Fertilisation

Question 1

what do sperm cells acquire in epididymis?

Answer 1

glycoprotein and sterol coat

Question 2

what do proteases in the uterine/cervical fluid do?

Answer 2

removes the sterol coat and glycoprotein, this causes the cell membrane to become more permeable to calcium ions

Question 3

what do calcium ions activate in sperm cells?

Answer 3

activate strong tail lashing and make the acrosome reaction possible later (indirectly, via cAMP)

Question 4

what happens when sperm meet the zona pellucida?

Answer 4

undergo an acrosome reaction

Question 5

what occurs during an acrosome reaction?

Answer 5

acrosome membrane and plasma membrane fuse at many points
acrosomal contents spill out and can digest the zona pellucida

Question 6

what happens after the acrosome reaction?

Answer 6

acrosome reacted sperm burrow towards the oocyte, one sperm reaches the oocyte membrane and fuses with the membrane

Question 7

what does fusion cause?

Answer 7

a wave of calcium entry, which keeps repeating ever 10 mins or so

Question 8

what is the effect of calcium waves?

Answer 8

cortical granules are released, these alter the zona pellucida and make it impenetrable by sperm
change in polarisation which blocks membrane fusion
meiosis of the oocyte resumes

Question 9

what occurs after fusion?

Answer 9

chromosomes decondense and form the female and male pronuclei

Question 10

what are the reasons for assisted fertilisation?

Answer 10

blocked or absent oviducts
blocked vasa deferentia/eferentia
low male fertility
impotence
female age

Question 11

what are the causes for blocked or absent oviducts?

Answer 11

pelvic inflammatory disease
chlamydia or gonorrhoea
congenital absence
endometriosis of earlier elective tubule ligation

Question 12

stages of assisted fertilisation?

Answer 12

superovulation
oocyte harvesting
sperm harvesting
capacitation of sperm
mixing of sperm and oocytes
observation of early development
embryo transfer

Question 13

how are oocytes harvested?

Answer 13

follicular aspiration
can be done laparoscopically or transvaginally
can be from either would be pregnant woman or a donor

Question 14

when is the best time to do follicular aspiration?

Answer 14

before follicle is released, the granulosa cells are cleaned away with a fine needle

Question 15

how is sperm harvested?

Answer 15

usually masturbation
can be done by aspiration from epididymis or even testis for ICSI

Question 16

what is capacitation?

Answer 16

artificial mimicking of the female environment

Question 17

how are sperm and oocytes mixed?

Answer 17

placed in a test tube together
intra-cytoplasmic sperm injection (direct injection of sperm into oocyte if sperm does not function properly)

Question 18

what occurs during observation?

Answer 18

often genetic testing of 1 cell

Question 19

what does the new embryo have to do?

Answer 19

gorw much bigger (adults are 1 million times larger than a fertilised egg
create internal differences
organise the axes and complex anatomy of the body

Question 20

what is cleavage?

Answer 20

mitosis with no growth

Question 21

when is development most likely to fail?

Answer 21

activation of embryonic transfer

Question 22

what begins at the 4 cell stage?

Answer 22

mRNA synthesis from embryo’s own DNA begins
maternal mRNA is destroyed at an increasing rate

Question 23

what is the morula?

Answer 23

ball of cells - cells on the inside have contact all round, cells on the outside have a free surface

Question 24

how does the morula begin to differentiate?

Answer 24

cells on the outside specialise into a simple epithelium and eventually form the placenta (trophoblast)
inner cells mass does not specialise (blastocyst)

Question 25

what does the blastocyst do?

Answer 25

hatches through the zona pellucida

Question 26

when does implantation occur?

Answer 26

2nd week after fertilisation, prior to this the embryo is unattached and travels down the fallopian tube

Question 27

what is implantation?

Answer 27

when the trophoblast of the hatched blastocyst invades the uterine epithelium

Question 28

what odes the trophoblast develop into?

Answer 28

placenta