GI 4

Question 1

Answer 1

Question 2

What is the function of the porta hepatis?

Answer 2

• lots of things going into and coming out of the liver
• hepatic portal vein delivering nutrient rich but oxygen poor blood
• hepatic artery comes off of celiac trunk
• bile ducts

Question 3

Describe the ducts going to the duodenum

Answer 3

• right and left hepatic ducts collect secretions of hepatocytes and send it into the common hepatic duct
• between meals, the bile can go into the cystic duct because the sphincter at duodenum would be closed
• when the sphincter opens, bile flows from the liver and gall bladder
• pancreatic duct joins common bile duct and forms the hepatopancreatic ampulla

Question 4

Describe the dual blood supply of the liver

Answer 4

• hepatic portal vein brings nutrient full but deoxygenated blood into the liver
• mixes with proper hepatic artery which is oxygenated blood
• forms a capillary bed and is drained away by hepatic veins to inferior vena cava

Question 5

What are the cell types of the liver?

Answer 5

• hepatocytes (primary): synthesis, storage, detoxification, metabolism
• kupffer cells: phagocytosis of microbes, cytokine production, recycle heme (one component that is toxic which will turned to bilirubin and it will be excreted)
• have liver sinusoids which are large capillary beds with spaces between the ECs and incomplete basement membrane where macrophages hang out (80% of all macrophages reside here)
• sinusoid endothelial cells (liver hepatocytes make most proteins in circulation which are big so they need this big gap)

Question 6

What is contained in a liver lobule?

Answer 6

• each side of the 6-sided shape will have duct work (arteriole, venule, and bile duct- portal triad)
• central vein; portal vein and hepatic artery drain into here
• blood moves from central vein to hepatic veins
• bile canaliculi move bile away to edges of lobule where it is collected in bile duct

Question 7

How does the liver process sugars?

Answer 7

• liver stores glucose from dietary sources as glycogen
• monosaccharide glucose –> polysaccharide glycogen
• if you just stored glucose, it has a high osmotic drive so it would bring water inside the hepatocyte
• can provide 1-2 days worth of glucose as glycogen (in between meals your liver will slowly release this into circulation- central nervous system can not store glucose so it needs it in circulation to stay running)
• liver can convert glucose into FAs or triglycerides
• liver can convert galactose and fructose to glucose
• liver can create new glucose: gluconeogenesis created from lactic acid, pyruvate, and amino acids (process makes ketones and other waste products), glycogenolysis (breaking up glycogen into glucose)

Question 8

What is different about glycogen in skeletal muscle?

Answer 8

• glycogen formed in skeletal muscle too
• when skeletal muscle puts glycogen away, when it breaks it down it can’t pass plasma membrane
• possessive of its glucose

Question 9

How does the liver process amino acids?

Answer 9

• essential amino acids are used for protein synthesis (eg. albumin, fibrinogen, etc.)
• liver also converts toxic ammonia to urea which can be excreted by kidneys
• ammonia is being produced during breakdown of amino acids for energy purposes (ATP production)

Question 10

How are fats processed by the liver?

Answer 10

• liver packages fatty acids into forms that can be transported or stored (lipoproteins)
• VLDL: to be delivered to adipocytes
• LDL: to transport cholesterol to tissues (starts to accumulate under ECs if you have too much, starts inflammation in BV because macrophage tries to attack it, causes atherosclerosis)
• many hormones are made from cholesterol so we need it for that, if we didn’t have cholesterol in plasma membranes the phospholipids would be solid rather than being more fluid
• HDL: returns excess cholesterol to liver (catabolized and secreted in bile salts)

Question 11

How are fat soluble vitamins processed?

Answer 11

Vitamin A: stored in hepatic stellate cells, converted to retinyl esters, used for vision, important for signalling with rods

Vitamin D: utilized in bone metabolism, communicates with duodenum where calcium is absorbed, can be synthesized through UV light

Vitamin E: antioxidant (scavenges free radicals)

Vitamin K: utlized by hepatocytes to form functional coagulation factors (prothrombin, VII, IX, X)

Question 12

How is the liver involved in protein synthesis?

Answer 12

• liver synthesizes most of the plasma proteins
• albumin: colloid osmotic pressure (don’t cross capillary bed), binds hormones, cations, bilirubin, drugs (if you take a drug that wants to bind to albumin with another that also wants to bind on albumin they start displacing each other- free circulating amount is why you get tissue effects so you can get levels that are too high)
• coagulation factors
• alpha and beta globulins: alpha globulins (antitrypsin), beta globulins (thyroxine-binding globulin, angiotensinogen)

Question 13

How does the liver detoxify drugs?

Answer 13

• most drugs pass through the liver
• excreted in bile, inactivated or converted into a form that the kidneys can excrete
• can also alter/excrete thyroid and steroid hormones

Question 14

What is the liver’s role in storage of iron?

Answer 14

• the liver stores about 10% of iron via ferritin
• iron is a 3+ cation which will react with DNA and cause damage to cells so it can’t be free floating
• in the liver, it is stuck on ferritin to store it temporarily in liver
• iron is moved from ferritin to transferrin to get to the bone marrow to make new RBCs
• heme from damaged RBCs returns to liver where iron is scavenged and the heme discarded as billirubin through bile to feces
• accumulation of billirubin= jaundice

Question 15

What is the liver’s role in fighting microbes?

Answer 15

• 80% of body’s macrophages (Kupffer cells) reside in the liver; phagocytose bacteria/toxins anddamaged RBCs and WBCs, produce buckets of cytokines
• also houses NKCs (control viral infections, control of atypical cells)

Question 16

What is bile?

Answer 16

• bile is essential for: lipid digestion & absorption, cholesterol metabolism, excretion of lipid-soluble drugs
• bile is composed of bile acids (salts) for emulsification, cholesterol, bilirubin, electrolytes
• bile is concentrated and stored in the gall bladder until needed
• recycled by the ileum

Question 17

Answer 17

D

Question 18

What is the gall bladder?

Answer 18

• thin green sack that is mostly muscle
• bile is concentrated and stored until needed
• if bile sits too long, it will be dehydrated which makes precipitate
• removal of gall bladder leads to expansion of the extrahepatic bile ducts
• bile is released in response to: parasympathetic stimulation, CCK

Question 19

How is bile secretion stimulated?

Answer 19