liver

Question 1

What separates the right and left lobes of the lung?

Answer 1

the falciform ligament

Question 2

The liver receives dual blood supply from which two arteries?

Answer 2

hepatic artery and the hepatic portal vein (blood from he gut)

NOTE: hepatic portal vein is the main supply

Question 3

What is the drainage system of the liver?

Answer 3

each segment has its own drainage which drain into the left, middle and right hepatic veins before joining the vena cava

Question 4

What is a hepatic lobule?

Describe its structure

Answer 4

a structural unit of liver tissue that is hexagonal

each corner of the hexagon has a portal triad (that links it 3 adjacent lobules)
at the centre of the lobule is a central vein, which. collects blood draining from the hepatic sinusoids

within the lobule, there are a row of hepatocytes with each hepatocyte having a sinusoid facing and a bile canaliculi-facing side

Question 5

Describe the portal triad

Answer 5

consist of mainly 3 conduit vessels/ducts

• a branch of the hepatic portal vein
• a branch of the hepatic artery
• a bile duct

Question 6

Describe the branch of the hepatic portal vein in the portal triad

Answer 6

contain mixed venous blood from the GI organs and the spleen
it is rich in raw nutrients, bacteria, toxins and waste products

the hepatocytes can process nutrients, detoxify the blood and excrete waste substances before returning back to the circulation

Question 7

Describe the branch of the hepatic artery in the portal triad

Answer 7

brings oxygen rich blood to support the hepatocytes high energy demands

Question 8

Describe the bile duct present in the portal triad

Answer 8

bile is produced by the hepatocytes and drains into bile canaliculi, which coalesce with the cholangiocyte-lined bile ducts located around the lobule perimeter

Question 9

What is the direction of blood and bile flow in the the lobule?

Answer 9

blood flows towards the centre of the lobule

bile flows towards the perimeter

Question 10

What is a hepatic acinus?

Answer 10

(a functional unit of the liver - it is harder to define anatomically than the hepatic lobule)
it consists of 2 adjacent 1/6 lobules that share 2 portal triads and extend as far into the lobule as the central veins

Question 11

What s the three-zone model?

Answer 11

the acinus can be split into 3 regions based on timing of exposure tiptoe blood vessels and its contents
zone 1 - oxygen = high, toxin risk = high
zone 2 - oxygen = medium, toxic risk = medium
zone 3 - oxygen = low, toxic risk = low

Question 12

Describe the supply of the blood to the liver

Answer 12

principle source is the the haptic portal vein (which contains mixed venous blood)
since this is MV blood, there is a hepatic artery, which has highly oxygenated blood (to increase the partial pressure)

Question 13

What are the branches of the portal vein?

Answer 13

sinusoids
NOTE: the hepatic arteriole branches also join this
sider then normal - so blood flows slower
leaky - so plasm can leak out

Question 14

Describe the endothelial cells of the liver

Answer 14

fenestrated, discontinuous epithelium
very leaky
no basement membrane

Question 15

Describe the Kuppfer cells of the liver

Answer 15

sinusoidal macrophage cells - detoxify substances from the portal circulation
adhere to the endothelial cells
stellate shaped

Question 16

Describe the hepatic stellate cells of the liver

Answer 16

are perisinusoidal (between sinusoid and hepatocytes)
exist in the quiescent state
they act as a storage for Vit A
activated in response to liver damage and Kuppfer cells
when activated —–> fibroblasts

Question 17

Describe the cholangiocytes of the liver

Answer 17

line the bile ducts

secrete bicarbonate and water to form bile

Question 18

What is the biliary tree?

Answer 18

describes the anatomical structures that are responsible for the transit and storage of bile

Question 19

Give the hierarchy/drainage of the biliary tree

Answer 19

starts with millions of bile cannaliculi —–> small ductules —–> small bile ducts —–> larger bile ducts —–> left/right hepatic ducts —–> common hepatic duct
common hepatic duct + cystic duct = common bile duct (extends towards duodenum)
joins pancreatic duct —–> ampulla of Vader, which opens up into the medial wall of the duodenum at the duodenal papilla

Question 20

What are the functions of the bile?

Answer 20

Cholesterol homeostasis
Abdorption and digestion (lipid and lipid-soluble vitamines-ADEK)
Toxin excretion

Question 21

Where is the bile produced?

Answer 21

primarily in the hepatocytes but also in the cholangiocytes, when it is drained into the bile cucts

Question 22

What are the 2 acids that are secreted into the bile?

Answer 22

chalice acid and chenodeoxycholic acid

Question 23

What happens to the bile salts as it gets to the end of the GI system?

Answer 23

95% is reabsorbed in the terminal ileum

5% excreted in the faeces

Question 24

Why does is the bile not secreted into the duodenum straight away, but into the gall bladder?

Answer 24

sphincter of oddi is closed so it goes into the cystic duct

Question 25

What is the enterohepatic circulation?

Answer 25

how substances can cycle between the liver and the gut by continuous reabsorption