Question

Что такое плацента? как вы думаете, как без неё обходятся яйцекладущие и сумчатые млекопитающие?

Answer 1

Плацента  — это важнейший и абсолютно уникальный орган, существующий только во время беременности. Она связывает между собой два организма — матери и плода, обеспечивая его необходимыми питательными веществами.Да обходятся.

Answer 2

What is the placenta?

The placenta is an organ that develops in the uterus during pregnancy. It plays a crucial role in supporting the growth and development of the fetus. The placenta is formed from both maternal and fetal tissues and serves as a connection between the mother and the developing baby.

Functions of the placenta:

The placenta performs several important functions during pregnancy:

1. Nutrient and oxygen exchange: The placenta allows for the exchange of nutrients, oxygen, and waste products between the mother and the fetus. It acts as a barrier, filtering out harmful substances while providing essential nutrients and oxygen to support the baby's growth.

2. Hormone production: The placenta produces hormones that are necessary for maintaining pregnancy. These hormones include human chorionic gonadotropin (hCG), progesterone, and estrogen, which help regulate the mother's body during pregnancy.

3. Waste elimination: The placenta removes waste products, such as carbon dioxide and urea, from the fetal bloodstream and transfers them to the mother's bloodstream for elimination.

4. Immune protection: The placenta acts as a barrier against certain infections, protecting the developing fetus from harmful microorganisms.

How do egg-laying and marsupial mammals manage without a placenta?

Egg-laying mammals, known as monotremes, and marsupial mammals have different reproductive strategies compared to placental mammals.

Egg-laying mammals (Monotremes): Monotremes, such as platypuses and echidnas, lay eggs instead of giving birth to live young. They do not have a placenta. Instead, the eggs are incubated outside the mother's body until they hatch. After hatching, the mother provides milk to the young through mammary glands.

Marsupial mammals: Marsupials, such as kangaroos, koalas, and opossums, give birth to relatively undeveloped young. They have a short gestation period, and the young are born at an early stage of development. After birth, the newborn marsupial crawls into the mother's pouch, where it attaches to a nipple and continues to develop. The mother provides milk and care for the young until they are mature enough to leave the pouch.

In both egg-laying and marsupial mammals, the absence of a placenta is compensated by alternative reproductive strategies that ensure the survival and development of their offspring.