T3 Liver and Pancreas Flashcards
What is the path of blood flow through the veins of the lobule?
portal vein –> sinusoids –> central vein –> hepatic veins.
What is the path of blood flow through the arteries of the lobule?
hepatic artery –> sinusoids –> central veins –> hepatic veins
How many layers of hepatocytes are liver cell places composed of?
two
Bile canaliculi lie between how many layers of hepatocytes in each cell plate?
two
What are liver lobule sinusoids lined with?
Endothelial cells and Kupffer cells
What is found between endothelial cells and hepatocytes of the liver lobule?
Space of Disse
The liver has _____ blood flow and ____ vascular resistance.
high; low
How much of the resting cardiac output does the liver use?
27%
What is the portal pressure into the liver?
9 mmHg
What is the pressure from liver to vena cava?
0 mmHg
What is the effect of cirrhosis on blood flow?
increases blood resistance to blood flow
What is the effect of a clot blocking portal vein or a major branch?
- blockage of return blood from spleen and intestines
- increase in capillary pressure in intestinal wall –> loss of fluid –> death
How much of the body’s blood volume is in the liver?
10%
High pressure in the atria increases back-pressure on the liver, increasing the blood volume in the liver. When might this occur?
during cardiac failure with peripheral congestion.
What organ can store blood in times of excess and supply blood in times of diminished volume?
Liver
Hepatic sinusoids are highly permeable to what?
proteins
What is the protein concentration of efferent lymph?
6 g/dl, almost equivalent to plasma concentration
What are the effects of higher than normal pressure in hepatic veins?
- back pressure causes fluid to transude into lymph
- fluid leaks through liver capsule into abdominal cavity
- fluid is almost pure plasma
- large amount of fluid in abdominal cavity = ascites
What are the functions fo the liver?
- Carbohydrate metabolism
- Fat metabolism
- Protein metabolism
- Vitamin storage
- Immune function
- Formation of coagulation factors
- Removal or excretion of drugs, hormones, and other substances
What are the main points of carbohydrate metabolism in regards to the liver?
- stores glucose as glycogen
- converts galactose and fructose to glucose
- gluconeogenesis
- forms many intermediate products of carbohydrate metabolism
- releases stored glucose into the circulation
What are the main points of fat metabolism in regards to the liver?
- oxidation of fatty acids for energy
- synthesis of cholesterol, phospholipids, and lipoproteins
- synthesis of fats from proteins and carbohydrates
What are the main points of protein metabolism in regards to the liver?
- deamination of amino acids
- formation of urea
- formation of plasma proteins
- interconversion of various aa and synthesis of other compounds from aa
What are the main points of vitamin storage in regards to the liver?
Vits A, D, and B12
What are the main points of formation of coagulation factors in regards to the liver?
Fibrinogen, prothrombin, accelerator globulin, Factors VII, IX, and X
What are the main points of removal or excretion of drugs, hormones, and other substances in regards to the liver?
- detoxifies or excretes into the bile: sulfonamides, penicillin, ampicillin, and erythromycin
- excretes excess calcium into the bile
- detoxification and removal of ammonia and ethanol
What factors stimulate the release of bile from the gall bladder?
presence of fatty food in duodenum
Bile is continuously secreted by what cells?
hepatocytes in the liver
Where is bile stored until its secreted?
gall bladder
Where is bile concentrated by active transport of sodium followed by secondary absorption of chloride ions, water, and other diffusible constituents?
gall bladder
Synthesis of bile salts are done by what?
liver
Bile salts are:
A. Hydrophobic
B. Hydrophilic
C. Amphipathic
Amphipathic
Bile salts orient themselves around lipid droplets and keep them dispersed. What is the name for this mechanism?
emulsification
What is the function of bile salts?
emulsification; complex with lipids to form micelles for absorption across the intestinal mucosa.
What is the map of a micelle?
bile salts are positioned on the outside of the micelles, and free fatty acids and monoglycerides are inside the micelle
Bile acids are concentrated in the gall bladder as a result of what?
absorption of solutes and water
Hepatic bile is produced and secreted by what?
liver
bile from the gall bladder is _______ that has been stored and concentrated
hepatic bile
What are the components of bile?
