GI System Flashcards
what are the important factors of the GI in Dentistry?
- Oral cavity is gateway to the digestive tract
- GI disorders have far reaching
consequences for systemic heath - Many oral conditions linked to GI
disorders - Nutrition is a big part of what we do as
dentists - Many drugs we prescribe have
implications for the GI system
oral manifestations of GI dysfunction (3)
Crohn disease
ulcerative colitis
angular cheilitis
digestive system is essentially a ______ plant
processing plant
steps:
receives raw products
break them down
extract the parts that are needed
extrudes the rest
two general parts of digestive system
intake and processing
extraction and disposal
gut tube starts at the …
esophagus
how many layers in esophagus?
4 layers
mucosa, submucosa, muscularis, serosa/advenrtitia
gut tube layers and tissue
1) Mucosa:
Epithelium, Lamina
Propria, Muscularis Mucosa
2) Submucosa:
Dense irregular
connective tissue
3) Muscularis:
Mostly smooth
muscle
4) Serosa/Adventitia:
Connective tissue binding
everything together
identify the layers
identify the tissues associated with each layer
adventitia vs serosa
serosa: connective tissue which is covered with mesothelium
adventitia: connective tissue without the lining layer, usually attaches one organ to another
mesothelium
simple squamous epithelium
forming internal lining
retroperitoneal organs will have both adventitia and serosa and are where …
adventitia where organs are attached to one another, serosa everywhere else
label
label
salivary glands
lubrication
amylase
what happens in the oral cavity (GI System)?
chewing: breaks down food into managable pieces, starts forming food into bolus
saliva: softens and lubricates bolus
amylase begins breakdown of starches
swallowing: voluntary muscle introduce bolus into the oropharynx
peristalsis of pharynx
label
“gatekeeper” in GI system
epiglottis
three parts of the pharynx
nasopharynx
oropharynx
laryngopharynx
what are the two smooth muscle layers in digestive tract?
longitudinal (outer layer)
circular (inner layer)
peristalsis
adjacent segments of alimentary tract
organs alternately contract and relax, moving food
along the tract distally
segmentation
non adjacent segments of
alimentary tract organs alternatively contract and
relax, moving food forward, then backward. Food
mixing and slow food propulsion occurs.
pharynx is a “____ ___”
muscular tube
what is the part of the digestive tract that doesn’t have 4 layers?
pharynx
what sections are missing from the pharynx that is present in the rest of GI system?
no muscularis mucosa
no submucosa
what are the three histological layers of the pharynx?
muscosa (non-keratinized stratified squamous epith)
muscularis externa
adventitia
active swallowing causes the ___ ____ to press against the back of the nasoppharynx, sealing it off
soft palate
the ____ blocks off the oral cavity
the _____ moves down to block the trachea
tongue
epiglottis
trachealis muscle allows for _____ _____ of trachea
partial collapse
the upper _____ _____ opens allowing the food bolus to engage the upper esophagus
esophageal sphincter
4 histological layers of the esophagus
1-Mucosa (with stratified squamous epithelium)
2-Submucosa
3-Muscularis externa
4-Adventitia
esophageal muscle types:
Upper 1/3 is skeletal
Middle 1/3 is mixed smooth and skeletal
Lower 1/3 is all smooth involuntary
esophageal glands are found in the ____ and ____ ____
Found in the submucosa and lamina
propria
*Add secretions to aid passage down the
tube
the esophagus meets the stomach at the ____ ____ ____
lower esophageal sphincter
esophageal sphincter is composed of ____ (tissue)
smooth muscle
*muscularis externa
when the esophageal sphincter dilates, what happens?
allow things into the stomach, then contracts the keep stomach contents in the stomach
stomach contents, including acid, enter the esophagus causing
irritation/inflammation
GERD
gastro-esophageal reflux disease
acidic fluid plus bolus =
chime
at the esophageal/stomach junctions, the epithelium changes from stratified squamous to …
simple columnar
lipase is secreted to break down ____ in the stomach
lipids
pepsin is secreted to break down ____ in the stomach
proteins
amylase breaks down _____ in the stomach/oral cavity
carbohydrates
what are the four main parts of the stomach
1) Cardia – the pathway into the stomach
2) Fundus – upper curvature
3) Body – main, largest region of the stomach
4) Pyloris – where stomach joins small
intestine
parasympatheitic nervous system will make muscularis externa do what?
contract when food is present in the stomach
stomach regions and there characteristics
Cardia: pits are shorter than glands (connect with lamina propria)
Body/Fundus: relatively long
glands, but pits are more defined
than in cardia
Pyloris: longer pits and shorter
glands
gastric gland vs pit
stomach cells are their secretants
gastric glands contain ____ and ____ cells
parietal and chief cells
parietal vs chief cells
Parietal cells – produce and secrete gastric acid and intrinsic factor
- Chief cells – produce and secrete pepsin and lipase
pyloric glands are primarily _____ glands
mucous
where are G cells found?
pyloric glands
what do G cells secrete?
gastrin
Stem cells are found in the ____ of the gland (in isthmus between pits and glands)
Stem cells are found in the TOP of the gland (in isthmus between pits and glands)
what does the mucous in the stomach lining do?
protects the tissues from acids and enzymes
Surface mucous cells are more _______in shape and secrete
______
Surface mucous cells are more “columnar” in shape and secrete
“bicarbonate”
surface mucous cells secrete _____ and ____
bicarbonate and mucous
Mucous neck cells are more _____ in shape, have apical granules,
but fewer of them.
