Portal Vein And Portal-systemic Anastomoses

Question 1

The portal vein
• Measures about — cm long
• Formed behind the ——- by the union of the ——- and the —— veins
• Infront of opening of lesser sac to porta hepatis, it divides into ——-

Answer 1

The portal vein
• Measures about 5 cm long
• Formed behind the neck of the pancreas by the union of the superior mesenteric and the splenic veins
• Infront of opening of lesser sac to porta hepatis, it divides into right and left terminal branches

Question 2

Portal circulation
• The portal circulation begins as a capillary plexus in the —— it drains and ends in a capillary circulation within the —— - venous sinusoids of the liver
• The portal vein drains poorly oxygenated but nutrient-rich blood from:
▪ ——-
▪ ——-
▪ ———-
▪ ——-
▪ ——-

Answer 2

Portal circulation
• The portal circulation begins as a capillary plexus in the organs it drains and ends in a capillary circulation within the liver- venous sinusoids of the liver
• The portal vein drains poorly oxygenated but nutrient-rich blood from:
▪ The gastrointestinal tract (from the lower end of the esophagus to the upper end of the anal canal)
▪ The pancreas
▪ Gallbladder
▪ Bile ducts
▪ spleen

Question 3

Portal-systemic anastomoses
• Under normal conditions the portal venous blood traverses the liver and drains into the IVC of the systemic venous circulation by way of the —— veins= this is the direct route
• The communications between the portal venous system and the systemic venous system are important clinically in the advent of an —— or —— portal venous block

Answer 3

Portal-systemic anastomoses
• Under normal conditions the portal venous blood traverses the liver and drains into the IVC of the systemic venous circulation by way of the hepatic veins= this is the direct route
• The communications between the portal venous system and the systemic venous system are important clinically in the advent of an intrahepatic or extrahepatic portal venous block

Question 4

Does the the portal vein and its tributaries have valves

Answer 4

No

Question 5

Does the the portal vein and its tributaries have valves

Answer 5

No

Question 6

When portal circulation through the liver is diminished or obstructed because of liver disease or pressure from a tumor, blood from the GIT can still reach the heart through the —— by way of several other collateral routes

Answer 6

IVC

Question 7

State the sites of portal-systemic anastomoses

Answer 7

1. At the lower third of the esophagus
2. Halfway down the anal canal
3. Anterior abdominal wall
4. Extra peritoneal surfaces of retroperitoneal organs
5. Bare area of the liver

Question 8

Explain the site of portosystemic anastomoses at the lower third of the esophagus

Answer 8

At the lower third of the esophagus
▪The esophageal branches of the left gastric vein (portal system) anastomose with the esophageal veins draining the middle third of the esophagus into the azygous veins (systemic system)
▪When dilated, these are esophageal varices

Question 9

Explain the site of portosystemic anastomoses halfway down the anal canal

Answer 9

Halfway down the anal canal
▪ The superior rectal veins (portal system) draining the upper half of the anal canal anastomose with the middle and inferior rectal veins (systemic system) draining into the IVC
▪ The submucosa veins involved are normally dilated (varicose in appearance) even in newborns
▪ When the mucosa containing them prolapses, they form hemorrhoids

Question 10

Portosystemic anastomoses halfway down the anal canal
▪ The submucosa veins involved are normally dilated (varicose in appearance) even in ——
▪ When the mucosa containing them prolapses, they form ——-

Answer 10

Halfway down the anal canal
▪ The superior rectal veins (portal system) draining the upper half of the anal canal anastomose with the middle and inferior rectal veins (systemic system) draining into the IVC
▪ The submucosa veins involved are normally dilated (varicose in appearance) even in newborns
▪ When the mucosa containing them prolapses, they form hemorrhoids

Question 11

At the lower third of the esophagus
▪The esophageal branches of the left gastric vein (portal system) anastomose with the esophageal veins draining the middle third of the esophagus into the azygous veins (systemic system)
▪When dilated, these are ———

Answer 11

Oesophageal varices

Question 12

Explain the site of portosystemic anastomoses at the anterior abdominal wall

Answer 12

▪The paraumbilical veins of the anterior abdominal wall (portal system) anastomosing with superficial epigastric veins (systemic system)
▪When dilated, these veins produce caput medusae
▪Varicose veins radiating from the umbilicus

Question 13

Anterior abdominal wall
▪The paraumbilical veins of the anterior abdominal wall (portal system) anastomosing with superficial epigastric veins (systemic system)
▪When dilated, these veins produce ——-
▪Varicose veins radiating from the ——

Answer 13

▪The paraumbilical veins of the anterior abdominal wall (portal system) anastomosing with superficial epigastric veins (systemic system)
▪When dilated, these veins produce caput medusae
▪Varicose veins radiating from the umbilicus

Question 14

Explain the site of portosystemic anastomoses at the extraperitoneal surfaces of retroperitoneal organs

Answer 14

Twigs of colic veins draining the ascending colon, descending colon, duodenum, pancreas and liver (portal system) anastomose with retroperitoneal veins (systemic system) - renal, lumbar and phrenic veins

Question 15

Explain the site of portosystemic anastomoses at the bare surface of the liver

Answer 15

Hepatic/portal veins (portal system) anastomose with inferior phrenic veins (systemic system)

Question 16

List 3 clinical implications

Answer 16

Clinical implications
• Portal-systemic anastomoses • Portal hypertension
• Portasystemic shunts