Embryology Flashcards
To cover most aspects of Early Embryonic Development for ESA 1 Note: lateral and cephalocaudal folding are not covered within this deck
What 3 changes allow for one cell to become a multicellular body?
- Growth
- Morphogenesis (form and structure development)
- Differentiation (specialisation for function)
How long does the pre-embryonic last?
2 weeks
Which period goes from the 3rd to 8th week?
Embryonic
What is the final stage of embryonic development called? (after the 9th week)
Fetal
Briefly describe the process of fertilisation (3 points)
- Oocyte released from ovary
- Travels down fallopian tube
- Fertilised by sperm in ampulla forming zygote
What is the ideal site for implantation of the zygote?
Posterior uterine wall
How long is an oocyte viable for?
1 day
How long is sperm viable for?
3 days
How long after fertilisation does it take for cleavage to occur?
30 hours
What does the process of cleavage result in?
A morula made of 2 blastomeres
What is the purpose of the zona pellucida?
This glycoprotein shells prevents polyspermy
How is the blastocyst formed?
Compaction of the blastomeres causes the hatching from the zona pellucida
What are the three main components of the blastocyst?
- Embryoblast (inner cell mass)
- Trophoblast (outer cell mass)
- Blastocyst cavity
What will the trophoblast later form?
Support structures for the embryo (like the placenta)
What will the embryoblast later form?
Bilaminar disc
What is the cytotrophoblast?
A derivative of the trophoblast forming the placental membrane around the yolk sac
What is the syncytiotrophoblast?
A derivative of the trophoblast which are cells that invade maternal sinusoids giving circulation to the foetus
At the stage of implantation how many cells does the conceptus have? What will they form?
107 cells - 8 will make the embryo and 99 will begin development of the foetal membrane
What does the embryoblast differentiate into?
Epiblast and hypoblast
What does the trophoblast differentiate into?
Syncytiotrophoblast and cytotrophoblast
What does the bilaminar disc consist of?
Epiblast and hypoblast
Describe the process of implantation
- The uterine epithelium is breached
- The conceptus implants within the uterine stroma
At which stage of pre-embryonic development are the cells totipotent?
Morula
What does PGD stand for and what is it for?
Pre-implantation Genetic Diagnosis - removal of an embryo to test for serious inheritable diseases
How is the embryonic pole formed?
Rapid development of the syncytiotrophoblast
How is the primitive yolk sac formed?
Heuser’s membrane spreading across blastocyst cavity
Why is the blastocyst cavity formed?
To provide nutrition to the inner cells of the morula
What is the inner cell mass called?
Embryoblast
What is the outer cell mass called?
Trophoblast
In the bilaminar disc which of the layers is closest to the trophoblast (outer cell mass)?
Epiblast
Which of the cells of the bilaminar disc will contribute to the embryo?
Epiblast
Which cavity does the epiblast make with the trophoblast?
Amniotic cavity