what are the major events of fertilization
- journeey of spem to the oocyte
- contact and recognition of sperm and the egg starting mieosis II
- regulation of sperm going into egg, blocks of polyspermy.
- completion of meiosis II secondary oocyte to mature ovum.
- fusion of the genetic material in sperm and in oocyte to form zygote.
- Activation of egg metabolism to start pre-implantation development.
where does fertilization happen
in the ampula but can occur outside if ivf or ectopic pregnancy. but most of the fertillized egg dont go to form embryo
what are some events prior to fertilization in females
ovulation and egg maturation timing.
changes in uteruine, vaginal and cervical secretions
developement of corpus letuem in ovary.
how does ovulaion happen
secondary ooctye is with a layer of granulosa is released into the peritoneal cavity with the help of fimbrae and estrogen which cause contractions in smooth muscles around uterine tube and beating of cilia on surfaces of oviduct cells.
what happens to the vaginal and cervical secretions at ovulation
before ovulation there is more water under the control of estrogen and after ovulation the mucus becomes sticky and dry under the control of progesterone. more alkaline is secreted during fertile window.
why does fertile phase start before ovulation
sperm can last 3-6 days so in the fertle stage it can wait for the egg to reach ovulation. but in ovulation the egg only lasts 24 hours.
what are the events prior to fertilization from the perspective of sperm in the male genital tract
- gametogenesis in testes
- storage and maturation in epididymis
- rapid transport cia cas deferens with addition of secretion via glands
events prior to fertilization from perspective of sperm female gential tract
- filtration via cervix so only the best swimers enter
- capacitation in uterus/ uterine tubes (the mucus and all)
- chemoattraction (signals sperm to the egg)
- acrosome reaction - to the sperm so it can get through the zona palusima
- fusion with oolema
whats the breakdown of semen
60% seminal fluid
30% prostate
10% bulbourethral
what are some health issues associated with the prostate gland
BPH: benign prostatic hyperplacsia enlarged prostate and this causes a feeling of constatnly watning to piss
prostate cancer.
Where does fertilization occur
whats the two main modes of sperm transport in female genital tract
Ampula
fast contractions in muscular wall of femal genital tracts
slow swiming of the spermatozoa. takes 30 min ot 2 hours long.
what are the potential barreirs to sperm
Low Ph
cervical mucus
uterine leukocytes
how does sperm gets it ability to swim and what does it need to get to the egg
spermatozoa produces in seminfurous tubles are nonmotile and will move through cooiled tube of epididymis to get motility
need capacitation from female tract which provides nutrients to the sperm to get to the egg.
explain capacitation/priming
occurs in the female genital tract. collected in the isthmus portion of the uterine tube by binding to the tubal epithelium
involves alterations in the plasma membrane to lower the cholestrol molecules at the head of the spemr so that the membrane is thin to release acrosome into later. this further helps motility and causes them to get through the corpus radiata in the secondary oocyte.
what is polyspermy and how do we prevent it
more than one sperm getting fertilized this would cause 3 haploid cells not good
- fast: depolarization of the cell
- slow cortical reaction - high calcium brings granulosa and blocks them sperm.
what are the interactions between sperm and secondary oocyte
penetration of corona radiata, contact with the zona pellucida and then acrosomal reaction to get through the zona pellucida and then binding of sperm to the oolema and this starts the block to polyspermy and then fusion and sperm entry and then cortical reaction.. completion of 2nd meiotic division and pronuclie form and contact each other.
explain how cortical reactions work
high amounts of calcium from the cytoplasm then zona inhibiting protiens take out other sperms that are attached and then hardens the zona pallucida and then mucopolysaccharides hydrate and sweell the zone pellucida causing it to be a impenetrable first membrane.
what is accomplished by fertilization
- mieosis II complete in female egg
- diploid number of cells restored in zygote
- sex determined for zygote
- formation of zygote
- metobolic activation of egg
what is morula and blastocyst and trophoblast
zygote morula is 16 cells and blastocyst is 70 to 100 cells trophoblast is the inner membrane.
whats going on in cleavage divisions
conceptus goes through 5-6 rapid divisions as it travells to the uterus, more cells but not increase in volume and these dauter cells are called blastomere and at 16 cells they fomr morula.
explain morula to blastocyst
once morula reaches 30 blastomeres and then cavitation starts outer blastomere secrete fluid into the morula via Na+ pumps rest slide 28 module 3a
talk about the pluripotent stem cells from ICM
self renewal
can differentiate to any primary 3 germ cell layers - skin cell skeletal muscle cell or nueral cell.
canot make exra-embryonic structures.
explain blastocyst hatching and implantation
zona pallucida prevents hatching in the oviduct, trophoblast cells secrete trypsin to digest ZP allowing for hatching and tophoblast attach to enometrial cells and secrete proteases.
what happens during implatiation with trophoblast and endometrium
trophoplast digests some of the endometrial cells so that the blastocyst can be in the endometrium.
