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What happens in the early stages of development?

1) 2 cell embryo
2) Embryo size stays the same, number of cell increase
3) The fertilised egg divides to form a ball (the morula)
4) This ball becomes morula become hollow (the blastocyst)
5) The outer cells are the trophoblast


What happens during early embryonic development?

Regulated series of mitotic divisions not accompanied by cell growth


Name the days related to the cell stages of early embryonic development

Day 1: 2 cell
Day 2: 4 cell
Day 3: 8 cell
Day 4: Morula
Day 5: Blastocyst (with inner cell mass)


What does the inner cell mass give?

Give rise to foetus
Get stem cell from here
PGD (Preimplantation Genetic diagnosis) taken at inner cell mass


What are embryonic stem cells?

ES cells are pluripotent stem cells derived from inner cell mass of blastocyst (early stage preimplantation embryo)


What is special about embryonic stem cells?

Able to differentiate into many cell types in the body


What is the outer cell mass and inner cell mass of blastocyst?

Outer cell mass: Trophoblast
Inner cell mass: embryoblast


What is preimplantation genetic diagnosis?

Used to identify genetic defect in embryo created through ART before pregnancy (this way you can transfer only unaffected embryo to the patient)


How do cells become different from each other?

Placing a labelled cell in the centre of the ball of cells means it will end up in the inner cell mass
Placing a labelled cell at the edge of the ball of cells means it will end up as trophoblast


What does positional information of the cells give?

Cells constantly respond to their positions and local signals in order to differentiate
Some trophoblast cells are in contact with the inner cell mass and some are not


During assisted reproduction, what is used to increase the chances of success?

Poking holes in Zona Pellicuda to help the hatched blastocyst


What is a requisite for implantation?

Hatching Blastocyst


How does a hatched blastocyst form?

Cells of blastocyst recreate proteases
- Proteases digest proteins in zona ->
Hatching blastocyst
- Embryo escapes through digested zone ->
Hatched blastocyst


For implantation, what does the uterus end up with?

With a hatching blastocyst


What is hCG used for?

Basis of pregnancy test


What is hCG used for?

Basis of pregnancy test


What is ectopic pregnancy?

Embryo implanting at the wrong place
Be quite serious if the embryo brings its own blood supply which causes haemorrhage


What is hCG used for?

Basis of pregnancy test


What happens during Day 7 of implantation?

1) Syncytiotrophoblast: infiltrate the cells of the endometrium
2) Blastocyst drawn into the uterine cell
3) Embryonic disc is bilaminar (consisting of epiblast and hypoblast layer)


What happens during Day 8 of implantation?

1) Amniotic cavity formed within epiblast
2) Growing syncytiotropoblast: Covers more of blastocyst


What happens during Day 9 of implantation?

1) Embryo completely implanted in the uterine endometrium
2) Amniotic cavity expanding
3) Formation of Heuser's membrane (hypoblast cells)
4) Coagulation plug in the endometrial surface


Can coagulation plug be seen on ultrasound?

yes in ultrasound on the uterine wall


What happens during Day 10 - 11 of implantation?

1) Extraembryonic mesoderm formed between Heuser's membrane and cytotrophoblast
2) Trophoblastic lacunae fill with blood (maternal capillaries)


Why is the maternal capillaries important?

Important to transfer nutrients to embryo


Embryonic proper has how many layer?

Two layers


What happens during Day 11 - 12 of implantation?

Extraembryonic mesoderm expands between the amnion and the cytotrophoblast


What happens during Day 12 - 13 of implantation?

1) Extraembryonic mesoderm splits into two layers
2) Space between the two layers is the chorionic cavity
3) Second wave of hypoblast cells migrate
4) Produce new membrane that migrates over the inside of extra embryonic mesoderm
5) Formation of secondary yolk sac lining


What happens during Day 13 of implantation?

1) Secondary (definitive) yolk sac develops
2) Primary yolk sac breaks up, and it is reduced to a collection of vesicles


What are the functions of the secondary yolk sac?

1) Haematopoeisis -> formation of new blood cell
2) Protein production
3) Provides sanctuary for germ cells (primordial germ cell)
4) Nutrition


How does the conceptus get nutrition during week 1?

