Choudhury - Intestines, Rectum, and Anal Canal Flashcards by E McDonald

Where are enteroendocrine cells localized and what do they produce?

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Where are Paneth cells localized and what do they produce?

found in base of intestinal crypts
contain large acidophilic granules

  function is not well defined
  secrete enzyme lysozyme & peptide defensins
  degrade components of bacterial cell wall

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Where are goblet cells localized and what do they produce?

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What type of neuronal cell bodies (division and order) are in ganglia of the submucosal plexus?

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What type of neuronal cell bodies (division and order) are in ganglia of the myenteric plexus?

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Describe and relate the functional significance of plicae circulares

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Describe and relate the functional significance of villi

evaginations of mucosa, w/ core of lamina propria, project into lumen
distinguishing characteristic of small intestine

ABSORPTION as well

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Describe and relate the functional significance of microvilli

increase in surface area involves 3 magnitudes of “folding” for ABSORPTION

“Extreme” evagination and invaginations

Gastric glands in stomach

Crypts in intestine

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Structure & function of plicae ciculares

circular folds of entire mucosa , w/ core of submucosa

permanent projections into lumen

begin in proximal duodenum
maximized in distal duodenum & proximal jejunum
diminish until virtually absent in distal half of ileum

plicae consists of multiple villi

“Great big villi”

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Structure & function of plicae semilunares

LARGE INTESTINE

incomplete (half-moon) folds in intestinal wall

(do not form complete circular fold, as plicae in small intestine do)

produce characteristic sacculation (haustra)

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Structure & function of plicae transversales

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What is the importance of the lacteal in the intestinal villi?

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Are villi found in the large intestine?

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What type of mucus is secreted in the jejunum region?

Basic mucus

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Where are enteroendocrine cells found?

In the stomach and small intestine…usually in crypts

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What do the enteroendocrine cells produce?

products include:

incretins (K-cells) (hunger, **increase insulin secretion**)

GIP (L-cells)

serotonin (enterochromaffin cells)

somatostatin

motilin (gut sound in PCM!)

cholecystokinin

neurotensin

VIP

substance P

endorphins (opiates)

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What do incretin cells (K-cells) increase?

They increase insulin secretion…before a big meal, when hungry

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What causes parastalsis and gut sounds?

Motilin (protein secreted from small intestine enteroendocrine cells)

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Where do the Paneth cells secrete their contents?

Into the lumen (not the bloodstream!)

What are M-cells?

They are specialized immune cells in epithelium

have limited, small microfolds

(compared to regular gut epithelial cells)

part of innate and classic immune systems

actively capture/transport Ag’s to APCs & B cells in lamina propria

           hard to identify

What do we need to know about M-cells?

Located in the small intestine and function in immune response

What does the lamina propria contain in the small intestine?

Contain mainly immune cells - B cells (plasma cells which produce IgA)

Where does the lymphatic lacteals originate?

In the lamina propria of the small intestine (blind ending villi)

What do lacteals absorb?

Digestive fats!

What are the lymph nodules of the small intestine called?

Peyer's patch...collection of lymphoid tissue/cells ## Footnote especially prominent in ileum may appear in lower jejunum M cells more prevalent in these areas (become more numerous in distal small bowel)

Where else are Peyer's patches located?

The appendix

Where are the submucosal glands (Brunner's glands) only found?

In the duodenum

Where are the plicae present?

duodenum and jejunum

Serosa details...

duodenum has serosa on anterior surface only (part of this organ is retroperitoneal) jejunum and ileum have serosa (continuous w/ supporting mesentery)

Describe ileocecal junction

site where ileum joins large intestine formed by folds of the mucosa and submucosa supported by mass of circular smooth muscle from muscularis externa

Cecum

small, blind pouch of large intestine structurally identical to colon

Appendix - characteristics

slender, blind diverticulum of cecum small, irregular lumen often containing cellular debris villi are absent intestinal crypts enteroendocrine cells some Paneth cells (vestigial structure - no real function)

Does the large intestine have villi?

NO!!!! agaaaaiiiin

What type of epithelium is the large intestine's lumen made up of?

simple columnar epithelium (same as small intestine)...only difference = more goblet cells

Are digestive enzymes released from the large intestine?

No...none. No Paneth cells either.

Why do antibiotics cause diarrhea?

They destroy the natural flora in the large bowel...thus decreasing the amount of water retained/reabsorbed.

Are plicae circulares present in the large intestine?

No. However, plicae semilunares are... ## Footnote incomplete (half-moon) folds in intestinal wall (do not form complete circular fold, as plicae in small intestine do) produce characteristic sacculation (haustra)

Define haustra

The haustra (singular haustrum) of the colon are the small pouches caused by sacculation, which give the colon its segmented appearance.

The large intestine's muscularis externa is...

... “incomplete” inner layer completely encircles submucosa outer longitudinal layer in three longitudinal bands bands known as **taeniae coli**

Taeniae coli definition and function

Three separate longitudinal ribbons of smooth muscle on the outside of the ascending, transverse, descending and sigmoid colons. They are visible, and can be seen just below the serosa or fibrosa. They are the Mesocolic, Free and Omental Coli. The teniae coli contract lengthwise to produce the haustra, the bulges in the colon.

Name of large intestinal crypts?

crypts of Lieberkuhn longer & more closely packed than in small intestine occasional enteroendocrine cells present Paneth cells absent

Goblet cells more numerous in...

LARGE INTESTINE

Diarrhea due to ABX?

"Bugs retain water", if they are killed and don't = watery stool, diarrhea

Change at pectinate line?

simple columnar becomes strat. squam. noncornified

Haustra only found where?

Large intestine

Is there the tenia coliae on the rectum?

NO, they blend to make a smooth muscle layer