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My Phase 1 > Liver Wrap-up > Flashcards

Liver Wrap-up Flashcards

1
Q

Describe the blood supply to the liver

A

75% from the hepatic portal vein (blood from the digestive tract and spleen to the liver)
25% from the hepatic artery (oxygenated blood from branches of the coeliac artery which comes off the aorta at T12)

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2
Q

Regions of the abdomen - where is the liver found?

A

Predominantly in the right hypochondriac region, extends into the epigastric region and into left hypochondriac region. Small part in right lumbar region.

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3
Q

What structures are visible in an anterior view of the liver?

A

Right lobe, left lobe with falciform ligament separating the two. Ligamentum teres from falciform ligament. IVC and fundus of gall bladder protruding.

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4
Q

What structures are visible in a posterior view of the liver?

A

Right lobe, left lobe, quadrate lobe, caudate lobe.
Gall bladder between quadrate lobe and right lobe. Porta hepatis: common bile duct, portal vein, hepatic artery.
Left and right triangular ligaments. Ligamentum teres.

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5
Q

Which veins come together to form the hepatic portal bein?

A

Splenic vein from the spleen
Inferior mesenteric vein from the large intestine
Superior mesenteric vein from the small intestine

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6
Q

Describe the venous drainage of the liver

A

Hepatic portal vein and hepatic artery bring blood to the liver.
Runs through the sinusoids to the central vein.
Central vein –> hepatic vein.
Hepatic vein drains into IVC

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7
Q

What are the portal triads made up of?

A

bile duct, portal vein, hepatic artery.

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8
Q

What is the direction of flow:
in the hepatic portal vein?
in the hepatic artery?
In the bile duct?

A

Blood drains towards the central vein.

Bile drains away from the central vein.

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9
Q

Microstructure of hepatic lobules:

cell types?

A

Kupffer cells = liver macrophages derived from monocytes
Ito cells = store vitamin A
Hepatocytes
Fenestrated capillaries allow easy movement of large proteins such as albumin.

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10
Q

What is the Space of Disse? Function?

A

Space between hepatocytes and sinusoids
Allows absorption of proteins and plasma components by the hepatocytes
Lymph flows through here ending in the thoracic duct

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11
Q

Lymph drainage of the liver

A

Responsible for 50% of the body’s lymphatic flow.

Thoracic duct drains into left brachiocephalic vein.

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12
Q

Liver acinus:
Zone 1 nearest to portal triads, zone 3 nearest to central vein zone 2 in between.
What are features of each zone? What differing functions take place in each zone?

A 
Zone 1:
- high in oxygen
- makes glycogen and involved in protein synthesis
Zone 2:
mix of 1 and 3
Zone 3:
- low in oxygen
- detoxification reactions, conjugation
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13
Q

List functions of the liver

A
  • detoxification and drug metabolism
  • fat metabolism
  • synthesis of plasma proteins
  • storage
  • biliary function
  • defense against infection
  • carbohydrate metabolism
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14
Q

What is meant be detoxification in the liver?

A

The conversion of lipid soluble drugs to soluble metabolites for sxretion via kidneys/biliary system.
Uses enzymes found in hepatocytes.
The activation of drugs such as aspirin.

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15
Q

Features of Phase 1 detoxification reactions in the liver

reaction types
key enzyme

A
  • non-synthetic catabolic reactions (oxidation, reduction, hydrolysis)
  • adds functional groups to prepare molecules for excretion or activation
  • activates drugs
    Microsomal enzymes such as CYP450 (key phase 1 enzyme) which carries out oxidation reactions to increase water solubility.

microsomal enzyme = located in the ER

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16
Q

Features of Phase 2 detoxification reactions

A
  • Synthetic anabolic reactions such as glucuronidation and sulphation
  • catalysed by transferases (non-microsomal enzymes - act elsewhere than ER)
  • for drugs that are already activated and prepares them to be eliminates
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17
Q

What are 3 alternative routes by which drugs can be metabolised?

A
  1. Elimination: usually polar drugs, excreted unchanged
  2. Straight to phase 2 then eliminated, drugs which are already activated so dont need to be functionalised by phase 1
  3. Enters Phase 1 to be activated, then cleared in phase 2 before elimination.
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18
Q

Give an example of a drug which is eliminated via a Phase 2 reaction only. Why is this possible?

A

Paracetamol: already activated on administration so only undergoes clearance by phase 2 reaction before being eliminated.

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19
Q

Give an example of a drug that takes part in a phase 1 reaction and a phase 2 reaction before elimination

A

Asirin: activated in phase 1 to salicyclic acid (active agent) before entering phase 2 to be cleared and eliminated.

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20
Q

How is nitrogen balance controlled in the body?

A

Proteins digested in the small intestine.
This increases ammonia levels (toxic)
Ammonia is absorbed in the venous system and transported to the liver mitochondria where it is converted to urea in the ornithine cycle.
3 ATP required.

21
Q

Describe the key steps of the ornithine cycle

A

carbon dioxide and ammonium combine to form carbamoyl physphate which enters the ornithine cycle:

  • it comines with ornithine to form citrulline.
  • citrulline converted to argininosuccinate.
  • argininosuccinate is converted to arginine.
  • arginine splits into urea (EXCRETED) ornithine (allows cycle to continue - combines with carbamoyl phosphate)

Takes place in mitochondria in liver.
3ATP required per cycle.

22
Q

The liver is involved in the storage of which molecules?

A
  • fat soluble vitamins: ADEK and B12
  • iron as ferritin
  • storage of energy as glycogen and triglycerides
23
Q

what is the role of the liver in plasma protein synthesis?