1) Lives off nutrients stored in ovum
2) Hatches
3) blastocyst enlarges by incorporation of secretion form uterine gland
4) Implants
5) Nutrition and elimination by simple diffusion


Why is the yolk sac of the human not as big as of the one of a chicken?

Because chicken don't have placenta and depend on yolk sac for constant nutrition


How does the conceptus get nutrition during week 2?

1) From day 9 onwards, development of the utero-placental circulation take place.
2) Vacuoles develop in the Syncytiotrophoblast = traphoblastic lacunae
3) nearby maternal capillaries (include in the lacunae) expand to become the maternal sinusoids


What takes place in the uteroplacental circulatory system?

Exchange of gases, nutrients, waste between fetus and maternal systems


How does getting rid of waste by embryo take place?

Basic metabolism, getting rid of toxic waste via maternal blood


What happens during development in relation to the chorion?

The chorion undergoes rapid proliferation and forms numerous processes, the chorionic villi,


What does the chorionic villi do?

which invade and destroy the uterine decidua and at the same time absorb from it nutritive materials for the growth of the embryo


What are the three different stages of chorionic villi?

Primary: contains trophoblast
Second: contains trophoblast and mesoderm
Tertiary: contains trophoblast, mesoderm and blood vessels


When does the different stages of chorionic villi occur during gestation?

Primary: 13 - 15 days
Second: 16 - 21 days
Tertiary: 21st day


What happens during the primary chorionic villi?

The chorionic villi are at first small and non-vascular.


What happens during the second chorionic villi?

The villi increase in size and ramify, while the mesoderm grows into them.


What happens during the tertiary chorionic villi?

Branches of the umbilical artery and umbilical vein grow into the mesoderm, and in this way the chorionic villi are vascularized.


What are factors that maintain pregnancy?

1) hCG
2) Oestrogen and progesterone
3) Oxytocin


What are the factors affecting fertility?

1) Genetics
2) Ageing
3) Nutrition
4) Environment
5) Drugs
6) Trauma
7) Disease


For women, what happens when age increases?

Decrease egg quality
Decrease egg number
Increase genetic abnormalities
At 20, 30%. At 30+, 20%. At 40, 5%


For men, what happens when age increases?

Increase life expectancy of child
Increase genetic abnormalities
At age 60, then there is a decrease in fertility


Why does life expectancy of child increase when age increases for men?

Telomeres at the end of the chromosome keep everything in place and the sperm increases telomere


What does ART stand for?

Assisted Reproductive Technologies such as invitro


What happens during in vitro fertilisation

1) Egg collection
2) Sperm and egg mixed together in a lab
3) Embryo transferred into the womb


What is Intracytoplasmic Sperm Injection?

Take sperm and insert into the cytoplasm of the egg


What are the different ART?

1) In vitro fertilisation
2) intracytoplasmic Sperm injection
3) preimplantation genetic diagnosis


What is preimplantation genetic diagnosis?

Used to identify genetic defects in embryo created through ART before pregnancy, transfer only unaffected embryos in the patient


How do you measure oocyte quality?

1) non invasive markers
2) biomarkers
-> nuclear stain: blue
-> ATRX -> green


What is the ovary?

An endocrine organ with tremendous potential and a huge wastage.


At puberty, girls have how many oocyte?

Approx. 500,000 oocytes


How many oocyte will girls ovulate in total?

A lot of oocytes are degenerated therefore only a total of 400 - 500 oocyte in total


What happens when to the follicles?

Remaining 99.9% of the follicles will degenerate


What is the life expectancy of girls today?

Estimated that half of all girls born today have a life expectancy of more than 100 years


Women live half their life in what?

In menopause


What does menopause cause?

1) osteoporosis
2) cardiovascular disease
3) various cognitive disabilities
4) decreased wellbeing and sexuality


50% of women are expected to have what?

>50 experience an osteoporosis related fracture in their lifetime


What can happen now due to technology in relation to ovation tissue?

1) Ovarian tissue can now successfully be cryopreserved and when translated restore function for prolonged period of time (delaying menopause onset) [esp: for cancer patients]
2) possible to provide excellent protection towards osteoporosis and cardiovascular diseases


When does oocyte degeneration take place?

as soon as you are born