acids, vitamins, monosaccharides directly into the bloodstream
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lacteal - absorbs fatty acids and glycerol into the lymphatic system
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have microscopic appendages called microvilli that further enhance the rate of absorption
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epithelial cells
- Capillaires - absorbs amino acids, vitamins, monosaccharides directly into the bloodstream
- lacteal - absorbs fatty acids and glycerol into the lymphatic system
Lacteal
Absorbs fatty acids and glycerol into the lymphatic system
Nuclease
Hydrolyzes nucleic acids into nucleotides
Lipase
breaks down fats
Pancreas
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Secretes Peptidases, protein-digesting enzymes, into small intestine
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Pancreatic proteases are stored in inactive froms called zymogens
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prevents damage to pancreatic tissues that occurs if proteases are prematurely active
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Produces amylas, trypsin, chymotrypsin
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Alkaline range pH; bicarbonate ion neutralizes acidity of the chyme
- prevents damage to pancreatic tissues that occurs if proteases are prematurely active
Peptidases/Proteases
Pepsin
Trypsin
Chymotrypsin
Amylase
breaks down starch
Liver
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Produces bile
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Sends bile to the gallbladder until its release into the small intestine
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Breaks down and recycles red blood cells
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Detoxifies blood - removes alcohol and drugs
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Produces cholesterol for structure of cell membranes
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Produces urea from protein metabolism
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Strorage of iron and vitamin B
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Regulate blood glucose levels
erythrocytes
Red blood cells
Hepatic Portal Vein
Delivers glucose and other monosaccharides absorbed in the small intestine during digestion to liver
