AIM: What happens to an egg between fertilization and birth? Lesson 29 DO NOW: If every cell in your body has the same DNA, then why do we have different looking and functioning cells? AIM: What happens to an egg between fertilization and birth?

Fallopian Tube- where fertilization occurs Uterus – where baby develops Ovary – Makes Egg Cervix Birth Canal – Baby exits body

Urethra- transports sperm & urine transport sperm into female Sperm Ducts- Transport sperm Penis - transport sperm into female Testes- Makes sperm

Don’t Copy During intercourse a male will ejaculate about 50 - 500 million sperm. These sperm will swim up through the female reproductive system. Not all of the sperm will reach the egg. Some sperm will reach the egg however only one will penetrate into the egg. The union of an egg and a sperm is called fertilization.

So what happens after fertilization? The process of combining a sperm with an egg is called fertilization. The majority of fertilization occurs in the fallopian tube. Once the egg is fertilized (zygote), it will have some DNA from the father and some DNA from the mother. The zygote will continue to move down the fallopian tube till it reaches the uterus. Once in the uterus, the zygote will implant itself into the uterine wall.

The sperm fertilizes the egg inside the fallopian tube, forming the zygote. Implantation Day 7 Fertilization Day 4 Day 3 Day 2 Day 1 Day 0 Egg released by ovary Uterine wall 4 cells 2 cells Zygote Ovary Fallopian tube

In two days, the zygote divides into two cells In two days, the zygote divides into two cells. After this first division, the developing organism is now called an embryo. Implantation Day 7 Fertilization Day 4 Day 3 Day 2 Day 1 Day 0 Egg released by ovary Uterine wall 4 cells 2 cells Zygote Ovary Fallopian tube

By day 4, the embryo has divided to form a ball of 50 identical cells. Implantation Day 7 Fertilization Day 4 Day 3 Day 2 Day 1 Day 0 Egg released by ovary Uterine wall 4 cells 2 cells Zygote Ovary Fallopian tube

By day 5, the embryo is a hollow ball of cells called a blastocyst. Implantation Day 7 Fertilization Day 4 Day 3 Day 2 Day 1 Day 0 Egg released by ovary Uterine wall 4 cells 2 cells Zygote Ovary Fallopian tube Day 5

By day 7 (1 week), the embryo becomes implanted into the wall of the uterus, where it continues to divide and grow. Implantation Day 7 Fertilization Day 4 Day 3 Day 2 Day 1 Day 0 Egg released by ovary Uterine wall 4 cells 2 cells Zygote Ovary Fallopian tube

http://www.dnatube.com/video/1127/Human-Reproduction-Fertilization-and-Fetal-Development http://video.google.com/videosearch?q=zygote&hl=en&emb=1&aq=f# http://www.youtube.com/watch?v=qhrZj2RuNgQ&feature=related

How can one tiny cell make all the different cells in your body? Inside the zygote is the DNA. The DNA contains all the information to make an organism. At first, all the cells in the zygote are identical but as the zygote divide, the cells begin to move to a specific place.

How can one tiny cell make all the different cells in your body? Once the cell reaches its position, certain genes “turn on” and some “turn off” This is called differentiation. Genes are piece of information on DNA that is responsible for a specific job in the body (example: eye color, height, skin color)

There is no up, down, left, right Now there is top and bottom cells Now there is a left side cell and right side cell Cells become more specialized

The cells in the embryo will eventually give rise to ALL 200 different specialized cells

Early in the division of the zygote, all the cells are exactly the same. These cells are said to be undifferentiated or Stem Cells.

What are stem cells and why are they important? Stem cells are the cells made during the zygote’s first few cell divisions. Because these cells are not differentiated yet, they have the ability to become any cell in the body. If a stem cell is removed and place in another part of the body, the stem cell will grow into that body part.

Obtaining Stem Embryonic Stem Cells

http://www.youtube.com/watch?v=8JTw2RpDo9o&feature=related http://www.youtube.com/watch?v=TEXPUrN2FiE&feature=fvsr

Problem with Stem Cells Currently medical stem cells only come from unwanted embryos. Removing these stem cells will kill the unborn child. An ethical problem occurs: Is it OK to “kill” a healthy embryo to save someone else?

When is the embryo called a fetus? At 8 weeks (2 months), the developing organism is called a fetus. 8 weeks

The fetus is suspended in a fluid-filled sac, called the amniotic sac. The fetus is totally surrounded by fluid (it is “underwater”). This fluid filled sac protects the fetus from bumps and shocks. (a pillow)

The placenta is a temporary organ that the baby makes inside the uterus. It allows nutrients and oxygen to diffuse from the mother’s blood to the fetus’s blood without letting the blood mix.

Also, the placenta allows wastes (like CO2) to go from fetal blood to the mother’s blood where they can be excreted. The placenta is attached to the fetus by the umbilical cord. Your belly button is a scar left from your umbilical cord.

CO2 & waste leaves the placenta and enters the mother’s blood From the baby No mixing of blood!!! Mother’s Blood Vessel To the baby O2 & nutrients leaves the mother’s blood and enters the placenta Placenta’s Blood Vessel

http://www.youtube.com/watch?v=yIrlwLQPRU0 http://www.youtube.com/watch?v=gJeRWGxOTcA

What goes in a mother, goes in the baby? Substances like drugs, alcohol and nicotine are small molecules. They can easily move through the placenta. These substances can harm the baby causing birth defects