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138 Cards in this Set

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4 tunics that characterize the general structure of the GI tract:
1. Mucosa
2. Submucosa
3. Muscularis externa
4. Adventitia
3 things that make up the mucosa:
-Epithelium
-lamina propria
-Muscularis mucosa
What type of epithelium forms the mucosal lining of the esophagus?
Nonkeratinized stratified squamous
What is the function of the nonkeratinized stratified squamous epithelial lining of the esophagus?
To protect against abrasions caused by food sliding down.
Which layer of the esophagus becomes more prominent as you get closer to the stomach?
Muscularis mucosa
What do submucosal glands in the esophagus do?
Produce mucous to help food slide down
What is the arrangment of the muscle layers in the muscularis externa?
Inner = longitudinal
Outer = circular
How does the muscularis externa change as you get closer to the stomach?
It gets thicker
Where are skeletal muscle fibers present in the esophagus?
In the upper and middle 1/3
How does the epithelium change as you transition from esophagus to stomach?
Esophag: stratified squamous

Stomach: simple COLUMNAR
What happens in Barrett's esophagus?
Acid refluxes causes the stratified squamous cells to transition to simple columnar.
How would you treat a patient with Barrett's esophagus?
With a proton pump inhibitor, laser ablation, or esophagectomy.
What is the concern with a Barrett's esophagus type of mucosa?
It is a precancerous lesion
What is Scleroderma?
A systemic disease of unknown cause that primarily affects women.
What happens to the GI tract in scleroderma?
The muscularis mucosa atrophies.
What symptoms might you expect in a patient whose systemic sclerosis has affected the alimentary tract?
Dysphagia, esophageal hypomotility, atony, and dilation. Acid reflux.
What are the 4 anatomical regions of the stomach?
-Cardia
-Fundus
-Body
-Pylorus
Which regions are histologically similar?
Cardia and Fundus
What is the characteristic feature of the mucosa in the cardia/fundus?
It is HIGHLY FOLDED to form GASTRIC PITS
What other characteristic feature is seen in the mucosa of the cardia/fundus?
Gastric GLANDS
Where are the openings of gastric glands?
At the bottoms of the gastric pits
What makes up tunic #1 of the stomach wall?
Mucosa - epithelium, lamina propria, and muscularis mucosa.
How many layers of muscle are in the muscularis externa? Why?
3 - because the stomach is a saccular organ
What are the 3 layers in the stomach's muscularis externa?
1. Inner oblique
2. Middle circular
3. Outer longitudinal
Is it easy to distinguish these layers?
No
What are special foldings of the mucosa + submucosa called? When are they present?
Rugae - only present when the stomach is empty.
Where in the stomach are these rugae seen?
Fundus
What is the shape of gastric glands in the CARDIA?
Coiled
What is the shape of gastric glands in the FUNDUS?
Straight
What is the shape of gastric glands in the PYLORUS?
Coiled
What type of epithelial cells are seen in the Fundus region? What are they called?
Still simple columnar, but called SURFACE LINING CELLS
What are the surface lining cells NOT in the stomach?
Goblet cells
What are the surface cells at the base of gastric pits called?
Neck mucous cells
What are the large round eosinophilic cells with central nuclei found within gastric glands called?
Parietal cells
What are the cells with a basophilic cytoplasm and basally located nuclei?
Chief cells
Where are chief cells distributed more within gastric glands?
Toward the base
What are the 5 total cells present in the CARDIAC gastric mucosa?
-Surface lining cells
-Neck mucous cells
-Stem cells
-Enteroendocrine cells
-Parietal cells
What cells are present in the FUNDUS region?
All that are in the cardiac region PLUS chief cells
What cells are present in the pyloric region?
All that are in the cardiac region
How can you distinguish a neck mucous cell?
It will be located in a gland at the base of a gastric cleft, and look like a goblet cell
How can you distinguish a Parietal cell?
It will be eosinophilic and have a round central nucleus
How can you distinguish a chief cell?
It will have basophilic cytoplasm and a basal-located nucleus.
How can you distinguish a neuroendocrine cell?
It looks like a purple splotch of nucleus surrounded by clear cytoplasm
How can you distinguish stem cells?
They will be mitotic
What is the product of surface lining cells and neck mucous cells? What is its function?
