1. Reproduction slides II

2. Fertilization
6.6.5 Outline the process of in vitro fertilization (IVF) Discuss the ethical issues associated with IVF Describe the process of fertilization, including the acrosome reaction, penetration of the egg membrane by a sperm and the cortical reaction Outline the role of HCG in early pregnancy Outline early embryo development up to the implantation of the blastocyst Explain how structure and function of the placenta, including its hormonal role in secretion of estrogen and progesterone, maintain pregnancy State that fetus is supported and protected by the amniotic sac and amniotic fluid State that materials are exchanged between the maternal and fetal blood in the placenta Outline the process of birth and its hormonal control, including the changes in progesterone and oxytocin levels and positive feedback.

3. 6.6.5 Outline the process of in vitro fertilization (IVF)
In vitro fertilization refers to fertilization that occurs outside the body ('in vitro' = 'in glass')
Stop normal menstrual cycle (with drugs)
Hormone treatments to develop follicles (FSH to stimulate follicle growth ; hCG for follicle maturation)
Extract multiple eggs from ovaries

4. Sperm selected, prepared (capacitation) and then injected into egg via intra-cytoplasmic sperm injection (ICSI)
Fertilization occurs under controlled conditions (in vitro)
Implantation of multiple embryos into uterus
Test for pregnancy is conducted to see if implantation was successful

5. 6.6.6 Discuss the ethical issues associated with IVF.
Advantages
Disadvantages
IVF is expensive and might not be equally accessible to all
Success rate is low (~15%) and therefore stressful for couples
It could lead to eugenics (e.g. gender choice)
Often leads to multiple pregnancies which may be unwanted, unable to be budgeted for and involves extra birth risks
Issues concerning storage and disposal of unused embryos (right to life concerns)
There are cultural and religious objections to embryo creation by such means
Inherited forms of infertility may be passed on to children
Chance for infertile couples to have children
Genetic screening of embryos could decrease suffering from genetic diseases
Spare embryos can be stored for future pregnancies or used for stem cell research

6. Describe the process of fertilization, including the acrosome reaction, penetration of the egg membrane by a sperm and the cortical reaction.
When the sperm enters the female reproductive tract, biochemical changes to the sperm occur in the final part of its maturation (capacitation). 
The sperm is attracted to the egg due to the release of chemical signals from the secondary oocyte (chemotaxis)
Fertilization generally occurs in the oviduct (fallopian tube)
To enter the egg membrane, the sperm must penetrate the protective jelly coat (zona pellucida) surrounding the egg via the acrosome reaction
The acrosome vesicle fuses with the jelly coat and releases digestive enzymes which soften the glycoprotein matrix

7. Fertilization video: 5:42
The membrane of the egg and sperm then fuse and the sperm nucleus (and centriole) enters the egg
To prevent other sperm from penetrating the fertilized egg (polyspermy), the jelly coat undergoes biochemical changes via the cortical reaction
The cortical granules release enzymes that destroy the sperm- binding proteins on the jelly coat

8. Now fertilized, the nucleus of the secondary oocyte completes meiosis II and then the egg and sperm nuclei fuse to form a diploid zygote (begin at 6:57 min. )

10. 11.4.11 Outline early embryo development up to the implantation of the blastocyst.
After fertilization, the zygote undergoes several mitotic divisions to create a solid ball of cells called a morula (at around 4 days)
Unequal divisions beyond this stage cause a fluid-filled cavity to form in the middle - this makes a blastocyst (at around 5 days)
The blastocyst consists of:
An inner mass of cells (this will develop into the embryo)
An outer layer called the trophoblast (this will develop into the placenta)
A fluid filled cavity (called the blastocoel)
These developments all occur as the developing embryo is moving from the oviduct to the uterus
When the blastocyst reaches the uterus, it will embed in the endometrium (implantation)

12. 11.4.10 Outline the role of HCG in early pregnancy
The endometrium is a blood-rich environment in which an implanted zygote can grow and it is sustained by the hormone progesterone
If progesterone levels aren't maintained (i.e. the corpus luteum degenerates), then the endometrium will be sloughed away (menstruation)
A fertilized zygote develops into a blastocyst that secretes human chorionic gonadotrophin (hCG)
hCG maintains the corpus luteum post- ovulation so that the blastocyst can remain embedded in the endometrium and continue to develop
Gradually the placenta develops and produces progesterone (at around weeks), at which point the corpus luteum is no longer needed

13. State one example of a fibrous protein and one example of a globular protein.

14. Explain how structure and function of the placenta, including its hormonal role in secretion of estrogen and progesterone, maintain pregnancy.
Structure and Function:
The placenta is a disc-shaped structure that nourishes the developing embryo
It is formed from the development of the trophoblast upon implantation and eventually invades the uterine wall
The umbilical cord connects the fetus to the placenta and maternal blood pools via open ended arterioles into intervillous spaces (lacunae)

15. Chorionic villi extend into these spaces and facilitate the exchange (diffusion of gases and nutrients) of materials between the maternal blood and fetal capillaries.
Nutrients, oxygen and antibodies will be taken up by the fetus, while carbon dioxide and waste products will be removed
The placenta is expelled from the uterus after childbirth

16. 11.4.14 State that materials are exchanged between the maternal and fetal blood in the placenta
The fetus relies on the exchange of materials across the placental wall to grow and develop:
The placental barrier separates maternal blood from fetal blood.
Exchange of waste products.
During birth – there is a possibility of exchange/exposure of blood between mother and infant – concerns arise for Rh- mothers with Rh+ babies.

17. 11.4.13 State that fetus is supported and protected by the amniotic sac and amniotic fluid
The fetus develops in a fluid-filled space called the amniotic sac
Amniotic fluid is largely incompressible and good at absorbing pressure, and so protects the child from impacts to the uterine wall
The fluid also creates buoyancy so that the fetus does not have to support its own body weight while the skeletal system develops
Finally, amniotic fluid prevents dehydration of the tissues, while the amniotic sac provides an effective barrier against infection

18. Outline the process of birth and its hormonal control, including the changes in progesterone and oxytocin levels and positive feedback.
The process of childbirth is called parturition and is controlled by the hormone oxytocin
After nine months, the fetus is fully grown and takes up all available space in the uterus, stretching the walls of the uterus
This causes a signal to be sent to the brain, releasing oxytocin from the posterior pituitary

19. Oxytocin inhibits progesterone, which was inhibiting uterine contractions
Oxytocin also directly stimulates the smooth muscle of the uterine wall to contract, initiating the birthing process
The contraction of the uterine wall causes further stretching, which triggers more oxytocin to be released (causing even more contraction)

20. Additionally, the fetus responds to the cramped conditions by releasing prostaglandins which cause further myometrial contractions
As the stimulus causing oxytocin release is increased by the effects of oxytocin, this creates a positive feedback pathway
Contractions will stop when labor is complete and the baby is birthed (no more stretching of the uterine wall)

21. Happy Birthday!