Lecture 17 - Pregnancy Flashcards
capacitation:
what is capacitation of sperm and why (3-1) /where does it occur?
what else supports sperm meeting with egg?
slide 3
- capacitation the process sperms must undergo to be able to swim properly and fertilize an egg. Capacitation includes changes to the sperm such as binding albumin (protein from blood), enzymes, and lipoproteins to it.
- The binding causes (1) removal of glycoprotein coat, (2) intracellular changes, (3) developing strong whip like motions so that it can pass through cervical mucus (takes 30 minutes and is thin with estrogen). this all occurs in the female reproductive tract.
- uterine and oviduct contractions also aid transport of sperm to egg
where does fertilization occur:
what is the pathway of sperm entering the female to create a zygote?
how long are oocytes and spermatozoa viable for in the female tract? what does this mean for fertilization?
slide 4
- sperm –> vaginal tract –> cervix –> uterus –> fallopian tube (where sperm meets egg to create zygote)
- the oocytes are viable for 24 hrs and the sperm is viable for 4-6 days
- this means that the sperm can be deposited into the female for 4-6 days before the female ovulates and fertilization can still occur.
sperm meeting oocyte:
how many sperm reach the oocyte in the fallopian tube?
how are the sperm attracted to the egg chemically?
what layers of cells do the sperm have to travel through for fertilization and how does it do that?
why is it that the first sperm fusing with the egg wins? what does this prevent?
slide 5-6
- 100 sperm reach the oocyte in the fallopian tube
- chemotaxis which are progesterones from cumulus cells that surround the oocyte, chemically attract the sperm to the egg
- the sperm has to go through the corona radiata cells and the zona pellucida border of the oocyte. it does this by conducting an acrosomal reaction using the enzymes in the sperm head (acrosome)
- the first sperm wins. otherwise there would be polyspermy where many sperms fertilize an egg and thus will cause an abnormal number of chromosomes and hindered embryo development.
steps of fertilization:
what are the 4 steps to fertilization, ie when the sperm meets the egg and makes a zygote nucleus?
slide 7
1. sperm and egg plasma membranes fuse –> triggering acrosomal reaction
2. sperm nucleus moves into egg cytoplasm by fusing the egg cortical granules with outer membrane
3. oocyte nucleus completes 2nd meiotic division (finally fertilized)
4. sperm and egg nuclei fuse to form zygote nucleus (second polar body expelled)
what happens after fertilization?:
what are the steps from ovulation (egg dropped) and when the egg is fertilized to formation of early embryo (5 steps) – state the days too after fertilization
- what are blastocyst and trophoblast
slide 8
1. day 0: ovulation occurs and egg enters fallopian tube
2. day 1: fertilization in fallopian tube
3. day 2-4: zygote cellular division takes place in fallopian tube
4. day 4-5: blastocyst (cell complex formed after fert./division to reach uterus) enters uterus from fallopian tube
5. day 5-9: blastocyst implants to uterus side to form trophoblast (early embryo + other structures that form the placenta)
hCG - fertilization hormone:
what does hCG stand for and when/where is it secreted?
what is the main role of hCG (2)?
what hormone structure is it similar to?
if fertilization occurs around 2 weeks after menses when does hCG rise and why then?
when does hCG levels spike? how about estrogen and progesterone?
slide 9
- hcG = human chorionic gonadotropin –> secreted from trophoblast when bound to uterus wall
- functions: (1) takes over from pituitary to maintain corpus luteum for secreting progesterone and estrogen (before placenta takes over after first trimester) (when fertilization sensed) and prevents the next menstrual cycle
- similar structure to LH
- occurs 3 week after menses (needs 5-6 days for trophoblast to implant and hcG to release)
- hCG spikes in the first trimester then decreases as estrogen/progesterone accumulate overtime from placenta and take on roles of hCG
hCG maintains the corpus luteum
- if not fertilized, what happens to the corpus luteum
- if fertilized, what happens to the corpus luteum
–> what hormone is continuously secreted as a result and why?
- why is the hypothalamic pituitary loop suppressed?
slide 10
- no fertilization = corpus albican
- fertilization = hcG hormone maintains corpus luteum so that it continues secreting progesterone to keep the endometrium stays intact (secretory phase) (no shedding bc no period bc pregnant)
- progesterone and estrogen is continuously secreted when pregnant (positive feedback loop). thus hCG maintains the corpus luteum to do this before the placenta takes over. to keep secreting progesterone and estrogen the GnRH and FSH/LH hormones are suppressed via negative feedback. This prevents the maturation of additional follicles and further ovulation/menses during pregnancy.
fetus and placenta:
- what type of organ/ gland is the placenta?
