Only a minority of therian mammals are marsupials. The embryo completes its development outside the mother’s body in a pouch on her belly.
A marsupial is a therian mammal in which the embryo is born at an early, immature stage. Marsupials have a different way of reproducing that reduces the mother’s risks. It may even result in the mother’s death. Giving birth to a large infant is also risky. Because the fetus is inside her, she can’t abandon it to save her own life if she is pursued or if food is scarce. As a result, she may be less able to escape from predators. She also becomes heavier and less mobile as the fetus gets larger. The mother has to eat more food to nourish the fetus. On the other hand, supporting a growing fetus is very draining and risky for the mother. As a result, the fetus can become large and mature before birth. The placenta permits a long period of fetal growth in the uterus. The placenta allows the exchange of gases, nutrients, and other substances between the fetus and mother. Thus, it protects the fetus from being attacked by the mother’s immune system as a “foreign parasite.” The placenta lets blood from the fetus and mother exchange substances without actually mixing. It also passes carbon dioxide and other wastes from the fetus to the mother. The placenta passes oxygen, nutrients, and other useful substances from the mother to the fetus. It consists of membranes and blood vessels from both mother and embryo (see Figure below). Placental mammals give birth to relatively large and mature infants. The placenta sustains the fetus while it grows inside the mother’s uterus. Placental mammals are therian mammals in which a placenta develops during pregnancy. Each group has a somewhat different reproductive strategy. Therian mammals are divided into two groups: placental mammals and marsupial mammals. The female reproductive system of all therian mammals is similar to that of humans. The vagina is also where the male deposits sperm during mating.įemale Reproductive System of a Therian Mammal (Human). The vagina is a tubular passageway through which the embryo or fetus leaves the mother’s body during birth.Muscular contractions of the uterus push the offspring out during birth. The embryo or fetus develops inside the uterus. The uterus (plural, uteri) is a pouch-like, muscular organ.Therian mammals also have two additional female reproductive structures that are not found in other vertebrates. These are the organs that produce eggs (see Figure below). Like other female vertebrates, all female mammals have ovaries. The three different ways mammals give birth – Kate Slabosky Only a few mammals lay eggs instead of giving birth to an infant or embryo. Mammals that are viviparous are called therian mammals. They are born either as relatively large, well-developed fetuses or as tiny, immature embryos. female reproductive organ that receives sperm during sexual intercourse and provides a passageway for a baby to leave the mother’s body during birth.female reproductive organ in therian mammals where an embryo or fetus grows and develops until birth.viviparous mammal that may be either a marsupial or placental mammal.therian mammal in which a placenta develops during pregnancy to sustain the fetus while it develops inside the mother’s uterus.temporary organ that consists of a large mass of maternal and fetal blood vessels through the mother’s and fetus’s blood exchange substances.type of mammal that reproduces by laying eggs.therian mammal in which the embryo is born at an early, immature stage and completes its development outside the mother’s body in a pouch on her belly.Outline reproduction in placental mammals.Describe female reproductive structures of therian mammals.
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