Life Before Birth

Question 1

perimplantation stage

Answer 1

week 1: fertilised embryo is not embedded into the uterus

Question 2

embryonic stage: organogenesis

Answer 2

week 2-8: implantation and placenta is developed

Question 3

fetal stage: growth and development

Answer 3

week 9-38: embryo is now a fetus

Question 4

cleavage

Answer 4

mitotic divisions of the fertilised oocyte - each division produces identical daughter cell

Question 5

zona pellucida

Answer 5

glycoprotein coat that prevents premature implantation

Question 6

isthmus

Answer 6

size of oocyte remains the same to allow passage down uterine tube

Question 7

morula

Answer 7

day 4, cells maximise contact with each other and form tight junctions then enters the uterus

Question 8

blastocyst formation

Question 9

ICM

Answer 9

forms the embryo and extraembryonic tissues

Question 10

trophoblasts

Answer 10

forms the placenta

Question 11

blastocyst cavity

Answer 11

fluid enters the zona pellucida into spaces of ICM

Question 12

implantation

Answer 12

blastocyst runs out of nutrients so needs to implant. ICM cells proliferate and fluid builds up
- blastocyst hatches from zona pellucida to facilitate implantation

Question 13

gastrulation (week 3)

Answer 13

cell division and migration resulting in 3 germ layers. forms the trilaminar embryo from the bilaminar epiblast

Question 14

primitive streak

Answer 14

where gastrulation begins, cells move towards primative streak where they invaginate

Question 15

invagination

Answer 15

cells move to primitive streak where they push down and out to the side to form 3 layers

Question 16

ectoderm

Answer 16

forms structures like epidermis, cornea, nervous system etc.

Question 17

mesoderm

Answer 17

forms structures like skeletal system, muscular system, dermis, reproductive system etc.

Question 18

endoderm

Answer 18

forms liver, pancreas, thymus, epithelial lining of resp/digest etc.

Question 19

weeks 1-2

Answer 19

pre-implantation
- fertilisation, cleavage, compaction and blastocyst formation

Question 20

week 2

Answer 20

implantation
- bilaminar germ disc
- decidualisation

Question 21

week 3

Answer 21

gastrulation
- trilaminar embryo

Question 22

totipotent

Answer 22

total power e.g., zygote

Question 23

pluripotent

Answer 23

very many e.g., ICM give rise to 3 germ layers

Question 24

multipotent

Answer 24

make multiple e.g., haemopoeitic stem cells