Fertilization and Pregnancy

imissyou419's version from 2017-04-02 22:22


Question Answer
Where does conception happen?critical the meeting of sperm (spermatozoa) and egg (secondary oocyte) happens in fallopian tube (ovulation under high level of estrogen cause contraction throughout repro tract, cilia and fibula wash ovary and sperm together)
- ovum is viable for 24 hours
- sperm is viable for 1-3 days (can have sperm ejaculate in repro tract when ovulation happens on day 14)
How does the sperm know which way to go?sperm can sense changes in temperature and chemicals (progesterone) so sperm goes that way
Sperm speeds vs. Ovum speedsSpeed sperm very quick (with huge loss from vagina to ampullary), ovum speed very slow
Capacitationstart in ejaculation in seminal, completed in the female reproductive tract in oviduct; alters:
1. sperm motility (hyperactivity) - go from swimming to whiplashing movement to get thru ZP due to increase Ca2+ from removal of Chol, activate cAMP, provide more energy for mitochondria,
2. sperm plasma membrane (prep for fusing, so it can do acrosome action) e.g. cholesterol removal make it more permeable,

Accessory glands promote intracellular alkalinization (activation) - Ca2+ influx (cAMP) from altering sperm plasma membrane from capacitation changes sperm metabolism and motility
Fertilization1. releases enzymes that allow it to bury through granulosa cells (corona radiata) to reach zona pellucida, ZP3 protein (lock and key mechanism - species-specific binding of sperm proteins to the extracellular matrix (ZP) of the egg) prevent sperm and egg of different species from fusing, lead up to acrosomal reaction
2. acrosome reaction to dissolve zona pellucida, whip-like action able to propel itself through
3. fuse with plasma membrane of ovum
4. corticol reaction - massive depolarization result in large amount of Ca2+ being released -> activate corticocapsucles that release Ca2+, Ca2+ trigger hardening of ZP;
5. sperm enters ovum; sperm mitochondria destroyed
6. meiosis II completed -> polar body (contained in ZP)
7. 2 pronuclei fuse - diploid #
8. zygote is created (1n,1c -> 1n,2c -> 2x 2n,2c, nuclear envelope disintegrate and nuclei come together)
9. rapid mitosis
Embryo developmentZygote (1 cell, fertilization and formation of zygote takes 24 hours) -> Morula -> Blasocyst [cell division, polar bodies maintained in ZP, hatched in uterus and implant]
Blastocystday 5, has cavity, formulation of inner cell mass (fetus) and trophectoderm (forms trophoblast & then placenta, hCG feeds back onto corpus luteum to continue making progesterone, pregnancy signal), hatches and implant
Dizygotic twins2 dominant follicles made, 2 sperms
Monozygotic twinsduring blastocyst they equally divide
Implantation occurs in which phase?luteal phase, endometrium primed by estrogen (it starts to decline now - estrogen get involved in contraction and get everything moving), activated by progesterone (override estrogen's dominating effect now), after implantation CL gets signal to hang around through hCG by trophophectoderm; nutrient supply to blastocyst by simple diffusion
hCGtrophophectoderm feeds back onto CL through hCG positively feedback to keep producing progesterone (keep the endometrium lining juicy) by hCG binding to LH receptor in granulosa cells (LH also induce completion of meiosis), progesterone negatively feedback and shut down GnRH, FSH & LH because do not want new follicle developing
Syncytiotrophoblastdigest endometrium, projections into endometrium occuring around day 5-6, by 10 is buried in, seek out blood supply
Cytotrophoblastmitotic, provide stem cell population
Lucanaeholes within syncytiotrophoblast, as it invades, filled with maternal blood to support development of circulatory system between mother and fetus, separated by the 2 trophoblast layers, maternal and fetal blood never mix, rely on diffusion for gases and transport system for nutrients (glucose, a.a., fatty acids, hormones)
Week 3conceptus implantation in uterus wall is complete and trophoblast cells continue to invade uterine wall in the process of early placentation (villi formation), gastrulation convert bilaminar -> trilaminar embryo (happens ~day12-16)
Source of placental estrogen and progesteroneprogesterone > estrogen, syncytiotrophoblast make progesterone and estrogen
Epiblastfetal component, leads to ectoderm, mesoderm, endoderm
Hypoblastextra embryonic component
Chorionic Villisyncytiotrophoblast develop villi (finger-like projections) inside villi is circulatory system that comes down from umbilical cord, intervillus space = pool of maternal blood where placenta villi hang bathed by maternal blood, diffusion occurs from blood in intervillus space across syncytotrophoblast into fetal circulation, veins take waste
Placentahappens in 1st and 2nd trimester, placenta facilitates growth and development
Gas exchange, exchange, endocrine tissue, immune barrier, waste removal
Functionality of 1g of placenta increases to meet fetal demand
Ectodermskin cells of epidermis, neuron, pigment cells
Mesodermcardiac muscle, skeletal muscle, kidney tubule, RBC, smooth muscle (in gut)
Endodermlung cell, thyroid cell, pancreatic cell
How long does embryonic period last until?week 8, then it is called fetus
When is gender decided ?week 7
TDF or SRYSRY carried on Y chromosome for transcription factor, it acts with SOX 9, results in maleness - ramp up Sertoli cell development, lack of SRY cause embryo to develop as physical female but females do have SOX9 just not upregulated
Cross-over for SRYif there is crossover then will carry XY but is female
FemaleWolffian duct breaks down, fallopian tube and uterus forms = default pathway
Male+SRY so SOX9 upregulated, Seroli cells upregulated and drive secretion of anti-mullerian hormone (AMH) which drives degradation of mullerian duct, Wolffian duct forms reproductive tract of males, hCG binding to LH receptor bind to Leydig cells -> drive testosterone production (drive differentiation of testosterone responsive signals, shut down aromatase (testosterone is high around week 7)
Prengnacy changes50% of CO goes to uterus, enlarged breast, change in balance, insulin resistance - support for fetal demand for glucose

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