Portal Vein, Portal Venous System, and Porto-Caval Anastomosis

Comprehensive practice flashcards covering the anatomy, tributaries, branches, relations, portocaval anastomoses, and clinical correlates of the portal venous system.

From which organs does the portal venous system collect and drain blood?

The abdominal part of the alimentary tract, the spleen, the pancreas, and the gall bladder.

Into which major vessel does blood from the portal system eventually drain after passing through the liver?

The inferior vena cava (IVC).

From which embryonic veins does the portal system develop?

The vitelline veins.

What is the normal physiological pressure range in the portal venous system?

Approximately $5\text{-}10\,\text{mmHg}$.

What is the typical rate of blood flow through the portal venous system?

About $1000\text{-}1200\,\text{mls/min}$.

What three anatomical regions are cited as primary sites of anastomoses with caval blood in the introduction?

The umbilicus, anal canal, and lower oesophagus.

Which two veins unite to form the portal vein?

The splenic vein and the superior mesenteric vein.

At what vertebral level does the portal vein form?

At the level of $\text{L2}$.

What is the length of the portal vein?

About $8\,\text{cm}$ ($3.2\,\text{inches}$) long.

In which peritoneal structure and boundary does the portal vein run?

In the free edge of the lesser omentum, located in the anterior boundary of the epiploic foramen.

Where does the portal vein divide into right and left branches?

At the porta hepatis.

What four structures lie anterior to the portal vein?

The neck of the pancreas, the first part of the duodenum, the bile duct, and the hepatic artery.

What major vessel lies posterior to the portal vein?

The inferior vena cava (IVC).

Where is the superior mesenteric vein situated relative to the superior mesenteric artery?

On the right side of the superior mesenteric artery in the root of the mesentery.

Which abdominal structures are crossed anteriorly by the superior mesenteric vein?

The third part of the duodenum and the uncinate process of the pancreas.

Where does the superior mesenteric vein terminate?

Posterior to the neck of the pancreas, where it joins the splenic vein to form the portal vein.

How is the splenic vein formed?

By the union of tributaries originating from the spleen.

Which three tributary veins drain directly into the splenic vein?

The short gastric veins, left gastroepiploic vein, and pancreatic veins.

Which two veins unite to form the inferior mesenteric vein?

The superior rectal vein and the sigmoid veins.

Which tributary vein from the colon drains into the inferior mesenteric vein?

The left colic vein.

Into which vessel does the inferior mesenteric vein usually drain?

The splenic vein.

Aside from the splenic vein, what are two variant termination sites for the inferior mesenteric vein?

The superior mesenteric vein or the junction of the superior mesenteric and splenic veins.

Where does the left gastric (coronary) vein normally drain?

Directly into the portal vein.

With which venous system do the esophageal tributaries of the left gastric vein anastomose at the lower esophagus?

With the esophageal veins of the azygos system.

In which ligament are the paraumbilical veins located?

The falciform ligament.

What is the typical condition of the paraumbilical veins, and under what circumstances do they enlarge?

They are virtually closed under normal circumstances, but they dilate during portal hypertension.

Which two vascular regions do the paraumbilical veins connect?

The left branch of the portal vein and the small subcutaneous veins in the region of the umbilicus.

Where does the cystic vein drain when present?

Into the right branch of the portal vein.

What smaller divisions arise from the right and left portal veins?

Lobular branches.

Which two structures accompany the lobular branches of the portal vein?

Branches of the hepatic artery and the bile duct.

Through which specialized vascular channels does portal blood flow before entering central canals in the liver?

The hepatic sinusoids.

Where are the hepatic veins located within the liver tissue, and where do they converge?

They lie in the intersegmental planes and converge on the inferior vena cava (IVC).

What fibrous sheath extends into the porta hepatis alongside the portal vessels and bile duct?

The perivascular fibrous (Glisson's) capsule.

What type of blood is transported by the portal venous system?

Deoxygenated blood containing absorbed nutrients.

What percentage of the liver's total blood flow is supplied by the portal venous system?

About $75\%$.

How does the blood pressure inside the portal venous system compare to that of the inferior vena cava?

The portal system maintains a higher blood pressure than the IVC.

Based on this schematic illustration, how does a portal circulation structurally differ from usual circulation?

Usual circulation passes from an arteriole through a single capillary bed directly to a venule, whereas portal circulation passes from a first capillary bed (stomach and intestine) through a portal vein to a second capillary bed (liver sinusoids) before reaching systemic veins.

What vessels participate in the portocaval anastomosis at the lower esophagus?

The left gastric vein (portal) and the esophageal vein of the azygos system (systemic/caval).

What vessels participate in the portocaval anastomosis at the rectum and anal canal?

The superior rectal vein (portal) and the middle and inferior rectal veins (systemic/caval).

What vessels participate in the portocaval anastomosis at the anterior abdominal wall?

The paraumbilical veins (portal) and radicles of the epigastric (superficial and inferior) veins (systemic/caval).

What vessels participate in the retroperitoneal portocaval anastomosis?

Retroperitoneal veins draining the colon (portal) and twigs of the renal, suprarenal, and gonadal veins (systemic/caval).

What vessels participate in the portocaval anastomosis located at the bare surface of the liver?

The portal venous system in the bare surface of the liver and the azygos system above the diaphragm.

How are haemorrhoids defined in the clinical correlates?

Engorgement and swelling of anal veins due to obstruction of venous return.

How are oesophageal varices defined in the lecture?

Engorgement and swelling of the veins of the oesophago-gastric junction, commonly due to portal hypertension.

What is the clinical definition of portal hypertension based on vascular pressure?

An increase in portal pressure beyond $10\,\text{mmHg}$.

What are the four pre-hepatic causes of portal hypertension listed in the lecture?

1. Congenital portal atresia, 2. Portal vein thrombosis (Neonatal sepsis), 3. Phlebitis of portal vein (abdominal infection), and 4. Trauma or thrombosed porto-caval shunt.

What are the three hepatic causes of portal hypertension listed in the lecture?

1. Cirrhosis (alcoholic most frequently), 2. Chronic Active hepatitis, and 3. Parasitic diseases (Schiatosomiasis).

What are the three post-hepatic causes of portal hypertension listed in the lecture?

1. Budd-Chiari syndrome (Hepatic venous thrombosis), 2. Constrictive pericarditis, and 3. Tricuspid valve incompetence.

What clinical term describes the prominent periumbilical collateral blood vessels seen in portal hypertension?

Caput Medusea (Caput Medusae).

What are the significant local and systemic effects of portal hypertension?

Local effect: varices rupture and cause significant bleeding; Systemic effects: blood carrying digestion products, toxins, and bile reaches the CNS, leading to jaundice and encephalitis.