Coitus, fertilisation and implantation Flashcards Preview

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Flashcards in Coitus, fertilisation and implantation Deck (31):
1

what is the EPOR model of sexual response

excitement- sexual arousal, tumesence and erection, engorgement,

plateau- intensification of arousal

orgasm- involuntary muscular contractions with intense pleasure

resolution- rearousal may be impossible

2

what is the length of the luteal phase

14 days

follicular phase is more variable

3

what is the time window for fertilisation

3 days before ovulation up to 1 day after

4

what percentage of pregnancies miscarry

10-15%

5

what proportion of couples are subfertile?

5%

6

what proportion of intercourse results in a blastocyst

20%

7

what proportion of blastocysts fail to implant

15%

8

what percentage of clincally detected pregnancies fail

15-20%

9

what proportion of conceptions survive until birth

20%

10

how long is the embryonic period

8 weeks

11

how long is the foetal period

8-40 weeks

12

what is the function of cumulus cells

aid transport from the surface of the ovary
cling to the ciliated surface of the fimbriae

13

why is sperm mortality high

acidic vagina
length and energy requirement of trip

14

describe capacitation

change from wavelike beats to whip like action to propel sperm
sperm plasma membrane is altered
destabilisation to enhance fusion with oocyte
increase in Ca permeability, removal of membrane proteins
depletion of cholesterol

15

where does ferlisation normally occur

ampulla

16

what does the sperm bind to

zona pellucida

17

what does a rise in Ca inside the sperm cell trigger

exocytosis of the acrosome which contains hydrolytic enzymes

18

what glycoproteins are involved in the acrosome reaction

ZP3 and ZP2

19

describe the acrosome reaction

fusion of the acrosome plasma membranes
releases contents of the acrosome, causes entry of more calcium
sperm digest the zona pellucida

20

describe fertilisation

1. The sperm cell weaves past follicular cells and binds to the zona
pellucida.
2. A rise in [Ca2+]i
inside the sperm cell triggers the exocytosis of the
acrosome (acrosomal reac/on) which contains hydroly/c
enzymes.
3. Hydroly/c enzymes contained in the acrosomal cap are released.
These enzymes locally dissolceolve the zona pellucida. The whiplike
ac/on of the tail pushes the sperm head towards the oocyte
membrane.
4. With the head of the sperm now on lying sideways, microvilli on
the oocyte surround the sperm head. The two membranes fuse.
The contents of the sprem-cell enter the oocyte; the sperm-cell
membrane remains behind.
A rise in [Ca2+]i
inside the oocyte triggers the cor/cal reac/on, in
which there is exocytosis of granules that previously lay
immediately beneath the plasma membrane. The enzymes
released lead to changes in the zona-pellucida proteins, causing
the zona-pellucida to harden, preven/ng the entry of other
sperm cells.
6. The rise in [Ca2+]i
inside the oocyte induces the comple/on of the
oocyte’s second meio/c division and the forma/on of the second
polar body, which usually lies next to the first polar body.
7. The sperm head enlarges to become the male pronucleus.
8. The male and female pronuclei fuse.
a. Sperm contributes its nuclear material and centrioles
b. All other organelles are present in the oocyte cytoplasm
c. Mitochondrial DNA inherited exclusively via maternal route

21

how long does it take for the blastocyst to reach the uterine cavity

5 days

22

when does hCG get secreted

from 9 days onwards

23

what are totipotent cells

can form all the cell types in a body, plus
the extraembryonic, or placental, cells. Embryonic cells
within the first couple of cell divisions a^er fer/liza/on
are the only cells that are to/potent.

24

what are pluripotent cells

can give rise to all of the cell types that
make up the body; embryonic stem cells are considered
pluripotent.

25

what are multipotent cells

can develop into more than one cell
type, but are more limited than pluripotent cells; adult
stem cells and cord blood stem cells are considered
mul/potent.

26

what does the trophoblast form

the placenta

inner cytotrophoblast and outer syncytiotrophoblast which invade the endometrium

27

what is the cortical reaction

a rise in Ca inside the oocyte triggers exocytosis of granules that lay immediately beneath the plasma membrane
this leads to changes to the zona which hardens to prevent entry of sperm

28

what triggers the completion of the oocytes second meiotic division

rise in Ca

29

what forms the male pronucleus

the head of the sperm enlarging

30

what surrounds the sperm head when it lies sideways against the oocyte

microvilli
this causes the two membranes to fuse

31

when does implantation happen

day 7