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GI Week 3 > Lecture 28: Histology of the ParaAlimentary Tract > Flashcards

Lecture 28: Histology of the ParaAlimentary Tract Flashcards

1
Q

What is the para-alimentary system?

A

That which lies alongside a system pertaining to food and digestion

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2
Q

What are the components of the para-alimentary system?

A
  1. Salivary glands
    • major
    • minor
  2. Pancreas
  3. Liver
  4. Gallbladder/biliary tree
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3
Q

How much fluid is secreted by the paraalimentary components?

A

4000ml/day
Pancreas = 2000
Salivary glands and liver/biliary system = 1000 each

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4
Q

What is the function of the salivary glands?

A
  1. Digestive enzymes
  2. lipids and proteins impede demineralization of teeth (keeps teeth enamel health)
  3. Lysozymes prevent bacterial growth (part of innate immunity)
  4. secretion of IgA
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5
Q

What are the two types of salivary glands?

A
  1. Major

2. Minor

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6
Q

What are the histological features of the parotid (major salivary) gland?

A

Cells are embedded in fat (like the Parathyroid)

Has acini that are the functional part of the gland

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7
Q

What secretes the enzymes in the parotid gland?

A

Acini

Secretes shit into 1) striated duct, 2) intralobular and then interlobular ducts

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8
Q

Why are acinar cells purple?

A

They secrete a lot of protein!
Indicative of SEROUS

Serous = protein = dark
Mucin = no protein = light
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9
Q

What are the histological features of the minor salivary glands?

A

Purely mucinous cells so are very clear

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10
Q

What are the characteristics of the major salivary glands?

A
  1. Parotid = SEROUS

2. Sublingual = serous AND mucinous

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11
Q

What are the characteristics of the minor salivary gland?

A

Mostly mucinous

Submucosa of the nose, paranasal sinuses, oral cavity, esophagus, etc.

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12
Q

What is the function of the pancreas?

A
  1. Exocrine secretions
    • bicarb
    • amylase, lipase, trypsinogen
  2. endocrine functions (insulin, glucagon, somatostatin)

What is the structure of the pancreas?
Ductal system
i. lobules = visible unit composed of all functional cellular elements which drain into intralobular duct
ii. interlobular duct = drains several lobules via several intralobular ducts into main pancreatic cells

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13
Q

What are the cells in the pancreas?

A
  1. glandular/mucinous
  2. acinar cells
  3. islet cells
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14
Q

What are the functions of the glandular/mucinous cells?

A
  1. secrete bicarbonate and the hrmone secretin

Secretes high molecular weight glycoprotines

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15
Q

What are the function of acinar cells?

A
  1. secretes enzymes for digestion in small bowel
  2. proteases, lipases, amylase
  3. low pH in granules, protease nhibitors in granules and zymogen granules to protect from autodigestion
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16
Q

What stimulates acinar cell secretion?

A

CCK

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17
Q

What are the histological features of the pancreas?

A
  1. acinar
  2. islet
  3. ducts
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18
Q

What is the peritoneality of the pancreas?

A

Secondarily retroperitoneal except for its tail

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19
Q

What is a pancreatic lobule?

A

Visible unit composed of all functional cellular elements which drain into intralobular duct

20
Q

What is the function of the pancreatic duct?

A
  1. conduit for secretions of acinar cells to lumen of duodenum
  2. secretes bicarb to duodenum
    Lined by CUBOIDAL cells
21
Q

Are the medulla and cortex of adrenal the same embryologically?

A

They are derived from different places embryologically

22
Q

Embryologically, where does pancreas derive from?

A

All the cells from pancreas come from the same place

23
Q

What is the structure of the acinar cell?

A

Pyramidal shape
Apex = acinar lumen, microvilli present
Eosinophilic cytoplasm = zymogen
Purple cytoplasm = RER…lots of protein made so the RER is dark

24
Q

What is the function of the liver?

A
  1. Synthetic
    • synthesizes LDL/VLDL
    • synthesizes bile (bile salts derived from cholesterol + bilirubin from hemoglobin)
  2. Clearing
    e. g. excretes copper through biliary secretion
  3. Detox
  4. Secretion
  5. Delivery
  6. Hormone converter (OH vit D and T4 to T3)
  7. Storage
25
Q

What does the liver detox/clear?

A
  1. bilirubin
  2. endogenous/exogenous toxins
  3. ammonia
  4. copper
26
Q

What does the liver store?

A
  1. lipid
  2. vitamin A
  3. glucose (glycogen)
27
Q

What does the liver synthesize?

A
  1. albumin

2. Vit K dependent factors, 2, 7, 9 and 10

28
Q

Where does the urea cycle take place?

A

Liver
So liver makes urea
Ammonium go to glutamine

29
Q

What is the function of the gallbladder/biliary tree?

A

Serves as conduit for bile

Stores bile

30
Q

What are the functions of the bile?

A
  1. remove bilirubin from blood
  2. enhance lipid absorption in small bowel
  3. rid the body of wastes/toxins
31
Q

What are the key characteristics of liver histology?

A

Repeating units of

i. hepatocytes
ii. portal tract
iii. sinusoids
32
Q

What is the terminal venule?

A

Where all the blood from the sinusoids
Ultimately drain to
(green stuff = hepatocytes
Fenestrated epithelium is UNIQUE to the liver and kidney to allow for exchange

33
Q

How many hepatic veins are there?

A

3 hepatic veins (left, right and middle)

34
Q

What separates the blood and the hepatocytes?

A

Fenestrated endothelium

35
Q

How do hepatocytes regenerate?

A

Every hepatocyte has the ability to re-enter the cell cycle

36
Q

What are the types of collagen? Significance?

A
  1. fibrillar
  2. network
  3. FACIT
  4. Tran membrane
    Holds together the portal tract, liver cords and central vein
    Collagen also is involved in SIGNALING
37
Q

What is the space of Disse?

A

The space between the fenestrated endothelium and hepatocyte

Blood  endothelial cell  space of Disse  hepatocyte

38
Q

What is the purpose of collagen signaling?

A

Helps with cell polarity

Also can signal regeneration of hepatocytes

39
Q

What is the mechanism of collagen signaling?

A

Matrix (fibronectin) binds to the integrin on cell surface

Integrin is bound to linker proteins and is attached to the F-actin

40
Q

How do you form bile salts?

A

Cholesterol is converted into bile salts

41
Q

Can you usually see bile canaliculi in a H&E stain?

A

No

Only can see it if the bile is blocked or backed up

42
Q

What is the canaliculus?

A

The space through which bile is transported

43
Q

What are the zones of the liver? Significance?

A

Zone 1: those heaptocytes exposed to the blood right after entry from the portal tract
Zone 2: in between 1 and 3
Zone 3: those hepatocytes that se the blood right before exit into the terminal venule
Enzymes are ZONALLY distributed
P450 rich in zone 3

44
Q

Which zone is most sensitive to ischemia?

A

Zone 3 (because farthest from hepatic artery0
Oxygen is LOWEST in zone 3
Oxygen is HIGHEST in zone 1

45
Q

What stimulates the gall bladder to contract and release its stores?

A

Cholecystokinin (CCK)

46
Q

How does the structure of the gallbladder differ from luminal gut?

A 
Gall bladder can and does alter luminal fluid above 290 osm
Has the following components
i. epithelium
ii. lamina propria
iii. muscularis propria
NO submucosa
47
Q

How does the pancreas prevent autodigestion?

A
  1. low pH in granules
  2. protease inhibitors in granules
  3. zymogen granules to protect from autodigestion

GI Week 3 (11 decks)

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