Embryo Implantation And Fetal Development 5.2.24 Flashcards
What are the stages in the ovarian cycle?
- Follicular phase , pre-ovulation
- Ovulation
- Luteal phase
How long is the average Ovarian cycle?
28 days
What is involved in the first stage of the Endometrial cycle?
1. Proliferative Phase
oestrogen - growth of the endometrium and myometrium , secretion of the mucus alongside the vagina and uterus
What is involved in the 2nd stage of the Endometrial cycle?
2. Secretory Phase
Oestrogen - grows the endometrium
Progesterone - softens the connective tissues in preparation for implantation and promotes secretion of nutrients ( fat and glycogen)
What is involved in the 3rd stage of the Endometrial cycle ?
3. menstrual phase
Only occurs if no fertilisation occurs
- Corpus leuteum decreases
- progesterone and oestrogen support is lost
- Uterine prostaglandins —> Vasoconstriction —> Tissue death
- Blood and endometrial debris (menses) lost through Vagina
How long can sperm survive for?
It can survive for up to 5 days but is only viable for 48 hours
What hormone does the Hypothalamus release?
GnRH
What hormone does the Anterior pituitary release?
LH/FSH
Which 2 hormones do the Ovaries release?
Oestrogen/ progesterone
What does GnRH stand for?
Gonadotropin hormone releasing hormone
What does a Rise in FSH stimulate?
Stimulates Oocyte (egg) development and follicular growth
What causes LH to spike?
Ovulation
IS ovulation a positive or negative feedback?
Positive
Is after ovulation positive or negative feedback?
Negative feedback due to progesterone
What process is Sperm is driven by to reach the oviduct?
Chemotaxis
How long after ovulation does fertilisation occur?
24 hours
what membrane do sperm penetrate?
The Corona Radiata
What do the sperm bind to after penetration?
Receptors on the Zona pellucida
What does the binding of sperm onto the receptors on Zona pellucida cause?
It causes an enzyme to be released form the acrosome that digest the Zona pellucida.
What reaction is triggered when the sperm head penetrates the ovum?
Cortical reaction
What does a cortical reaction trigger?
Inactivation of ZP3 receptor as and prevents polyspermy
when does Fusion of Nuclei occur?
Occurs within an hour triggering embryonic development
What are the 4 Stages of Ovum development?
1 - Ovum
2 - Cleavage
3 - Morula
4 - Blastocyst
What are the Stages of implantation?
- Blastocyst surface becomes sticky and adheres to endometrium
- The trophoblastic cells release protein-digesting enzymes
- Cords of trophoblastic cells go deeper into the endometrium
- The embraces of trophoblastic cells disintegrate
- Underlining endometrium produces prostaglandins that increase vascularisation and nutrients
- The embryo is implanted into the endometrium
What is the endometrium called after its been modified by prostaglandins?
Decidua
What is an ectopic pregnancy?
When implantation occurs outside of the uterus. Most typically in one of the fallopian tubes.
What is the cause for molar pregnancy?
Abnormal fertilisation
What is a molar pregnancy?
It’s where the trophoblastic tissue over grows and shows as a mass of cysts.
when there is a problem with fertilisation so the embryo and placenta don’t form correctly.
What is a molar pregnancy also known as?
Hydatiform pregnancy
What is the placenta responsible for?
Delivery of oxygen and nutrients
Removal of wastes and CO2 from the fetus