How could a man become pregnant?

How could a man become pregnant? Where would you put the embryo so that it is close to a source of nutrients?

placenta A temporary organ (gland) forming from the outermost layer of the embryo and the lining of the mother’s uterus What are the functions of the placenta?

1. source of nourishment for embryo Functions of the Placenta 1. source of nourishment for embryo 2. respiratory surface for embryo 3. excretory organ of embryo 4. attaches embryo/fetus to wall of uterus 5. secretes chorionic gonadotropin, progesterone, estrogen - regulation of pregnancy

Placenta Fetus Uterus Umbilical Cord Amniotic Fluid Amniotic Sac (Amnion)

Umbilical Vein Umbilical Artery Placenta Chorionic Villus Fetal Capillary http://www.youtube.com/watch?v=u7eZHzYxPec&feature=related

The blood of the embryo/fetus and the mother do not mix! (embryonic and maternal circulatory systems are not connected ) How do substances get for the mom’s blood to the fetus and vice versa?

Substances diffusing through the placenta From mom to embryo/fetus Oxygen Nutrients Antibodies From embryo/fetus to mom Wastes Human Chorionic Gonadotropin

Dangerous substances can pass through the placenta Viruses (e.g. measles, AIDS) Drugs (e.g. nicotine, prescription drugs) Alcohol

What is the function of amniotic fluid? 6 weeks http://health.howstuffworks.com/adam-200127.htm - Keeps baby warm - Lubrication keeps body parts from growing together - Allows movement of baby (exercise) - Shock absorber

Why do biologists classify egg-laying monotremes, such as the duckbill platypus, as mammals? Monotremes have mammary glands, bodies covered with hair, and other mammalian characteristics

Monotremes Their eggs of contain a large amount of yolk. Why do they have much more yolk than placental mammals?

Monotremes do not have a placenta. Yolk provides nourishment for the developing embryo. Placental mammals do not have much yolk in their eggs since the embryo gets nutrients through the placenta.

Mammals Monotremes lay eggs ex. echnida, platypus Marsupials - ex. Kangaroo, oppossum How does the embryo get nutrients? Placentals - humans, whales embryo completes development in a pouch, attaches to nipple (milk)

Birth of kangaroo embryo, climb to pouch http://www.youtube.com/watch?v=MQ_eeDvCo8U

Why have placental mammals been more successful than the nonplacental mammals? developing young are protected within the uterus of the female until embryonic development is completed (internal development).

Who has a larger egg cell, an elephant or a chicken?

Why doesn’t an elephant need a large egg? It has a placenta

Why does a chicken need a larger egg? Chicken Egg - Trials of life – Arriving chapter 6 External development – no placenta

amniotic fluid chorion allantois Chicken embryo airspace shell yolk sac albumin yolk

           Animal Internal Fertilization External Fertilization Internal Development External Development Amphibians Reptiles Birds Mammals nonplacentals placentals           