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Gastrointestinal > Lecture 8- Pancreas and liver > Flashcards

Lecture 8- Pancreas and liver Flashcards

1
Q

chyme enters the duodenum from the stomach, what sort of osmolarity does this chyme have

A

its hypertonic - more solute compared to solvent (compared to plasma)

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2
Q

why is chyme that leaves the stomach hypertonic

A
  • When we break a molecule it gets broken down into say 5 molecules- therefore gores from osmotic pressure of 1 to 5
  • Stomach wall impermeable to water- cannot dilute solute in chyme- toncity
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3
Q

why does this hypertonic solution become isotonic in the s.intestin

A

Duodenum is permeable to water

  • chyme creates conc gradient for water- water secreted from ECF. ciruclation–> reduces toncity
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4
Q

chyme is

A
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5
Q

what happens to the partially digested, acidic chyme from the stomach

A
  • pancreas releases enzymes into the duodenum
  • bicarbonate ins secreted from pancreas and liver and bile
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6
Q

what causes bicarbonate secretion into the duodenum

A
  • Controlled by secretin- released from S cells in response to low pH
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7
Q

exocrine and endocrine proportions of the pancreatic secretions

A
  • Exocrine portions approx. 90% of pancreas
  • 2% endocrine functionà into blood
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8
Q

Major pancreatic duct and common bile duct

A

come into the duodenum at the same point, through the sphincter of oddi (when it is relaxed).

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9
Q

exocrine cells of the pancreas

A

acinar

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10
Q

production of enzymes and water by exocrine ducts of pancreas stimulated by

A

vagus nerve and cholecystokinin (CCK)

  • in response to
  • Hypertonicity/ small peptides/ fats detected in duodenum
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11
Q

acinus of the pancreas produce

A
  • Acinus produces enzymes (acinar cells)
    • Amylase/lipases (active)
    • Proteases (inactive)- trypsin, chymotrypsin, elastase, carboxypeptidase
  • water (centroacinar cells)
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12
Q

symapthetic innervation of pancreas exocrine function

A

inhibits release of enzyme

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13
Q

parasympathetic innervation of pancreas exocrine function

A

vagus nerve- stimulates (and CCK)

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14
Q

what controls how much HCO3- is released

A

At a higher flow rate of chyme, increased secretion of HCO3- due to increased pancreatic secretion

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15
Q

Formation of pancreatic enzymes in acinus

A
  1. Formed on RER
  2. Moved to golgi
  3. Condensing vacuoles
  4. Concentrated in zymogen granules
  5. Released with appropriate stimulus
    1. Parasympathetic/ CCK
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16
Q

zymogens are

A

inactive precursors e.g. trypsinogen instead of trypsin

(stop autodigestion)

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17
Q

detection of pancreatitis

A

finding amylase/lipase in the blood

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18
Q

the liver is the

A

single largest organ

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19
Q

liver function

A
  • Function
    • Energy metabolism
    • Detoxification
    • Plasma protein production
    • In the gut- secretion of bile
      • 250ml-1l/ day
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20
Q

dual blood supply of the liver

A
  • Hepatic artery (20%)
    • Low in nutrients
  • Portal vein (80% of all blood)
    • High in nutrients from intestines
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21
Q

bile is made up of

A

bile acids and alkaline juice

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22
Q

bile release causes

A

excretion of bile pigment and digestion of fat

23
Q

hepatocytes are the

A

chief cells of the liver

24
Q
A
25
Q

hepatocytes produce

A

bile

  • Very active producing proteins/ lipids for export
    • Contain lots of RER/ SER
    • Stacks of golgi membranes
  • Good store of glycogen
26
Q

the liver is made up of

A

lobules

27
Q

at the corners of the lobules you find

A

portal triads

28
Q
  • Each portal triad has three components
A
  • Hepatic artery- coming in
  • Bile duct (bile produced by hepatocytes)- going out
  • Portal vein- coming in
29
Q

blood flow into the liver

A
  • Blood flow comes from the portal triads and merge at the central vein the middle of the lobule
  • Central veins of lobules drain into hepatic veins (x3 which drain into the inferior vena cava) – which takes blood away from the liver to be oxygenated (different from the hepatic portal vein which takes blood to the liver)
30
Q

bile flow in the liver

A
  • Along canaliculi- opp direction to blood
  • Canaliculi merge to form bile ducts which deliver it to the duodenum
31
Q

