Reproductive Physiology - 22/23 Flashcards
Ovary homeostasis
Ovary homeostasis
* LH and FSH are made in the ant pituitary, released due to GnRH (gonadotropin releasing
hormone from hypothalamus)- causes some follicles to develop (eggs with less receptors
are activated and ovulated first because they require less LH and FSH)
* If there’s low estrogen, it stimulates the ovaries to release estrogen
* Continued estrogen production stimulates FSH and LH production (positive FBL)
* The pressure developed from LH surge causes the follicle to rupture and the egg to be
released into the peritoneum
Menstrual cycle (uterine cycle)
- Layers of uterus (deep to superficial)
o Uterine cavity (lumen)
o Endometrium (stratum basalis and stratum functionalis; functionalis grows with
estrogen)
o Myometrium - Purpose is the develop the stratum functionalis for an embryo (usually 21-40 days) and
then shed it
o Less than 21- harder to get pregnant
o More than 40- may indicate an endocrine issue - Endometrial glands- produce ‘food’ in preparation for a fertilized egg (the glands build up
with each cycle) - There’s lots of blood vessels (for oxygen)
- Counted from day 1 of menstrual bleed
- Menstrual phase: loss of functionalis days 1-4ish
- Proliferative phase: endometrial BVs and glands develop, days 4-14
- Secretory phase: endometrial glands begin to secrete, days 14-48
- Menstrual phase occurs again
- Occurs because the ovaries send hormonal signals to the functionalis layer
o Estrogen causes the functional layer to grow in the proliferative phase - Around 14 days, the egg is released from the follicle and the granulosa cells make
estrogen and progesterone (makes the glands secrete) - The corpus luteum stops producing estrogen and progesterone after 14 days, resulting in
the menstrual phase
Maintaining endometrium
- Called ‘rescuing’ the endometrium
- Implanted embryo causes release of hCG; sends out a signal to the corpus luteum to keep
making estrogen and progesterone - Progesterone prevents the uterus from contracting
- Takes 5 days for a fertilized egg to implant and make hCG- fertilization at day 14 is
optimal to ensure the uterus is not already in its menstrual phase
Sperm construction
- Acrosome in the head- contains a nucleus, contains digestive enzymes to penetrate zona
pellucida
o Haploid - Midpiece supplies energy for the flagellum
- Flagellum provides motility for the sperm- they need contractions of the uterus and
uterine tube to reach the egg
Spermatogenesis
- Spermatogonia constantly go through meiosis to create 4 sperm
o Count below 20 million are considered as infertile - Sperm meet in the seminal vesicle (ejaculatory duct) from vas deferens, goes to prostate,
released with semen
Semen
- Both rely on pituitary gonadotropins, LH, and FSH
- FSH stimulates growth of gametes
- LH stimulates production of hormones from gonad
- Hormones produced by ovary/testicle feedback decreases gonadotropin production
Fertilizing Egg
slide 3
Egg to Blastocyst
slide 4
slide 5
label slide 6, 7
3 Main phases of development
- The pre-embryonic phase
*<14 days after fertilization
*The conceptus is about 1.5 mm in length by the end of this phase and
the very poorly differentiated
*By the end of this period there is a tiny trophoblast (the beginning of the
fetal part of the placenta)
*For much of the earlier parts of this phase the zona pellucida is still
present and the embryo is isolated from the maternal environment. - Embryo
*2-8 weeks after fertilization
*All major organs are assembled in this time, so it is called the
organogenesis phase
*The embryo grows to about 3 cm
*The placenta is far larger than the embryo at this point and there is
complete access to materials in maternal circulation - Fetus
*>8 weeks to term
*The organs grow during this period, so it is called the histogenesis
phase
Watch slide 12 13
label 14
15-21 review placenta, blood flow and umbilical cord
Maternal Adaptation to Pregnancy
During this time, maternal physiology has to adapt.
– Cellular immunity decreases
* The fetus is an allograft (i.e., not the mom) but the mother has to
remain tolerant of paternal antigens and yet maintain normal
immune competence for defense against microorganisms
* The placental villi do not exhibit very many antigens and the activity
of many types of helper-T cells decreases
– The placenta requires a lot of blood
* blood volume increases 30-50%
* cardiac output increases 20-30%
– Tidal volume increases 30-40% and airway resistance
decreases to increase CO2 loss.
* Lower maternal CO2 levels create a stronger concentration gradient
between mom and fetus.
– Myometrial mass increases from 60-80g to 900-1200g
(about a 15X increase) to accommodate the fetus.
