Organs associated with the GIT

Question 1

List the functions of the liver

Answer 1

Bile synthesis and secretion
Excretion of bilirubin
Protein metabolism
Carbohydrate metabolism
Lipid metabolism
Storag eof vitamins
Conjugation and elimination of metabolites and toxins

Question 1

List and explain the vasculature of the liver

Answer 1

Hepatic artery - O2 blood from branches of aorta. Empties into sinusoids

Hepatic portal vein - Blood from digestive tract and spleen to liver. Enters liver at porta hepatis

Sinusoids - Surrounded by hepatocytes.

Question 2

Explain the structure and function of the hepatic sinusoids

Answer 2

Lined by fenestrated endothelium separated from hepatocytes by space of Disse

Space of Disse - It is also the main site for material transfer between blood-filled sinusoids and hepatocytes.

Sinusoids also contain Kupferr cells which are phagocytic cells

Question 3

Explain the structure of the hepatocytes

Answer 3

They are polyhedral with a wide range of organelles in the cytoplasm

Large, central spherical nuclei, scattered chromatin and prominent nucleoli - many are bi-nucleate

Question 4

Explain the 3 different surfaces of the hepatocytes

Answer 4

Sinusoidal surface - Separated from sinusoid by space of Disse. Covered in short microvilli

Canalicular surface - Bile drains from hepatocytes into canaliculi

Intercellular surface - Between adjacent hepatocytes

Question 5

Explain the arrangement of a classic liver lobule

Answer 5

Central terminal hepatic venule - Sinusoidal channels drain into

Interconnecting plates of hepatocytes surround sinusoidal channels

Peripherally arranged portal tracts - contain terminal branches of hepatic artery and portal vein

Question 6

Explain the 3 zones of the hepatocytes

Answer 6

Zone 1 - closest to poratl tract: synthesizing clycogen and proteins

Zone 2 - between zone 1 and 3

Zone 3 - Adjacent to central venule: Containing estarases and conjugating enzymes

Question 7

Explain the flow of bile in the intrahepatic billiary tree

Answer 7

• Bile produced by hepatocytes enter bile canuculi
• Carry bile to portal tract
• Canuculi open into canals of Herring close to bile ductules
• Bile ductules anastamose, fuse, increase in size to form trabecular ducts
• Trabecular ducts fuse to form intahepatic ducts
• Converge near hilum into main hepatic ducts

Question 8

Explain the structure and function of the gall bladder

Answer 8

Concentrates and stores bile

Thin muscle layer
Outer dense fibrous layer
Mucosa covered by tall columnar epithelium - absorption
Microvili on luminal surface

Question 9

What are the 3 froms of the neuroendocrine component of the pancreas

Answer 9

• Islets of Langerhans
• Isolated nests or clumps of neuroendocrine cells
• Single cells

Question 10

What are the 4 main cell types of the Islets of Langerhans

Answer 10

β-cells: 70% - insulin and amylin secreting - Lacated centrally
⍺-cells: 20% - Glucagon secreting - Located peripherally
δ-cells: 5-10% - Somatostatin secreting cells - Scattered randomly
F-cells: 1-2% - Pancreatic polypeptide secreting cells

Question 11

What are the purpose of pancreatic acinar cells

Answer 11

Produce and secretes precursors of enzymes involved in the breakdown of food in lumen of duodenum

Question 12

Explain the structure and function of the spleen

Answer 12

Red pulp - composed of sinusoids and vascular sinuses
White pulp - Aggregates of lymphoid tissue

Acts as filter, removes particulate matter and aged/abnormal RBC, plateltes