fertilisation, implantation, hormonal control Flashcards
What are hormones and where are they produced?
Hormones
- chemical messengers that regulate bodily processes - metabolism and reproduction.
- Produced by endocrine glands to control and synchronise the ovarian and menstrual cycles.
outline the features of implantation.
The process of the blastocyst attaching to the endometrium, typically occurring one week after fertilisation.
- Blastocyst attaches to the endometrium, signalling the start of pregnancy.
- It accesses nutrients from surrounding blood vessels to develop into an embryo.
- Placenta forms, facilitating the exchange of gases and nutrients between mother and embryo.
- The placenta secretes hCG, maintaining the corpus luteum to continue progesterone production, preventing the shedding of the endometrium.
outline the features of fertilisation
- The fertilisation process and fusion of gametes occurs in the fallopian tube of
female’s body - The zygote will develop into a living organism that has mixed genetic information
from the parents, allowing for the continuity of a species.
Process:
1. Male and female haploid gametes fuse in the oviduct to form a zygote, a single cell
with 46 chromosomes.
2. The zygote rapidly undergoes mitosis, progressing to the morula (16-cell) stage to form the blastocyst.
-It then moves from
the oviduct into the uterus.
3. The inner cell mass of the blastocyst forms the embryo and the outer layer of cells, the trophoblast, forms the placenta.
What stimulates the release of FSH and what does it do? Outline the process
The hypothalamus secretes GnRH which travels to the anterior pituitary glands which secretes the FSH which travels to the ovaries to stimulate follicle maturation.
What happens as the follicles mature?
More oestrogen is released both increasing more FSH to be secreted and endometrium line to also be thickened.
What happens when oestrogen levels peak?
LH starts to surge causing the mature follicle to release the egg which is ovulation and the end of the follicular phase.
How long does the follicular phase last for? What phase occurs after follicular phase
7-14 days, then comes luteal phase.
what happens to the follicle after the egg is released?
it becomes the corpus luteum.
what does the corpus luteum do?
It releases progesterone which develops the endometrium for implantation.
What happens to the corpus luteum if pregnancy does not occur?
It regresses into the corpus albican which results in low progesterone levels meaning the endometrium also sheds leading to menstruation.
What are the main hormones that help maintain pregnancy?
hCG, oestrogen, progesterone
What’s the source hCG?
What role does hCG have in pregnancy and what are the patterns on the ovarian cycle graph?
- Secreted by the developing embryo.
- Stops the degeneration of the corpus luteum, causes the corpus luteum to grow larger to support the endometrium.
- levels increase from 4-12 week and then starts to decrease 12-24 weeks then plateaus
What’s the source oestrogen?
What role does oestrogen have in pregnancy and what are the patterns on the ovarian cycle graph?
- Corpus luteum then placenta after 12-14 weeks as corpus luteum withers away
- Stimulates the growth of uterus to accommodate the growing foetus+mammary glands during pregnancy to prepare for breastfeeding
- Last few weeks levels increase
What’s the source progesterone?
What role does progesterone have in pregnancy and what are the patterns on the ovarian cycle graph?
- Corpus luteum then placenta after 12-14 weeks as corpus luteum withers away
- causes endometrium to become thickened and very vascularised to deliver nutrients to embryo
- inhibits FSH and LH secretion to prevent more ova released
- prevents uterine walls from contracting to prevent labour
- Last few weeks:
levels decrease
what causes birth (contractions)
the decrease in progesterone and oestrogen
