Types of placenta

Summary

In this video, Malinki discusses the different types of placentas found in mammals, classifying them based on factors such as intimacy between the placenta and uterus, implantation types, distribution of chorionic villi, and involvement of fetal and maternal tissues. She explains key concepts like non-deciduous, deciduous, and contra-deciduous placentas, as well as superficial, eccentric, and interstitial implantation. The video also covers the various tissue barriers in placentas, ranging from epitheliocorial to hemo-endothelial types. Viewers can access notes and further resources via the provided links.

Takeaways

• 🌱 The placenta in mammals can be classified based on four criteria: degree of intimacy, type of implantation, distribution of chorionic villi, and involvement of fetal and maternal tissues.
• 👶 Based on the degree of intimacy, there are three types of placentas: non-deciduous, deciduous, and contra-deciduous.
• 🩸 In non-deciduous placentas, implantation is superficial, and there is no fusion with the endometrium, minimizing uterine damage at birth.
• 🐒 Deciduous placentas have a more intimate connection, with the chorionic villi fusing with the endometrium. This results in tissue shedding and blood loss at birth.
• 🦠 Contra-deciduous placentas involve both maternal and fetal tissues breaking down after delivery, which are then absorbed by the mother's leukocytes.
• 🔍 There are three types of placentas based on implantation type: superficial, eccentric, and interstitial, each involving different levels of embedding within the uterine wall.
• 🍃 Chorionic villi distribution classifies placentas into five types: diffuse, cotyledonary, zonary, discoidal, and meta-discodial, with varied arrangements of villi.
• 🐄 Diffuse placentas have uniformly scattered chorionic villi, seen in animals like pigs and horses.
• 🦓 Epitheliochorial, syndesmochorial, endotheliocorial, hemocorial, and hemoendothelial placentas describe types based on the number of tissue barriers between fetal and maternal blood.
• 📜 The number of tissue barriers in placentas can range from six (epitheliochorial) to one (hemoendothelial), influencing the efficiency of maternal-fetal exchange.

Q & A

What are the four different ways to classify the placenta in mammals?

The placenta can be classified in four ways: based on the degree of intimacy, types of implantation, distribution of chorionic villi, and the degree of involvement of fetal and maternal tissues.

What is a non-deciduous placenta, and in which animals is it found?

A non-deciduous placenta, also called a semi-placenta, involves superficial implantation where the chorionic villi do not fuse with the endometrium, and the uterine tissue remains undamaged at birth. It is found in animals like cattle, horses, and pigs.

How does a deciduous placenta differ from a non-deciduous placenta?

A deciduous placenta involves more intimate implantation, where the chorionic villi fuse with the endometrium. Uterine tissue is shed with blood during birth, unlike in the non-deciduous placenta where the tissue remains intact. It is found in primates, rodents, cats, and dogs.

What happens to the placenta in a contra-deciduous placenta after birth?

In a contra-deciduous placenta, both the maternal and fetal portions of the placenta are absorbed by the mother's leukocytes after delivery. This type is found in animals like primates and talpa.

What are the three types of placenta based on implantation?

The three types of placenta based on implantation are superficial placenta, eccentric placenta, and interstitial placenta.

What is the difference between a superficial and eccentric placenta?

In a superficial placenta, the embryo is attached superficially within the uterine lumen, while in an eccentric placenta, the embryo lies within the uterine fold and is almost enclosed by the epithelial fold. Superficial placenta is found in animals like cows and pigs, while eccentric placenta is found in rats and squirrels.

Which type of placenta involves the embryo burrowing into the uterine mucosa?

The interstitial placenta involves the embryo burrowing into the uterine mucosa, becoming completely surrounded by endometrial tissue. It is found in humans, chimpanzees, and bats.

What is the difference between diffuse and cotyledonary placenta based on chorionic villi distribution?

In a diffuse placenta, the chorionic villi are numerous and uniformly scattered over the chorion, as seen in pigs and horses. In a cotyledonary placenta, the chorionic villi are aggregated in specific regions to form small tufts, leaving the rest of the chorion smooth. This type is found in deer, sheep, and cattle.

Which animals have zonary placentas, and how are they structured?

Zonary placentas are found in animals like cats, dogs, and seals. In this type, the chorionic villi form a belt or band around the middle of the embryo.

What is the hemocoreal placenta, and in which animals is it found?

The hemocoreal placenta involves three tissue barriers between fetal and maternal blood. In this case, the uterine epithelium, endometrial connective tissue, and the maternal blood vessel endothelium are lost, allowing the chorionic epithelium to bathe directly in the maternal blood. It is found in primates, bats, and shrews.