Pregnancy, parturition + lactation Flashcards
Semester 1 year 1
What are oocytes surrounded by?
Granulosa cells
What must happen to allow the sperm to penetrate the egg?
-sperm undergo physiological changes to their membrane + increase mobility in the vagina
-smooth muscle contractions in uterus + fallopian tubes to aid sperm trajectory
-cervical mucus made into channels to help sperm be propelled
How does fertilisation occur?
-sperm undergo acrosomal reaction that allows penetration
-acrosome contains enzymes that break down the egg
-a cortical reaction activated the oocyte - increase in Ca2+, causing 2nd meiotic division + prevents polyploidy
Describe what happens to the fertilised egg pre-implantation
-it’s nourished by oviduct secretions as it moves along it for 3 days
-when it reaches uterus, it floats freely for another 3 days
-then forms a blastocyst (becomes lined by trophoectoderm layer)
-after 6 days, blastocyst is implanted
Why does it take 3 days for the fertilised egg to move along the fallopian tube?
-impeded by contractions of isthmus stopping it from reaching uterus
-allows womb lining to generate for implantation
Describe the process of implantation of the fertilised egg
-blastocyst received into endometrium supported by secretory phase, where there’s a low oestradiol to progesterone ratio
-blastocyst promotes transition of endometrial stromal cells into decidua cells (predecidualisation)
-blastocyst trophoblast cells used to gain nourishment from endometrium
Describe inner and outer cytotrophoblasts
-inner = single mitotic layer that differentiates into:
-outer = produces hormones
What are the stages of endometrial invasion?
- hatching
- apposition
- adhesion
- invasion
Describe the hatching stage of endometrial invasion
The zona pellucida surrounding the blastocyst begins to disintegrate
Describe the apposition stage of endometrial invasion
-trophoblastic + endometrial epithelium membranes meet
-complete degradation of zona pellucida
Describe the adhesion stage of endometrial invasion
-adhesion between maternal + developing trophoblast cells
-have intracellular + extracellular integrins
Describe the invasion stage of endometrial invasion
-trophoblastic cell proliferation + differentiation to syncytiotrophoblast
-syncytiotrophoblast penetrates the endometrium
Describe the structure of the placenta
-maternal spinal arteries bring food
-intervillous space reduces force + velocity to allow for exchange
-syncytiotrophoblast lacunae merge + fill with maternal blood
-cytotrophoblast + syncytiotrophoblast form villi/microvilli projecting into maternal blood
In a mature placenta, what separates maternal and foetal blood?
-foetal capillary endothelium
-mesenchyme
-cytotrophoblasts
-syncytiotrophoblast
What substances are transported between maternal and foetal blood and how?
-from M to F: glucose (F. diffusion), amino acids (2 active transport), vitamins (active transport)
-from F to M: waste urea + creatinine
-large molecules move by receptor-mediated endocytosis
-oxygen exchange facilitated by higher oxygen affinity of foetal haemoglobin