Functional unit of the liver- Acinus

A
  • Region of adjoining liver lobules
  • Diamond shape
  • Has different zones
    • 1- closes to the portal triads
    • 2
    • 3- nearest to the central vein
32
Q
  • Any toxins coming into the liver will affect zone ………. more than zone ……..- closest proximity to blood coming in
    *
A
  • Any toxins coming into the liver will affect zone 1 more than zone 3- closest proximity to blood coming in
33
Q

Zone …… much more likely to be damaged by ischaemia- furthest away from the blood coming in

A

Zone 3 much more likely to be damaged by ischaemia- furthest away from the blood coming in

34
Q

All the blood from the gut drains into the liver

A

From the hepatic portal vein (not as deoxygenated as a normal vein, high in nutrients)

35
Q

Bile drains into the ………………… of the duodenum from the common bile duct into the sphincter of Oddi – stored in the gall bladder.

A

second part

36
Q

most of bile is made up of

A

bile salts

37
Q

2 primary bile acids

  • (bile salts are bile acids conjugated with amino acids e.g. glycine and taurine)
A
  • Cholic acid
  • Chenodeoxycholic acid- further bile acids formed in gut
38
Q

why do we need bile salts

A
  • Why bile salts?
    • Bile acids not soluble at duodenal pHs- bile salts generally are
      *
39
Q

role bile acids play in digesting fats

A
  • Amphipathic structure
    • Hydrophilic end (water soluble)and hydrophobic lipid soluble)
    • Act at oil/water interface
    • Crucial for emulsification of dietary lipids
    • larger SA for lipases to work on
40
Q

bile is made up of …… choelsterol

A

10%

41
Q

2 major compenents of bile

A

bile acids dependent

bile acids independent

42
Q
  • Bile acid dependent
A
  • Secreted into canaliculi by hepatocytes
  • Contains bile acids and pigments
43
Q
A
44
Q
  • Bile acid independent
A
  • Secreted by duct cells
    • Similar alkaline solution to pancreatic duct cells
    • Stimulated by secretin
45
Q

Digestions of fats and bile acids

A
  • Lipids tend to form large globules by the time they reach duodenum
  • Low surface area for enzymes to acid
  • Bile acids emulsify fats into smaller units
    • Help disperse fatty droplets
    • Increases surface area for lipases to acid
  • Bile acids then from micelles with products of lipid breakdown
46
Q

Micelles

A
  • Vehicles to carry hydrophobic molecules through aqueous medium
  • Products of lipid digestions e.g.
    • Cholesterol
    • Monoglycerides
    • Free fatty acids

Diffuse with products to brush border of epithelial cells

47
Q

Absorption of lipids

A
  1. Lipids diffuse down conc gradient into intestinal epithelial cells (in the micelle)
  2. Inside cell re-esterified back to:
    • Triglycerides
    • Phospholipids
    • Cholesterol
  3. These reformed lipids are packed with apoproteins to form chylomicrons
  4. Chylomicrons exocytosis from basolateral membrane
    • Too large to enter capillaries
    • Enter lymph capillaries
      • Travel through lymphatic system
      • Re-enter vascular circulation via the thoracic duct
48
Q

Chylomicrons enter lymph capillaries and travel through lymphatic system

How do they re-enter vascular circulation

A

via the thoracic duct

49
Q

Enterohepatic circulation of bile acids

A
  • Don’t enter gut epithelial cells with lipids
    • Remain in gut and reabsorbed in terminal ileum
      • Returned to liver in portal blood
      • Liver extracts bile salts –> therefore liver doesn’t have to resynthesise all bile acids
50
Q

the gall bladder sits on the

A
  • on inferior surface of liver, in the transpyloric plane – plane at L1
51
Q

function of gall bladder

A
  • Bile produced all the time but we only need it intermittently
  • Stores bile
    • Concentrates bile (removes water/ions)
    • Can lead to gall stones
52
Q

which hormones triggers release of bile from gall bladder

A
  • CCK released from duodenum stimulates gall bladder contraction
    • Relaxes sphincter of Oddi
53
Q
  • If bile acids (salts) or pancreatic lipases are not secreted in adequate amounts
A

Steatorrhea and bile pigments

  • Pale poo
  • Floating
  • Foul smelling
54
Q

bilirubin and bile

A
  • Breakdown product of Hb
  • Conjugated into the liverà soluble
  • Secreted into bile
  • Excreted in faeces
  • Accumulates in blood if cannot be excreted à causing jaundice

Gastrointestinal (35 decks)

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