EXAM 3 - Respiratory System, Digestive System, and Metabolism Flashcards
mucosal epithelium
most variable feature in GI
enterocytes, endocrine, exocrine
cell/cell junctions
GI stem cells
lamina propria
connective tissue contains nerve fibers, vessels, and lymph nodes
wandering immune cells, Peyer’s patch
muscularis mucosae
thin layer of smooth muscle
shape intestinal folds, move the villi
mucosa
important in secretion, digestion, and absorption
digestive enzymes
secreted by exocrine glands or epithelial cells
may remain bound to apical membranes of intestinal cells
exocrine galnds
salivary glands, pancreas
epithelial cell secretion
in stomach and small intestine
brush border enzymes
digestive enzymes that remain bound to apical membranes of intestinal cells
zymogens
need to be activated into enzyme
mucus
secreted by exocrine cells
exocrine cell
mucous cells, salivary glands, goblet cells
function of mcuus
protect GI mucosa; lubrication
mucus stimulation
parasympathetic
neuropeptides
cytokines
submucosa
loose connective tissue containing larger blood and lymph vessels
transport absorbed nutrient
submucosal plexus
meissner’s plexus
nerve supply to muscularis mucosae
muscularis externa
two layers of smooth muscle
Inner: circular
outer: longitudinal
myenteric plexus
auerbach’s plexus
in muscularis externa
between 2 muscle layers
GI smooth muscle spontaneous contraction
peristalsis
segmentation
peristalsis
move food along
segmentation
mix food and break it down
contraction frequency of GI smooth muscle is set by
Basic Electrical Rhythm (BER) and chemical input
basic electrical rhythm
slow waves (3-20s) set by pacemaker cells (interstitial cells of Cajal)
interstitial cells of cajal
modified smooth muscle cells between muscle and nerve plexus that set BER
phasic contractions
posterior portion of the stomach; small intestine
tonic contractions
sphincters; anterior portion of the stomach
after a meal
peristalsis and segmentation
peristalsis after a meal
contraction AND distal relaxation
esophagus
stomach
intestinal
segmentation after a meal
contractile rings
small and large intestine
between meals
migrating motor complex for housekeeping
enteric nervous system (ENS)
acts independently, shares many features of CNS
primarily on motility and secretion
features of ENS
intrinsic neurons
responds to many NTs and GI peptides
glial cells
diffusion barrier
integrating center
motility excitatory NTs and GI peptides
ach (gi) substance P (gq)
motility inhibitory NTs and GI peptides
NO
vasoactive intestinal polypeptide (VIP)
secretomotor ENS
Ach, VIP
GI peptides
secreted by isolated endocrine cells in mucosa
not limited to GI functions
long reflex
can originate anywhere
integrated in the CNS
cephalic reflex
short reflex
originate in ENS, integrated in ENS
gastric emptying
the cephalic phase of digestion
long reflexes initiated in the brain
function and secretion of saliva swallowing reflex
functions of saliva
softens and lubricates food
chemical digestion
taste
protection
saliva: chemical digestion
salivary amylase and some lipase
saliva: protection
lysozyme, immunoglobulins, fluoride, HCO3-
saliva: glands
parotid glands
sublingual glands
submandibular glands
parotid glands
watery solution
sublingual glands
mucus solution
submandibular glands
mixed secretion
salivary secretion
2 steps:
acinar cells
ductal cells
acinar cells
resembles extracellular fluid
ductal cells
absorb Na+ and Cl-
secrete K+ and HCO3-
net removal of solute
impermeable to water
stimulation of salivary secretion
ductal modification reduces
HCO3- remains high by action of secretagogues
swallowing reflex
primary peristalsis and secondary repetitive peristalsis
gastroesophageal junction
resting pressure: 30mmHg
substances that reduce pressure of gastroesophageal junction
alcohol
caffeine
cigarette smoke
chocolate
pathological conditions of gastroesophageal junction
Gastroesophageal reflux disease (GERD)
achalasia
achalasia
nerve cells (myenteric plexus) that innervate esophageal muscle degenerate
symptoms of achalasia
solid dysphagia
fullness in chest while eating
chest pain
weight loss
gastric phase
series of short reflexes initiated when food enters the stomach
topics in gastric phase
secretion of the stomach
motility of the stomach
proximal anatomy of stomach
anterior
cardia
fundus
body
distal anatomy of stomach
posterior
antrum (pyloric region)
pyloric sphincter
functional regions of the stomach
proximal (reservoir)
distal (pump, grinder)
structures to support stomach functions
rugae
oblique layer overlying mucosa
LES (esophagus) and cardia secretion
mucus
HCO3-
LES (esophagus) and cardia motility
prevention of reflux
entry of food
regulation of belching
fundus and body secretion
H+ intrinsic factor mucus HCO3- pepsinogens lipase
fundus and body motility
reservoir
tonic force during emptying
antrum and pylorus secretion
mucus
HCO3-
antrum and pylorus motility
mixing
grinding
sieving
regulation of emptying
gastric secretions
gastrin
acid
enzyme
paracrine
gastric secretion: gastrin secretion
G cells
gastric secretion: gastrin is triggered by
vagus nerve stimulation (Gastrin-Releasing Polypeptide, GRP)
amino acids
gastrin increases with food intake because acid denatures proteins
gastric secretion: gastrin is inhibited by
acid, somatostatin
gastric secretion: gastrin function
acts on parietal and ECL (arterial) cells (CCK-B receptor)
stimulates acid release
stimulates mucosa growth in stomach, small and large intestine
gastric secretion: acid is secreted by
parietal cells in gastric glands
gastric secretion: acid is stimulated by
gastrin, Ach, histamine
gastric secretion: acid is inhibited by
prostaglandin E2 and somatostatin
what inhibits the gastrin feedback loop?
