Lectures 17 & 18 - GI Pathophysiology III & IV Flashcards
What is the largest organ in the body?
Liver
Blood supply of liver?
- Hepatic artery
2. Portal vein
O2 saturation in the portal vein?
60-70%
Functional unit of the liver?
Lobule
Shape of lobule?
Cylindrical
Number of lobules in liver?
50,000 - 100,000
Describe the organization of a liver lobule.
- Organized around a central vein that empties into the hepatic vein, and then to the vena cava
- Terminal bile ducts (from caniculi) and small branches of the portal vein and hepatic artery are located in the periphery
Can liver lobules be regenerated?
YUP
Lining of blood supply in liver lobule?
Less than 2 hepatocytes thick
What are Kupffer cells?
Cells between endothelial cells (incorporated into lining) of liver sinusoids that are resident macrophages for surveillance and response and play a large role in the recycling of RBCs
Other name for Kupffer cells?
Stellate macrophages
What are stellate cells?
Cells between endothelial cells and hepatocytes that store lipids and vitamin A as retinyl esters and are fibrotic (make collagen and ECM when activated)
What % weight of the liver to the stellate cells comprise?
5%
When do stellate cells lay down fibrotic tissue? Consequences?
When they go from quiescent state to activated
Consequences:
- Diffusion of nutrients from liver sinusoids to hepatocytes is impaired
- Increased pressure in liver sinusoids and veins => damage to hepatocytes
7 functions of liver?
- Regulation of carbohydrate, lipid, and protein metabolism
- Regulation of cholesterol production
- β-oxidation of fatty acids
- Endocrine functions: secretion of angiotensinogen and insulin-like growth factor 1 (IGF1), steroid hormone metabolism
- Detoxification
- Vitamin and iron storage
- Bile production
What do the half-lives of steroid hormones depend on? What does this mean?
Liver function
The plasma levels of these hormones increase when the liver fails
Purpose of bile?
Critical for transport of lipids through the unstirred water layer to the enterocytes
What does bile contain?
- Water
- Bile salts
- Bilirubin
- Cholesterol
- Others
What is cholestasis?
Decrease in bile flow through the intrahepatic canaliculi causing materials normally transferred to the bile (bilirubin, cholesterol, and bile acids) to accumulate in the blood
Symptoms of cholestasis? Which is most common?
- ***Pruritus
- Skin xanthomas
- Nutritional deficiencies of fat-soluble vitamins: A, D, K
What does pruritus mean?
Itching of the skin due to high cholesterol
What are skin xanthomas?
Fatty growths underneath the skin
What happens to the bilirubin once it is transported by albumin to the liver?
Conjugated by liver => secreted in bile => gallbladder => small intestine => conjugated bilirubin turned into urobilinogen => excreted in feces (mainly) and reabsorbed to be placed into bile again or excreted by the kidneys
What is jaundice? 4 causes?
Abnormally high accumulation of bilirubin in the blood
Causes:
PREHEPATIC JAUNDICE
1. Excessive hemolysis (destruction of RBCs)
INTRAHEPATIC JAUNDICE
2. Impaired uptake of bilirubin by the liver
3. Decreased conjugation of bilirubin
POSTHEPATIC JAUNDICE
4. Obstruction of bile flow between liver and intestine
5 common causes of prehepatic jaundice?
- Hemolytic blood transfusion
- Sickle cell anemia
- Hemolytic disease of newborn
- Autoimmune hemolytic anemia
- Dyserythropoiesis
3 common causes of intrahepatic jaundice?
- Hepatitis
- Cirrhosis
- Cancer of the liver
3 common causes of posthepatic jaundice?
- Strictures of the bile duct
- Gallstones
- Tumors of the bile duct or near the bile duct (e.g. pancreatic cancer, duodenal cancer)
How to tell the difference between pre/intra and posthepatic jaundice?