Mucous neck cells are more “round” in shape, have apical granules,
but fewer of them.
parietal cells secrete…
gastrin, acetylcholine, histamine, and gastric intrinsic factor (GIF)
gastric intrinsic factor for _____ absorption
B12
loss of gastric intrinsic factor leads to…
pernicious anemia (B12 not absorbed)
chief cells secrete…
pepsinogen (pepsin)
gastric lipase
where are chief cells found?
bottom of the gastric glands
G cells are part of the _____
DNES
diffuse neuroendocrine system
in the stomach, DNES cells secrete 4 main things:
1 - Gastrin and Histamine: triggers
HCl secretion by parietal cells
2 – Ghrelin: peptide hormone –
signals hunger to the brain
3 – Serotonin: neurotransmitter -
Produces psychotropic effects from
eating etc.
what cells are the messengers to the rest of
the body signaling what is in the stomach and
how much is there?
G cells
what controls parietal cell acid production
Gastrin Releasing Peptide (GRP)
three phases of the gastric secretion control
- cephalic phase
- gastric phase
- intestinal phase
what phase?
cephalic phase
what phase?
gastric phase
what phase?
intestinal phase
label
three segments of the small intestine
duodenum
jejunum
ileum
duodenum is the site of…
most chemical digestion
Bile from Gall Bladder – fat digestion
Bicarbonate and digestive enzymes from
Pancreas – fat, protein, carb digestion
Mucous produced by Brunner’s Glands
bile is ____ digestion
bile
bicarbonate and digestive enzymes from pancreas digest (3)
fat
protein
carbohydrates
jejunum absorbs the digested things from the…
duodenum
ileum absorbs ____-____ ____
bile-lipid micelles
and anything not absorbed in the jejunum
peyer’s patches?
ileum?
organs that contribute to digestion (4)
liver
bile duct
gallbladder
pancreas
liver, gallbladder, and bile duct produce ___ for ___ digestion
bile
fat digestion
pancreas makes ____ and ________ to digest (3)
bicarbonate and digestive enzymes
fat, protein, carbohydrate digestion
small intestine has an extremely large surface area due to ..(4)
length (22 ft)
plica circulares (circular folds - absorb area 3X)
villi (absorb area 10X)
microvilli (absorb area15-40X)
plica circulares
circular or semilunar folds in the lining of small intestine
plica circulares consist of … (2 layers)
mucosa
submucosa
plica circulares is most pronounced in…
jejunum
villi are …
dense covering of fingerlike projections
internal tissue of villi
lamina propria
with microvasculature, lacteals and lymphatics –
absorb fats
external tissue of villi
columnar epithelium
where are microvilli found?
apical ends of villi in the small intestine
microvilli increase absorption by
15-40 X
brush border is…
closely packed microvilli
____ glands secrete an alkaline fluid composed of mucin
Brunner
*in duodenum
what does the the alkaline fluid (mucin) do? (secreted by Brunner’s gland in the duodenum)
this exerts a physiologic anti-acid function by coating the duodenal epithelium, protecting it from the acid chyme of the stomach
Brunner’s Gland
circular folds in the jejunum force ____ to spiral through the lumen
chyme
*this slows it down for nutrient absorption
what feature of the jejunum help slow the speed at which chyme travels?
plica circulares (circular folds)
Ileum has ____ patches
Peyer’s Patches
what are Peyer’s patches?
in the ileum
Lymphoid tissue seen as thickened patches in the ileum (storage unit for immune cells)
Peyer’s patches in the Ileum
what do the Peyer’s patches store in the ileum?
immune cells
MALT stands for
Mucosal Associated Lymphatic Tissue
how doe Peyer’s patches recognize antigens in the lumen?
- M cells
- endocytosis of antigens (bring them to lymphocytes and dendritic cells)
- immune response (AB production)
- MALT (lymphoid tissue)
MALT is _____ tissue found in carious _____ ______ sites
lymphoid tissue
submucosal membrane
MALT contains what four cells
T cells, B cells, Plasma cells, and Macrophages
plus M cells
the epithelium of the small intestine is ….
simple columnar with microvilli projections
enterocytes are…
absorptive columnar cells in the mucosa of small intestine
goblet cells are…
mucous-producing cells in the mucosa of small intestine
enteroendocrine cells are…
local and systemic signals relating to digestion and transit
in mucosa of small intestine
paneth cells are…
antimicrobial molecule secreting cells that regulate immune response
in mucosa of small intestine
whare are four cells in the mucosa of small intestine?
