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GI- Week 4 > Downing: Histology of Large Intestine, Rectum, Appendix, Pancreas and Gallbladder > Flashcards

Downing: Histology of Large Intestine, Rectum, Appendix, Pancreas and Gallbladder Flashcards

1
Q

What are the functions of the LI?

A

Absorb water

Secrete mucous to lubricate dehydrated feces

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2
Q

What are the major histological features that distinguish the LI?

A

No villi

No plicae circularis

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3
Q

What are the major layers of the LI?

A 
Mucosa--LP
Submucosa
Muscularis
Serosa
Adventitia
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4
Q

What are the 5 types of cells typically seen in mucosal glands?

A 
absorptive columnar
Goblet
Enteroendocrine (DNES)
Paneth (rare)
STEM (replace cells every 5-6 days)
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5
Q

Is there a LP present in the mucosa of the LI? What does it contain?

A

Yes, but it’s not really evident b/c the crypts of lieberkuhn extend down to the muscularis

Lymphatic tissue (diffuse and nodular)

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6
Q

What do the large intestinal glands look like?

A

crypts of lieberkuhn

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7
Q

What does the submucosa of the LI look like?

A

similar to the SI

can contain lymph nodules extending from the LP

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8
Q

What does the muscularis of the LI look like?

A

inner circular layer

outer longitudinal forms taeni coli

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9
Q

Where is the serosa/adventitia present in the LI?

A

Ascending/descending- adventitia

Transverse- serosa

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10
Q

What are the taeni coli?

A

3 longitudinal bundles around the LI

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11
Q

How does the rectum appear histologically?

A

Similar to LI (6-8”)

NUMEROUS GOBLET w/ few columnar

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12
Q

What is the anal canal?

A

The last 1- 1 1/2” of the LI

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13
Q

How does the epithelium change in the anus?

A

Simple columnar> stratified sq non-keratinizing at the anus

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14
Q

What part of the anus is susceptible to varicosities?

A

submucosa that contains large VEINs

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15
Q

What forms the internal anal sphincter?

A

inner circular layer of smth muscle of hte musclaris externa

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16
Q

What forms the external anal sphincter?

A

skeletal muscle

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17
Q

Which sphincter provides voluntary control of defecation?

A

external anal sphincter

18
Q

What are the histological features of the appendix?

A
  1. Mucosa= like LI
    columnar, goblet, enteroendocrine, paneth, undifferentiated cells (like LI)
    crypts of lieberkuhn are POORLY developed
    LP contains MANY lymphocytes and lymphatic nodules
  2. Submucosa
    lymphatic nodules
    fat
  3. Muscularis
    inner circular
    outer longitudinal
    taeni coli NOT present
  4. serosa
19
Q

What does the extrinsic nervous system do and what is it composed of?

A

Modulates the INTRINSIC innervation

Composed of (autonomic NS):

  1. Sympathetic supply- inhibits gut activity
  2. parasympathetic supply- stimulate gut activity
20
Q

What is the diff between the sympathetic and parasympathetic supply of the extrinsic NS?

A

SYMPATHETIC:
POST adrenergic fibers
Cell bodies= coeliac, S/I mesenteric and hypogastric ganglia

PARASYMPATHETIC:
PRE adreneric fibers from VAGUS terminate in MYENTERIC and SUBMUCOSAL PLEXI

21
Q

What are the components of the intrinsic innervation to the gut?

A
  1. afferent neruons in the wall of gut (chemo/mechano)
  2. interneurons in the MYENTERIC/SUBMUCOSAL plexi in wall of gut (connect sensory to motor neurons)
  3. efferent neurons in wall of gut to smooth muscle and secretory cells
22
Q

What is the fxn of intrinsic innervation?

A

coordinate GI activity in absence of extrinsic innervation

23
Q

What is the difference between the myenteric (auerbach’s) plexus and the submucosal (meissener’s) plexus?

A

Myenteric–between circular and longitudinal fibers of muscularis externa

Submucosal– derived from myenteric and located on submucosa of the intestine

24
Q

What type of gland is the pancreas?

A

Exo and endo

similar to parotid

secretes 1200 ml of digestive juice

25
Q

What are the histological features of the pancreas?

A

Excretory duct
Intralobular duct
Intercalated duct
Acinus

26
Q

What type of cells is the acinus composed of?

A

Serous cells

27
Q

What features distinguish serous cells?

A

Basophilic staining (RER)
Round nucleus
Stored zymogen granules

28
Q

How do you identify a pancreatic acinar cell?

A

Eosionphilic staining of apical cytoplasm

RER> golgi> apical cytoplasm> zymogen granules (contain the ENZYMES)

29
Q

What proenzymes/enzymes do the pancreatic acinar cells contain?

A 
Zymogens for protein digestion:
trypsinogen
chymotrypsinogen
proelastases
procarboxypeptidases

Lipolytic enzymes

alpha amylases

nucleases

Forms the pancreatic juice!!

30
Q

What distinguishes the pancreas from the parotid gland

A

Parotid: more fat cells, prominent intralobular duct

Pancreas: centro-acinar cells, islets of langerhans

31
Q

What is the nerve supply to the pancreas?

A

Celiac plexus > sympathetic nerves

Vagus nerve> parasympathetic nerves> causes secretion of pancreatic enzymes

32
Q

What cells produce secretin?

A

S cells (enteroendocrine cells)

33
Q

What is secretin? Where does it act?

A

polypeptide hormone

Stimulates cells of duct to secrete a large volume of ALKALINE FLUID into the DUO containing high conc of bicarb (little enzyme)

34
Q

What are the functions of secretin?

A

Neutralize acid chyme from the stomach

Provide NEUTRAL pH for pancreatic enzymes to function

35
Q

What cells produce CCK?

A

I cells (enteroendocrine cells) in the DUO

36
Q

What stimulates the secretion of CCK?

A

peptides

37
Q

What is the fxn of CCK?

A

Stimulates the release of digestive enzymes and zymogens stored in zymogen granules from the pancreas and gallbladder

38
Q

What are the functions of the gallbladder?

A

Reservoir for bile

Concentrates bile by resorbing lots of water and mineral salts to increase bile concentration

39
Q

What are the histological features of the GB?

A

MUCOSA
Microvilli indicate that it has an absorptive fxn

LP
small blood vessels
Rokitansky aschoff sinuses

40
Q

What are Rokitansky aschoff sinuses?

A

Infoldings of epithelial membranes extending through the LP and muscular layer

41
Q

What affect does CCK have on the gall bladder?

A

FAT>
stimulates CCK release by I cells in the duodenum>
causes GB to CONTRACT and expel concentrated bile into the intestine

42
Q

What does CCK specifically bind to?

A

Receptors on smth muscle cells> contraction of GB

Receptors on smth muscle sphincter of Oddi> relaxes sphincter

GI- Week 4 (12 decks)

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