Lect 2

Question 0

When does a blastomeres become a morula?

Answer 0

When 8 or more cells, compaction occurs! Usually Day 4

Question 1

What are the events in the pre- embryonic week 1?

Answer 1

There are 5

1. ) cleavage : mitioc divisions - blastomeres
2. ) compaction: tightening to form morula
3. ) cavitation: uterin fluid in morula - blastocyst
4. ) hatching : blastocyst hatches from ZP
5. ) implantation : blastocyst implants in endometrium of uterin wall

Question 2

When does implantation occur?

Answer 2

Day 6

Question 3

Explain cleavage

Answer 3

Repeated cell divisions ( zygote/ polar bodies) 2 blastomeres continues until 16- morula compaction stage

Question 4

When is nondisjunction less sever?

Answer 4

During week One of pre embryonic stage! Called mosaicism

Question 5

At what stage does an inner and outer cell mass form?

Answer 5

Compaction

Question 6

What cells form from the inner cell mass?

Answer 6

Inner cell mass - embryoblast (form embryo foetus and amnion) - epiblast and hypo blast

Question 7

What originates from the outer cell mass?

Answer 7

Outer cell mass- trophoblast - cytotrophoblast and synctiotrophoblast ( form placenta and chorion)

Question 8

When end has the embryoblast attached?

Answer 8

Embryonic pole!

Question 9

Which end is the abembryonic pole?

Answer 9

Opposite the embryoblast cells

Question 10

Which cells attach to the uterine wall during implantation?

Answer 10

Trophoblast: day 6

Question 11

Where do the nutrients during implantation come from?

Answer 11

Uterine gland secretions in endometrium getting broken down by synctiotrophoblast

Question 12

What events occur during week 2?

Answer 12

Week 2 is the pre embryonic stage:

1. ) Implantation is complete! - UTERAPLCENTAL CIRCULATION
2. ) Bilaminar Disc - embryoblast differentiates

Question 13

What cells creat the Bilaminar disc?

Answer 13

Embryoblast

Question 14

When is Uteroplacental circulation established?

Answer 14

Week 2 of pre embryonic period

Question 15

After implantation how does the cell type used for implantation change?

Answer 15

Trophoblast then become either cytotrophoblast or synctiotrophoblast ( erode uterine wall and blood vessels)

Question 16

When does nutrition change from uterin gland secretions to Uteroplacental circulation ?

Answer 16

Uterin gland secretions during implantation, once completed week 2 begins Uteroplacental circulation

Question 17

When can pregnancy be detected?

Answer 17

Day 8 from the hCG secreted by Sybctiotrophoblast

Question 18

What is ectopic pregnancy?

Answer 18

When implantation is outside the uterus, usually uterine wall. If further down can cause placental Previa obstructing the cervix. Fixed with c section

Question 19

What is a molar pregnancy?

Answer 19

Trophoblast implants, but embryoblast is absent or incomplete! ( no embryoblast, no epiblast or no hypoblast : all of which develope the embryo/ foetus and amnion) …yields a tumour HYDATIDIFORM mole ..give hCG from synctiotrophoblast so + preggers test

Question 20

What is the bilaminar disc?

Answer 20

Embryoblast lamination to give rise to —- hypoblast (line blastocyst cavity which develops into primary yolk sac ) and epiblast ( line amniotic cavity)

Question 21

When does the blastocyst cavity become the primary yolk sac

Answer 21

Week 2 of pre embryonic period

Question 22

What cavity do the hypoblast form?

Answer 22

Hypoblast from blastocyst cavity- which will turn into the primary yolk sac! ( epiblast form amniotic cavity)

Question 23

When does the extra embryonic cavity form?

Answer 23

Week two, adjacent to the hypoblast ( that form the blastocyst cavity) the Extraemryonic mesoderm will form spaces and slowly enlarge to form Extraemryonic cavity! ( cavity outlines the cytotrophoblast and turns the pYS into a secondary yolk sack! And developers an exocoelomic cyst

Question 24

What is the chorionic cavity?

Answer 24

Also known as the Extraemryonic cavity! Lined by the Extraemryonic mesoderm.

Chorion includes : cytotrophoblast, synctiotrophoblast and EM