enterocytes
goblet cells
enteroendocrine cells
paneth cells
5 steps of lipid absorption
5 steps (in words): lipid absorption
- Bile acids emulsify fats to micelles (liquid droplets)
- Gastric lipase digests lipids to produce glycerol, FA (fatty acid) and monoglycerides
- These are packaged as micelles and diffuse across the cell membrane entering the cell
- Resynthesized in SER to triglycerides (glycerol plus 3 fatty acids) then pass through the RER, Golgi - eventually packaged into chylomicrons (lipid and protein)
- Chylomicrons enter the lymphatic system and are
transported throughout the body
Because of Lipid entry into the lymph circulation, fats
end up in the tissues, bypassing the liver, unlike
_____ and _____
carbohydrates and proteins
enterocytes secrete
disaccharidase & amino
peptidases
disaccharides and dipeptides are digesting into
monosaccharides and amino acids
amino acids are absorbed via
active co-transport with sodium
carbohydrates are absorbed via __ with __ or __
active co-transport
with sodium (glucose, galactose)
or direct diffusion
(fructose)
Water absorption in small intestine
- Sodium comes in with co-transporters and is
pumped out of the lumen of the intestines - This creates a high sodium concentration in the
intercellular space - Water diffuses from the lumen into the intercellular
space and eventually into capillary blood
the vessels responsible for absorption are located in the…
lamina propria in the center of each villus
blood vessels for ____ and _____
lacteals for _____
blood vessels for proteins and carbohydrates
lacteals for lipids
diarrhea is caused by…
an imbalance in the physiologic
mechanisms of the GI tract,
resulting in impaired absorption
and excessive secretion
____ million children die yealry from diarrhea
1.6 mil
one of the main functions of the GI tract is to reabsorb ____
water
types of diarrhea
paneth cells are…
Paneth Cells are secretory epithelial cells located
at the ends of intestinal crypts
Crypts of Lieberkuhn
intestinal crypts
what cells are intestinal crypts
paneth cells
function of paneth cells in the intestinal crypts
secretion of antibacterial proteins into the crypt lumen, thereby providing protection for the stem cells which line the crypt walls
Enteroendocrine cells are
distributed throughout the small
intestine. They regulate digestion by responding to certain
chemical signals and environmental cues
They help the GI Tract keep track of what is where so it can
respond appropriately.
secretin…
stimulates HCO3 and H2O secretion by the pancreas
and bile ducts. It inhibits H+ production by the parietal cells in stomach.
CCK (cholecystokinin)…
stimulates pancreatic acinar cell secretion and smooth muscle contraction by the gall
bladder. Signals immediate satiety to the brain.
GIP (gastric inhibitory peptide, glucose dependent insulinotropic hormone)…
stimulates insulin secretion by beta cells in
pancreas
Peptide YY…
signals long term satiety to the brain
Muscularis mucosa (intestinal motility)
produce local movements of villi and plica
circulae in order to gently mix/expel
contents in the intestinal crypts.
submucosal plexus (intestinal motility)
submucosal plexus is a collection of
parasympathetic nerve fibers which
regulate contraction
muscularis externa (intestinal motility)
-Primary source of intestinal motility
-Same circular/longitudinal bands as
upper tract
-The myenteric plexus (Aeurbach’s
plexus) – collection of both sympathetic and
parasympathetic nerve fibers as well as
sensory nerves that regulate GI function
large intestine consists of
cecum
colon
rectum
anal canal
functions of the large intestine
1- absorb water, electrolytes, little nutrients
2- secrete bicarbonate and mucous
3- store indigestible material as feces
The large intestine is ___ meters long
1.5 meters
colon layers
in the colon, the mucosa lacks ____
villi
what penetrates the mucosa in the colon?
tubular intestinal glands
what cells are in the mucosa of the colon?
goblet cells
absorptive cells (colonocytes)
the colon has active fluid absorption that ______ the feces
dehydrates
tubular intestinal glands are ____ (epithelium_
simple columnar
The outer layer of colon has three extra longitudinal
bands called the
taeniae coli
In the colon, the taeniae can produce a
‘___ ____’ designed to empty whole
sections of the colon
mass movement
what is the transitional zone between mucosa of the GI tract and the external skin, which sort of wraps around and “tucks in.”
anal canal junction
what tissue is in the external anal sphincter?
skeletal muscle
when swallowing and it “goes down the wrong tube”, which of the following has occurred:
a. upper esophageal sphincter relaxed and let food enter trachea
b. lower esophageal sphincter relaxed and let food enter trachea
c. epiglottis action delayed or incomplete, allowing food to enter the trachea
d. esophageal glands are not working and the esophagus inadequately lubricated to receive food bolus
c. epiglottis action delayed or incomplete, allowing food to enter the trachea
the pharynx differ histologically from the rest of the GI tract by this feature:
a. has both circular and longitudinal muscle fibers in the muscularis ecterna
b. does not have muscularis mucosa or a submucosa
c. is covered by an adventitia layer not a serosa layer
d. contains Auerbach’s plexis of nerves in muscularis external to control motility
b. does not have muscularis mucosa or a submucosa
question #3-7 from mal
