Implantation & Germ Layers

Question 1

When does an embryo adhere to the endometrium

Answer 1

About 6 days after fertilisation

Question 2

Where does implantation tend to occur in the uterus

Answer 2

Question 3

Compare cell quantities of inner cell mass and trophoblast during the very early blastocyst stages

Answer 3

Inner Cell Mass: Approx 5 Cells

Trophoblast:
Approx 55 Cells

Question 4

How does blastocyst implant

Answer 4

Invades the uterine wall and in some sense digests its way

Question 5

Decidual reaction

Answer 5

Thickening of endometrium around gestational sac caused by Blastocyst implantation

Nourishes embryo at this early stage

Question 6

Colours used to depict ectoderm and endoderm

Answer 6

Blue
Primitive Ectoderm

Yellow
Endoderm

Question 7

Amniotic Cavity

Answer 7

Cavity formed by primitive ectoderm cells moving to the edge of the trophoblast

Question 8

Epiblast and Hypoblast

Answer 8

Epiblast: Primitive Ectoderm

Hypoblast: Primitive Endoderm

Remember:
Epi (epidermis)

Hypo (idk lol)

Question 9

What does the extraembryonic mesoderm do

Answer 9

Pushes the epiblast and hypoblast ‘balloons’ to the middle of the trophoblast and forms cavities between cells

Question 10

Conceptus

Answer 10

Embryo/Foetus

Question 11

Which embryonic cells form the placenta

Answer 11

Trophoblast and its derivatives

Question 12

Chorionic Cavity/Extra Embryonic Coelom and Function

Answer 12

Cavity formed between extraembryonic mesoderm lining the trophoblast and embryo (between amnion and chorion)

Used to make space for foetal development

Question 13

Connecting Stalk

Answer 13

Connection between embryo and trophoblast which serves a role as the umbilical cord

Question 14

Yolk Sac

Answer 14

Cavity formed by Endoderm

Question 15

Bilaminar Disk

Answer 15

Ectoderm and Endoderm joining location

Question 16

Summarise Second Week of Embryological Development

Answer 16

Period of 2s

2 Layers - Ecto- and Endo- Derm
2 Cavities - Amniotic and Yolk Sac
2 Trophoblast Derivatives - Cyto- and Syncytio-

Question 17

Cervical Mucus Plug

Answer 17

Produced by glands in the cervix as stimulated by Oestrogen; forms a plug/barrier which acts in a mechanical and antibacterial manner

Question 18

Ectopic Pregnancy

Answer 18

Implantation of a fertilised egg outside the womb, usually in a fallopian tube

Question 19

Molar Prenancy

Answer 19

Pregnancy where only trophoblast layers proliferate and there is no embryo
mimics real pregnancy; releases hCG

Essentially a tumour and having one increases the risk for a second (idk cause and effect)

Think of it as a mole that just grows

Question 20

Where is the intraembryonic mesoderm

Answer 20

Question 21

Summarise Third Week of Embryo development

Answer 21

3 Germ Layers
3 Important structures
 - Primitive Streak
 - Notochord
 - Neural Tube

Question 22

How are intraembryonic mesoderm cells formed and where does this occur

Answer 22

From ectodermal cells tumbling down at the Primitive streak

Question 23

What do the intraembryonic mesoderm cells do to the endodermal cells

Answer 23

Displacing them out of the way to make a new layer called definitive endoderm

Question 24

What happens at the prochordal plate

Answer 24

Thickening of cells like a press stud/velco so that no cells coming from the primitive streak (notochord) can get between them

Question 25

What does the cloacal plate form

Answer 25

Anus

Question 26

Primitive Node

Answer 26

Pushes a region of condensed mesoderm which gives off signals as it grows towards the prochordal plate (becomes notochord) telling the ectoderm above that it will become neural cells; forming a neural plate

Question 27

How does the embryonic length accomodate the length of the expanding notochord

Answer 27

The embryo expands in length

Question 28

What are at the ends of the notochord

Answer 28

Prochordal Plate and Primitive Node (Streak before that)

Question 29

What happens to the ectodermal tissue above the notochord

Answer 29

It rises up at the neural plate to form neural folds - neural groove.
Commits to becoming neuro-ectoderm

Rises up and up and eventually the ridges meet which detatches from the ectoderm to form a neural tube