The placenta is the organ that connects the foetus to the mother during pregnancy. The placenta is responsible for facilitating the transfer of nutrients and oxygen to the foetus. It is also in charge of collecting carbon dioxide and waste products from the foetus during the pregnancy. The placenta seems to be disk-shaped and can measure up to 22 cm in length when fully developed. The placenta has a significant number of blood arteries.

The placenta is a structure found only in mammals. The umbilical cord connects the foetus to the placenta, allowing for the passage of materials between the two structures. The placenta is normally linked to the uterus at one of the following locations: the top, bottom, side, front, or back. As a result of this attachment, the placenta can become connected to the lower section of the uterus, resulting in the condition known as placenta previa.

Structure

Placental mammals, such as humans, have a chorioallantoic placenta, which is formed from the chorion and allantois throughout the pregnancy process. Among humans, the placenta measures approximately 22 cm (9 inches) in length and 2–2.5 cm (0.8–1 inch) in thickness, with the thickest portion in the middle and thinnest portions at the edges of the placenta. On average, it weighs about 500 grammes (about) (just over 1 lb). A dark reddish-blue or crimson tint can be seen on its surface. For the foetus to be connected to the mother, an umbilical cord measuring around 55–60 cm (22–24 inches) in length is used. This cord contains two and one umbilical arteries as well as one umbilical vein. The umbilical cord is inserted into the chorionic plate during pregnancy (has an eccentric attachment). Placental vessels branch out across the surface of the placenta, where they further divide to form a network of vessels that is covered by a thin layer of cells. The creation of villous tree structures is the result of this process. Villous tree structures, which are found on the maternal side of the tree, are organised into lobules known as cotyledons. The placenta in humans is typically shaped like a disc, but the size of the placenta varies greatly between mammalian species.

The placenta can occasionally take on a shape in which it is divided into multiple different pieces that are linked together by blood arteries. The sections, which are referred to as lobes, might be two, three, four, or more in number. Bilobed/bilobular/bipartite placentas are one type of placenta, whereas others are classified as trilobed/trilobular/tripartite placentas, and so on. It is referred to as a succenturiate placenta when the main lobe and auxiliary lobe are readily distinguishable from one another. During labour, the blood veins linking the lobes can get in the way of the foetal presentation, which is known as vasa previa (obstructed foetal presentation).

Factors that influence the health of the placenta

Various factors can have an impact on the health of the placenta during pregnancy, some of which can be controlled and others that cannot. As an illustration:

• The age of the mother. Several types of placental issues are more common in older women, particularly those over the age of 40.
• Take a break in the water before going into labour. During pregnancy, the infant is protected and cushioned by a fluid-filled membrane known as the amniotic sac, which surrounds and cushions the foetus. If the sac leaks or breaks before labour begins, which is referred to as water breaking, the risk of certain placental issues rises significantly.
• Hypertension (high blood pressure). High blood pressure has been shown to affect the placenta.
• Pregnancy with twins or other multiples. If you are a woman who is pregnant with more than one child, you may be at greater risk of developing certain placental abnormalities.
• Disorders of the coagulation process. Placental issues can occur as a result of a variety of factors, including conditions that impede the blood’s capacity to clot or increase the likelihood of blood clotting.
• Previous uterus surgery has been performed. If a woman has had previous uterine surgery, such as a C-section or surgery to remove fibroids, she is at a higher risk of developing certain placental abnormalities during her pregnancy.
• Previous issues with the placenta. If a woman has had a placental issue during a prior pregnancy, she may be at a higher risk of suffering one during this pregnancy.
• The usage of illegal substances. Some placental abnormalities are more likely in pregnant women who smoke or take cocaine, and some of these problems are preventable.
• Trauma to the abdomen. Trauma to the abdomen, such as that caused by a fall, an automobile accident, or another sort of trauma, increases the likelihood of the placenta separating early from the uterus (placenta abruption).

Conclusion

The placenta is a transient foetal organ that develops from the blastocyst immediately after implantation and continues to develop throughout the pregnancy. This organ is essential for the exchange of nutrients, gaseous waste, and waste products between the physically separate maternal and foetal circulations, and it is also a significant endocrine organ responsible for the production of hormones that regulate both maternal and foetal physiology during pregnancy. The placenta connects to the foetus through the umbilical cord, while on the other side, it attaches to the maternal uterus in a species-dependent manner, depending on the species. When the placenta is removed from the uterus following birth, a thin layer of maternal decidual (endometrial) tissue is expelled with it (this is frequently referred to as the ‘maternal component’ of the placenta, which is inaccurate). In addition to being a distinguishing property of placental mammals, placentas can also be found in marsupials and some non-mammals, however at differing developmental stages.