ORGANUM
The umbilical cord contains two arteries and one vein. The two arteries carry deoxygenated blood from the fetus to the placenta and the oxygenated blood returns to the fetus via the umbilical vein. Absence of one artery occurs in about 1 in 200 deliveries and is associated with a 10-15% incidence of cardiovascular anomalies.
The vessels are surrounded by a hydrophilic mucopolysaccharides known as Wharton's jelly, and the outer layer covering the cord consists of amniotic epithelium. The cord length varies between 30 and 90cm. The vessels grow in a helical shape - this configuration has the functional advantage of protecting the patency of the vessels by absorbing torsion without the risk of kinking or snarling of the vessels.
The few measurements that have been made in situ of blood pressures in the cord vessels indicate that the arterial pressure in late pregnancy is around 70 mmHg systolic and 60 mmHg with a relatively low pulse pressure and a venous pressure that is exceptionally high, at approximately 25 mmHg. This high venous pressure tends to preserve the integrity of the venous flow and indicates that the pressure within the villus capillaries must be in excess of the cord venous pressure. The cord vessels often con