The umbilical vein is a temporary blood vessel crucial for fetal development. During pregnancy, this vein serves as the primary conduit for oxygenated, nutrient-rich blood from the placenta to the developing fetus. It delivers vital resources essential for growth, bypassing the fetal lungs which are not yet functional. Its importance is singular, as it is the sole vessel responsible for bringing these crucial elements from the placenta directly into the fetal circulation.
Immediate Closure
Following birth, the umbilical vein undergoes rapid functional closure. When the umbilical cord is clamped and cut, blood flow through the umbilical vein ceases. This cessation triggers an immediate physiological response within the vein’s muscular walls, leading to sustained vasoconstriction. Strong muscular contractions constrict the vessel’s lumen, preventing any further blood passage.
This initial functional closure is often aided by the formation of a blood clot, or thrombosis, within the constricted vessel. Venous flow in the umbilical cord can cease within minutes after birth, even before mechanical clamping, as the vein naturally constricts.
Long-Term Transformation
Beyond the immediate functional closure, the umbilical vein undergoes a more gradual yet complete anatomical transformation. Over a period of weeks to months after birth, the vessel’s lumen, its inner channel, progressively fills with connective tissue. This process is known as fibrosis, where the muscular and endothelial layers of the vein are replaced by dense, non-vascular fibrous tissue. The proliferation of this connective tissue ultimately leads to the complete structural obliteration of the vessel.
This extensive remodeling results in the formation of a solid, cord-like structure. This fibrous remnant is known as the round ligament of the liver, or ligamentum teres hepatis. It extends from the umbilical region to the liver, serving as a permanent anatomical landmark in the adult body. This transformation ensures that a vessel no longer needed for blood transport is safely and permanently sealed off.
Relevance in the Adult Body
In adults, the round ligament of the liver, the remnant of the umbilical vein, serves primarily as an anatomical landmark. It appears as a fibrous cord extending from the umbilicus to the liver, specifically joining the falciform ligament of the liver. This location is important for surgeons and clinicians, providing a clear reference point during abdominal procedures.
While it no longer carries blood, its historical path from the umbilicus to the liver is sometimes utilized in medical contexts. For instance, in neonates, the umbilical vein can be temporarily catheterized to provide quick intravenous access for fluid, medication, or blood administration, capitalizing on its patency for a period after birth.
In rare instances, the umbilical vein may not fully obliterate, or the paraumbilical veins associated with the remnant can become enlarged. This can occur in conditions like portal hypertension, where increased pressure in the liver’s portal vein system can cause these remnant vessels to recanalize or become engorged, forming visible collateral pathways on the abdominal wall, sometimes referred to as a “caput medusae.”