6.4. Exocrine secretion of pancreas and its regulation. Bile production of the liver. Metabolism and secretion of bile pigments. Flashcards
I. Pancreatic secretion
1. What are the features of Pancreatic secretion?
98% of pancreatic cells are responsible for exocrine secretion into the intestine
2% of the cells are responsible for endocrine secretion into the blood
I. Pancreatic secretion
2. What is the amount of pancreatic juice secretion per day?
700-900 mL/day
I. Pancreatic secretion
3. What are features of pancreatic juice?
- Isosmotic
- Alkaline (bc it neutralizes the acidic content)
I. Pancreatic secretion
4. What are the 2 Functions of pancreatic juice secretion?
- Neutralize acidic content of stomach
- Protection of intestinal mucosae (sensitive to low pH)
- Digestive enzymes in the small intestine require neutral pH (~7) to work - Pancreatic juice contributes to digestion of the meal
- Has many digestive enzyme
I. Pancreatic secretion
5. What is Sequential secretion mechanism?
- Not just acinar cells, but also duct cells produce fluid (actually more)
- The acinar cells work similarly as in the salivary gland, but there are some differences: acinar cells here produce much more enzymes (digestive enzymes)
II. Make a schematic diagram of function of Acinar cells
III. Duct cells
1. What is the role of duct cells?
produce vast majority of fluid
III. Duct cells
2. What are 2 types of duct cells?
proximal + distal
III. Duct cells
3A. What is the role of proximal duct cells?
- H2O secretion
- Important to wash out protein that are exocytosed by the acinar cells
=> If CFTR is mutated -> H2O transport not present => Protein clogged in the system => Pancreatitis
III. Duct cells
3B. Make a schematic diagram of the function of proximal duct cells?
- H2O secretion
- Important to wash out protein that are exocytosed by the acinar cells
=> If CFTR is mutated -> H2O transport not present => Protein clogged in the system => Pancreatitis
III. Duct cells
4A. What is the role of distal duct cells?
If the distal duct cell have time. they will re-absorb some HCO3- ions
III. Duct cells
4B. Make a schematic diagram of the function of distal duct cells?
III. Duct cells
5. What happen When we have low rate of secretion?
- When we have low rate of secretion, the HCO3—secretion is not so big
III. Duct cells
6. What happen if the secretion rate↑?
- If the secretion rate↑, then distal duct cells have no time to exchange back HCO3-
-> [HCO3-]↑ -> pH of pancreatic juice↑
=> In response to meal: PARA activity↑ + pancreatic juice↑ + GA secretion↑
-> except more acid coming to stomach = need more HCO3- to neutralize
IV. Cystic fibrosis (CF)
1. What is Cystic fibrosis (CF)?
A genetic disease caused by mutation in CFTR (cystic fibrosis transmembrane conductance regulator)
=> impaired Cl- secretion
IV. Cystic fibrosis (CF)
2. What are the consequences of Cystic fibrosis (CF)?
- Pancreas (clogging of dig.enzymes -> autodigest tissue) – pancreatitis
- Lungs (H2O-secretion onto the airways requires Cl—transport) -> if mutation, dense mucus-rich layer = mucociliary clearance not possible
- Biliary system + intestines
V. Regulation of pancreatic juice formation
1. What are the 2 types of Regulation of pancreatic juice formation?
- Neural regulation
- Hormonal regulation
V. Regulation of pancreatic juice formation
2A. Explain the parasympathetic regulation of pancreatic juice formation
- ACh (Gq) – acinar cells -> enzyme secretion↑ (M3-R)
- VIP (Gs) – vessels -> vasodilation -> volume of pancreatic juice↑
V. Regulation of pancreatic juice formation
2B. Explain the sympathetic regulation of pancreatic juice formation
- NE (α1-AR) – vessels
-> vasoconstriction
-> pancreatic juice production↑
V. Regulation of pancreatic juice formation - hormonal regulation
3. What are the 2 hormones participating in hormonal regulation of pancreatic juice formation?
- Secretin
- CCK (cholecystokinin)
V. Regulation of pancreatic juice formation - hormonal regulation
4. What are the features of secretin?
- Produced by S-cells in response to low pH in duodenum
- Acts on duct cells (main site of HCO3-) => neutralize low pH
V. Regulation of pancreatic juice formation - hormonal regulation
5. What are the features of CCK (cholecystokinin)?
- Produced by I-cells in response to protein degradation
- ↑Pancreatic juice secretion (stimulates aff.arm of vagovagal reflexes to acinar + duct cells)
=> Secretin and CCK can enhance each other’s effect
V. Regulation of pancreatic juice formation - hormonal regulation
6. Explain the negative-feedback loop that responds to a fall in luminal pH in luminal pH in the duodenum
=> Make a schematic diagram if needed
Participation of secretion and HCO3- secretion in a classified negative-feedback loop that responds to a fall in luminal pH in luminal pH in the duodenum