Lecture 37 Flashcards
What happens during fertilization?
- Happens soon after ovulation when the developing oocyte is moving through the fallopian tube
- early embryo will start dividing as it is moving through the fallopian tube
- eventually differentiates
- by the time it gets to the uterus, it will be in early embryonic phase and implant (hitting the wall of the uterus and forming a placenta)
- if egg gets fertilized, it will finish meiosis 2
What happens to blood flow after the fetal circulation develops?
Blood doesn’t actually flow from maternal circulation into fetal circulation, they are separate
once fetal circulation develops, it is independent
What is exchanged at the placenta?
gases, nutrients can be diffused between the two
why is the endometrium the lining of the uterus was thickened?
- vascularized
- provide a hospital area for placenta to form
embryo grows into the uterine wall
Why are there so many tiny villi and capillaries in the placenta?
Maximize surface area for transport (diffusion)
maternal blood to fetal blood
What diffuses in and out of the placenta?
- O2 from maternal circulation diffuses in the placenta
- CO2 from fetal circulation is diffusing out
- nutrients/ hormones are moving by a different process (active transport.. etc)
What are some physiological changes that occur near the end of gestation in preparation for delivery (parturition)?
- Chronic changes: Uterine smooth muscle prepare them to produce coordinated contractions; epithelial/ connective tissues of the uterus and cervix (increasing flexibility)
- more acutely, rhythmic uterine contractions amplified by cervical stretch and maternal oxytocin release provide the force to move the fetus out of the reproductive tract
- positive feedback (by endocrine signaling- fetal steroid)
Why is endocrine signaling important?
Communication between fetus and parent
What is the Oxytocin- mediated positive feedback (Ferguson reflex) loop?
involves both mechanorecpetion and secretion of the posterior pituitary hormone (oxytocin)
What does Oxytocin do?
triggers uterine contraction
- stimulates the smooth muscle cells of uterine to contract
What happens when contraction starts to occur?
infant is pushing against the back side of the cervix
- mechanoreceptors detect the stretch
- stretch triggers more oxytocin to be released (positive feedback)
- eventually leading to delivery
What happens after males go through puberty?
Males are steadily capable of reproduction (potentially throughout their lifespan)
- sex steroids begin to drop as they get old (70-80)
- no positive feedback
- HPG axis is stable
Describe the secretion of GnRH in the male reproductive system
After puberty, there is a pulsatile release of GnRH every ca. 90 mins , maintaining constant HPG axis activity and sexual maturity
Describe the function of FSH and LH in males
FSH acts more directly on the developing gametes to trigger spermatogenesis
LH acts more on the production of sex steroids (testosterone)
How does it all start?
When we are born, we cannot reproduce until puberty
- HPG axis throughout lifespan
- When developing in utero there is high HPG axis activity (sex steroid release.. etc.)
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