A

synthesises:

  • albumin (maintains oncotic pressure)
  • all clotting factors except Von Willebrand factor
  • complement factors
  • Vitamin K dependent factors (10, 9 , 7 and 2)
24
Q

Described the basic steps involved in fat metabolism

A
  1. Fat digested
  2. Emulsified by bile salts
  3. Intestinal lipases breakdown triacylglycerides
  4. Micelle formation
  5. Absorbed in the small intestine
  6. Triacyleglycerides are transported via lymphatics as chylomicrons
  7. Converted to free fatty acids and glycerol
  8. Absorbed by tissues and oxidised as fuel or reesterified for storage
25
Q

How is cholesterol synthesised and used in the body?

A
  • synthesised in liver and obtained from diet

- used to make steroid hormones, bile salts, vitamin D

26
Q

What are 2 pathways involved in the fasting metabolism of fats?

A
  • lipolysis

- ketogenesis

27
Q

Describe the steps involved in lipolysis?

A
  1. Adipose tissues broken down
    triglyceride –> fatty acid + glycerol
  2. Glycerol taken up by the liver to undergo gluconeogenesis
  3. Fatty acids used as an energy source
28
Q

Describe the steps involved in ketogenesis

A
  • free fatty acids are converted in the liver to acetyl-CoA
  • too much acetyl-CoA is formed to enter the Kreb’s cycle
  • these form ketones which are used for energy: e.g. acetone, acetoacetate, beta-hydroxybutyric acid
29
Q

Describe the biliary tree

A

Left and right hepatic ducts join to form the common hepatic duct.
This joins the cystic duct from the gall bladder to form the common bile duct,
The pancreatic duct joins.
Empties into the duodenum (2nd portion) through the Ampulla of Vater via the sphincter of Oddi.

30
Q

Function of the gall bladder

A
  • concentrates and stores bile acid: epthelium absorbs water

- when stimulates, bile released into the 2nd part of the duodenum via the sphincter of Oddi

31
Q

Histology of the gall bladder

A

simple columnar epithelium

32
Q

Composition of bile

A
  • bile acids
  • water and electrolyte
  • lecithin
  • cholesterol
  • pigments (bilirubin)
33
Q

What is the role of bile salts?

A
  • emulsification of fats

- excretion of the products of detoxification from the liver

34
Q

Describe the action of bile in fat metabolism

A
  • food in duodenum
  • CCK released from enteroendocrine cells
  • contraction of the gall bladder
  • bile enters dueodenum
  • fat emulsification
  • micelle formation
  • micelles absorbed by the intestinal epithelia
  • transport to cells
35
Q

Describe the basic anatomy of the pancreas

A

4 main parts: head, neck, body and tail

Head is made up of the head proper and the uncinate process.

36
Q

Define endocrine

A

hormones secreted directly unto the circulatory system

37
Q

define exxocrine

A

release of hormones via ducts onto epithelial surface

38
Q

describe the exocrine pancreas

  • cell types
A
  • accounts for 90% of pancreas mass
  • ducts are lined by simple cuboidal epithelium
  • acinar cells produce enzymes such as amylase and lipase, stored until activation by duodenum
  • centrilobular cells have mucin + HCO3-
  • apical cells have pro-enzymes (enzymes secreted in inactive form)
39
Q

How is the exocrine function of the pancreas stimulated?

A
  • Presence of fats in the duodenum stimulates CCK release by enteroendocrine cells
  • CCK stimulates apical cell pro-enzyme secretion
  • acid in duodenum stimulates release of secretin by S cells.
  • secretin stimulates secretion of mucin/ HCO3- by centrilobular cells
40
Q

What cells are involved in the endocrine pancreas?

A

Islets of Langerhans
Beta cells release insulin
Alpha cells release glucagon
Delta cells release somatostatin

41
Q

What hormone(s) decrease plasma glucose?

A

insulin

42
Q

What hormone(s) increase plasma glucose?

A

glucagon
adrenaline
cortisol
growth hormone

43
Q

What processes increase plasma glucose?

A

Release of glucagon from alpha cells of the pancreas

  • increase in gluconeogenesis and glycogenolysis
  • less fat uptake
  • fasting state (low insulin) leads to gluconeogenesis and lypolysis - free fatty acids are taken up and utilised as energy
44
Q

What processes decrease plasma glucose?

A
  • release of insulin from beta cells of the pancreas
  • increases glucose uptake from blood by tussies, inhibits gluconeogenesis and glygogenolysis: formation of glycogen stimulated
  • post prandial state (high insulin): 40% of glucose goes to the liver where it is converted to glycogen and hepatic glucose production is suppressed
    60% glucose goes to peripheries where lipolysis is repressed and glycogen stores are replenished
45
Q

Key points in liver embryology

A

3rd week: liver bud appears as an endodermal out growth from the distal part of the foregut
But proliferates as epithelial liver cord and penetrates central mesentery.

46
Q

Describe the basic embryology of the gall bladder

A

Connection between liver diverticulum and dueodenum narrows forming the bile duct.
Small central outgrowth develops from the duct forming the gall bladder and cystic duct.
Bile is produced from the age of 12 weeks.

47
Q

When does bile start being produced in the embryo?

A

from 12 weeks

48
Q

Describe the basic embryology of the pancreas

A
  • retroperitoneal structure
  • forms from the endodermal lining of the duodenum as dorsal and ventral buds
  • ventral bud develops into ucinate process and inferior part of the head
  • dorsal bud = rest of pancreas
    Duct system:
    Ducts of ventral and dorsal part fuse with each other
    Dorsal= Accessory pancreatic duct
    Main pancreatic ducts= dorsal and ventral buds

My Phase 1 (14 decks)

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