Bile acids, water and electrolytes, cholesterol and phospholipids (esp lecithin), and pigments and organic molecules (major pigment is bilirubin).
Free bilirubin is transported in the blood stream attached to what and transported to liver hepatocytes?
plasma albumin
Free bilirubin is released from plasma albumin within the liver cells and what?
conjugated
Conjugated bilirubin is secreted by what mechanism in to the intestines? OR is excreted where?
active transport; urine
What is jaundice?
the yellowish tint to the body tissues, usually caused by quantities of bilirubin in the extracellular fluids.
What are the common causes of jaundice?
increased hemolysis and obstruction on bole ducts or damage to liver
What do the alpha cells of the pancreatic islet secrete?
glucagon
What do the beta cells of the pancreatic islet secrete?
insuline and amylin
What is the function of insulin?
inhibit glucagon secretion
What is the function of amylin?
inhibits insuline secretion
What do the delta cells of the pancreatic islet secrete?
somatostatin
What is the function of somatostatin?
inhibit insulin, glucagon, and gastrin secretion
Communication among islet cells via gap junctions allows what kind of cells to talk to each other? A. beta to beta B. alpha to alpha C. beta to alpha D. all of the above
All of the above
Communication among islet cells via islet portal blood supply allows what kind of cells to talk to each other?
beta cells to alpha and delta cells
What are the digestive enzymes for proteins?
trypsin, chymotrypsin, and carboxypolypeptidase
Trypsin inhibitor is secreted by what cells, and is necessary to prevent the action of trypsin on the pancreatic tissues themselves?
glandular cells
What is the digestive enzyme for carbohydrates?
Pancreatic amylase
What are the digestive enzymes for fat?
Pancreatic lipase, cholesterol esterase, phospholipase.
Are pancreatic secretions: A. hypotonic B. isotonic C. hypertonic D. all of the above
isotonic
What are the characteristics of pancreatic secretions?
- high volume
- isotonic
- same Na+ and K+ concentrations as plasma
- higher bicarb concentration than plasma
- lower chloride concentration than plasma
What is occurring during low flow rates of pancreatic secretions?
isotonic fluid composed mostly of sodium and chloride ions
What is occurring during high flow rates of pancreatic secretions?
isotonic fluid composed mostly of sodium and bicarb ions
What pancreatic cell secretes a small volume of mainly sodium and chloride?
Acinar cells
What do ductal cells of the pancreas secrete?
bicarbonate ion and reabsorb chloride ion via chloride-bicarb exchange mechanism.
What is the mechanism that makes ductal cells isotonic?
ducts are permeable to water, so water moves into ducts to make secretions isotonic
What stimulates the release of secretin?
the presence of acidic foods in upper intestines
What secretes secretin?
duodenal and upper jejunal S mucosal cells
What is the action of secretin?
stimulates release of large amounts of sodium bicarbonate by ductal cells
What is the second messenger for secretin?
cAMP
When insulin is circulating and not bound to receptors, it is destroyed. Where is it destroyed?
in the liver
What are the results of insulin binding to receptor?
Increased:
- uptake of glucose
- permeability to amino acids, potassium, and phosphate ions
- uptake of fatty acids
- activity of levels for many enzymes
-Changes in rates of translation and transcription
How does blood glucose concentration change when insulin binds a receptor?
decrease in blood glucose
How does blood aa and potassium concentration change when insulin binds a receptor?
decrease in blood aa and potassium
How does blood fatty acid concentration change when insulin binds a receptor?
decrease in blood fatty acids
What molecule receptor is a tetramer with two extracellular alpha subunits and two intracellular beta subunits?
insulin receptor
Intrinsic tyrosine kinase activity of the insulin receptor auto-phosphorylates what subunit (alpha or beta), which then phosphorylates intracellular proteins?
beta
Does insulin down regulate or up regulate its own receptor?
down regulate
What are the effects of down-regulated insulin/insulin receptors?
increase in starvation and decrease in obesity
What is the normal volume of liver?
