Thematic AnalysisThe reproductive systems of marsupials differ markedly from those of placental mammals. During embryonic development, a choriovitelline placenta is formed in all marsupials. In bandicoots, an additional chorioallantoic placenta forms, although it lacks the chorionic villi present in eutheric placentas. Female marsupials have two lateral vaginas, leading to separate uteruses, but both open externally through the same orifice. A third canal, the median vagina, is used for childbirth. This channel can be transient or permanent. Like all marsupials, the female kangaroo has 3 vaginas and uteruses (wombs). The two outermost vaginas are used to transport sperm into the uteruses. Babies are born in the middle. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original essay With this unusual reproductive system a female kangaroo can be in a continuous state of pregnancy, with a fertilized egg in one uterus waiting to be released, a baby growing in the second uterus, one in the pouch, and another he jumps out but goes to his mother for milk. Another unique feature of these animals is that during periods of extreme drought and starvation the female kangaroo can practice birth control by placing babies growing in the womb "on hold", interrupting their future development until conditions they don't improve. This is called embryonic diapause. When the mother's pouch releases, the next baby will be born and move into the pouch, and the fertilized egg "retained" in the uterus will begin to develop into a new fetus. Because of this multiple offspring strategy and other adaptabilities unique to kangaroos, populations can increase rapidly when food is plentiful. Female kangaroos get pregnant on a regular basis. They shed an egg from their ovaries and it slides down the fallopian tubes where, if it meets sperm, the egg is fertilized and then becomes embedded in the wall of the mother's uterus. BUT, here's the big difference between us normal mammals and marsupial mammals, no placental connection is formed. As soon as the marsupial egg has consumed its yolk to survive and develop (just like a bird's egg), it must be born. So the entire pregnancy only lasts about 28 days! At the end of the pregnancy the expectant mother sits up and cleans her pouch. The baby emerges from an opening at the base of the tail called the cloaca. The baby is very small, about the size of a lima bean. It is pink and largely undeveloped, except for the two front arms which are crucial for climbing up the mother's abdomen to the pouch. The child, who is little more than a fetus, manages to climb completely without help and guided only by instinct. Once inside the pouch the baby finds one of the mother's four nipples and takes the end into his mouth. The baby does not have the muscles to suck at this stage. Instead, the nipple swells inside the baby's mouth so that it cannot come off, and milk is secreted very slowly into the baby's mouth. Later, once the baby's jaw is more developed, he will be able to release and suck at will. BABY 1: Firmly attached to the teat, mother kangaroo can practically clean your paws. Red kangaroo pups spend about 235 days in the pouch before emerging, while gray kangaroo pups remain in the pouch for much of the year. He begins to explore outside his mother's pouch. As Joey experiments with new carbohydrate-rich plant foods, he sucks less. This lets the mother know that the baby is ready for BABY 2, at which point she allows another 2.