Digestion Flashcards
Parts of Digestion
- Mechanical - breaking up food into small pieces
- Chemical - breakign down polymers with enzymes into small pieces
- Absorption - taking nutrients up into cells
Alimentary canal
- path of food through the body
- mouth - pharynx - esophagus - stomach small intestine - large intestine - rectum
Mouth
- Mechanical and chemical digestion begins here
- the enzyme salivary amylase in saliva begins starch digestion
- tongue and teeth break down food mechanically
- incisors for cutting, canines for tearing, molars for grinding
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Where does starch digestion begin?
Peristalsis
- wavelike muscular action conducted by smooth msulce
- esophagus, stomach, small intestine, large intestine
- involuntary contractions
salivary amylase
- pytalin
- breaks starch into maltose
Esophagus
- NO digestion occurs here
- transports food from throat to stomach
- peristalsis
- 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
- Mechanical and chemical digestion
- Protein digestion begins here
- thick, muscular wall churns food mechanically
- gastric glands produce hydrochloric acid and the enzyme pepsin
- acidic, low pH(2-3) necessary from pepsin; destroys ingested microoragnisms
Hydrochloric Acid
- begins the breakdown of muscle(meat)
- 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
- at the top of the stomach
- keeps acidified food in the stomach from backing up into the esophagus and burning it
Pyloric Sphincter
- bottom of stomach
- keeps food inthe stomach long enough to be digested
- Through it, Chyme enters the duodenum
Where does protein digestion begin?
Stomach
What does excessive acid do?
- cause an ulcer to form in the esophagus, stomach, or duodenum
- another common cause of ulcers is Heliobacter pylori, bacterium
Duodenum
- 1st 10in of small intestine
- Chyme enters the duodenum through the pyloric sphincter
- All digestion is completed here
Chyme
partially digested food in the stomach
Small Intestine
- All digestion is completed(duodenum) and nutrients are absorbed here
- pH - 8
- intestinal enzymes are amylases, proteases, lipases, nucleases
- Pancreatic amylases are secreted in here
- glands produce aminopeptidases for polypeptide digestion and disaccharidases
- Peptidases(ex/ trypsin, chymotrypsin) continue to break down proteins
- Millions of villi line the small intestine and absorb all the nutrients from digested food
Villus(pl. Villi)
- fingerlike projections that line the small intestine and absorb all nutrients from digested food
- each contains:
- Capillaires - absorbs amino acids, vitamins, monosaccharides directly into the bloodstream
- lacteal - absorbs fatty acids and glycerol into the lymphatic system
- have microscopic appendages called microvilli that further enhance the rate of absorption
- epithelial cells
Lacteal
Absorbs fatty acids and glycerol into the lymphatic system
Nuclease
Hydrolyzes nucleic acids into nucleotides
Lipase
breaks down fats
Pancreas
- Secretes Peptidases, protein-digesting enzymes, into small intestine
- Pancreatic proteases are stored in inactive froms called zymogens
- prevents damage to pancreatic tissues that occurs if proteases are prematurely active
- Produces amylas, trypsin, chymotrypsin
- Alkaline range pH; bicarbonate ion neutralizes acidity of the chyme
Peptidases/Proteases
Pepsin
Trypsin
Chymotrypsin
Amylase
breaks down starch
Liver
- Produces bile
- Sends bile to the gallbladder until its release into the small intestine
- Breaks down and recycles red blood cells
- Detoxifies blood - removes alcohol and drugs
- Produces cholesterol for structure of cell membranes
- Produces urea from protein metabolism
- Strorage of iron and vitamin B
- 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
Gluconeogenesis
- When liver syntesizes glucose from noncarbohydrate precurors when blood glucose levels are low
What processes glucose-rich blood?
- Liver converts excess glucose to glycogen for storage in the liver
What happens when blood has a low glucose concentration?
- liver converts glycogen into glucose and releases it into the blood, restorign blood glucose levels to normal
- gluconeogenesis
Zymogens
- Pancreatic proteases in inactive forms
- activated after secretion when they are cleaved by another protease
- prevetns dame to the pancreatic tissues that occurs if proteases are prematurely active
Bile
- Produced in liver; Stored in gallbladder
- emulsifies fats in small intestine
- pH 11; neutralizes chyme entering the small intestine
Gallbladder
- Stores bile
- Can function without
Large Intestine/Colon
- No digestion
- Egestion
- Vitamin production - bacteria symbionts livign in the colon produce the B vitamins, vitamin K, and folic acid
- Reabsorption of water
- Constipation
- Diarrhea
Egestion
- Large intestine
- removal of undigested waste
Constipation
Too much water is reabsorbed from large intestine into body
Diarrhea
Too little water absorbed back into body
Rectum
- Egestion
- last 7-8 inches of the gastrointestinal tract
- Stores feces until release through anus
