GI 4 Flashcards
1
Q
A
2
Q
What is the function of the porta hepatis?
A
- 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
3
Q
Describe the ducts going to the duodenum
A
- 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
4
Q
Describe the dual blood supply of the liver
A
- 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
5
Q
What are the cell types of the liver?
A
- 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)
6
Q
What is contained in a liver lobule?
A
- 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
7
Q
How does the liver process sugars?
A
- 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)
8
Q
What is different about glycogen in skeletal muscle?
A
- 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
9
Q
How does the liver process amino acids?
A
- 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)
10
Q
How are fats processed by the liver?
A
- 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)
11
Q
How are fat soluble vitamins processed?
A
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)
12
Q
How is the liver involved in protein synthesis?
A
- 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)
13
Q
How does the liver detoxify drugs?
A
- 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
14
Q
What is the liver’s role in storage of iron?
A
- 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
15
Q
What is the liver’s role in fighting microbes?
A
- 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)
17
Q
A
D
18
Q
What is the gall bladder?
A
- 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
19
Q
How is bile secretion stimulated?
A
