REPRODUCTIVE (PART 3) Flashcards
Where does fertilisation (conception) occur?
In the fallopian tubes, when a sperm fertilises the ovum (egg)
What is a zygote?
The first cell formed after fertilisation, containing genetic information from both sperm and ovum
What is the acrosome reaction?
A biochemical reaction triggered when a sperm reaches the ovum, allowing it to penetrate the ovum’s outer layer
What are the two main parts of a blastocyst?
Inner cell mass (forms embryo, amnion and umbilical cord) and outer cell mass (forms placenta and chorion)
How many sperm can fertilise an ovum?
Only one
After fertilisation, the ovum changes to prevent other sperm from entering
What is the role of hCG (human chorionic gonadotropin)?
Produced by the trophoblast, it prepares the endometrium for implantation by causing decidualization (structural changes)
What is implantation?
The attachment of the blastocyst to the endometrium of the uterus
What is the difference between fertilisation and pregnancy?
Fertilisation is the fusion of sperm and ovum
Pregnancy begins with implantation of the fertilised egg (zygote) in the uterus
What are the three main stages of embryonic development?
Pre-embryonic (weeks 1 - 2): Implantation
Embryonic (weeks 2 - 8): Early organ formation
Foetal (weeks 8 - birth): Growth and development of organs and systems
What happens to the zygote after fertilisation?
It travels to the uterus, dividing into a morula and then a blastocyst
How does the foetus receive nutrients and oxygen?
Through the placenta, which increases in size and function throughout pregnancy
What is the placenta’s role?
An organ formed from the trophoblast that allows nutrient and gas exchange between mother and embryo/foetus
What are the three stages of labour?
Stage one: period from onset of uterine contractions until dilation of the cervix is complete
Stage two: period from the time of maximal cervical dilation until the baby exits through the vagina i.e. birth
Stage three: process of expulsion of the placenta through the vagina
What separates maternal and foetal blood in the placenta?
The placental membrane (barrier) with five layers
Why doesn’t maternal blood directly mix with foetal blood?
So substances pass through the placental barrier between the two circulations
How do uterine arteries change during pregnancy?
The trophoblast remodels them, making them wider and less resistant for increased blood flow to the placenta
What is a multiple birth?
The birth of two or more babies from the same pregnancy
Twins are most common
What are the risks of multiple births for babies?
They are more likely to be born prematurely and have complications in infancy
How can identical twins develop?
From a single fertilised egg (zygote) splitting early in development, like the inner cell mass dividing in a blastocyst
What is the role of oxytocin in labour?
Oxytocin causes contractions, and its release is a positive feedback loop that strengthens them
What can cause multiple ovulation?
Genetics or fertility drugs used in procedures like in vitro fertilisation (IVF)
How do fraternal twins develop?
From two separate eggs fertilised by two separate sperm
This often requires multiple eggs released in one menstrual cycle
How can labour be medically induced?
By introducing oxytocin to stimulate contractions
What triggers the hormonal changes that lead to labour?
High cortisol levels near the end of pregnancy causes falling hCG levels
