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For humans, male fetuses normally gestate several days longer than females and multiple pregnancies gestate for a shorter period. [2] Ethnicity in humans is also a factor that may lengthen or shorten gestation. [4] In dogs, there is a positive correlation between a longer gestation time and fewer members of the litter. [5]
Glucocorticoids have been implicated in fetal maturation, regulation of immune response and many other pregnancy associated changes. [15] As well as its function in parturition, Prostaglandin E2 is vital for fetal lung maturation. Additionally, there is an abundance of 11β-hydroxysteroid dehydrogenase 1 expressed in the foetal membranes.
The placenta is a critical organ that develops in the maternal uterus during pregnancy to support the fetus. It connects to the fetus via the umbilical cord in order to allow nutrient transport, waste excretion and gas exchange between mother and fetus. [2] The morphological features of the placenta differ among species, but the function is ...
The term "umbilical cord" or just "umbilical" has also come to be used for other cords with similar functions, such as the hose connecting surface-supplied divers to their surface supply of air and/or heating, or space-suited astronauts to their spacecraft. Engineers sometimes use the term to describe a complex or critical cable connecting a ...
After birth the umbilical cord is clamped and cut, the baby starts to breathe air, and blood from the right ventricle starts to flow to the lungs for gaseous exchange and oxygenated blood returns to the left atrium, which is pumped into the left ventricle, and then pumped into the main arterial system. As a result of these changes, the blood ...
The amniotic sac and its filling provide a liquid that surrounds and cushions the fetus. It is a site of exchange of essential substances, such as oxygen, between the umbilical cord and the fetus. [9] It allows the fetus to move freely within the walls of the uterus. [citation needed] Buoyancy is also provided.
During pregnancy, placentation is the formation and growth of the placenta inside the uterus. It occurs after the implantation of the embryo into the uterine wall and involves the remodeling of blood vessels in order to supply the needed amount of blood. In humans, placentation takes place 7–8 days after fertilization.
Occasionally, during pregnancy, there is a single umbilical artery (SUA) present in the umbilical cord, as opposed to the usual two. [1] This is sometimes also called a two-vessel umbilical cord, or two-vessel cord. Approximately, this affects between 1 in 100 and 1 in 500 pregnancies, making it the most common umbilical abnormality.