Embryology Flashcards
On what day does the primary heart field form?
16-18
When does the secondary heart field develop?
Days 20-21
What forms the primary heart field?
Migration of progenitor heart cells
What does the primary heart field go on to form?
Atria, left ventricle and most of right ventricle
What does the secondary heart field become?
Remainder of right ventricle and the outflow tract
Where are the heart fields from?
Mesoderm
What does the inner cell mass of the morula become?
Embryo proper
What does the outer cell mass of morula become?
Trophoblast then placenta
What does the inner cell mass of the blastocyst become?
Embryoblast
What does the outer cell mass of the blastocyst become?
Trophoblast
What are the 2 layers the trophoblast differentiates into on day 8?
Cytotrophoblast (mononucleate)
Syncytiotrophoblast
What forms when the oocyte and spermatozoa fuse?
Zygote
Where does fertilization take place?
Ampullary region of fallopian tube
What are the two processes that must take place for fertilization?
Capacitation and Acrosome reaction
What happens in capacitation?
In the female reproductive tract
Period of conditioning sperm
Glycoprotein coat and seminal plasma over the acrosome removed for easier enzyme release
Sperm must undergo this to be able to continue
What happens in the acrosome reaction?
After binding to ZP, capacitated sperm can pass through corona radiata
Penetration of the ZP through enzyme release (e.g. acrosin)
What are the phases of fertilization?
Penetration of corona radiata by capacitated sperm
Sperm release acrosin to penetrate ZP
Sperm contact oocyte
Enzymes released from oocyte cortical granules
Zona reaction initated by enzymes prevent more sperm entering by inactivating receptors
Sperm and egg plasma membranes fuse
What is cleavage?
Series of fast mitotic divisions of zygote
Starts on Day 2 to reach 2 cell stage
When does the 16-cell morula form?
Day 3
What does the embryoblast differentiate into?
Hypoblast and epiblast
What happens on day 9?
Lacunar stage of trophoblast development
When is uteroplacental circulation established?
Day 12
What does the epiblast give rise to?
The 3 germ layers
What is gastrulation?
A process in week 3 that establishes the 3 germ layers
What forms during gastrulation on day 15-16?
The primitive streak on the embryo
What makes up the primitive streak?
Primitive node (containing pit) and groove
Groove separates body into left and right
What do the different cells of the trilaminar disc become?
Some epiblast displace ventral hypoblast and form endoderm
Some other epiblast in groove from mesoderm
Epiblast cells not in groove form ectoderm
What happens on day 15?
Cranial and caudal ectoderm fuse with endoderm to form two bilaminar regions