450 mL, 10% of the body’s blood volume
How much blood from the portal vein and how much blood from the hepatic portal artery flows into the sinusoid each minute?
1050 ml from the portal vein and 300 ml from hepatic artery each minute
Most of the glucose absorbed after a meal is stored as what? Where is it stored?
Glycogen; liver
What is the mechanism for glucose uptake in the liver?
- insulin inactivates liver phosphorylase
- Insulin activates glucokinase and enhances uptake of glucose from blood
- insulin increases activities of enzymes needed for glycogenesis
One of the most important functional roles of insulin in the body is to do what?
control from moment to moment whether fat (decreased insulin) or carbohydrate (increased insulin) will be used by cells for energy
Name three things that cause the liver to release glucose into blood.
- decreased blood glucose resulting in decreased insulin secretion
- lack of insulin reverses glycogen synthesis pathway
- lack of insulin activates phosphorylase which splits glycogen into glucose phosphate
- glucose phosphatase removes phosphate from glucose and allows it to diffuse back into blood
- insulin inhibits gluconeogenesis.
Insulin promotes the conversion of excess _______ into fatty acids and decreases utilization of fat.
glucose
What are the effects of insulin on fat storage? Name three things.
- increase transport of glucose into liver creating excess
- excess glucose is converted to acetyl-CoA
- Fatty acid synthesis is initiated
- Newly synthesized fatty acids are converted to triglycerides and transported from liver as lipoproteins
- triglycerides are split into fatty acids in capillaries and taken up into fat cells.
- insulin promotes uptake of glycerol by fat cells
What are the effects of lack of insulin on fat storage? Name three things.
- large amounts of acetoacetic acids are formed in the liver
- carnitine transport mechanism in the liver is activated.
- beta-oxidation results in excess acetyl CoA
- excess acetoacetic acid causes acidosis
- increase of ketone bodies in blood
What splits glycogen into glucose phosphate?
phosphorylase
When phosphorylase acts on glycogen, what is the product?
G6P/glucose-P
The removal of the phosphate from G6P allows what to occur?
It allows glucose to diffuse back into the blood.
What are the major effects of glucagon?
breakdown of liver glycogen and increased gluconeogenesis.
Where does glucagon act?
on liver and adipose tissue
What is the result of the blood when glucagon is activated?
increased blood glucose
What is the cascade of events from glucagon to increase blood glucose levels?
activation of adenyl cyclase in hepatic cell membrane –> causes formation of cAMP –> activates protein kinase –> activates phosphorylase b kinase –> converts phosphorylates b into phosphorylase a –> promotes the degradation of glycogen to glucose-1-phosphate –> increases blood glucose.
What increases urea production (due to deamination of amino acids used for gluconeogenesis)?
glucagon
Glucagon increases lipolysis which has what effect on the blood?
increases blood fatty acids, which increases blood keto acids.
What is the major factor that regulates glucagon secretion?
blood glucose concentration
Increased blood amino acids stimulates _______________, which prevents hypoglycemia due to unopposed insulin in response to high protein meal?
glucagon secretion
Somatostatin is secreted by what?
Delta cells
Inhibition of insulin, glucagon, and gastrin, decreased motility of stomach duodenum and gallbladder, and decreased secretion and absorption of GI tract are all functions of what?
somatostatin
What are the negative effects of increased blood glucose levels?
- increased osmotic pressure in extracellular fluid
- loss of glucose in urine
- osmotic diuresis (dehydration and loss of electrolytes)
- damage to tissues and blood vessels
-Obesity (abdominal fat)
-insulin resistance
-fasting hyperglycemia
-increased lipid triglycerides
-decreased HDL levels
-hypertension
are all characteristics of what syndrome?
Metabolic syndrome, characteristic of Diabetes Mellitus
What are the characteristics of type 1 diabetes?
Lack of insulin, due to injury to beta cells (viral infection or autoimmune disorders)
What are the characteristics of type 2 diabetes?
Due to insulin resistance, obesity is a major risk factor, preceded by metabolic syndrome.
