7: Gastrulation And Embryonic Germ Layers Flashcards
What type of oocyte is released at ovulation?
Secondary oocyte
Three types of granulosa cells in follicle
Cumulus oophorous, mural granulosa cells, corona radiata
Cumulus oophorous
Anchor oocyte to follicle wall
Mural granulosa cells
Line wall of follicle
Corona radiata
Firmly anchored to ZP, remains around oocyte after fertilization
Acrosome reaction
Head of sperm releases enzymes for passage through corona radiata and ZP
Zona reaction
Changes in ZP make it impermeable to other sperm once penetrated by one sperm
When does cleavage begin?
About 30hrs post-fertilization
Compaction
Cells divide but dont grow much in early stages bc they are limited in space by ZP
Blastocyst two parts
Trophoblast, embryoblast (AKA inner cell mass)
What does the trophoblast differentiate into
Cytotrophoblasts, syncytiotrophoblasts
What does embryoblast differentiate into?
Hypoblast, epiblast
What layer of cells is the hypoblast continuous with?
Exocoelomic membrane surrounding the exocoelomic cavity
What space is the epiblast surrounding?
Amnionic cavity
Early spontaneous abortion rate
~45%
Two major causes of early spontaneous abortions
Inadequate hormones from the CL; chromosomal abnormalities
What two cell layers form the primary umbilical vesicle (yolk sac)?
Hypoblast, exocoelomic membrane
What does the primary umbilical vesicle give rise to
Extraembryonic coelom
How does the secondary umbilical vesicle form?
Hypoblast cells migrate inside primary umbilical vesicle
What type of cells have thier origin in the secondary umbilical vesicle
Primordial germ cells
What two types of mesoderm form from the extraembryonic mesoderm, and what separates the mesoderm into these two parts?
Extraembryonic coelom: separates extraembryonic mesoderm -> extraembryonic somatic + splanchnic mesoderm
Extraembryonic somatic mesoderm: lines what two things
Trophoblast + amnion
Extraembryonic splanchnic mesoderm: surrounds what
Umbilical vesicle
Two structures that form the chorionic sac
Extraembryonic somatic mesoderm + trophoblast
Chorion
Fetal component of the placenta
Where is the most common location for ectopic pregnancies
Oviduct
Gastrulation
Epiblast cells migrate to form the primary germ layers
What is the starting point of gastrulation
Formation of the primitive streak
What germ layer is epithelia from?
All three
5 things that come from ectoderm
- Epidermis and derivatives
- CNS and PNS
- NCCs
- Eyes
- Internal ears
8 things that come from mesoderm
- Skeletal and smooth muscle
- Serosal linings
- Urogenital ducts and organs
- CV system and blood cells
- Endothelium
- Cartilage, bones, tendons, ligaments
- Dermis
- Stroma of trunk organs
3 Things that come from endoderm
- GI and resp epithelium
- GI tract glands
- Glands of accessory GI organs (liver, pancreas)
What germ layer is formed by the notochordal process?
Mesoderm
What day is the notochordal process complete by?
Day 20
What does the notochordal process extend from -> to?
Primitive node -> prechordal plate
What does the notochordal process form?
Notochord
Notochord major function
Primary signaling center for early embryo
Two things the notochord signals for
- Formation of neural plate
2. Development of axial musculoskeleton
What does the notochord degenerate into?
Nucleus pulposus
In notochord formation, what happens when the floor of the notochord and the endoderm fuse?
The layer degenerate, allowing notochord canal and umbilical vessel to have contact
Caudal eminence
Tail bud; a group of median mesodermal cells in the caudal region
What forms the caudal eminence?
Swelling of the primitive streak caudally
Three cell types formed by the caudal eminence?
Caudal neural tube, NCCs, caudal somites
Cell type that forms sacrococcygeal tumors
Primitive streak cells (from any/all germ layers)
Population most affected by sacrococcygeal teratomas
Females
