Liver Structure and Function

Question 1

1. T/F: Liver is the largest organ in the body weighing 1.4kg.
2. Where is it located?
3. Name it’s major and minor lobes.

Answer 1

1. True
2. Upper right quadrant of abdomen (tucked against inferior surface if diaphragm)
3. Two major lobes: right > left. 2 minor lobes: caudate & quadrate

Question 2

Where do blood and lymphatic vessels, ducts & nerves (hepatic nerve plexus) enter/exit?

Answer 2

Porta on inferior surface

Question 3

What is found in the centre of each lobule?

Answer 3

Central veins that drain into hepatic veins which then drains into IVC.

Question 4

What radiates out from central veins (like spokes of wheel)?

Answer 4

Hepatic cords

Question 5

1. What are hepatic cords composed of?
2. What lies between cells within each cord?
3. What are the spaces between hepatic cords called?

Answer 5

1. Hepatocytes (functional cells of liver)
2. Bile canaliculus (cleft-like lumen)
3. Hepatic sinusoids (blood channels)

Question 6

What is a portal triad and where is located?

Answer 6

Triad consist of hepatic portal vein, hepatic artery, hepatic duct. Located at each corner of hexagonal lobule (also nerves & lymph vessels).

Question 7

What is the function of liver?

Answer 7

Alimentary role of liver = production & secretion of bile.

Question 8

1. What are the 6 components of bile?

2. T/F: all of the 6 components are secreted by hepatocytes.

Answer 8

1. Bile acids, lecithin, cholesterol (synthesised in liver, soluble fat). Bile pigments (bilirubin from Hb). Toxic metals (detoxified in liver). Bicarbonate (neutralisation of acid chyme).
2. No, only 1-5 are. bicarbonate is secreted by duct cells.

Question 9

What are bile pigments?

Answer 9

Breakdown products of Hb from old/damaged erythrocytes.

Question 10

Where is bilirubin (predominant bile pigment) extracted from and secreted into?

Answer 10

Extracted from blood by hepatocytes & secreted into bile (yellow bile)

Question 11

Bilirubin is yellow but why does your poo look brown?

Answer 11

Looks brown because it is modified by bacterial enzymes.

Question 12

Why is urine yellow?

Answer 12

Reabsorbed bilirubin (yellow) excreted in urine.

Question 13

Bile acids are synthesised where and from what?

Answer 13

In liver from cholesterol (0.5g/day excreted (that’s 5% of total production)).

Question 14

Before secretion bile acids are conjugated with what to form what and why?

Answer 14

Glycine or taurine to form bile salts that increases solubility.

Question 15

How are secreted bile salts recycled?

Answer 15

Via enterohepatic circulation. Liver to bile duct to duodenum to ileum to hepatic portal vein to liver etc..

Question 16

What is found on the inferior surface of liver?

Answer 16

Gallbladder

Question 17

Describe the layers of gallbladder wall.

Answer 17

Mucosa (folded into rugae which can expand). Muscularis made of smooth muscle that produces contraction. Serosa (connective tissue).

Question 18

What drains gallbladder?

Answer 18

Cystic duct which then drains into common bile duct.

Question 19

How is bile secretion reduced/stopped?

Answer 19

Sphincter of Oddi: controls release of bile & pancreatic juice into duodenum. When contracted (closed), bile forced back into gallbladder.

Question 20

How is bile secretion increased/stimulated?

Answer 20

Fat in duodenum stimulates release of CCK which then relaxes sphincter of Oddi & makes gallbladder contracts. So, bile is discharged into duodenum where it solubilises fat. CCK stimulates secretion of bile & pancreatic enzyme.

Question 21

What is the function of gallbladder?

Answer 21

Concentrates bile 5-20 times (absorbs Na+ & H2O).

Question 22

Liver covered by connective tissue capsule and visceral peritoneum except for?

Answer 22

Bare area (small area on diaphragmatic surface surrounded by coronary ligament)

Question 23

What follows septa throughout liver and what does it divide liver into?

Answer 23

At the porta, there is a connective tissue branching through the liver, which is called septa (used for support). Vessels, ducts and nerves follow septa throughout liver.
Septa divide liver into hexagonal lobules

Question 24

Outline how blood from alimentary canal flow.

Answer 24

From alimentary canal, O2-depleted/nutrient-rich blood flows into hepatic portal vein which together with O2-rich/nutrient-depleted blood (to oxygenate hepatocytes) from hepatic artery drains into hepatic sinusoids which either drains into central veins > hepatic veins > IVC. Or Hepatic sinusoids <> hepatocytes > canaliculi > hepatic ducts.