- what is the role /exchange factors of the placenta
slide 11
- the placenta is a temporary organ and endocrine gland (secretes and creates hormones)
- from the trophoblast that forms part of the placenta
- function: performs the role and exchange of digestive (nutrients, proteins, chemicals), respiratory (O2 exchange), and renal (waste) systems for the fetus
placental circulation:
- what type of blood does the umbilical vein and artery carry?
- how are nutrients, gases, etc. exchanged between the mother and baby if the vasculature are not physically linked? ie. explain lacunae and chorionic villi
slide 12
- vein = oxygenated blood to the embryo from placenta, artery = deoxygenated blood to the placenta from the embryo
- even tho the mother and baby vasculature are not physically linked, the maternal blood forms a lacunae (lake) which bathes the embryonic/fetal chorionic villi so there can be an exchange of gases and solutes between the mother and fetus
ovary to placenta endocrine features:
- which hormone signals to the ovaries to produce progesterone in the first trimester
- when does the placenta take over the role of the ovaries for hormone production
slide 13
- hCG, made by trophoblast but travels to the ovaries, rises in the first trimester and maintains the corpus luteum in the ovaries to secrete progesterone
- before the end of the first trimester, the placenta is matured and takes over for hormone (estrogen and progesterone) production. this is when hCG drops – not needed to support corpus luteum.
hormones:
- what is the diffusion and production of hormones like in the mother’s blood, placenta, fetal blood, and fetal adrenal cortex like – draw the map out
slide 14
- look at slides
function of placental hormones:
state the functions of
- hCG
- progesterone
- estrogen
- human placental lactogen
slide 15
- hCG = maintains corpus luteum for continuous secretion of progesterone when fertilization occurs
- progesterone = suppresses premature uterine contractions for full development of baby, cervical plug (protect baby from infection), mammary gland development (milk in breasts)
- estrogen = uterine development (growth, blood supply, oxytocin receptors) – needs to be developed as fetus is housed here, breast duct development for breastfeeding, etc
- human placental lactogen = structurally related to growth hormone and prolactin
- inc. in mother, dec. in fetus
- Decreases maternal cellular uptake of glucose, enhances maternal lipolysis (diverting energy needs to baby rather than mother)
terms of pregnancy:
- when is the first, second, and third trimester in terms of weeks from last day of last period
- when is normal birth
- when is preterm and postterm birth
slide 16
First trimester: 0-12 weeks embryo development
Second trimester: 12-28 weeks fetal development,
Third trimester: 28 weeks to delivery fetal maturation
Normal birth: 37-42 weeks after last menstrual cycle
Preterm: fetus born > 28 weeks usually viable without
intervention (artificial surfactants used to help premature lung development of baby)
postterm : >42 weeks (induced females or delivered by c-section)
maternal adaptations to pregnancy:
- what are the renal, cardiovascular, immune system, and calcium homeostasis changes that occur to a pregnant women?
slide 17
- Renal: inc. ADH = inc. blood volume (females need more blood volume to support baby), inc. sodium and fluid water retention
- cardiovascular = increased output = to reach new organs in fetus and pump blood throughout the baby
- immune: suppressed = growing new foreign species = we don’t want an autoimmune reaction
- calcium: inc. hyperparathyroidism = inc. PTH/calcitonin in mother so that maternal bone is not reabsorbed. also send Ca to baby to develop bones
how is labour triggered:
- what is parturition
- what hormone is released to help with labour? where (2)? what does it do physiologically (2)
- what are the stimuli and positive feedback loops (4) in labour
- what are the 4 triggers/initiations of labour?
slide 18
- parturition = when baby is ready to be delivered
- relaxin hormone is released from the ovary and placenta to loosen the ligaments in the pelvic bone and cause the cervix to soften
- stimuli = fetus drops lower in uterus, cervix stretches
- positive feedback loops: cervix stretch = oxytocin released from posterior pituitary = prostaglandins from uterine wall stimulated = uterine contraction (positive until baby born)
- increases 1. estrogen/oxytocin, 2/3. fetal cortisol + CRH (stress hormone), 4. prostaglandins for contractions
