Germinal stage

Question 1

What period is the germinal stage?

Answer 1

time from fertilisation to end of 2nd week.

Question 2

What is the gestational age?

Answer 2

time from last menstruation (embryonic age + 2 weeks)

Question 3

What is the embryonic age?

Answer 3

time since fertilisation

Question 4

What is the foetal period?

Answer 4

9th- 38th week

Question 5

What is the embryonic period?

Answer 5

3rd week - end of 8th week

Question 6

Where does fertilisation take place?

Answer 6

ampullae region of the fallopian tubes

Question 7

How much before ovulation must sperm be introduced to fallopian tube?

Answer 7

at most 5 days

Question 8

What is capacitation of the sperm and why does it occur?

Answer 8

A change in sperms plasma membrane enabling it to fertilise the egg and a induction to swim faster.
occurs due to projesterone when they come close to the egg

Question 9

How long is a secondary oocytes viable for in the fallopian tubes and uterus?

Answer 9

12-24 hrs

Question 10

Why are sperm not rejected from father? (theyre forgein)

Answer 10

there are tight junctions in testicles so sperm never touch blood

Question 11

What does semen contain to decrease risk of rejection of embryoblast and what does it do to female behavoir?

Answer 11

immuno surpressants and makes them more aggressive but happier

Question 12

Describe what happens during fertilisation?

Answer 12

• Sperm starts to burrow through corona radiata- an outer lining of granulosa cells
• sperm then secrete digestive enzymes to break down zona pellucida
• when break through zona pellucida it reaches plasma membrane and binds with receptor
• receptor activates 2nd meiotic division of the ovum, and a male pronucleus to be formed ready for first mitotic division

Question 13

Outline the changes to the ovum post fertilisation until implantation

Answer 13

• as it starts dividing in the early cleavage phases (1-3 days) it is a mass of cells within the zona pellucida called a ZYGOTE
• Then becomes morula for 3-4 days post fetilisation
• Then becomes blastocytst as the trophoblast starts to develop (4-5 days)
• The zona pellucida is still present at this stage and this prevents implanation, so the blastocyts goes through contractions and expansions in order to hatch out of the zona pellucida.
• The blastocyst now composes of an outer layer of trophoblast, an embryoblast layer at the top, a primitive endoderm just below this and a blastocysts cavity filling the rest of the space
• Implantation occurs at the 6th day

Question 14

What is the role of the trophoblast?

Answer 14

provides nutrients before it implants. Will later become the yolk sac and placenta

Question 15

Where is the normal implantation site?

Answer 15

upper, posterior part of the uterus in the endometrium

Question 16

Where does the embryo implant for ectopic pregnancies?

Answer 16

fallopian tubes

Question 17

What is the first stage to implantation?

Answer 17

The trophoblast differentiates into syncytiotrophoblast, which surrounds the blastocyst as it enters into the endometrium. The rest of trophoblast remains as a outer layer of cells but is now called the cytotrophoblast.

Question 18

What does the embryoblast layer differentiate into on day 8?

Answer 18

the hypoblast and the epiblast, which form the bilaminar embryonic disc

Question 19

What cavities does the hypoblast go on to create by day 13?

Answer 19

the chorionic cavity (largest, goes around everything) and yolk sac (on inside of hypoblast)

Question 20

What cavity does the epiblast create?

Answer 20

the amniotic cavity