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Liver 2 (Bilirubin (Urine colour-urobilin, Brown faeces- stercobilin,…
Liver 2
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Function
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Immune function
Reticuloendothelial system: immunologically active cell, sieve for antigens carried to it via portal system
Storage
Glycogen, Vit A, Vit D, Vit B12, iron and copper
Metabolic functions
Produces albumin, major osmolar component of blood serum
Manufacturing
Angiotensinogen: hormone, raises blood pressure (activated by renin)
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Synthesis
- Mainstay protein metabolism (synthesis and degradation)
- Liver produces and secretes bile
- bile drain: duodenum and gallbladder store
- IGF 1: childhood growth & anabolic effects adults
- Thrombopoieten production: glcyoprotein hormone: regulates production of platelets by bone marrow
Lipid metabolism:
- Coagulation factors, fibrinogen, protein C & S
and antithrombin
- first trimester: liver main site red cell production
Bile salts
Production
- Liver cells (p450 mediated oxidation of chol: 8 forms)
- Down regulated by cholica cid, upregulated by chol, inhibited by ileal FGF15/19
Structure
- Steroid structure, 4 rings
Functions
- Amphiatic molecules
- Form Micelles: aid lipases digest lipids
- Moves lipids near brush border - fat absorption
- Eliminate cholesterol
- Drives bile flow
- Emulsify fat soluble vitamins (DEAK) to help absorption
- Reduce bacterial flora in small intestine and biliary tract
- Hormonal actions: farnesoid X receptors (FXR) and TGR 5
- Synthesis bile acids, major route cholesterol metabolism
- 95% bile acids re-absorbed by transport ileum and recycled further use biliary system (Enterohepatic circulation)
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- Surfactant - reduce surface tension
- Pancreatic lipase - digests triglycerides & fatty acids
- TG form - *2 fatty acids and a monoglyceride
Blood supply
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Hepatic portal vein
Carries venous blood drained from spleen, GI tract and associated organs
Bile
- Bitter tasting - green/yellowish brown
- Produced in liver
Discharged by duodenum
- 97% water, 0.7% bile salts, 0.2% bilirubin, 0.51% fats (cholesterol/fatty acids/lecithin), inorganic salts
Function
- Neutralize gastric acid in SI
- Aids excretion of bilirubin (from recycled RBC's)
Bile acids
- Steroid acids found in bile
- Bile acids + taurine/glycine = bile salts (conjugation)
- Primary bile acids: synthesized liver
- Secondary bile acids : result of baceterial actions in colon
- 80% organic compounds in bile
(others: phospholipids and chol)
Regulation
Toxic to cells, tight regulation of concs:
- FXR activation inhibits bile acid synthesis
- FXR activation during absorption in intestine increase transcription and synthesis of FGF19, INHIBITS bile acid synthesis in liver
- FXR activation alters triglyceride and glucose metabolism and liver growth
Gallbladder
- Vagal stimulation: weak GB contractions
- presence of Acid in duodenum causes release secretin
- Liver stimulates liver parenchymal secretions and CCK
- CCK causes GB contraction and relaxation of sphincter of Oddi
- Fats in duodenum facilitate release of CCK