Introduction to the Liver Flashcards
Describe the anatomy and structure of the liver
Describe the blood supply and drainage of the liver
- The largest gland in the body. Its major aspects are the vascular system, biliary tree, and 3d arrangement of Hepatocytes with the vascular and biliary systems.
The biliary system is the system of ducts to transport the bile out of the liver and into the small intestine.
- 75% comes from the HPV and the remaining 25% is from the Proper hepatic artery. Blood is drained by hepatic vein, before going into the IVC.
What are the cells of the liver?
Describe the structure of the Hepatic Lobule
Describe where the bile comes from and goes
LOOK AT DIAGRAMS!
- The 2 main cells in the liver are the Hepatocytes and Kupffer cells (type of macrophage that carries out phagocytic activity). Other cells present are liver endothelial and stellate cells.
- At each corner of the hexagon is a ‘3 lane structure’, which consists of a branch of the HPV, Hepatic artery and Bile duct. Blood enters the lobules through the branches of the HPV and Hepatic artery, flowing through channels called Sinusoids. As blood passes, the hepatocytes remove toxic substances like alcohol, from the blood, before it goes into the central vein.
- Bile flows in the opposite direction (away from central vein) into the bile duct.
How does the liver’s microstructure support its role?
What is the role of the Kupffer cells? Where are they found?
- Large surface area - efficient exchange
Distinct separation of blood from bile - Found in sinusoids - Work as the liver’s protective barrier. As blood flows through the sinusoids, these cells remove the gut bacteria and antigens. So, a very small number of bacteria from the HPV can survive past the liver.
What is Bile?
How is Bile secreted?
- Complex fluid of water, electrolytes and organic molecules. The organic molecules include bile acids, cholesterol, bilirubin, phospholipids.
- Secreted in 2 stages:
1. By Hepatocytes - bile salts, cholesterol, lechthin etc.
- By Epithelial cells of the bile duct - large watery solution of Na+ and HCO3- - its stimulated by Secretin in response to ACID in the duodenum; will neutralise acid.
Describe the pathways that the bile can take after its production
What sphincter controls the entry of the common bile duct into the duodenum?
What stimulates the release of bile from the gallbladder?
LOOK AT DIAGRAM!
- Bile is secreted by the hepatocytes, travelling down the Canaliculi in the hepatic lobule before draining into the hepatic ducts. The hepatic ducts go into the common bile duct.
The common bile duct can go directly into the duodenum OR can be diverted into the cystic duct to reach the gallbladder, where its concentrated and stored.
- Sphincter of Oddi
- Cholecystokinin (CCK) - in response to FAT in the duodenum.
What are Gallstones?
What are the 2 types of gallstones?
What causes this condition?
What are the risk factors?
Why can they lead to many other conditions?
- Abnormal condition caused by chemical imbalance in the gallbladder
- Cholesterol (80%) and Pigment (20%) stones
- • High fat diet - ↑Synthesis of Cholesterol
• Inflammation of gallbladder epithelium - changes absorptive characteristics of mucosal layer - Excessive water and bile salts absorption = cholesterol concentrates. - More common in women than men due to obesity, excess oestrogen, HRT
- Can form anywhere along the biliary tree = obstruction
How are Bile acids formed?
LOOK AT DIAGRAM!
From Cholesterol in Hepatocytes:
- Cholesterol → Cholic and Chenodeoxycholic Acids
- These bile acids are then conjugated with Glycine/Taurine to form more soluble bile acids.
- The conjugated forms are then secreted into the Canaliculi
- Exist as Bile SALTS in the intestine, where bacterial metabolism converts them into Secondary Bile acids.
What occurs in the enterohepatic circulation of bile acids?
LOOK AT DIAGRAM!
Bile acids play a role in FAT ABSORPTION.
95% of bile is reabsorbed back into the veins at the TERMINAL ILEUM (enterohepatic circulation), where it’s taken back to the liver and taken up by hepatocytes for re-secretion.
The remaining 5% of bile is lost in the faeces.
What is the physiological significance of Bile?
- Essential for fat digestion and absorption via emulsification
- Bile and pancreatic secretions neutralises gastric fluids as it enters the duodenum - helps digestive enzymes
- Role in elimination of waste products from blood e.g. Bilirubin and Cholesterol
What is Bilirubin?
- Yellow pigment formed from the breakdown of haemoglobin - has no use and is very TOXIC
Explain the process in the the formation and elimination of Bilirubin
What will be increased in the urine in hepatitis or damage to hepatopcytes?
LOOK AT DIAGRAM!
- • In phagocytes, RBCs are broken down into globin, iron, and Haem
• Haem is converted into free Bilirubin
• Bilirubin is released into plasma, bound to Albumin.
• The free Bilirubin then taken up by Hepatocytes and are conjugated with Glucuronic acid.
• The Conjugated bilirubin is secreted into bile and eliminated in faeces/urine.
In faeces, its excreted as Stercobilin - brown colour
In urine, its excreted as Urobilin and Urobilinogen - yellow colour
- Urobilin and Stercobilinogen
What is Jaundice?
What plasma [Bilirubin] will cause jaundice?
What are the 3 causes of Jaundice?
- Excessive quantities of free/conjugated Bilirubin, which accumulates in the ECF = yellow discolouration of skin, sclera, and mucosal membranes.
- Plasma [Bilirubin] > 1.5mg/dL
- Pre-hepatic:
• Excessive RBC breakdown
• Excess Free Bilirubin
- Pre-hepatic:
- Hepatic:
• Hepatocyte damage e.g. cirrhosis
• Excess conjugated/free Bilirubin - Post-hepatic:
• Excess conjugated Bilrubin
• Obstruction to passage into duodenum
• It enters the circulation and into urine - dark
CARBOHYDRATE METABOLISM:
Why is it important?
What occurs in it?
- Important in maintaining blood glucose concentration - Known as the Glucose Buffer Function
- • Glycogenesis - stimulated by Insulin
• Glycogenolysis - stimulated by Glucagon
• Gluconeogenesis
• Glycolysis - ATP formation
FAT METABOLISM:
What occurs during it in the liver?
- TG’s oxidised in hepatocytes = produce energy
- Lipoproteins made in liver
- Excess carbohydrates and proteins are converted into FA and TG’s - stored in adipose
- Synthesis of lots of cholesterol and phospholipids - some packaged as lipoproteins.
PROTEIN METABOLISM:
What occurs in it?
- Deamination & Transamination of AAs, where they’re converted into glucose and lipids
- Synthesis of non-essential AAs
- Synthesis of most plasma proteins
- Synthesis of urea - removes toxic ammonia from body
