EXSS 276: DIGESTION
65 Cards in this Set
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what occurs in SI?
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chem/mech digestion nd absorption of nutrients, vitamins, water
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what occurs in large intestine
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absorb water electrolytes and vitamins
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basic processes of digestion
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1. indigestion
2.secretion
3.mixing an propulsion
4.digestion
5.absorption of nutrient
6.defacation
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chemical digestion in mouth invovles
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salvia---makes bolus
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solutes in salvia
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salivary amylase, lingual lipase, lysozome, bicarbonate and phosphate, IgA, mucous
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salivary amylase
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-mouth
-activated by Cl
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lingual lipase secreted by
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glands in tongue. activated in stomach
begins breakdown of triglycerides
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GERD
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stomach acid coming up to esophagus if lower esophageal sphincter fails to close
-causes heartburn
-smoking and ROH make sphincater relax worsening the situation
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if lower sphincter fails to open in GERD
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distension of esophagus feels lke chest pain/heart attack
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to control symptoms of GERD
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avoid coffee, chocolate, tomatoes, fatty foods, onions and mint
-tums maalox
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functions in stomach
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continue breakdown of starch
begin breakdown of proteins and triglycerides
-acts as a reservoir for mixing and holding food
-formation of chyme to give to SI
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Secretions in gastric glands
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1. parietal cells
2. surface mucous and mucous neck cels
3. chief cells
4. g cells
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parietal cells
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Hcl
-intrinsic factor (absorption of vitamin b12, needed for RBC formation)
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surface mucous and mucous neck cells
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mucus
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chief cells
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pepsingogen
gastric lipase
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g cells
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gastrin
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mechanical digestion waves of stomach
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gentle mixing waves (ever 15 to 25 seconds)
-turns into chyme
more vigorous waves: body to pylroic region
intense waves near pylorus: 1-2 teaspoons emptied into duodenum
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What chemical digestion occurs in stomach?
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protein
2. lipid
3. carb digestion continues**
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How does protein digestion begin?
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-HCl denatures protein
-HCl transforms pepsinogen into pepsin that breaks peptide bonds between AA
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What happens in lipid digestion?
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-gastric lipase splits the triglycerides in milk fat
-lingual lipase splits triglycerides into fatty acids and diglycerides
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Carb digestion in stomach
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Salivary amylase active when stomach contents not mixed with gastric juice
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HCl in chemical digestion
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denatures proteins
-kills microbes in food
-stimulates secretion of hormones that promote flow of bile and pancreatic juice into small intestine
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What protects the stomach walls from being digested /
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mucous cells
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Pancreas role in digestion
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-pancreatic juice: buffers acidity of gastric juice in chyme. stops the action of pepsin from stomach
-pancreatic enzymes
-proteases secreted in inactive form
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pancreatic enzymes
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1. pancreatic amylase--carb
2. pancreatic lipase--fat
3. trpysin, chymotrypsin, carboxypeptidases---protein
4. ribonuclease, deoxyribonuclease---nucleic acid
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proteases
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trypsinogen-->trypsin
chymotrypsinogen-->chymtrypsin
procarboxypeptidase-->carboxypeptidase
proelastase-->eleastase
the second ins the active form in the small intestine
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Liver Digestive Functions
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-2nd largest organ -detox
-energy metabolism
-production of bile
-storage of vitamins
-synthesis of choesterol
-synthesis plasma proteins
-excretion of bilirubin (RBC breakdown)
-synthesis of nile salt
-activation of vitamin D
-phagocytosis of afed RBC and WBC
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Energy and metabolism functions of liver
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-gluconeogenesis (from lactate and AA)
-glycogenesis
-glycolysis
-breakdown of AA by deamination
-lipogenesis
-breakdown of fatty acids
-synthesis of lipoproteins
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Bile
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partially digestive secretion and partially excretory product
-major pigment: bilirubin
-emulsifies and absirption of lipids
-neutralize chyme
-makes cholesterol solube
-STORED in gallbladder--delivers to duodenum
-MADE in liver
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Small Intestine parts
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duodenum
jejunum
ileum
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ROLE of SI
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chemical digestion of carbs, proteins, lipids, nucleic acids
-absorption of monosacs, aa, dipeptides, lipids, electrolytes, vitamins, water
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villi and crypts found in
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small intestine
-villi form brush border
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epithelial cells of small intestine
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-endocrine cells secrete: gastrin, CCK, secretin
-columnar cells secrete: CI and bicarbonate ions
-Goblet cells: mucous
-Paneth Cells: secrete lysozomel capable of phagocytosis
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segmentations
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SI
-localized mixing contractions ---chyme
-mixes chyme with digestive juices
-brings food into contact with mucosa for absorption