Increase in conjugated bilirubin levels will be seen in POSThepatic jaundice ONLY
2 types of hemolytic disease of newborn?
- Normal: immature hepatocytes and short RBC half-life
- Abnormal: newborn blood type is different from mother’s blood type (especially Rh difference) and the birth process causes many maternal antibodies to enter the newborn’s bloodstream
3 types of portal HT?
- Prehepatic
- Posthepatic
- Intrahepatic
Referring to the liver lobulues
How to treat newborn’s that have a different Rh blood type than their mother?
Mother is given Rhogam: purified antibody against Rh positive that binds Rh parts of fetal RBCs that passes the placenta and targets them for destruction so that maternal immune surveillance does not get involved
3 effects of portal HT?
- Splenomegaly
- Ascites
- Portosystemic shunts
What is dyserythropoiesis?
The production of inappropriate RBCs in the bone marrow, which get destroyed
2 examples of prehepatic portal HT?
- Emboli/thrombus in the portal circulation
2. Tumors in GIT putting pressure on the portal circulation
3 examples of intrahepatic portal HT?
- Hepatitis
- Cirrhosis
- Cancer of the liver
Example of posthepatic portal HT?
Heart failure (especially right heart failure)
What are ascites? How do they form?
Accumulation of fluid in the peritoneal cavity
Decrease liver function leads to:
1. Portal hypertension => pooling of blood and lymph in liver sinusoids => increased hydrostatic pressure =>
- Decreased albumin production => decreased oncotic pressure =>
- Decreased aldosterone metabolism => increased Na and H2O kidney reabsorption => increased BP => increased hydrostatic pressure =>
=> increased transudation of fluid AND proteins from the plasma and space of Disse into peritoneal cavity
What type of portal HT causes ascites mainly?
Intrahepatic portal HT
What are the 6 portosystemic shunts and what do they lead to in portal HT?
- Lower esophagus: esophageal branches of left gastric vein and azygos veins => esophageal varices
- Upper anal canal: superior rectal vein and middle/inferior rectal veins => internal hemorrhoids
- Umbilical: veins of the ligamentum teres and superor/inferior epigastric veins => caput medusa
- Bare area of the liver: hepatic veins and inferior phrenic veins
- Patent ductus venosus: left portal vein and IVC
- Retroperitoneal: colonic veins and body wall veins
Why are esophageal varices dangerous?
High venous pressure inside the esophagus, so they can rupture, which can cause significant hemorrhaging => life threatening
What % of hepatic tissue is required for the liver to remain functional?
10%
5 effects of liver failure?
- Hematologic disorders
- Endocrine disorders
- Skin disorders
- Hepatorenal syndrome
- Hepatic encephalopathy
What are 3 hematologic disorders caused by liver failure? Explain each.
- Anemia due to lack of iron and fat-soluble vitamins necessary for the production of RBCs
- Thrombocytopenia due to lack of iron and fat-soluble vitamins necessary for the production of RBCs
- Coagulation defects due to lack of coagulation factors produced by the liver and vitamin K deficiency
What endocrine disorders are caused by liver failure? Explain each.
- Decrease in sex hormone metabolism => disturbances in gonadal function:
- Women: menstrual irregularities (amenorrhea), loss of libido, and sterility
- Men: testicular atrophy, loss of libido, impotence, and gynocomastia - Decrease in aldosterone metabolism:
- Increase in salt and water retention
- Hypokalemia
What is thrombocytopenia?
Low platelet count
3 skin disorders caused by liver failure? Explain each.
- Jaundice
- Vascular spiders: incompetent valves in epidermal arteries and veins due to high estrogen levels causing dilation
- Palmar erythema: red hot palms due to high levels of estrogen causing increased blood flow
Other name for vascular spiders?
Vascular nevi
In what other patients (other than liver failure) are vascular spiders and palmar erythema seen?
Patients with high estrogen levels:
- Estrogen-secreting tumor
- PCOS
- Pregnancy