Fertilisation And The Luteal Phase

Question 1

What are removed as the ejaculated semen moves through the cervical mucus?

Answer 1

Seminal fluid, morphologically abnormal sperm and cellular debris

Question 2

What is the benefit of sperm getting caught in the cervical crypts?

Answer 2

They form a reservoir and release sperm later = greater chance of fertilisation

Question 3

How does the sperm get to the egg?

Answer 3

Uterine currents, chemoattractants released from the oocyte cumulus complex and hyperactivity of the sperm

Question 4

What is the hyperactivity of the sperm caused by?

Answer 4

Calcium ion influx via CatSper channels

Question 5

How is capacitation achieved?

Answer 5

Removing sperm from the seminal fluid and factors from uterine or Tubular fluid

Question 6

What must happen before the acrosomal reaction occurs?

Answer 6

Biochemical rearrangement of the surface glycoprotein and changes in membrane composition (ie capacitation)

Question 7

Where does the acrosome reaction happen?

Answer 7

When the sperm comes into contact with the zona-cumulus complex

Question 8

What happens in the acrosome reaction?

Answer 8

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

Question 9

What happens in the secondary oocyte during ovulation?

Answer 9

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

Question 10

What happens to the empty follicle after ovulation?

Answer 10

Theca and granulosa cells mix and form the corpus luteum

Question 11

What does progesterone do in the luteal phase?

Answer 11

Makes the endometrium secretory and receptive to implantation, supresses cilia in the uterine tubes and makes cervical mucus viscous again

Question 12

What is the role of oestrogen in the luteal phase?

Answer 12

Helps to maintain the endometrium

Question 13

What is the job of the cumulus oophorus?

Answer 13

Protect the egg

Question 14

Where is the cumulus oophorus derived from?

Answer 14

Granulosa cells

Question 15

Where is the corona radiata found?

Answer 15

Innermost layer of the cumulus cells, in contact with the zona pellucida

Question 16

What forms the corona radiata?

Answer 16

Granulosa cells adhering to the oocyte before it leaves the ovarian follicle

Question 17

What is the zona pellucida secreted by?

Answer 17

The egg

Question 18

What happens to the zona pellucida after fertilisation?

Answer 18

It becomes inpenetrable

Question 19

What do the cortical granules contain?

Answer 19

Lots of enzymes

Question 20

What are the cortical granules involved in?

Answer 20

Zona pellucida formation

Question 21

What are the basic steps of sperm binding and penetration?

Answer 21

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

Question 22

What are released in the egg when the wave of calcium sweeps it?

Answer 22

Proteases, peroxides and hyaline

Question 23

What does phospholipase zeta cause?

Answer 23

The completion of meiosis II

Question 24

What happens after meiosis II has taken place in syngamy?

Answer 24

Expulsion of second polar body, sperm nuclear membrane breaks down and chromosomes decondense and separate

Question 25

What happens 4-7 hours after sperm penetration?

Answer 25

The two sets of haploid chromosomes become surrounded by distinct membranes forming two pronuclei

Question 26

What happens in the pronuclei?

Answer 26

DNA synthesis in preparation for the first mitotic division

Question 27

What happens after the pronuclei fuse in syngamy?

Answer 27

Mitotic metaphase spindle forms and the chromosomes assume their position at the equator of the cell