acid and somatostatin
somatostatin
B cells secrete this; local (paracrine)
arterial cells
secrete histamine
histamine
stimulator for acid secretion
alkaline tide
after eating, HCO3- enters blood
parietal cell activation
tubulovesicular membrane and intravesicular caniculus fuse with cell membrane and eachother
H+/ATP pump is rate limiting factor
What mechanism will inhibit HCl secretion?
A. M3 receptor agonist
B. H2 receptor agonist
C. Activation of Gi-coupled receptor
D. Activation of Gq-coupled receptor
Activation of Gi-coupled receptor
gastric secretion: enzyme secretion
pepsin and gastric lipase
pepsin is effective on
collagen
gastric secretion: enzyme secretion process
chief cells secrete pepsinogen
HCl in stomach activates to pepsin
gastric lipase is co secreted with pepsin
in small intestine pepsinogen is neutralized with bicarbonate and inactivates pepsin
gastric secretion: paracrine secretion
histamine
intrinsic factor
somatostatin
paracrine secretion: histamine
secreted by ECL cells and stimulated by gastrin and Ach
paracrine secretion: intrinsic factor
secreted by parietal cells; critical for B12 absorption
paracrine secretion: somatostatin
secreted by D cells; primary feedback signal
Which of the following treatments will alleviate the symptoms of peptic ulcer disease?
A. H+/K+/ATPase activator
B. H2 receptor agonist
C. M3 receptor agonist
D. Somatostatin release
D. somatostatin release
All the rest would cause increase of acid
A drug that blocks the fusion of tubulovesicular membrane and intracellular canaliculus in parietal cells would result in…
A. an increased production of HCl
B. an increased production of pepsinogen by chief cells
C. an increased protein digestion in the stomach
D. a decreased somatostatin production
E. an increased catalytic activity of pepsin
D. a decreased somatostatin production
control of gastric secretion
vagal activation stimulates multiple cell responses via NT (Ach and GRP)
what stimulates the parietal cell?
Ach, gastrin, histamine
what inhibits gastrin?
acid in the antrum stimulates somatostatin release to inhibit meal-stimulated gastrin secretion
motor functions of the stomach: storage
proximal portion (fundus and body)
receptive relaxation
adaptive relaxation
receptive relaxation in the stomach
relaxation of stomach muscles as food moves through esophagus and enters stomach
adaptive relaxation of stomach
relaxation of stomach muscles when filled
motor functions of the stomach: mixing
distal portion (antrum) peristalsis
control of gastric motility in the gastric phase
neural control (vagovagal reflexes) mechanical stimulation chemical stimulation
absorption by the stoamch
aspirin, other weak acids; EtOH
stomach wall is not specialized for absorption
protection of the stomach wall
thick, alkaline mucus
tight junctions between epithelial cells
rapid replacement by GI stem cells
gastric ulcers
destruction of the lining of gastric mucosa
results of Warren & Marshall’s study
when treated with antibiotics, 80% of patients were permanently cured of their ulcers
primary causes of ulcers
infections (H. pylori)
NSAID
NSAID
inhibits mucus production, causes ulcers
Zollinger-ellison syndrome
ulcers caused by over secretion of gastric acid
rare
intestinal phase
series of responses after chyme enters the small intestine
intestinal phase topics
gastric emptying
motility and secretion of small intestine
secretion of accessary organs
digestion and absorption of fat, carbohydrates, and proteins
gross anatomy of small intestine
duodenum (common bile duct + pancreatic duct) to jejunum to ileum
ileum
peyer’s patches or lymph nodules
ileocecal valve
structures to support small intestine functions
plicae (circular folds)
villi
microvilli
gastric emptying
strong peristaltic waves in gastric pump
increased tone in gastric reservoir
opening of pylorus
inhibition of duodenal segmental contractions
increase gastric emptying
hormonal: gastrin
gastric volume
neural
decrease gastric emptying
distension plus acid in duodenum (enterogastric reflex)
hormonal: GIP, CCK, secretin
The gastric emptying rate can be increased by
increased peristaltic wave in gastric pump
increased tonic contraction in gastric reservoir
increased action of VIP in the pyloric sphincter
dumping syndrome
gastrectomy may lead to loss of feedback control of emptying
partly digested food draws excess fluid into intestine
may have malabsorption
intestinal secretion
cholecystokinin (CCK)
secretin
cholecystokinin is secreted by
I cells (mucosa of the upper small intestine)
cholecystokinin functions
stimulates pancreatic enzyme secretion (augment secretin functions)
