Umbilical vessels (both umbilical arteries & umbilical vein) do not have vasa vasorum because:
Thin Vessel Walls – The umbilical vessels, especially umbilical vein, have thin walls compared to large systemic vessels, reducing need for additional blood supply.
High Oxygenation in Umbilical Vein – The umbilical vein carries oxygenated blood from the placenta, meaning its wall is already well-supplied with oxygen & nutrients from its lumen.
Short Functional Duration – The umbilical vessels are temporary structures, functioning only during fetal life. Since they are not long-term vessels, they do not develop complex vascular support systems like vasa vasorum.
Surrounding Wharton's Jelly – The umbilical vessels are embedded in Wharton’s jelly, a gelatinous connective tissue that protects them from external compression and maintains their patency, reducing the need for additional microvasculature.
Lower Wall Metabolic Demand – Unlike large systemic arteries like the aorta, which have thick muscular and elastic walls requiring extra nourishment, the umbilical vessels have a relatively lower metabolic demand, making vasa vasorum unnecessary.
In contrast, large systemic vessels such as the aorta require vasa vasorum to supply nutrients and oxygen to their thick walls, particularly in the outer layers where diffusion from the lumen is insufficient.
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