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ANT 3120: Chapter 24 (PHYS)
Digestive System
137
Anatomy
Undergraduate 1
04/19/2013

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Term
five major processes of the digestive system
Definition
1) ingestion
2) motility
3) digestion
4) absorption
5) elimination
Term
ingestion
Definition
mastication of food and deglutition (swallowing)
Term
motility
Definition
contraction of digestive tract unitary smooth muscle
Term
digestion
Definition
breakdown of food into their simplest forms (nutrients)
Term
mechanical digestion
Definition
physical breakdown (mastication/mixing)
Term
chemical digestion
Definition
breakdown of large molecules into small molecules
Term
absorption
Definition
transport of nutrients to the blood and lymph
Term
purpose of absorption
Definition
allows nutrients to be utilized by the body
Term
elimination
Definition
removal of undigested and unabsorbed material from the body
Term
regulation of digestive system is by
Definition
1) autonomic nervous system
2) hormones
3) paracrines
Term
autonomic nervous system consists of
Definition
1) enteric nervous system
2) sympathetic nervous system
3) parasympathetic nervous system
Term
function of enteric nervous system
Definition
stimulates/inhibits the digestive system
Term
enteric nervous system is influenced by the
Definition
sympathetic and parasympathetic nervous system
Term
enteric nervous system consists of
Definition
submucosal plexus and myenteric plexus
Term
function of sympathetic nervous system
Definition
inhibits the digestive system
Term
function of parasympathetic nervous system
Definition
stimulates the digestive system
Term
hormones of the digestive system
Definition
1) gastrin
2) cholecystokinin
3) secretin
4) glucose-dependent insulinotropic peptide
Term
gastrin is secreted by
Definition
stomach, duodenum, jejunum
Term
function of gastrin
Definition
1)stimulates gastric acid secretion
2)stimulates gastric motility
Term
what stimulates the release of gastrin?
Definition
protein, distension of the stomach, parasympathetics
Term
CCK is secreted by
Definition
duodenum, jejunum, ileum
Term
functions of CCK
Definition
1) causes gallbladder to contract
2) stimulates secretion of pancreatic enzymes
3) inhibits gastric emptying
Term
what stimulates the release of CCK?
Definition
1) protein/lipid/carbohydrate in small intestine
2) decrease in small intestine pH
Term
secretin is secreted by
Definition
duodenum, jejunum, ileum
Term
functions of secretin
Definition
1) stimulates secretion of HCO3 from pancreas
2) stimulates release of bile from liver
3) inhibits release of gastrin
4) inhibits gastric emptying
Term
what stimulates the release of secretin?
Definition
1) decrease in small intestine pH
2) lipid in small intestine
Term
GIP is secreted by
Definition
duodenum
Term
functions of GIP
Definition
stimulates secretion of insulin
Term
what stimulates the release of GIP
Definition
glucose in duodenum
Term
paracrines
Definition
1) somatostatin
2) histamine
Term
somatostatin is secreted by
Definition
stomach
Term
function of somatostatin
Definition
inhibits gastric acid secretion
Term
what stimulates the release of somatostatin?
Definition
decreased gastric pH
Term
histamine is secreted by
Definition
stomach
Term
function of histamine
Definition
stimulates gastric acid secretion
Term
what stimulates the release of histamine?
Definition
parasympathetics
Term
function of mastication
Definition
1) mechanical digestion
2) mixes food with saliva to form bolus
Term
bolus
Definition
semi-solid mass that is swallowed
Term
involuntary component of mastication
Definition
involves reflexes initiated by presence of food
Term
voluntary component of mastication
Definition
can override involuntary component
Term
3 phases of deglutition/swallowing
Definition
1) oral phase
2) pharyngeal phase
3) esophageal phase
Term
oral phase (voluntary)
Definition
tongue pushes bolus to back of throat (oropharynx)
Term
pharyngeal phase (involuntary)
Definition
presence of bolus causes activation of swallowing center in medulla
Term
motor output from swallowing center during pharyngeal phase
Definition
1) causes soft palate to pull upward
2) causes epiglottis to cover the glottis
3) causes upper esophageal sphincter to relax
Term
in what phase is breathing inhibited during?
