Week 2 - Pregnancy Flashcards
How long does the zygote remain in the fallopian tubes? why does it happen?
3-4 days
Due to balance of actions of estrogen (induces smooth muscle contraction) and progesterone (slows smooth muscle contractions)
Fertilisation to Implantation full process diagram
What happens during the window of implantation (days 20-23 of menstrual cycle)
- trophoblast cell begin to rapidly proliferate and secrete enzymes
- enzymes degrade endometrial tissue
- blastocyst buries itself in endometrial layer
Is implantation failure common?
yes at least 2 out of 3 blastocysts fail to implant
What are reasons for implantation failure?
- Scarring of uterus
- Hormonal imbalances
- Non-receptive endometrium
Describe placentation
- combination of interlocking foetal and maternal issues serving as organ of exchange between mother and foetus
- Chorionic villi (finger-like projections of trophoblast cells) extend from chorion into the endometrium
- Villi contain a rich network of capillaries that are part of embryo’s circulatory system
List functions of the placenta
- provides substrates for foetal metabolism (gut)
- Disposes of wastes (kidney)
- Exchanges resp gases (lungs)
- partial immunological barrier
- produces important pregnancy hormones
What hormones does the placenta produce?
Progesterone
Estrogens
Chorionic Gonadotropin
HGH
CRH
Transport mechanisms of PLacenta
What is the placenta permeable and impermeable to?
Impermeable to:
- large proteins
- blood cells
Permeable:
- alcohol, nicotine, drugs -> leading to complications
Chorion, Amnion, Yolk Sac, Allantois defintion and diagram
Describe amniotic fluid. what does it consist of? what does it do?
Consists of mostly foetal urine
Functions:
- provides fluid reservoir allowing dev of tube structures
- cushions foetus from trauma
- prevents uterus from compressing foetus
- maintains constant temp
Hormonal changes during pregnancy visualised
What does Human Chorionic Gonadotropin do?
Maintains viability of corpus luteum thus increasing steroid production
- also used to detect whether pregnant or not bc very high levels at start
What do Trophoblast cells of the placenta do?
secrete large amounts of progesterone and estrogen from 3-9 months so no menstrual cycles occur during pregnancy
List 4 Anatomical changes occurring during pregnancy
List 4 Metabolic changes occurring during pregnancy
List 4 Physiological changes occurring during pregnancy
+ CVS -> Blood volume increases 40% // BP rises // Decrease in total peripheral resistance // RBC increases
