Principles of Embryology Flashcards
How long is the human gestation period?
9 months
Describe when the term embryo and foetus are used
Embryo:
Fertilization –> week 8
Foetus:
Week 9 –> birth
Define gametogenesis
The production of gametes
By which process are oocytes and spermatozoa produced
Oogenesis –> Oocytes
Spermatogenesis –> spermatozoa
What cell is produced by the fusion of the sperm and the oocyte?
What is this called?
Forms a zygote
This is fertilization
Is the zygote an embryo?
Yes
anything from fertilization –> week 8 is an embryo
Define cleavage
Period of rapid cell division with no increase in total size
Days 1-4
List the stages of cleavage
Zygote --> Morula --> Blastocyst
List the stages of embryogenesis
Gametogenesis --> Fertilization --> Cleavage --> Gastrulation --> Embryonic folding --> Organogenesis starts --> FOETAL PERIOD
Define gastrulation
- Formation of the germ layers
- Body axis is defined
Week 3
List the 3 germ layers
And describe how they are layered
- Ectoderm (outer)
- Mesoderm (middle)
- Endoderm (inner)
Describe embryonic folding
- Gut tube forms within the body wall
- Other folding occurs
week 4
Describe organogenesis
- The formation of organs and organ systems
- By the end of the embryonic period (week 8) the basis of all organs/systems is in place
Describe the foetal period
- Growth
- Tissues mature, become functional
- Overt sexual differentiation
- Bone laid down
- CNS connections made
What terms are used instead of superior, inferior, posterior, and anterior when describing an embryo/foetus?
cranial = superior caudal = inferior dorsal = posterior ventral = anterior