Definition
pharyngeal phase
Term
peristalsis
Definition
wavelike contractions of the digestive tract that propel contents
Term
circular layer of peristalsis
Definition
contracts behind and relaxes in front of contents
Term
longitudinal layer of peristalsis
Definition
relaxes behind and contracts in front of contents
Term
mixing
Definition
series of contractions and relaxations of circular layer that mix the contents
Term
esophageal motility
Definition
peristalsis propels bolus toward the stomach during the esophageal phase of swallowing
Term
duration of bolus through esophagus
Definition
approx 3 to 10 seconds
Term
esophageal peristalsis causes
Definition
relaxation of lower esophageal sphincter
Term
function of stomach motility
Definition
mixing (mixes bolus with gastric juice to form chyme)
Term
gastric emptying
Definition
peristalsis moves from fundus to body and down to antrum
Term
each peristaltic wave empties
Definition
approx 1% of stomach contents
Term
peristaltic waves per minutes
Definition
approx 3
Term
peristalsis during gastric emptying causes
Definition
opening of pyloric sphincter so contents empty into duodenum
Term
duration of gastric emptying
Definition
takes approx. 2 to 3 hours to empty
Term
contents that empty the fastest
Definition
carbohydrates
Term
contents that empty the slowest
Definition
lipids
Term
stimulation of gastric emptying
Definition
1) increased volume of contents in stomach
2) increased fluidity of chyme in stomach
3) parasympathetics
4) gastrin
Term
inhibition of gastric emptying
Definition
1) decreased fluidity of chyme in stomach
2) lipids in duodenum (strongest inhibitor)
3) chyme below pH 2.0 in duodenum
4) hypertonic/hypotonic contents in duodenum
5) sympathetics
Term
small intestine motility is via
Definition
segmentation (most prevalent movement of small intestine)
Term
duration of peristalsis of small intestine
Definition
3 to 5 hours for chyme to move through small intestine
Term
stimulation of small intestine motility
Definition
1) distension of duodenum
2) hypertonic/hypotonic chyme in duodenum
3) low pH of chyme in duodenum
4) protein digested contents in duodenum
5) parasympathetics
Term
large intestine motility
Definition
1) haustration
2) mass movement
3) elimination
Term
haustration
Definition
aids in the formation of feces
Term
feces contain
Definition
1) water, undigested material, mucus, flora (30% of dry weight)
2) bile pigments (urobilinogen from conjugated bilirubin)
Term
what makes feces brown
Definition
bile pigments
Term
mass movements involve
Definition
1) gastrocolic reflex
2) duodenocolic reflex
Term
gastrocolic reflex
Definition
initiation of mass movement by presence of food in stomach
Term
duodenocolic reflex
Definition
initiation of mass movement by presence of chyme in duodenum
Term
mass movement typically occurs
Definition
several times per day
Term
duration of mass movement
Definition
18 to 24 hours to pass through large intestine
Term
mass movement allows for incubation of
Definition
good flora
Term
purpose of flora in large intestine
Definition
1) feed off of nutrients left in chyme
2) produce vit K and B-complex vitamins
Term
elimination is via
Definition
defecation reflex
Term
defecation reflex is caused by
Definition
distension of rectum
Term
function of teeth
Definition
mechanically break down food
Term
function of tongue
Definition
mechanically break down food; moves food around to be chewed and presses food against hard palate
Term
function of salivary glands
Definition
produce saliva at a rate of 1 to 1.5 liters per day
Term
components of saliva
Definition
1) aqueous component
2) organic component
Term
organic component of saliva
Definition
1) salivary amylase
2) lingual lipase
3) mucus
4) antibacterials
Term
function of salivary amylase
Definition
1) begins chemical digestion of starch
2) inactivated by acidic environment of stomach
Term
function of lingual lipase
Definition
1) digests emulsified fats
2) minor role in lipid digestion in adults
Term
function of mucus (salivary)
Definition
1)lubricates mouth and esophagus
2) softens food to help form bolus
Term
antibacterials in saliva
Definition
1) IgA
2) lysozyme
Term
regulation of saliva production
Definition
1) parasympathetic
2) sympathetic
Term
function of parasympahetics in saliva production
Definition
stimulates aqueous and enzyme secretions
Term
function of sympathetics in saliva production
Definition
stimulates mucus secretion
Term
what stimulates the release of saliva?
