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The fetal circulation is composed of the placenta, umbilical blood vessels encapsulated by the umbilical cord, heart and systemic blood vessels. A major difference between the fetal circulation and postnatal circulation is that the lungs are not used during the fetal stage resulting in the presence of shunts to move oxygenated blood and ...
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The placenta (pl.: placentas or placentae) is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation.It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate maternal and fetal circulations, and is an important endocrine organ, producing hormones that regulate both maternal and fetal ...
The form of the human placenta is generally classified as a discoid placenta. Within this, the cotyledons are the approximately 15-25 separations of the decidua basalis of the placenta, separated by placental septa. [3] Each cotyledon consists of a main stem of a chorionic villus as well as its branches and sub-branches. [3]
The umbilical arteries are one of two arteries in the human body, that carry deoxygenated blood, the other being the pulmonary arteries. The pressure inside the umbilical artery is approximately 50 mmHg. [4] Resistance to blood flow decreases during development as the artery grows wider. [5]
The unpaired umbilical vein carries oxygen and nutrient rich blood derived from fetal-maternal blood exchange at the chorionic villi.More than two-thirds of fetal hepatic circulation is via the main portal vein, while the remainder is shunted from the left portal vein via the ductus venosus to the inferior vena cava, eventually being delivered to the fetal right atrium.
Oxygenated blood from the placenta travels through the umbilical cord to the right atrium of the fetal heart. As the fetal lungs are non-functional at this time, the blood bypasses them through two cardiac shunts. The first is the foramen ovale (the valve present between them called eustachian valve) which shunts blood from the right atrium to ...
Umbilical cord compression can result from, for example, entanglement of the cord, [16] a knot in the cord, [16] or a nuchal cord, [16] (which is the wrapping of the umbilical cord around the fetal neck) [17] but these conditions do not always cause obstruction of fetal circulation.