Fertilisation And The Luteal Phase Flashcards
What are removed as the ejaculated semen moves through the cervical mucus?
Seminal fluid, morphologically abnormal sperm and cellular debris
What is the benefit of sperm getting caught in the cervical crypts?
They form a reservoir and release sperm later = greater chance of fertilisation
How does the sperm get to the egg?
Uterine currents, chemoattractants released from the oocyte cumulus complex and hyperactivity of the sperm
What is the hyperactivity of the sperm caused by?
Calcium ion influx via CatSper channels
How is capacitation achieved?
Removing sperm from the seminal fluid and factors from uterine or Tubular fluid
What must happen before the acrosomal reaction occurs?
Biochemical rearrangement of the surface glycoprotein and changes in membrane composition (ie capacitation)
Where does the acrosome reaction happen?
When the sperm comes into contact with the zona-cumulus complex
What happens in the acrosome reaction?
The acrosomal membrane on the sperm head fuses and releases enzymes that cut through the zona-cumulus complex. Acrosin then binds to the inner membrane that digests the zona pellucida so the sperm can enter
What happens in the secondary oocyte during ovulation?
The basement membrane breaks so blood pours into the middle. The oocyte-cumulus complex is extruded and caught by the fimbrae of the uterine tube
What happens to the empty follicle after ovulation?
Theca and granulosa cells mix and form the corpus luteum
What does progesterone do in the luteal phase?
Makes the endometrium secretory and receptive to implantation, supresses cilia in the uterine tubes and makes cervical mucus viscous again
What is the role of oestrogen in the luteal phase?
Helps to maintain the endometrium
What is the job of the cumulus oophorus?
Protect the egg
Where is the cumulus oophorus derived from?
Granulosa cells
Where is the corona radiata found?
Innermost layer of the cumulus cells, in contact with the zona pellucida
What forms the corona radiata?
Granulosa cells adhering to the oocyte before it leaves the ovarian follicle
What is the zona pellucida secreted by?
The egg
What happens to the zona pellucida after fertilisation?
It becomes inpenetrable
What do the cortical granules contain?
Lots of enzymes
What are the cortical granules involved in?
Zona pellucida formation
What are the basic steps of sperm binding and penetration?
Acrosome reaction,
the sperm binds to the zona pellucida,
sperm enzymes break through the ZP and fuses with the plasma membrane.
They’re taken in by phagocytosis and a wave of calcium sweeps the cell
Release of chemicals to prevent polyspermy
What are released in the egg when the wave of calcium sweeps it?
Proteases, peroxides and hyaline
What does phospholipase zeta cause?
The completion of meiosis II
What happens after meiosis II has taken place in syngamy?
Expulsion of second polar body, sperm nuclear membrane breaks down and chromosomes decondense and separate