Mucous; it lubricates the epithelium and protects it from autodigestion
What is the product of Parietal cells?
HCL and IF
What is hte product of chief cells?
Pepsinogen
What is the product of enteroendocrine cells? Function?
Hormones for regulating digestion, peristalsis and bloodflow.
What is the function of Stem cells?
To replace other cell types except enteroendocrine cells.
What is the ratio of gastric pit length to gastric gland length in the Cardiac, Fundic, and Pyloric regions?
Cardiac: 1:1
Fundic: 1:3
Pyloric: 3:1
So the characteristic feature of the pyrloric region is that its gastric pits are ____ and its gastric glands are _____:
Pits = deep
Glands = short
What does the fundus have that the pylorus does not?
Chief cells - NOT in the pylorus.
What is the prominent feature of the pylorus?
Its inner circular muscle layer THICKENS to form the pyloric SPHINCTER.
What type of epithelium does the stomach have?
Simple columnar
What type of epithelium does the duodenum have?
Simple columnar
What do we call the epithelial cells in the stomach?
Surface lining cells
What do we call the epithelial cells in the duodenum?
Goblet cells and Absorptive cells!
Where the stomach is characterized by PITS, the small intestine is characterized by:
villi!
What is the ratio of length for gastric pits vs glands in the stomach near the pyloric sphincter?
3:1 - long pits, short glands
Distinguishing feature of the duodenum that makes it different from any other part of the SI, or the stomach:
Brunner's glands in the submucosa
4 ultrastructural features of enterocytes that contribute to their function:
-Microvilli
-Intercellular junctional complexes
-Numerous mitochondria
-Glycocalyx
What is the function of the secretory product of submucosal glands of brunner?
To neutralize acidic chyme!
Why does the small intestine have a large surface area?
To facilitate its functions of digestion and absorption.
What projects into the lumen of the small intestine?
Intestinal villi
What are intestinal villi composed of?
Finger-like projections of lamina propria and its overlying epithelium, with underlying muscularis mucosa too.
What type of epithelium covers a villus?
Simple columnar
What is the principle cell type within the epithelium of the villi?
Enterocytes
What is the function of enterocytes?
To absorb nutrients and produce digestive enzymes.
What specialization of the apical membrane is present on enterocytes?
Brush border formed by microvilli
What is the function of the brush border?
To increase the surface area for absorption
Does the submucosa extend into the core of a villus?
NO
Are goblet cells present within the mucosal epithelium?
YES
What do goblet cells produce? What is their secretion's function?
Mucin to lubricate and protect the epithelium.
What makes these cells readily apparent?
Carbohydrate, which stains brightly with PAS staining.
What are the spaces between villi called?
Intestinal Crypts of Lieberkuhn
Where is the muscularis mucosa with reference to the crypts?
It lies at their base.
What cells are found at the base of crypts?
Paneth cells
What allows you to distinguish Paneth cells?
They are eosinophilic and have secretory granules in their apical cytoplasm.
How do Paneth cells behave that is different from the other cells in the mucosa?
They don't migrate to the villus epithelium, but are long lived and stay at the crypt.
What do Paneth cells secrete?
-Defensins
-Lysozyme
What is the function of the Paneth cell secretions?
To protect the organism from bacteria and viruses.
list the 6 cell types prsent in the mucosa of the small intestine:
-Enterocytes
-Goblet cells
-Paneth cells
-Enteroendocrine cells
-Stem cells
-T cells
Where are enteroendocrine cells' secretory granules stored? Why?
At their BASAL side; Because they secrete into the bloodstream, whereas Paneth cells secrete into the lumen.
What do enteroendocrine cells secrete again?
Locally acting hormones that regulate GI motility and secretion.
If enteroendocrine cells have their granules at the basal side, where is their nucleus displaced?
Toward the apical side.
Where do T-cells cluster?
In the submucosa and lamina propria
How could you positively identify enteroendocrine cells in a section of gut?
By immunocytostaining.
Are stem cells found in crypts? How do you know?
Yes - because they are mitotic figures.
What do we call diffuse, unencapsulated lymphoid tissue in the GI tract mucosa?
GALT - Gut associated lymphatic tissue.
What very important structures lie at the center of a villus?
Lacteals and capillaries
Where are stem cells located?
In the crypts of lieberkuhn
What would you look for on an esophagogastroduodenoscopy (EGD) if a patient had acid reflux and was tired?
