Which of the following statements is INCORRECT with respect to portal vein?

AIIMS Jodhpur SNO-2023

Applied Anatomy

Easy

Appeared in: AIIMS Jodhpur SNO-2023

Explanation

The statement that portal blood is rich in oxygen is physiologically incorrect.
The portal vein carries venous blood from the gastrointestinal tract, which has already undergone oxygen exchange in the capillary beds of the digestive organs.
While it is rich in absorbed nutrients, it is relatively poor in oxygen compared to arterial blood.
The liver's primary oxygen supply comes from the hepatic artery, not the portal vein.

Option A: This is a correct statement. The primary function of the portal circulation is to transport water-soluble nutrients absorbed from the digestive tract to the liver for processing.
Option C: This is a correct statement. The portal vein is formed by the confluence of veins draining the gastrointestinal system, including the stomach, intestines, pancreas, and spleen.
Option D: This is a correct statement. The portal vein is responsible for supplying the majority (approximately 75-80%) of the total blood flow to the liver.

Visual 1: Diagram - Hepatic Portal System. A diagram showing the portal vein collecting blood from the digestive organs and spleen and carrying it to the liver, alongside the hepatic artery supplying oxygenated blood. This clarifies the dual blood supply and the origin of portal blood.
Visual 2: Flowchart - Liver Blood Flow. A flowchart illustrating the two pathways of blood entering the liver (portal vein and hepatic artery), what each carries (nutrients vs. oxygen), and how they mix in the sinusoids before exiting via the hepatic vein.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Anatomy and Physiology of the Hepatic Portal System as background academic context rather than a clinical decision trigger.
Understanding the dual blood supply is crucial for pharmacology, particularly the 'first-pass effect,' where drugs absorbed from the gut are metabolized by the liver before reaching systemic circulation, often reducing their bioavailability.
In liver diseases like cirrhosis, scarring can obstruct blood flow through the portal vein, leading to a dangerous increase in pressure known as portal hypertension. This can cause complications like esophageal varices and ascites.
What if the question asked about the hepatic artery? If the question were about the hepatic artery, the correct statements would be that it is rich in oxygen and supplies about 20-25% of the liver's blood flow. A statement saying it is rich in nutrients would be incorrect.

How to Approach the Question

First, identify the keyword 'INCORRECT' in the question stem. This signals that you must find the false statement among the four options.
Next, recall the basic physiology of the liver's blood supply. Remember it has a unique dual supply system.
Evaluate each option against your knowledge:
Option A: Does the portal vein carry nutrients? Yes, that's its main job after a meal.
Option B: Does the portal vein carry oxygen-rich blood? No, it's venous blood coming from other organs; it's deoxygenated.
Option C: Does it come from the GI system? Yes, it drains the intestines and stomach.

Concept Tested & Keywords

Concept Tested: Anatomy and Physiology of the Hepatic Portal System
Stem keywords: portal vein, INCORRECT
Lead-in keywords: INCORRECT
Negative lead-in flag: The question asks for the INCORRECT statement, meaning three options are correct facts and one is false.

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