The umbilical cord is a deciduous, and therefore temporary, anatomical formation containing the blood vessels connecting the fetus to the placenta.
At birth, the umbilical cord or cord measures an average of 50-60 centimeters in length and 20 mm in diameter; the appearance is the twisted one of a pearly colored cord, which reveals the dark shades of the blood contained in the vessels.
The knotty aspect of the umbilical cord is linked to the twisted course of its vessels and to the presence of swellings (the so-called false knots) in correspondence with vascular loops.
What is it for and How "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. way, the so-called "placental barrier" can prevent the passage of many harmful substances, although some can still cross 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, coiled around it, on the other. The latter, unlike those of the systemic circulation, 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 tract, these blood vessels go to the placental disc; 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 quickly stop blood flow in the event of a rupture of the umbilical cord. Furthermore, the vessels are immersed in a mucous connective tissue (Warthon's jelly), which envelops and protects them, drawing nourishment through the interstitial route.
How it forms
The umbilical cord begins to designate itself around the fifth week of gestation, replacing - from a functional point of view - the yolk sac, which guarantees nutritional supplies in the early stages of embryo development.
The yolk sac is initially connected to the chorion (membrane that encloses the embryo and connects it with the mother through the chorionic villi), but this relationship regresses with the development of the allantoid, an extra-embryonic membrane that allows breathing. nutrition and embryo excretion. It is precisely from the maturation of the allantoid that the umbilical cord develops.
Diseases of the umbilical cord
The most frequent anomalies affecting the umbilical cord are those relating to its shape or length.
We speak of excessive length when the umbilical cord exceeds 80 cm at birth, and absolute shortness when it does not reach 30 cm. There may also be a relative shortness if the funicular tract 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 funiculus will break abruptly during labor must be considered.
- In the case of relative brevity, the danger is that the knots tighten further during labor, causing fetal distress.
A too thin umbilical cord is associated with intrauterine growth retardation (IUGR) and hypotrophic placenta; moreover, due to the reduced quantity of Warthon's jelly, the folds of the funiculus can cause occlusive episodes, with more or less severe fetal asphyxia.
Normally the umbilical cord is inserted on the fetal face of the placenta, in a roughly central position. In about 10% of 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 the amnion and the chorion, before reaching the placental border (velamentous insertion). The lack of Warthon's jelly in this tract exposes the umbilical cord vessels to a greater risk of dangerous injury during rupture of the membranes.
Umbilical cord, pathologies and stem cells "