B8 L7 Flashcards
Innermost Mucosal Layer
consists of epithelium, lamina propria, muscularis mucosae
Epithelium
digests and absorbs food
secrete regulatory substances
Lamina Propria
beneath epithelium
CT
glands, nerve endings, capillaries, lymph vessels
Muscularis Mucosae
smooth muscle
increases epithelial surface area by folding mucosal layer
Muscularis Externus
smooth muscle
in contact with myenteric plexus
Myenteric Plexus
integration and coordination center of nervous system
Serosa
mesentery
holds GI tract in place with connections to abdominal wall
4 Layers of GI
Mucosa
Submucosa
2 Muscular Layer
Serosa
Gastrin
from Gastric Antrum
causes stim of parietal cells to secrete H+ and ECL cells to secrete histamine
CCK
from duodenum
inhibits gastric emptying and H+ secretion
stim pancreatic enzyme secretion, gallbladder contraction, inhibit food intake
Secretin
from duodenum
stim pancreatic duct secretion
GIP
from intestine K cells
stim insulin secretion
Extrinsic Center
ANS innervation
Extrinsic PNS Division
increases GI function
Extrinsic SNS Division
reduces GI function
Extrinsic Afferents
back to CNS
info on meal contents and wall stretch
reflex arcs on vagus- vagovagal reflexes
Intrinsic Center
input from sensory cells in gut
integrate and send info to mm and enteroendocrine cells
modulated by ANS
Intrinsic w/o ANS
gut can function w/o
release NE/ Ach and GI hormones
GI Reflex Arc W/in Gut
control secretions, motility
GI Reflex Arc to Prevertebral Ganglia
info sent from one area of gut to another
GI Reflex Arc to Brain
pain, motor function, defecation reflex
Slow Waves
generated by pacemaker cells in gut wall
carried via gap junctions to rest of smooth muscle
Spike Potentials
when slow waves initiate APs
higher slow wave = more spikes
threshold = -40 mV
through slow calcium channels
Peristalsis
contraction moves food through intestines
relaxation before food mvmt
requires myenteric plexus
Segmentation
splits up food in intestines
no forward mvmt
Local Control of Blood Flow
dependent upon metabolic demand (02) of tissue- increases after a meal
Hormonal Control of Blood Flow
CCK, VIP, and other paracrine substances released by gut to increase flow
Neural Control of Blood Flow
SNS reduces flow
PNS increases flow
Cephalic Response to Meal
prepares tract for food
initiated by smell, sight, thought of food
Oral Response to Meal
same as cephalic
food in mouth increases response
Esophageal Response to Meal
propelling food from mouth to stomach
Gastric Response to Meal
storage, mixing, protein digestion
Duodenal Response to Meal
SI
digestion and absorption
Intestinal Response to Meal
LI or Colonic digestion and absorption reabsorb water gut flora produce vitamins storage and excretion
Cephalic and Oral Phase Stim to GI
increases salivary secretions
gastric acid secretions
exocrine pancreas secretion
release of bile from gallbladder
Saliva
begins digestion
from filtered plasma
Saliva Composition
hypotonic and alkaline- decrease with higher flow rates
high K+ and HCO3- lvls
Amylase
in saliva
breaks down carbs
Lipase
in saliva
digest lipids
Mucin
in saliva
lubrication
Lysozyme
in saliva
antibacterial- cleans teeth
Acinar Secretion
SNS (B1 and B2)- increases a little
PNS (M3)- increases a lot
Saliva and Blood Flow
SNS (a1)- reduce flow- less made
PNS (M3)- increase flow- more made
Ends oral phase and begins esophageal phase
swallowing
Upper Sphincter of Esophagus
striated mm; protects trachea from swallowed food and gastric reflux
opens due to swallowing reflex
Lower Sphincter of Esophagus
smooth mm; protects esophagus from gastric reflux
Stomach Chemical Secretion
acid, mucus, water, HCO3-, pepsinogen, intrinsic factor
Cardia
behind Lower Esophageal Sphincter
makes mucous
Parietal
proximal stomach
oxyntic glands containing parietal and chief cells
Pyloric
distal stomach
pyloric glands w/ G cells and mucous cells
Chief Cells
secrete pepsinogen
Parietal Cells
secrete acid
pH of 0.8
G Cells
secrete gastrin
Mucous Cells
secrete mucous
Carbonic Anhydrase
makes H+ and HCO3-
H+ = pumped into stomach
HCO3- = exchanged for Cl- w/ blood
Stomach’s Mucous Coat is….
alkaline- lots of HCO3-
Pepsinogen
activated by low pH, converted to pepsin
starts protein digestion
Ach increases releases
Intrinsic Factor
secreted by parietal cells
needed for B12 absorption
ECL Cells
release histamine onto parietal cells
increases acid production
activated by gastrin
Gastrin is released in response to _____ in meal
protein
Somatostatin
from D cells
inhibit gastrin release
Stomach Receptive Relaxation
vasovagal reflex where stretch of wall causes relaxation and more stretch
mainly upper parts
Every 5 mixing waves make…
peristaltic wave
moves chyme through pyloric sphincter
Increasing Gastric Emptying
PNS
stretch
gastrin
faster SI digestion time
CCK released in response to…
fats in chyme
inhibit emptying
Secretin released in response to…..
acidic chyme
inhibit emptying
Gastric Inhibitory Peptide (GIP) released in response to….
fat and carbs in chyme
inhibit emptying
Peptic Ulcer Disease
damage to lining of GI tract
Pernicious Anemia
Loss of intrinsic factor
no B12 absorption
no new RBCs
Duodenum
most digestion
Jejunum
most absorption
Ileum
absorbs bile, B12, leftovers
Intestinal Phase
increased pancreatic secretions
increased gallbladder contraction
Acinar Cells
secrete amylase and lipase in response to PNS and CCK
S Cells
sense pH and release secretin which increases HCO3- secretion
CCK
increases enzyme secretion
Secretin
increase HCO3-
Bile
aids to digest and absorb lipids via micelles
Brunner’s Glands
in Si
secrete mucus that protects wall from acid
reduced by SNS
Amylase
breaks down starch to maltose
SGLT1 Transporter
co transport glucose and galactose with sodium into cell
GLUT2
glucose and galactose transport into blood
GLUT5
Transports fructose into blood
Activates Pepsinogen
low pH
Fat Soluble Vitamins
A, D, E, K
Large Intestine
reabsorbs water and bacteria- made products
Haustration
mixing w/ forward movement in LI