Polyps or ulcers that could cause internal bleeding.
What changes can be seen in a patient with Sprue?
Loss of villi and hyperplasia of the crypts - so it all looks solid instead of nice dips and peaks of villi/clefts.
What symptoms would you expect in an adult with Celiac disease (sprue)?
-Weight loss
-Diarrhea
-Lassitude
-Anemia
What will children with celiac disease complain of?
Chronic abdominal pain (but then don't they all?)
What will infants exhibit?
Failure to thrive
What treatment would you recommend for celiac disease?
Gluten free diet
What would you order to follow up for a patient diagnosed with sprue?
Follow-up biopsy
What should the followup biopsy show?
Normal villous architecture after some months of gluten-free diet.
How many layers of muscle are in the muscularis externa of the small intestine? What is their orientation?
Two:
-Inner circular
-Outer longitudinal
What are the functions of the muscularis externa in the small intestine?
Mixing and propulsion
What important structure is located between the muscle layers in the small intestine?
Auerbach's plexus
-Myenteric plexus
How can you identify the ganglia of the myenteric plexus?
-Clusters of large basophilic cells
-LARGE cell bodies
-Large nuclei
-Prominent nucleoli
What division of the ANS innervates the myenteric plexus?
The Parasympathetic division; CN 10 - innervates the fore/midgut
S2-S4 innervate the Hindgut
What is the additional tissue on the left of the slide of duodenum?
Pancreas
what are the large folds that have submucosa at their core and villi projecting from their surfaces in the jejunum?
PLICAE CIRCULARES
What lies deep to the plicae circulares within jejunum?
Muscularis externa
Do these plicae circulares obliterate when the jejunum is extended?
no
What is the function of plicae circulares?
To slow the passage of intestinal contents and increase the surface area for absorption.
What is located at the base of villi in the jejunum?
Still Crypts of Lieberkuhn
What cells are located at the base of the crypts in the jejunum?
Still Paneth cells
How do you know they're paneth cells?
Their apical cytoplasm is filled with red secretory granules.
What important structure is present within the submucosa of the jejunum slide?
Submucosal plexus (Meissner's)
How can you tell whether you're looking at the Myenteric or Submucosal nerve plexus?
By looking to see if it's surrounded by muscle or submucosa stuff.
What won't be in that submucosal stuff?
Brunner's glands - they're ONLY in the duodenum.
What is cresyl violet used to stain for?
Nissl substance - of neurological structures.
What is nissl substance?
Rough ER
What disease results when neural crest cells fail to migrate into the developing small intestine?
Hirschprung's disease
What would happen to regions affected by lack of nerve structures?
Reduced diameter and no peristalsis
What happens to downstream areas even if they do have neurological structures?
The flow through upstream "constricted" areas is blocked, so nothing gets to the downstream areas.
What is the general result of Hirschprung's disease?
Blockage of the colon - failure to pass meconium.
3 main features of the ileum:
-Presence of villi
-Abundance of GALT
-no brunner's glands
What are collections of HUUUUGE lymphoid aggregates called?
Peyer's patches
What selection is representative of the large intestine?
Cecum and appendix
Are there villi in the large intestine?
NO
What type of epithelium lines the large intestine?
Simple columnar
What are 2 nutrients absorbed by the enterocytes of the large intestine?
-Water
-Electrolytes
Are there crypts of lieberkuhn's in the large intestine?
I think so, yes
What cells are ABUNDANT in the simple columnar epithelium of the large intestine? Why?
Goblet cells - to secrete mucus to facilitate the passage of feces thru the large intestine.
What covers the outside of the large intestine?
The serosa (adventitia)
What is prominent within the large intestine submucosa and lamina propria?
GALT
What is the arrangement of the layers of the muscularis externa in the large intestine?
Outer = longitudinal
Inner = circular
Why does it look like the simple columnar epithelial cells of the appendix are underneath another layer?
Because there's JUNK in the lumen (crap)
What type of epithelium lines the anal canal?
Stratified squamous
What is present in the anal skin?
Sweat glands, sebaceous glands, and hair follicles.
What is the general term for varicose dilations of the rectal venous plexus?
Hemorrhoids
What causes hemorrhoids?
Portal obstruction
What is the rectum good for?
Delivering meds like Diazepam for seizures.