Implantation & Germ Layers Flashcards
(29 cards)
When does an embryo adhere to the endometrium
About 6 days after fertilisation
Where does implantation tend to occur in the uterus
Compare cell quantities of inner cell mass and trophoblast during the very early blastocyst stages
Inner Cell Mass: Approx 5 Cells
Trophoblast:
Approx 55 Cells
How does blastocyst implant
Invades the uterine wall and in some sense digests its way
Decidual reaction
Thickening of endometrium around gestational sac caused by Blastocyst implantation
Nourishes embryo at this early stage
Colours used to depict ectoderm and endoderm
Blue
Primitive Ectoderm
Yellow
Endoderm
Amniotic Cavity
Cavity formed by primitive ectoderm cells moving to the edge of the trophoblast
Epiblast and Hypoblast
Epiblast: Primitive Ectoderm
Hypoblast: Primitive Endoderm
Remember:
Epi (epidermis)
Hypo (idk lol)
What does the extraembryonic mesoderm do
Pushes the epiblast and hypoblast ‘balloons’ to the middle of the trophoblast and forms cavities between cells
Conceptus
Embryo/Foetus
Which embryonic cells form the placenta
Trophoblast and its derivatives
Chorionic Cavity/Extra Embryonic Coelom and Function
Cavity formed between extraembryonic mesoderm lining the trophoblast and embryo (between amnion and chorion)
Used to make space for foetal development
Connecting Stalk
Connection between embryo and trophoblast which serves a role as the umbilical cord
Yolk Sac
Cavity formed by Endoderm
Bilaminar Disk
Ectoderm and Endoderm joining location
Summarise Second Week of Embryological Development
Period of 2s
2 Layers - Ecto- and Endo- Derm
2 Cavities - Amniotic and Yolk Sac
2 Trophoblast Derivatives - Cyto- and Syncytio-
Cervical Mucus Plug
Produced by glands in the cervix as stimulated by Oestrogen; forms a plug/barrier which acts in a mechanical and antibacterial manner
Ectopic Pregnancy
Implantation of a fertilised egg outside the womb, usually in a fallopian tube
Molar Prenancy
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
Where is the intraembryonic mesoderm
Summarise Third Week of Embryo development
3 Germ Layers 3 Important structures - Primitive Streak - Notochord - Neural Tube
How are intraembryonic mesoderm cells formed and where does this occur
From ectodermal cells tumbling down at the Primitive streak
What do the intraembryonic mesoderm cells do to the endodermal cells
Displacing them out of the way to make a new layer called definitive endoderm
What happens at the prochordal plate
Thickening of cells like a press stud/velco so that no cells coming from the primitive streak (notochord) can get between them
