Liver

Question 1

Name the major vessels of the portal system

Answer 1

Superior Mesenteric Vein (deoxygenated blood from small intestine, leads into portal vein)
Inferior Mesenteric Vein (deoxygenated blood from large intestine, leads into portal vein)
Splenic vein
Portal vein (deoxygenated blood to liver)
Coaliac trunk (blood from aorta, splits into…..)
Splenic artery
Hepatic artery (oxygenated blood to liver)

Question 2

How much bile is produced per day?

Answer 2

1 litre

Question 3

What is a portal system?

Answer 3

• Two capillary systems in series. Blood from the first set of capillaries collects in portal vessels which then begin to branch again to supply a capillary network to a second location before entering a series of veins which will lead to the heart. There are two such systems in humans
– Hepatic portal system
– Hypothalamo-hypophyseal portal system

Question 4

Where are the 2 capillary beds of the hepatic portal system located?

Answer 4

1: stomach and intestine - nutrients and toxins absorbed
2: liver cells - nutrients and toxins leave

Connected by the hepatic portal vein

Question 5

What is in the hepatic portal vein?

Answer 5

• Water
• Water soluble vitamins
• Electrolytes including sodium, potassium, chloride, bicarbonate, calcium, magnesium, iron
• Carbohydrates
– Glucose, galactose and fructose
• Proteins
– Amino acids, dipeptides and tripeptides
• Intestinal hormones, particularly pancreatic hormones
• Toxins, including ammonia

Question 6

What does the liver convert ammonia into?

Answer 6

Urea via the ornithine cycle

Urea is then excreted in the urine

Question 7

What is not travelling in the portal vein?

Answer 7

• Lipids
– Dietary lipid is mostly triglycerides, cholesterol and phospholipids
– Digested by lipases, this process needs bile acids to form micelles
– Lipids are taken into the cells and processed into chylomicrons
– Chylomicrons are taken up by lymphatics, called lacteals. Lacteals contain chyle

Question 8

What are lacteals?

Answer 8

These specialised lymphatic vessels drain into the abdominal lymphatics that then drain into the thoracic duct which joins the venous system at the junction of the left internal jugular vein and subclavian vein. The chylomicrons can then enter the liver via the hepatic artery

Question 9

Which vitamins are fat soluble?

Answer 9

A D E & K

Question 10

Name some functions of the liver

Answer 10

Metabolism 
Storage
Detoxification
Bile production 
Exocrine
Endocrine

Question 11

What is stored in the liver?

Answer 11

Iron
Vitamin A
Vitamin B12
Vitamin D
Vitamin K
Glycogen

Question 12

What is produced in the liver (anabolic function)?

Answer 12

Plasma proteins e.h. Albumin, Numerous coagulation factors, Cu, circulating lipoproteins
Complement components of the immune system
Haematopoiesis in foetus (can be revived in adult if bone marrow failing)
Glycogen

Question 13

What is catabolised in the liver?

Answer 13

• Drugs (cytochrome P450)
• Hormones
• Haemoglobin
• Poisons (cytochrome P450)
• Can take over removal of aged red cells after splenectomy

Cytochrome p450 - a family of chemicals containing isoenzymes which are located in the SER of several tissues

Question 14

What is involved in the filtering function of the liver?

Answer 14

Kupffer cells (macrophages)

Question 15

Describe the exocrine function of the liver

Answer 15

Bile is an exocrine secretion of the liver

Question 16

Describe the endocrine function of the liver?

Answer 16

• It produces
– Angiotensinogen
– Thrombopoetin
– Insulin like growth factor 1 (IGF-1)

• It modifies to active forms
– Vitamin D
– Thyroxine

• It breaks down
– Insulin
– Glucagon
– Oestrogen and progesterone

Question 17

What do hepatocytes contain2

Answer 17

• Constitute 80% of liver cell population
• Can regenerate remarkably!
• Compared to other cells contain

– Numerous mitochondria
– A lot of peroxisomes (organelles full of oxidising agents)
– Numerous free ribosomes
– A lot of rough endoplasmic reticulum
– A lot of smooth endoplasmic reticulum
– Numerous Golgi complexes
– Glycogen deposits

Question 18

What is a sinusoid?

Answer 18

A sinusoid is an irregular tubular space for the passage of blood, taking the place of capillaries and venules in the liver, spleen and bone marrow. Its endothelial cells have large gaps

Question 19

What does a hepatic triad comprise?

Answer 19

Bile duct, portal vein, hepatic artery

Question 20

Describe a lobule

Answer 20

Hexagonal shape, triads around it, terminal hepatic venule (central vein) in the centre, sinusoids draining into central vein

Question 21

Where do lymphatics arise?

Answer 21

Lymphatics arise from the periportal space of Mall (between triads and lobule) and drain to the liver hilum and then onto the thoracic duct

Question 22

What are bile canaliculi?

Answer 22

A thin tube that collects bile secreted by hepatocytes - merge and form ductules which eventually become the common hepatic duct

Question 23

What is the space of disse?

Answer 23

Space between sinusoid and basolateral membrane

Question 24

What is a kupffer cell?

Answer 24

Kupffer cells are monocyte derived specialist macrophages that form part of the lining of the sinusoids. Kupffer cells constitute 80% of the tissue macrophages present in the body. They are constantly
exposed to gut-derived bacteria, microbial debris and bacterial
endotoxins
Kupffer cells are specialized macrophages that patrol tiny vessels in the liver called sinusoids, recycling old red blood cells and ingesting pathogens. The endothelium of these vessels is perforated with large holes, allowing the Kupffer cells to migrate into liver tissue at sites of inflammation and damage.

Question 25

What are Stellate (Ito) cells?

Answer 25

• Stellate (Ito) cells are full of cytoplasmic vacuoles containing Vitamin A. For many years, fish liver oils (e.g., cod liver oil) were medically and important nutritional sources of vitamin A. In liver cirrhosis, hepatic stellate cells lose their vitamin A storage capability and differentiate into myofibroblasts. These synthesize and deposit collagen within the perisinusoidal space, resulting in liver fibrosis. This collagen surrounds the central vein, constricting it and leading to
portal hypertension