Fetal Veins, Portal vein formation, Derivatives of the embryonic veins - NEET PG Anatomy

Knowledge of Fetal Veins, Portal vein formation, and Derivatives of the embryonic veins is important for understanding the development and anatomy of various organs and structures in the body. This knowledge is crucial in making a correct diagnosis and determining appropriate treatment options for various medical conditions. Additionally, questions related to these topics are commonly asked in the NEET PG exam, making it essential for medical students to have a thorough understanding of these concepts.

Let’s learn more about this important anatomy topic for NEET PG exam preparation.

• Vitelline veins → they drain the yolk sac. They contribute to form the portal venous circulation. 
• Umbilical veins → they drain the yolk sac. After removal of the placenta after birth, the umbilical vessels degenerate 
• Cardinal veins → they drain the body wall.
  • Anterior cardinal vein → it drains the venous blood of the body above the diaphragm.
  • Posterior cardinal vein → it drains the venous blood of the body below the diaphragm.
• All these veins (vitelline veins, umbilical veins & cardinal veins) drain into the venous end of the heart tube (sinus venosus).

Sinus venosus

↓

Truncus arteriosus

(arterial end)

↓

Aortic sac

↓

Aortic arches

↓

2 dorsal aorta

• Aortic arches in the head & neck region later contribute to form the carotid artery, subclavian artery, arch of the aorta and the pulmonary artery.

Also Read: Gametogenesis - Definition, Stages and Types - NEET PG Anatomy

Sinus venosus

• Anterior cardinal vein 
  • It drains the body above the diaphragm. 
  • Right anterior cardinal vein later contributes to form the SVC.
  • Left anterior cardinal vein regresses.
• Posterior cardinal vein 
  • It drains the body below the diaphragm.
  • Right posterior cardinal vein later contributes to form the IVC.
  • Left posterior cardinal vein regresses.
• Anterior and posterior cardinal veins on either side join to form the right and left common cardinal veins. 
• 3 veins each draining into the right and left horn of the sinus venosus: 
  • Common cardinal vein
  • Umbilical vein
  • Vitelline vein
• Umbilical veins are coming from the placenta. Later in the fetal circulation, the right umbilical vein regresses and only the left umbilical vein is left. 
• The persisting left umbilical vein in the fetal circulation also degenerates and forms ligamentum teres of the liver (having no function at all).
• Vitelline veins drain the yolk sac, which forms the gut tube.
• The right and left vitelline veins are passing through the septum transversum.
• The septum transversum breaks the vitelline veins into right and left hepatic-cardiac channels.
• Right hepatic-cardiac channel later contributes to form the terminal part of the IVC, which carries the blood from the liver towards the heart.
• Right vitelline vein (along with some contribution from the left vitelline vein) forms the portal vein. 

Important information: Persisting left anterior cardinal vein → leads to double SVC. Persisting left posterior cardinal vein → leads to double IVC. Septum transversum is a structure developing in the mesenchyme. It later contributes to the central tendon of the diaphragm and connective tissue of the liver.

Also read: How to Prepare Anatomy for PG Entrace Exams ?

Portal Vein formation

• Here, we can see that the yolk sac has developed into a gut tube (duodenum) with the right and left vitelline veins running on either side.
• Portal vein contribution:
  • Right vitelline vein (major contribution).
  • Dorsal anastomosis between the right and left vitelline vein.
  • Left vitelline vein (minor contribution)
• The portal vein passes behind the 1st part of duodenum to form the right & left branch of the portal vein inside the liver (at porta hepatis). 
• In fetal circulation, the left umbilical vein is connected to the IVC directly via ductus venosus. This is important as it bypasses the liver. This way the oxygen carried by the left umbilical vein can straight away enter the circulation and not go through the liver, because the fetal liver is immature.

Also Read:

Development of the Nervous System - NEET PG Anatomy         

Gametogenesis - Definition, Stages and Types - NEET PG Anatomy

Inguinal Canal & Spermatic Cord - NEET PG Anatomy

Development of Skull - NEET PG Anatomy

Derivatives of the embryonic veins

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