-does not propel contents along GI tract
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migrating motility complexes
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-type of persistalsis
-starts at lower portion of stomach, pushes chyme forward a short stretch before dying out
-slowly migrates toward the ileum before beginning agin at the stomach
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chemical digestion in small intestin
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complete digestion of macronutrients invovled intential juice, pncreatic juice, bile
-carb
-proteins
-lipids
-neucleic acids
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chemical digestion of carbs
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-pancreatic amylase: glycogen and tartch
-adeztrinase: smaller starch
-sucrase, lactase, maltase: disacs
-end produt=monosacs
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chemical digestion of proteins
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proteases in pancreatic juice
-peptidases
end product = AA
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chemical digestion of lipids
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-bile salts
-pancreatic lipase
-END PRODUCT= fatty acids and monoglyerides
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chemical digestion of nucleic acids
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pancreatic nucleases
-nucleosidases and phosphatases
-end product: pentoses, phosphates, nitrogenous bases
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Large Intestine mechanical digestion
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-gastroileal reflex-->chyme form SI to LI
-haustral churning: relaxes while filing, then contracts to send chyme
-mass peristalsis: beings at middle transveerse colon drives to rectum
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large intestine chemical digestion
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-bacterial fermintation of remaining carbs
-breakdown AA
-bacteria decompose bilirubin
-absorption of some vitamins, water, Na , Cl
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defecation reflex of large intestine
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production of feces
-distention of walls-->stretch receptors
-PNS stimulates descending colon, rectu, anus. pressure increases from contract--opens of internal sphincter
-external sphincter voluntary control
-ab and diaphragm aids
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Neural Regulation of Digestion
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-Under control of the ANS
-enteric nervous system (controls smooth muscle, glands, endocrine cells)
sym and para have diff effects
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Sym effects on digestion
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gallbladder: relaxes
stomach and intestines: decreased motility and tone, contraction of sphincters
-vasoconstrict of gland arterioles (decrease secretion)
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parasym effects on digestion
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contraction of gallbladder: increased release of bile
-increased motitlity and tone of stomach, relaxation of sphincters
-dialate glands and arterioles
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Hormonal Regulation of Digestion
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-Gastrin
-CCK
-Secretin
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Gastrin
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-stimulated by distension of stomach, semidigest proteins, caffiene in stomach, high pH of stomach chyme
-stimulates HCl secretion, gastric juice secretion, motitlity in the SI and LI, relaxes pyloric, ileocecal sphincter, constricts esophageal sphincter
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CCL
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stimulated by partial digested proteins, trigly, fatty acids in SI
-stimulates secretion of pancreatic enzymes and release of the bile induces satiety
-inhibits gastric emptying
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secretin
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-stimulated by acidic chyme in SI
-stimulates secretion of pancreatic juice, production of bile
-inhibits secretion of gastric juice
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Phases of Digestion (4)
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interdigestive
cephalic
gastric
intestinal
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Interdigestive
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-tract is quiet
-low pH in stomach inhibits gastrin secretion and stimulates somatostatin secretion
-somatostain inhibits gastrin, secretin, CCK and HCl secretion
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Cephalic
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Initial influence=neural (ANS)
-senses thought actives cerebral cortex, hypothal, medulla
-Parasym impulse to GI tract via vagus nerve: secretion of pepsinogen, Hcl into chyme, gastrin into blood, increased stomach motitlty
-if increase Sns: inhibit GI activity
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Gastric
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intial influence=sensory receptors in stomach: stretch receptors stimulated when sotmach walls are distended
-chemoreceptors stim when pH rises
-PNS and ENS: increase peristalsis, gastric juice production, secretion of gastrin
-increase HCl secretion
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gastrin secretion inhibited when
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pH, 2.0
stimulated when pH rises
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intestinal phase
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initial influence:activation of receptors in small intestine: inhibt effect on stomach secretory and motility
-slows exist of chyme to prevent verload in duodenum
-secretion of secretin and CCK
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reg of gastric empyting
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reg by nervous system and endocrine system
stimulation of empyting: distension of stomach, partially digestion proteins, alcohol, caffience (increased gastrin secretion and PNS )
inhibition: enterogastric reflex-distension of duodenum, fatty acids, glucose, partially digested proteins…
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monosacs
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glucose, fructose, galactose
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disacs
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sucrose= glu+fru
lactose=glu+galac
maltose=glu+glu
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polysacs
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glycogen, celuloes, starch
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majority of water absorped
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small intestine
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large intestine absorbs what vitamins
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b and k
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small intestine absorbs what vitamines
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a , d,e k, c, b12
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large intestine absorbs what electrolytes
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Na Cl
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small intestine absorbs what electrolytes
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Na, K, bicarbonate, Cl, I, nitrate, Ca, Fe, Mg Phosphate
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EXSS 276: EXAM 2