Embryology - Gastrulation Flashcards
What has happened by the end of week 2?
Oocyte has been fertilised
Zygote has undergone cleavage and compaction to produce a blastocyst
Blastocyst has begun implantation and begun to differentiate
Extraembryonic spaces starting to organise
When is the embryonic period?
Weeks 3-8 inclusive
What happens generally in week 3?
Three cavities are established
Three germ layers
What is gastrulation?
The process establishing the three germlayers and hence the origin of all tissues of the body
What are the axes set in gastrulation?
Anterior-posterior
Dorsal-ventral
Right-left
How does gastrulation begin?
The primitive streak appears on the dorsal surface of the epiblast
Describe the features of the primitive streak
Primitive node located at the cranial end of the streak
Primitive pit located at the centre of the node
How is the trilaminar disc formed?
Migration and invagination of epiblast cells through the streak
Displacement of the hypoblast to produce a third layer
What does the epiblast and hypoblast become?
Ectoderm and endoderm respectively
Significance of the notochord?
Basis for axial skeleton
Drives formation of the nervous system (neurulation)
How is the notochord made?
Pre-notochordal cells of epiblast migrate through the cranial part of the primitive pit. Form a solid rod of cells running in the midline with an important signalling role.
What is the remnant of the notochord in adults?
The nucleus pulposus of IV discs
Derivatives of the ectoderm?
Organs and structures that maintain contact with the outside world such as nervous system and epidermis
Derivatives of the mesoderm?
Supporting tissues such as muscle, cartilage, bone, vascular system
Derivatives of the endoderm?
Internal structures such as epithelial lining of GI and respiratory tracts
Parenchyma of glands
