embryology week one & two

Question 1

embryology

Answer 1

study of origin and development of an individual

Question 2

prenatal period

Answer 2

time between conception and birth

Question 3

2 periods within prenatal period

Answer 3

embryonic and fetal period

Question 4

embryonic period

Answer 4

first 8 weeks

Question 5

fetal period

Answer 5

remaining 30 weeks

Question 6

adult human body plan

Answer 6

skin, outer body wall (trunk), body cavities & inner tube

Question 7

what happens in week 1?

Answer 7

fertilization & zygote formation, cleavage & blastocyst formation, beginning of implantation

Question 8

how does the fertilization process begin?

Answer 8

with the release of an oocyte (immature egg) from the ovary uniting with a sperm

Question 9

what happens when the sperm reaches the oocyte?

Answer 9

they bind to receptors on the zona pellucida around the oocyte

Question 10

zona pellucida

Answer 10

external membrane around oocyte

Question 11

zygote

Answer 11

chromosomes from the male & female gametes coming together within the ovum

Question 12

cleavage

Answer 12

cell division, produces large number of cells that become building blocks of the embryo

Question 13

blastomeres

Answer 13

zygote divides to create 2 daughter cells

Question 14

morula

Answer 14

solid cluster of cells, 12-16 cells, that cleavage has created by day 3

Question 15

compaction

Answer 15

tight alignment of morula cells allowing greater cell-to-cell interactions

Question 16

blastocyst

Answer 16

tight cluster of cells with a cavity in the middle, cavity contains uterine fluid, will split into 2 groups

Question 17

two distinct groups of blastocyst

Answer 17

trophoblast & embryoblast

Question 18

trophoblast

Answer 18

outer cell layer surrounding the blastocyst cavity, helps from the placenta

Question 19

embryoblast

Answer 19

inner cell mass, forms the embryo

Question 20

how long does the blastocyst stage last?

Answer 20

3 days from days 4-7

Question 21

what does the blastocyst do in those 3 days?

Answer 21

floats freely inside the uterine cavity where it will burrow into the uterine wall on day 6

Question 22

implantation

Answer 22

begins on day 6 and takes one week to complete, time frame specific

Question 23

what happens during the implantation time frame?

Answer 23

the trophoblast erodes the uterine lining units the entire blastocyst becomes embedded within the uterine wall

Question 24

ectopic pregnancy

Answer 24

implantation does not attach on the wall of the uterus, very dangerous

Question 25

when does week 2 begin?

Answer 25

day 9

Question 26

day 9

Answer 26

inner cell mass has divided into two flat sheets of cells; epiblast & hypoblast

Question 27

bilaminar embryonic disk

Answer 27

two layered disk made up from the epiblast and hypoblast, becomes precursor for entire body

Question 28

amniotic sac

Answer 28

formed as an extension of the epiblast, amniotic fluid acts as cushion to protect embryo & fetus

Question 29

yolk sac

Answer 29

formed as an extension of the hypoblast, gives rise to parts of the digestive tube and earliest blood vessels, nourishes embryo for short time

Question 30

hCG hormone (human chorionic gonadotrophin)

Answer 30

produced in a layer of trophoblast at the end of implantation, basis for pregnancy tests