Exam 4 (Lecture 44) - Small/Large Intestine Secretion of Water and Electrolytes Flashcards
All water secretion is _________. Will hyperosmotic ingesta cause an increase or decrease in water secretion into the small intestine lumen?
The _______ intestine provides more/less (choose one) volume of secretions compared with the large intestine.
1) Osmotic
2) Increase
3) Small; more
Describe the small intestine secretion pathway for electrolytes and water.
Electrolytes and Water from blood capillaries > Lateral Space > Basolateral Membrane > Enterocyte > Lumen of small intestine
What is the function of the small intestine crypt cells?
Secrete Cl-
What are the functions of the liver?
1) Modify nutrient-rich blood
2) Detoxify (NH3 –> Urea)
3) Regulates nutrient concentration of blood reaching tissues
GI blood flows through two capillary beds. List the two capillary beds. Is arterial hydrostatic pressure high or low in each capillary bed?
1) Blood capillaries in the lamina proprietor of small intestinal villi
- high arterial hydrostatic pressure
2) Sinusoidal capillaries of liver
- low arterial hydrostatic pressure
Where is a normal pressure gradient required for normal GI blood flow?
Between the caudal vena cava and hepatic portal vein
How does right sided heart failure and diffuse liver disease cause ascites (increased fluid accumulation in the abdomen)?
Right-Sided Heart Failure:
- Pumping capacity of the heart becomes reduced, unable to remove returning venous blood
- Accumulation of blood, increases blood volume which directly increases thoracic vena cava pressure
- Increase in pressure interferes with blood flow out of liver, which reduces blood flow out of the intestine
Diffuse Liver Disease:
- Interferes with GI blood flow
- Increased sinusoidal capillary pressure
- Increased resistance to hepatic blood flow
- Slight increases in hepatic blood flow resistance have large effects on small intestinal blood flow
Describe the HVPG (hepatic venous pressure gradient).
Small pressure gradient (3-6 mmHg); offsets the osmotic and hydrostatic forces thereby inhibiting water absorption in the small intestine
List the dietary lipids.
1) Triglycerides (primary dietary lipid)
2) Phospholipids
3) Cholesterol
4) Waxes (from plants)
List the four phases of lipid digestion and absorption.
1) Emulsification
2) Hydrolysis
3) Micelle Formation
4) Absorption
Phase 1: Define emulsification. Where and how is the emulsification phase completed?
_________ the surface tension of the lipids and allows the droplets to become even further divided and reduced in size. This _________ the surface area for action of lipase, colipase, and bile acids for fat digestion.
Reduction of lipid droplets to a size that dorm stable suspensions in water.
Completed in the small intestine by detergent action of bile acids and phospholipids.
Reduces surface tension; Increases surface area
Phase 2: Hydrolysis (Pancreatic lipase and colipase)
________ cannot penetrate the coat of bile products surrounding the emulsified liquid droplets. __________ clears a path through the bile products, giving lipase access to the underlying triglycerides.
Lipase; colipase
Phase 3: Micelle Formation
_______ and _______ combine with bile acids and phospholipids to form ________.
What are micelles?
All components of the micelle diffuse into the enterocyte except __________.
Soluble micelles allow the lipids to _______ into the unstirred water layer and into close contact with the absorptive surface of the apical enterocyte membrane.
The majority of bile acids are recycled via ________ circulation. Briefly describe this type of circulation.
Fatty acids and monoglycerides; micelles
Micelles = small water-soluble aggregations of bile acids and lipids
Bile acids
Diffuse through the gut lumen
Enterohepatic circulation
- Bile acids transported back to the liver by the portal vasculature
- Bile acid is extracted by the liver and recycled into the bile
- Occurs repeatedly, so its circulated through small intestine several times per day
Phase 4: Absorption
Within the enterocyte, fatty acids (FA) and monoglycerides are transported to the smooth muscle ER and used to synthesize ______. The TG is packaged with __________, ___________, and other lipids forming a ____________.
Where are chylomicrons absorbed?
Triglyceride
Packaged with:
- cholesterol
- lipoproteins
Forms:
- chylomicron (absorbed in the lacteal)
* lacteal = lymphatic capillary
Define diarrhea.
Increase in the frequency of defecation and increase in fecal water volume
