Menstrual Cycle and Pregnancy Flashcards
What stages is the menstrual cycle split into?
Ovarian cycle and uterine cycle driven by hormone level changes
What makes up the Ovarian cycle?
follicular phase
Ovulation
Luteal phase
What compromises the Uterine cycle?
(Endometrial cycle)
Menstrual phase
Proliferative phase
Secretory phase
What Feedback loops and hormones regulate the menstrual cycle?
Driven by feedback loops between hypothalamic GnRH, Pituitary LH and FSH, and ovarian oestrogen, progesterone, inhibin and activin release
What induces Tubular fluid reabsorption resulting in concentrated fluid? ( male )
Oestrogen
What induces Fructose and glycoprotein secretion in epididymal fluid
Androgens
What is the capacitation of sperm?
Achieve fertilising capability in the female reproductive tract by:
Loss of glycoprotein coat
Change in surface membrane characteristics
Develops whiplash movements of tail
Where does Capacitation take place and why?
Ionic and proteolytic environment of the fallopian tube
- Oestrogen dependent
- Ca2+ dependent
What reaction takes place at the Acrosome and Zona Pellucida?
Sperm binds to the ZP3 glycoprotein sperm receptor
Ca2+ influxed into sperm by progesterone
Release of hyaluronidase and proteolytic enzymes from acrosome
Spermatozoon penetrates the Zona pellucida
Where does Fertilisation take place?
Fallopian tube
What does fertilisation trigger?
Cortical reaction
Cortical granules release molecules which degrade Zona Pellucida e.g. ZP2, ZP3 preventing further binding
Haploid develops into Diploid
How does the zygote develop into a Conceptus ( Embryo which zygotic membranes )
Continues to divide as it moves down Fallopian tube to uterus (3-4 days)
Receives nutrients from uterine secretions
This free-living phase can last for ~ 9-10 days
8 cell conceptus which form a morula
Inner cell mass will form the embryo
Describe Implantation?
Attachment phase: outer trophoblast cells contact uterine surface epithelium
THEN
Decidualisation phase: changes in underlying uterine stromal tissue (within a few hours)
Requires progesterone domination in the presence of oestrogen
How does the Blastocyst attach to the endometrial lining?
IL-11 promote attachment alongside Leukaemia inhibitory factor.
Describe Attachment?
Leukaemia inhibitory factor (LIF) from endometrial cells stimulates adhesion of blastocyst to endometrial cells
Interleukin-11 (IL11) also from endometrial cells is released into uterine fluid, and may be involved
Many other molecules involved in process (e.g. HB-EGF)
What is Decidualisation?
Endometrial changes due to progesterone:
Glandular epithelial secretion
Glycogen accumulation in stromal cell cytoplasm
Growth of capillaries
Increased vascular permeability (→oedema)
Factors involved:
Interleukin-11 (IL11), histamine, certain prostaglandins & TGFb (TGFb promotes angiogenesis)
How does hCG change over the duration of the 40 weeks of pregnancy?
hCG peaks before 10 weeks and then falls to low levels
How does Progesterone levels change throughout pregnancy?
Increases steadily until 30-40 weeks where it drops
How do Oestrogens and Human placental Lactogen change throughout pregnancy?
Lower levels then progesterone, Lactogen lower thean Oestrogens
Steadily increase from start to week 40 then drops
What do progesterone and Oestrogen do during pregnancy?
First 40 days
Produced in corpus luteum (in maternal ovary)
stimulated by hCG (produced by trophoblasts) which acts on LH receptors
Essential for developing fetoplacental unit
Inhibits maternal LH & FSH (-ve feedback)
From day 40
Placenta starts to take over
Where is Progesterone and Oestrogen formed during pregnancy?
In the placenta post day 40
- Placenta makes progesterone from cholesterol – pregnenolone- prog
What is the main substrate for Oestrogens during pregnancy?
DHEAS which can be made by mother AND fetus
What maternal hormones increase during pregnancy?
ACTH Adrenal steroids Prolactin IGF1 (stimulated by placental GH-variant) Iodothyronines PTH related peptides
What maternal hormones decrease during pregnancy?
Gonadotrophins
Pituitary GH
TSH
Describe Endocrine control of partruition ( labour )?
Main hormone is oxytocin from post pituitary:
- Uterine contraction with increased numbers of oxytocin receptors in late pregnancy
- Cervical dilation
- Milk ejection
Contributions from cortisol and oestrogen
Milk production is prolactin
Oxytocin receptorsare expressed by the myoepithelial cells of the mammary gland, and in both the myometrium and endometrium of theuterusat the end of pregnancy.
