Early Development

Question 1

What is an oocyte?

Answer 1

Unfertilized egg.

Question 2

What is a zygote?

Answer 2

A fertilized egg.

Question 3

When does the 4 cell stage occur?

Answer 3

After 2 days.

Question 4

What is a morula and when does it occur?

Answer 4

A solid ball of blastomeres after 3 days.

Question 5

What is a blastocyst and when does it occur?

Answer 5

Early blastocyst is hollow and fluid filled (blastocyst cavity) 4 days. Implanting blastocyst has trophoblast, blastocyst cavity and an inner cell mass. 7 days.

Question 6

What does a 9 day pre-embryo consist of?

Answer 6

Chorion, amnion, amnionic cavity, embryonic disc (epiblast, hypoblast)

Question 7

What does a 20 day embryo consist of?

Answer 7

Chorion, amnion, amnionic cavity, yolk sac, embryo.

Question 8

What are the germ layers?

Answer 8

Ectoderm, mesoderm, endoderm.

Question 9

What structures do the epiblast and hypoblast become?

Answer 9

Germ layers and yolk sac.

Question 10

What structures form the chorion, amnion, and yolk sac?

Answer 10

Trophoblast: Chiron, epiblast: amnion, hypoblast: yolk sac.

Question 11

What does a 25 day to 4 week embryo consist of?

Answer 11

Embryonic membranes: Chorion, chorionic villi, amnion and amnionic cavity, yolk sac; umbilical cord; embryo: head, heart, tail.

Question 12

What order does the embryo form in?

Answer 12

4 cell stage, morula, blastocyst. 9-day pre embryo