Umbilical cord

Generality

The umbilical cord is a deciduous, therefore temporary, anatomic formation containing the blood vessels connecting the fetus and the placenta.

At birth, the umbilical cord or cord measures on average 50-60 centimeters in length and 20 mm in diameter; the appearance is the twisted one of a pearly-colored string, which reveals the dark shades of the blood contained in the vases.

The knotty aspect of the umbilical cord is related to the twisted course of its vessels and to the presence of swellings (the so-called false nodes) in correspondence of vascular loops.

What it is for and how it is done

The umbilical cord is the link between the placenta and the product of conception. Its presence allows the transfer of gas and other substances between mother and fetus, without there being a direct exchange between the blood of the two organisms. In this way, the so-called "placental barrier" can prevent the passage of many harmful substances, although some can still pass through it and harm the fetus.

As a rule, three blood vessels run inside the umbilical cord: the umbilical vein on one side and the two umbilical arteries, wrapped in a spiral around it, on the other. The latter, unlike those in the systemic circle, carry venous blood, while blood rich in oxygen and nutrients flows in the umbilical vein.

Inside the abdominal wall of the fetus, the umbilical vessels take different directions: the umbilical vein carries arterial blood to the heart, while the umbilical arteries surround the bladder and carry venous blood outside.

Outside the abdominal wall, along the funicular section, these blood vessels travel to the placental disk; from it, the umbilical vein receives oxygenated blood rich in nutrients, while the two umbilical arteries carry venous blood, poor in oxygen, but rich in carbon dioxide and other waste substances. The fibers of the umbilical blood vessels are particularly rich in muscle cells; the physiological significance of this feature is inherent in the need to rapidly interrupt the blood flow in the event of umbilical cord rupture. Furthermore, the vessels are immersed in a mucous connective tissue (Warthon jelly), which wraps them and protects them, drawing nourishment from the interstitial area.

How to form

The umbilical cord begins to be designated around the fifth week of gestation, replacing - from the functional point of view - the yolk sac, which guarantees nutritional supply in the early stages of embryo development.

The yolk sac is initially connected to the chorion (the membrane that encloses the embryo and puts it in relationship with the mother through the chorionic villi), but this relationship regresses with the development of the allantois, an extra-embryonic membrane that allows breathing, nutrition and excretion of the embryo. It is from the maturation of the allantois that the umbilical cord develops.

Umbilical cord diseases

The most frequent anomalies affecting the umbilical cord are those related to its shape or length.

Length anomalies

We talk about excessive length when the umbilical cord exceeds 80 cm at birth, and of absolute brevity when it does not reach 30 cm. There may also be a relative brevity, in case the funicular section has single or multiple turns around the neck or other parts of the fetal body.

• In the case of absolute brevity, the serious possibility that the cord may break sharply during labor should be considered.
• In the event of relative brevity the danger is that the knots further tighten during labor, causing fetal distress.

Thickness anomalies

An excessively thin umbilical cord is associated with an intrauterine growth retardation (IUGR) and a hypotrophic placenta; moreover, due to the reduced amount of Warthon's gelatin, the folds of the funiculus can determine occlusive episodes, with more or less severe fetal asphyxia.

Listing anomalies

Normally the umbilical cord is inserted on the fetal face of the placenta, in a roughly central position. In about 10% of the cases this insertion is marginal, while in about one case out of 100 the umbilical vessels run for a more or less long stretch between amnios and chorion, before reaching the placental border (veiling insertion). The lack of Warthon's gelatin in this section exposes the umbilical cord vessels to a greater risk of dangerous lesions during the rupture of the membranes.

Umbilical cord, pathologies and stem cells "