Lecture 8- Pancreas and liver Flashcards
(54 cards)
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)
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
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
4
Q
chyme is
A
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
6
Q
what causes bicarbonate secretion into the duodenum
A
- Controlled by secretin- released from S cells in response to low pH
7
Q
exocrine and endocrine proportions of the pancreatic secretions
A
- Exocrine portions approx. 90% of pancreas
- 2% endocrine functionà into blood
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).
9
Q
exocrine cells of the pancreas
A
acinar
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
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)
12
Q
symapthetic innervation of pancreas exocrine function
A
inhibits release of enzyme
13
Q
parasympathetic innervation of pancreas exocrine function
A
vagus nerve- stimulates (and CCK)
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
15
Q
Formation of pancreatic enzymes in acinus
A
- Formed on RER
- Moved to golgi
- Condensing vacuoles
- Concentrated in zymogen granules
- Released with appropriate stimulus
- Parasympathetic/ CCK
16
Q
zymogens are
A
inactive precursors e.g. trypsinogen instead of trypsin
(stop autodigestion)
17
Q
detection of pancreatitis
A
finding amylase/lipase in the blood
18
Q
the liver is the
A
single largest organ
19
Q
liver function
A
- Function
- Energy metabolism
- Detoxification
- Plasma protein production
- In the gut- secretion of bile
- 250ml-1l/ day
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
21
Q
bile is made up of
A
bile acids and alkaline juice
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
hepatocytes produce
bile
* Very active producing proteins/ lipids for export
* Contain lots of RER/ SER
* Stacks of golgi membranes
* Good store of glycogen
26
the liver is made up of
lobules
27
at the corners of the lobules you find
portal triads
28
* **Each portal triad has three components**
* Hepatic artery- coming in
* Bile duct (bile produced by hepatocytes)- going out
* Portal vein- coming in
29
blood flow into the liver
* 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
bile flow in the liver
* Along canaliculi- opp direction to blood
* Canaliculi merge to form bile ducts which deliver it to the duodenum
31
Functional unit of the liver- Acinus
* Region of adjoining liver lobules
* Diamond shape
* Has different zones
* 1- closes to the portal triads
* 2
* 3- nearest to the central vein
32
* Any toxins coming into the liver will affect zone .......... more than zone ........- closest proximity to blood coming in
*
* Any toxins coming into the liver will affect zone 1 more than zone 3- closest proximity to blood coming in
33
Zone ...... much more likely to be damaged by ischaemia- furthest away from the blood coming in
Zone 3 much more likely to be damaged by ischaemia- furthest away from the blood coming in
34
**All the blood from the gut drains into the liver**
From the hepatic portal vein (not as deoxygenated as a normal vein, high in nutrients)
35
**Bile** drains into the ..................... of the duodenum from the common bile duct into the sphincter of Oddi – stored in the gall bladder.
second part
36
most of bile is made up of
bile salts
37
2 primary bile acids
* (bile salts are bile acids conjugated with amino acids e.g. glycine and taurine)
* Cholic acid
* Chenodeoxycholic acid- further bile acids formed in gut
38
why do we need bile salts
* Why bile salts?
* Bile acids not soluble at duodenal pHs- bile salts generally are
*
39
role bile acids play in digesting fats
* 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
bile is made up of ...... choelsterol
10%
41
2 major compenents of bile
bile acids dependent
bile acids independent
42
* Bile acid dependent
* Secreted into canaliculi by hepatocytes
* Contains bile acids and pigments
43
44
* Bile acid independent
* Secreted by duct cells
* Similar alkaline solution to pancreatic duct cells
* Stimulated by secretin
45
**Digestions of fats and bile acids**
* 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
**Micelles**
* 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
**Absorption of lipids**
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
Chylomicrons enter lymph capillaries and travel through lymphatic system
How do they re-enter vascular circulation
via the thoracic duct
49
**Enterohepatic circulation of bile acids**
* 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
the gall bladder sits on the
* on inferior surface of liver, in the transpyloric plane – plane at L1
51
function of gall bladder
* Bile produced all the time but we only need it intermittently
* Stores bile
* Concentrates bile (removes water/ions)
* Can lead to gall stones
52
which hormones triggers release of bile from gall bladder
* CCK released from duodenum stimulates gall bladder contraction
* Relaxes sphincter of Oddi
53
* If bile acids (salts) or pancreatic lipases are not secreted in adequate amounts
**Steatorrhea and bile pigments**
* Pale poo
* Floating
* Foul smelling
54
bilirubin and bile
* 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
