Umbilical cord diameter. This diameter decreases rapidly within the placenta. The fully patent umbilical artery has two main layers: an outer layer consisting of circularly arranged smooth muscle cells and an inner layer which shows rather irregularly and loosely arranged cells embedded in abundant ground substance staining metachromatic. The smooth muscle cells of the layer are rather poorly differentiated, contain only a few tiny myofilaments and are thereby unlikely to contribute actively to the process of post-natal closure. The umbilical cord contains Wharton's jelly, a gelatinous substance made largely from mucopolysaccharides which protects the blood vessels inside. It contains one vein, which
Studies of the Fetus in the Womb imbricato" ("Ask Biagino Crivelli's wife how the capon rears and hatches the eggs of hens when he is unplucked"). Da Vinci theorized that the umbilical cord was responsible for taking the fetus’ urine outside of the uterus. The studies were initially bequeathed to Francesco Melzi. In c. 1582–90 they were bought from his heirs by Pompeo Leoni and by 1630 they belonged to Thomas Howard, 2nd Earl of Arundel. Since 1690 the studies have been housed in the Royal Collection, United Kingdom. Studies of the Fetus in the Womb Studies of the Fetus in the Womb are two colored annotated