Histo Lecture 18
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What are some functions of the liver?
- Flitration of blood
- Metabolism of proteins, fats, carbohydrats
- Formation of bile
- Storage of vitamins and iron
- Formation of coagulation factors, plasma proteins
- Detoxification of metabolites and exgenous compounds
What are the liver lobules arranged around?
The Central Vein
Which lobule has bile-producing capabilities?
All of them
What does the portal vein do?
Transports intestinal venous blood to the liver
What does the portal venule do?
Brings blood into lobuls from portal vein
What are cellular plates?
- Layers of hepatocytes
- Aligned along the sinusoids
- Provide filtering, detoxification & metabolic functions
- Produce bile
What are hepatic sinusoids?
- Endothelium-lined spaces, surrounded by cellular plates
- Receive portal (venous) blood
What are hepatic arterioles?
- Arterial blood supply to lobule cells
- empty into sinusoids for filtration of arterial blood
What is the Central Vein?
- Collects blood from lobule
- Empties into the hepatic vein and then the IVC
What are Reticulo-sinusoidal cells?
- Kupffer cells
- Resident macrophages of the liver
What are the peri-sinusoidal spaces?
- Disse Space
- Between the endothelial cell and the hepatocytes
- Area of interaction between hepatocytes and blood
- Some areas continuous with lymphatics
What do the stellate cells do?
- Store vitamins
- Produce scar tissue
Approximately how much blood is stored in the liver?
Liver contributes almost how much lymph that is formed in the body?
What is Cirrhosis?
- Damaged hepatocytes are replaced with fibrous CT
- Fibrous CT compresses sinusoids and reduces hepatic blood flow
What is Portal Hypertension?
- Increased venous pressure in the liver
- Increased pressure promotes fluid transudation from sinusoids to the lymph and the surface of the liver
- -Results in ascites (fluid build-up in the abdomen)
- Can also cause esophageal varices, caput medusa, internal anal hemorrhoids
How does the liver control blood glucose?
- Stores excess glucose as glycogen; releases it as needed (glucagon)
- Produce glucose from amino acids and glycerol (gluconeogenesis)
- converts disaccharides into glucose
What can the liver synthesize in terms of fat metabolism?
- Bile from cholesterol
What does deamination from the liver provide?
- Convert amino acids into a form for energy release
- Provides precursor molecules for lipid synthesis
How does the liver play a role in urea formation?
- Ammonia is formed during deamination by bacteria within the GI tract
- Liver converts it to urea for renal excretion
What does the liver synthesize in terms of plasma proteins
- Complement proteins
- Coagulation proteins
- Osmotic proteins
- Synthesize all non-essential amino acids
- Interconvert various amino acids
What vitamins can the liver store?
- Vitamin A
- Vitamin D
- Vitamin B12
What are some of the major liver functions?
- Vitamin storage
- Iron storage
- Removal, excretion, detoxification
What are some methods of liver detoxification?
- Limits release of substances into circulation
- Extracts toxic substances and converts them for excretion
- -Altered to water soluble products that can be easily excreted
- Conversion and conjugation to other molecules
How/what does the liver eliminate toxic waste through feces?
- Addition of wastes to bile
- Large catabolites
- Molecules bound to plasma proteins
- Steroid hormones
What are some components of bile?
- Bile acids
- Electrolytes and water
What are primary bile acids?
Bile acids that are intially synthesized by hepatocytes
What are secondary bile acids?
Colonic bacteria that are converted into different acid molecules and and added to primary bile acid
Primary and secondary bile acids can be conjugated with what?
- Yields ionized molecules capable of diffusing through cell membranes
Where are most bile acids reabsorbed?
What are some functions of the Gall Bladder?
Storage and concentration unit for bile
What causes the gall bladder to expel bile?
Stimulated by GB by parasympathetics and CCK to contract and expel bile
What stimulates greater PNS outflow?
What is Ammonia?
- By-product of protein catabolism and bacterial metabolism
- Product of kidney function, RBC removal, mucle cell activity
Liver converts ammonia into what?
What unit in the liver convers ammonia to urea?
What are some ways to asses liver function?
- Hepatocyte injury/dysfunction
- Determine dysfunction of bile excretion
- Cholangiocyte injury/dysfunction
- Response to liver therapy/transplantation
What are some hepatocyte markers in blood serum?
- ALT - alanine aminotransferase
- AST - aspartate aminotransferase
- Serum albumin
- Prothrombin time (clotting factors)
What are some biliary system markers in blood serum?
- ALP - alkaline phosphatase
- GGT - gamma-glutamyl transpeptidase
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