Menstrual Cycle Flashcards
(40 cards)
What occurs in the ovarian cycle?
Follicular phase (0-14 days): FSH and LH remain at steady levels in the pre-ovulatory phase but then ovulation occurs as the LH surge happens and there is also a small peak of FSH
Luteal phase (14-28 days): FSH and LH trail off and the post-ovulatory phase ensues
What occurs in the uterine cycle?
Menses (0-7 days): levels of oestrogen are slowly rising
Proliferative phase (7-14 days): oestrogen is rising more and peaks whilst progesterone also starts to rise
Secretory phase (14-28 days): estrogen levels start to drop with 1 more small peak and progesterone reaches its peak and declines again
What are the different layers of the endometrium?
Myo
Basalis
Functonalis (contains uterine natural killer cells)
What happens to the endometrium in the menstrual cycle?
Rapid growth of endometrium (1-10mm) but only the funtionalis layer is shed at menstruation because the basalis has blunted hormone responses
What happens to the myometrium in the menstrual cycle?
Hormone-dependent differentiation that parallels that endometrial changes which eventually forms the placental bed in pregnancy - specialist contraction waves occur here throughout the cycle
What are the layers of the uterus from inner to outermost?
Endometrium: made up of glandular cells making secretions
Myometrium: thickest muscular layer
Perimetrium: outer serous layer
How do steroid hormones act on endometrial cells?
- Ovarian hormones activate nuclear receptors and gene expression
- This causes the cell to release chemokines, cytokines and GFs which have autocrine, paracrine and junctacrine affects
- The mediators can cause the cell to proliferate, differentiate or apoptose
- Mediators also feedback to cell
What is the main point of the menstrual cycle?
Unparalleled tissue remodelling (x400) involving a luteal phase at 14 days and a proliferative phase which has a more variable time limit at 10-16 days - sequential actions of E2/P4 bestow specific functions on cervix and uterus
What are the typical time points for menarche and menopause?
Menarche = 12yrs (8-16yrs) - although 1st uterine bleed occurs after birth in 5% of newborns
Menopause = 52yrs (45-55yrs)
What intercycle variability exists?
Regular: < 8 days between cycles
Irregular: 8-20 days between cycles
Very irregular: > 20 days between cycles
Who do women have menstrual cycles?
From embryonic to maternal control of decidualization involving:
- Trophoblast invasion
- Haemostasis
- Immunomodulation
- Oxidative stress defences
What are the functional windows in the menstrual cycle?
- Regeneration (1-5 days) in menstrual phase
- Fertile window (11-14 days) in proliferative phase
- Implantation window (19-21 days) in the secretory phase
- Selection window (23-27 days) also in the secretory phase
What are the key features of the fertility window?
- Ovarian hormones peaking
- Ovulation is occurring
- Cervix is thinner, open and changing with a watery weak
- Spinbarkeit (spinnability) of cervical mucus
- Basal body temp is higher
What is the fertile window?
Probability of intercourse resulting in pregnancy in > 5% of women spanning on average 4-5 days before and 1 day post-ovulation involving coordinate changes in the cervix (mucus, positioning, softness), JZ contractions and basal body temp. which allow estimations of fertile and infertile days
What fertility awareness methods exist?
Calendar-based methods/apps
Ovulation prediction kits
Fertility monitors
What occurs in the first 10 days if an egg is fertilized in the ovary?
0: ovulation occurs and oocyte is fertilized at ovary forming a zygote
1: first cleavage
2: 2-cell stage
3-4: 4-cell stage forms the 8-cell compacted morula
5: early blastocyst with trophectoderm, blastocoel and inner cell mass
6-7: late-stage blastocyst that is hatching with the zona pellucida present
8-9: implantation of blastocyst now containing epiblast and hypoblast
What is the implantation and selection window?
A defined window at 2-4 days that synchronises embryo development and endometrial milieu which is a step-wise process involving apposition and adhesion of embryo to luminal endometrial epithelium, followed by invasion of underlying stroma - decidual but not undifferentiated stromal cells have the propensity to migrate and encapsulate the embryo and engage in ‘sensoring’ embryo quality.
What is classed as a miscarriage?
Pre-clinical loss at 6 weeks (pregnancy tests can detect pregnancy before/at this early stage now though)
When do most people lose their babies?
Pre-implantation or pre-clinically RATHER than clinically
Why can pregnancy cause complications for the mother?
The placenta moves from having extreme embryonic diversity to total maternal commitment so it heavily controls the mum making the prime role of the body to take care of the growing baby
What are most human embryos?
Mosaic i.e. have a mix of normal and abnormal cells
What complications can occur as a result of pregnancy?
HYN
Eclampsia
What are the quality control checkpoints in pregnancy that help in natural selection of human embryo?
Before implantation:
1. Self-correction: apoptosis/lineage allocation
After implantation:
2. Decidual biosensing (+ve/-ve selection)
3. Placental fitness hormones (hCG/hPL)
4. Stress test of placental perfusion (if not well establish O2 tension will cause free radical production)
What are implantation genes?
27 existing genes highly enriched in metabolic enzymes and that are lost in evolution but tell the body to keep the embryo as it is competent - poor quality embryos will instigate a stress response facilitating the body to get rid of it
