GI III Flashcards
Describe the epithelium of small intestines
mainly absorptive columnar cells with well-developed brush borders
What type of lymphocytes are located in the mucosa of the small intestines?
intraepithelial lymphocytes (T cells)
Loose connective tissue that extends into the villi
Lamina propria of the small intestines
What are lacteals?
well endowed with blood and lymphatic vessels (within the lamina propria)
Where are goblet cells found in the small intestines?
their numbers increase as the ileum is approached
What is another name of intestinal glands found in lamina propria of the small intestines?
crypts of Lieberkuhn
What type of epithelium does crypts of Lieberkuhn have?
simple columnar
What are the three different cell types of the intestinal glands?
1) paneth cells
2) enteroendocrine cells
3) stem cells
What’s the function of paneth cells?
secrete lysozyme, defensins, and tumor necrosis factor alpha
Paneth cells extend into which structure?
right colon
Where are the stem cell niche located?
at the base of the gland (different than the stomach)
Where does enteroendocrine cells secrete their products, toward the lumen or tissues?
Toward the tissues NOT the lumen
Which segment is the shortest of small intestines?
duodenum
Which layer are the glands located in the duodenum?
submucosa
Which gland is a signature feature of the duodenum?
Brunner’s glands
What’s the function of Brunner’s glands?
secrete mucus and human epidermal growth factor
Which part of the duodenum are Brunner’s glands most developed?
proximal
Which has a thicker wall, jejunum or ileum?
jejunum
Which is more richly vascularized, jejunum or ileum?
jejunum (redder than ileun)
Which part of the small intestines are Peyer’s patches located?
ileum
Which part of the small intestines will you find M cells?
Peyer’s patches of the ileum and lymphoid tissues of gut as well
Instead of plicae circulares, what does the large intestines have?
plicae semilunares - permanent folds of mucosa and submucosa
Does the large intestines have villi?
NO
Does the large intestines have brush border?
Yes, but it’s poorly developed
True or False. Goblet cells are more numerous in the small intestine than the large intestine
False, it’s the other way around
Does the crypt density increase or decrease in large intestine? What about goblet cell density?
Both increase
Why is paucity of lymphatic channels significant?
an intramucosal carcinoma has little or no potential to metastasize
In which direction does the lymphatics of large intestine extend, radially or longitudinally?
radially
Which smooth muscle layer does not completely surround the large intestine?
outer longitudinal
What is teniae coli?
three longitudinal bands of smooth muscle found in the muscularis externa
Appendix - mucosa resembles ____ while submucosa resembles ____
mucosa - large intestine
submucosa - small intestine
The appendix has lack of which two structures?
teniae coli and villi
What are two mechanisms of appendicitis?
1) fecalith and intraluminal pressure
2) infection and mucosal ulceration
What’s the name of the three permanent folds found in the rectum?
transverse rectal folds or valves of Houston
Valve of Houston is a permanent fold of which layers?
1) mucosa
2) submucosa
3) portions of muscularis externa
What are anal columns?
longitudinal folds of submucosa and mucosa
What is the significance of the pectinate line?
lymphatics drain differently above an below this line due to derivation.
Superior to pectinate line, which layer contains plexus of veins?
submucosa
Inferior to pectinate line, which layer contains plexus of veins?
lamina propria
What are the three anal cushions?
1) left lateral (3 o’clock)
2) right anterior (7 o’clock)
3) right posterior (11 o’clock)
What are anal cushions composed of?
connective tissue, smooth muscle, and blood vessels
What’s the function of anal cushions?
anal continence
Where are anal valves located?
between distal adjacent anal columns
Where are anal sinuses located?
lateral to the valves
What type epithelium will you find below the pectinate line?
Stratified squamous
What divides non-keratinized epithelium versus keratinized epithelium in the anal canal?
intersphinctic groove
Will you feel pain if you had hemorrhoids above the dentate (pectinate) line?
no
Will you feel pain if you had hemorrhoids below the dentate (pectinate) line?
yes
What are anorectal abscess?
gland secretions and/or fecal matter can plug up anal sinuses, causing inflammation and infection. pus then accumulates
What is fistula in ano?
anorectal abscesses that develop into tubes that penetrate skin of the perineum, connecting the anal canal with it
What is colonic diverticula?
outpouching of the diverticula (large intestine), sites of weakness between tenia coli
Why is it called false diverticula?
because it involves mucosa and submucosa
What layers are affected in true diverticula?
all wall layers
What are polyps?
hyperproliferative cells that start to pile up on luminal surface
Which is more likely to be invasive, tubular adenoma or villous adenoma?
villous adenoma is more likely to be invasive
Does the lamina propria of the large intestine have well endowed lymphatic vessels?
No
In the presence of inflammatory bowel disease, is lamina propria better or poorly developed?
better developed
Which inflammatory bowel disease is typically confined to large intestine?
ulcerative colitis
Which inflammatory bowel disease can be found anywhere along the GI tract?
Crohn’s disease
Which inflammatory bowel disease is more likely to cause fissures or fistulas?
Crohn’s disease
What occurs in Hirschsprung’s disease?
neural crest cells do not make proper migration to the involved segment of colon
Hirschsprung’s disease always involves…
rectum and may also more proximal segments
What is aganlionosis?
both myenteric and submucosal plexuses are absent