contraction of gallbladder
relaxation of sphincter of Oddi
inhibit gastric emptying and gastric secretion
cholecystokinin is triggered by
amino acids, peptides, and fatty acids
cholecystokinin is inhibited when
products of digestion move on to the lower portion
secretion is secreted by
S cells (mucosa of the upper small intestine)
secretion functions
stimulate pancreatic bicarbonate secretion (augment CCK functions)
inhibit gastric emptying and gastric secretion
secretion is triggered by
acid, products of protein digestion
secretion is inhibited when
products of digestion move on to the lower portion
small intestine motility
segmentation
peristalsis
migrating motor complex (MMC)
segmentation in small intestine
mixing
slow propulsion possible due to frequency gradient
peristalsis in small intestine
weak
migrating motor complex (MMC) and MOTILIN
stimulating
migrating motor complex (MMC) and FEEDING
inhibits MMCs
digestion of carbohydrates
can only be absorbed as monosaccharides
amylase for smaller glucose chains and disaccharides
brush border enzymes
brush border enzymes
disaccharidases
absorption of carbohydrates: apical side
SGLT1
GLUT5
SGLT1
secondary active; glucose and galactose
high affinity for glucose; regulated by glucose in intestine
GLUT5
facilitated diffusion
fructose
absorption of carbohydrates: basolateral side
GLUT2 for all monosaccharides
digestion of protein
endopeptidases
exopeptidases
endopeptidases
proteases; attack peptide bonds
endopeptidase secretion
by stomach, intestine, and pancreas as inactive proenzymes
exopeptidases
release single amino acids
secreted by the pancreas
endopeptidase examples
pepsin, trypsin
exopeptidase examples
carboxypeptidase
absorption of a protein
absorbed as amino acids, dipeptides and tripeptides, and rarely larger peptides
absorption of a protein as amino acids
Na+ dependent active transport
absorption of a protein as dipeptides and tripeptides
H+ dependent; PepT1
absorption of a protein as larger peptides
transcytosis
may elicit allergic response
more in infant
digestion of fat
emulsification
enzymatic fat digestion
formation of bile micelles
digestion of fat: emulsification
bile salts
breaks down large lipid droplets to smaller ones
increase surface available for lipase action
digestion of fat: enzymatic fat digestion
lipase and colipase digest triglycerides into monoglycerides and fatty acids
phospholipase digests phospholipids
digestion of fat: formation of bile micelles
break down and reform constantly
break down to be absorbed
absorption of fat
enter apical membrane
inside the cells
leave basolateral membrane
absorption of fat: monoglycerides and fatty acids in apical membrane
diffusion
absorption of fat: cholesterol in apical membrane
transporter
absorption of fat: inside the cells
monoglycerides and fatty acids recombine
chylomicrons formation
absorption of fat: leave basolateral membrane
via exocytosis
transport of absorbed nutrients
products of carbohydrates and proteins are absorbed into the hepatic portal system
products of fat digestion (chylomicrons) enter lacteal
product of fat digestion
chylomicrons
hepatic portal system
blood leaving gut enters hepatic portal vein
brought directly to liver
second exchange site at liver sinusoids
most absorbed nutrients go to liver first (except products of fat digestion)
functions of liver
metabolic regulation
synthesis
storage
detoxification
functions of liver: metabolic regulation
maintain normal blood glucose levels
carbohydrate, lipid, amino acid metabolism
functions of liver: synthesis
plasma protein; clotting factors; bile; cholesterol
functions of liver: storage
iron, glycogen, blood, fat-soluble vitamins
functions of liver: detoxification
alcohol and other drugs
peritoneum
serous membranes within abdominal cavity
supports blood vessels, nerves, and lymphatic vessels
parietal peritoneum
inside surface of body wall
visceral peritoneum
surface of internal organs
peritoneal fluid
produced by serous membrane lining
provides lubrication
intraperitoneal organs
retroperitoneal organs
duodenum
common bile duct and pancreatic duct
ileum
peyer’s pathches or lymph nodules
ileocecal valve
structures in small intestine
plicae (circular folds)
villi
microvilli
mesentery
continuous, formed by peritoneum
mucus secretion is stimulated by
parasympathetic NS
neuropeptides
cytokines
digestive enzymes
secreted by exocrine glands and epithelial cells
remain bound to apical membranes or secreted as zymogens
exocrine glands
salivary and pancreas
epithelial cell secretions
stomach and pancreas
mucus
protects, lubricates
motilin
released during fasting, targets GI and stomach, MMC effector