GI physiology Flashcards
GI tract Layers (4)
relatively uniform throughout
- mucosa
- submucosa (blood, nerves, connective tissue)
- Muscularis (longitudinal, circular)
- serosa
oblique muscles in
stomach only–responsible for enhanced churning
nerves in SUBMUCOSA. func.
meissner’s plexus:
–senses environment w/in lumen–regulating BLOOD FLOW, directiong epithelial cell function
neves in muscle layers: func.
Myenteric (Auerback Plexus)
–digestive tract motility
nerves embedded in walls of GI tract
PNS–enteric enervation–
most common nT of:
symp:
parasymp:
- norepi & some ACh (mainly inhibitory of motility and veins))
- ACh (excitatory)
Myenteric responsible for:
both function under PNS control and independently
GI movement:
- ^ tonicity, intensity, rate, velocity of conduction
- v schincter tone
Meissner (submucosal) responsible for
GI secretion and local blood flow
1. –> unfolding of walls
Electrical System of GI:
Smooth muscle is ______ unit–when AP received, ______ travels in all direction.
single,
contraction
resting membrane potential exhibits ______ ______ ______. Do not cause contractions.
rhythmic slow waves–in response to food in instestines
Increasing positive charge of SLOW WAVES excite appearcance of ______ _______, exciting ______ ______
SPIKE POTENTIALS,
muscle contraction
AP caused by rapid ____ ______, only _____ so no contraction
Na+ entry,
sodium
much _____ enters leading to long duration of AP
Ca++ – much like heart
blood flow w/ nutrients from gut, spleen and panc travel to the ___ wia the ____ ____
SPLANCHNIC FLOW,
liver,
portal vein
____ do not go through the portal vein–instead travel through the ____ _____ bypassing liver
fats,
lymphatic system
reticuloendothelial cells of liver in ____ _____ remove ______
Liver sinusoids,
bacteria
Salivary glands and products–
- Parotid (serous–ptyalin–amylase)
- sublingual (serous and mucus)
- submandibular (serous and mucus
Saliva constituents (9): Hypotonic 6-7 pH
stimulated by PNS and SNS
- water,
- mucus
- bicarbonate
- K+
- salivary amylase
- lingual lipase
- Cl-
- Na+
- IgA
lingual lipase pH– digests?
4.5-5.4
digest fats
stimulates gastic and salivary response
cephalic phase
- sour, smooth
- aggression
- insulin secretion
- irritation/ nausea
Inhibition of salivary response
- anxiety, fear, dehydration, rage
2. ROUGH testure
2 phases of swallow
- voluntary component
2. involuntary comp
swallow reflex and respiration inhibited by _____ ______ _______
medulla swallowing center (involuntary component)
pathophys of disruption to mucosal surface as from (3).
Apthous Ulcers (mouth/ oropharynx): -trauma, infection, or inflammation
Esophagus from–how long
C6-T10/11
25 cm
______ _______ _______must relax from ______ ____ ____ innervation for food to pass into esophagus
upper esophageal sphincter,
medulla swallowing center
____ _____ rises to close off nasopharynx
soft palate
GI muscle contraction takes ____ and ____ activity
Na+ and Ca++
esophageal mucosa layers (3)
- epithelium w/ mucus secreting cells
- lamina propria
- muscularis mucosa
UES
LES
Characteristics
Upper esophageal sphincter (both functional not anatomic)
Lower esophageal sphincter
–normally HIGHER tonicity so air won’t descend and acid won’t ascend
esophageal submucosa components: (5)
“out from mucosa”
- loose connective tissue
- blood vessels
- lymphatic and lymphoid follicels
- MEISSNER plexus
- mucus secreting glands
esophageal muscularis propria characteristic:
- Inner: circular layer for ring contractions
- AUERBACH plexus
- outer layer logitudinal–shortening contractions
- muscularis propria muscle
a. top 1/3 skeletal muscle
b. middle 1/3 smooth/skeletal
c. bottom 1/3 smooth
- muscularis propria muscle
Stimulation of esophagus (3)
- meissner plexus
- auerbach plexus
- vagus nerve (along adventitia)
LES tone relaxes w/ (3)
- non-adrenergic, non-cholinergic vagal impulses
- progesterone and glucagon
coordinated contractions to propel bolus down esophagus–gravity assisted
PRIMARY peristalsis–from mouth –> anus
If bolus gets stuck, stretch receptora signal swallowing center for
secondary waves of peristalsis until clear
Pathophys of esophagus–greater stretch leads to ^ ________
Esophageal spasm,
contraction
narrowing of esophagus from scar tissue
Esophageal stricture–as from GERD (irritation)
LES fails to relax–food backs up
Achalasia
Thick bands of muscle form in lower esophagus
Esophageal rings–as from GERD (irritation)
space btwn peritoneal membranes
peritoneal cavity
Stomach functions: (4)
- stores food
- digestive juices secreted
- mixes food via peristalsis
- proples chyme into duodenum
proximal boundary of stomach:
distal boundary of stomach:
- LES
- pyloric sphincter
serous membrane with visceral and parietal surfaces
peritoneum
inner surface of stomach–increase volume w/out increasing pressure–^area utilized for digestion
rugae
oxyntic glands in ______ and _______
fundus and body
parietal cells secrete (2) (in OXYNTIC glands)
HCl, intrinsic factor (imp for Vit B12 absorption)
Chief cells secrete (in OXYNTIC glands)
(aka peptic cells),
pepsinogen (HCl splits into pepsin)
Enterochromiffin cells secrete
ECL cells,
histamines (encourages acid secretion)
Goblet (aka) secrete (in OXYNTIC and PYLORIC glands)
(mucous neck cells),
mucus
G cells secrete–stimulates? (in Pyloric glands)
gastrin (stimulates gastric acid secretion)
churning of stomach imp for (2)
- breakdown of macromolecules
2. introduce molecules to mucosa throughout stomach
point at which esophagus enters stomach
cardia (just area no function)
lateral boundaries of stomach
greater and lesser curbatures
D cells secrete–function? (in Pyloric glands and OXYNTIC)
somatostatin–inhibits HCl secretion
abundance of very ALKALINE viscid mucus for stomach protection secreted by
surface mucous cells
somatostatin _________ ECF, Parietal, and G cells
inhibits
pyloric glands in
antrum
Histamine binds to ____ _______ on ______ ______ –>
H2 receptors (as in H2 channel blocker)
parietal cells,
^ HCl production
stimulation of gastric phase of digestion (4)
- ^est in afternoon/evening vest in morning
- ^w/ aggression
- cephalic phase stimulates before food arrives
- ParaNS
Inhibition of gastric phase of digestion (2)
- SNS (inhibs GI secretns, sphincter and vessel contractions)
- bad tastes, rage, fear, pain
PNS’ role in gastric phase
- stimulates release of HCl, hist, intrinsic factor, mucus)
- contractions of GI tract
- relaxation of sphincters
Swallowing causes ____ to relax
fundus (distends and pH lowers)
_____ _____ inactive in mouth–needs low ____ to break down ____
lingual lipase,
pH,
fats
pace of stomach peristalsis mediated by ____ of _____
cells of cajal (pacemakers for slow waves)
protein digestion (in stomach) products ____ the acid
buffer–increasing the pH