Definition
1) sight/smell of food
2) presence of anything in mouth
3) nausea
Term
what inhibits the release of saliva?
Definition
dehydration and sleep
Term
stomach contains
Definition
1) pepsin
2) gastric lipase
3) intrinsic factor
4) mucus
5) gastric acid
Term
pepsin is released by
Definition
chief cells
Term
function of pepsin
Definition
digests protein
Term
gastric lipase is released by
Definition
chief cells
Term
gastric lipase digests
Definition
emulsified fats
Term
gastric lipase plays a minor role in
Definition
lipid digestion in adults
Term
intrinsic factor is released by
Definition
parietal cells
Term
intrinsic factor is necessary for
Definition
proper vit. B12 absorption
Term
stomach mucus (function)
Definition
protects stomach from gastric acid and enzymes
Term
gastric acid is released by
Definition
parietal cells
Term
functions of gastric acid
Definition
1) decreases pH in stomach to activate pepsin
2) breaks down connective tissue in meat
3) kills bacteria
Term
regulation of gastric acid secretion is by
Definition
1) parasympathetics
2) gastrin
3) histamine
4) somatostatin
5) secretin
Term
parasympathetics (gastric acid secretion)
Definition
1) stimulates release of gastric acid
2) stimulates gastrin and histamine
Term
gastrin (gastric acid secretion)
Definition
stimulates release of gastric acid
Term
histamine (gastric acid secretion)
Definition
1) stimulates release of gastric acid
2) blocked by H2 antgaonists
Term
somatostatin (gastric acid secretion)
Definition
inhibits release of gastric acid
Term
secretin (gastric acid secretion)
Definition
inhibits gastrin
Term
3 phases of gastric acid secretion
Definition
1) cephalic phase
2) gastric phase
3) intestinal phase
Term
cephalic phase accounts for
Definition
30% of gastric acid secretion
Term
gastric phase accounts for
Definition
60% of gastric acid secretion
Term
early phase of the intestinal phase accounts for
Definition
10% of gastric acid secretion
Term
most digestion occurs in
Definition
small intestine
Term
lysosomal enzymes (small intestine) are released by
Definition
intestinal glands
Term
intestinal glands
Definition
glands that extend down between villi into the mucosa
Term
function of lysosomal enzymes
Definition
help maintain fluidity of chyme
Term
mucus of small intestine
Definition
protects lining from acidic chyme and digestive enzymes
Term
enzymes produced by small intestine
Definition
1) disaccharidases
2) peptidases
Term
disaccharidases (function)
Definition
final digestion of carbohydrates
Term
disaccharidases
Definition
1) maltase
2) sucrase
3) lactase
Term
maltase
Definition
digests maltose into glucose + glucose
Term
sucrase
Definition
digests sucrose into glucose + fructose
Term
lactase
Definition
digests lactose into glucose + galactose
Term
peptidases (function)
Definition
digestion of protein
Term
disaccharidases and peptidases are both
Definition
surface bound to microvilli
Term
peptidases
Definition
1) peptidase
2) aminopeptidase
Term
bile is comprised of
Definition
water, cholesterol, lipids, conjugated bilirubin, protein, electrolytes, bile acids
Term
what organ produces bile
Definition
liver
Term
bile acids + certain amino acids
Definition
bile salts
Term
functions of bile
Definition
1) neutralize acidic chyme via HCO3
2) emulsify lipids via bile salts
Term
liver produces approx. ________ of bile per day
Definition
600 to 1000 mL per day
Term
organic component of pancreatic digestive secretions
Definition
1) pancreatic amylase
2) pancreatic lipase
3) proteases and peptidases
Term
pancreatic amylase
Definition
contingues digestion of starch into dissacharides
Term
pancreatic lipase
Definition
digests triglycerides into fatty acids and monoglycerides
Term
proteases and peptidases
Definition
digest protein into polypeptides, tripeptides, dipeptides, and amino acids
Term
proteases and peptidases
Definition
1) trypsin
2) chymotrypsin
3) carboxypeptidase
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