S8) The Liver

Question 1

Describe the hepatic portal system

Answer 1

The hepatic portal circulatory system involves blood passing through two sets of smaller vessels before returning to the heart

Question 2

Identify 6 types of substances which travel to the portal vein

Answer 2

• Water
• Water soluble vitamins
• Electrolytes
• Carbohydrates e.g. glucose, galactose, fructose
• Proteins e.g. amino acids, dipeptides, tripeptides
• Toxins e.g. ammonia, chemicals, pathogens

Question 3

Identify 2 types of substance which do not travel through the portal vein

Answer 3

• Lipids
• Fat soluble vitamins (ADEK)

Question 4

What are dietary lipids?

Answer 4

Dietary lipids are mostly triglycerides, cholesterol and phospholipids

Question 5

How are lipids absorbed?

Answer 5

• Lipids are digested by lipases
• Lipids are taken into the cells and processed into chylomicrons
• Chylomicrons are taken up by lacteals

Question 6

Identify the 5 major functions of the liver

Answer 6

• Storage
• Anabolism
• Catabolism
• Exocrine secretion
• Endocrine secretion

Question 7

Identify 3 substances which are stored by the liver

Answer 7

• Iron
• Glycogen
• Vitamins

Question 8

Identify 3 substances which are produced by the liver

Answer 8

• Albumin
• Glycogen
• Coagulation factors

Question 9

Identify 3 substances which are broken down by the liver

Answer 9

• Drugs
• Hormones
• Haemoglobin

Question 10

Identify an exocrine secretion of the liver

Answer 10

Bile via bile duct

Question 11

Identify 3 substances which are secreted by the liver into the blood

Answer 11

• Angiotensinogen
• Thrombopoietin
• IGF-1

Question 12

Hepatocytes constitute 80% of the liver cell population and can regenerate.

Describe 6 other unique features of hepatocytes

Answer 12

• Numerous mitochondria
• Numerous peroxisomes (full of oxidising agents)
• Numerous free ribosomes
• Numerous rough and smooth ER
• Numerous Golgi complexes
• Glycogen deposits

Question 13

What are Kupffer cells and what do they do?

Answer 13

• Kupffer cells are monocyte derived specialist macrophages that form part of the lining of the sinusoids.
• They patrol the sinusoids, recycling old red blood cells and ingesting pathogens

Question 14

What is a sinusoid and what is unique about its structure?

Answer 14

• A sinusoid is an irregular tubular space for the passage of blood in the liver, spleen and bone marrow
• Its endothelium is perforated with large holes, allowing Kupffer cells to migrate into liver tissue at sites of inflammation and damage

Question 15

What are stellate cells?

Answer 15

Stellate cells are liver cells which are full of cytoplasmic vacuoles containing Vitamin A

Question 16

In three steps, describe what happens to stellate cells during liver cirrhosis?

Answer 16

⇒ Differentiate into myofibroblasts

⇒ Synthesise and deposit collagen within the perisinusoidal space, resulting in liver fibrosis

⇒ The collagen surrounds and constricts the portal vein, leading to portal hypertension

Question 17

Where do lymphatic vessels rise and drain in the liver?

Answer 17

Lymphatics arise from the periportal space of Mall and drain to the liver hilum and then into the hepatic duct