Early embryonic development 2 Flashcards
Define bilaminar disk
The Epiblast and hypoblast. Derived from the embryoblast. This will later become the trilaminar disk with the formation of the primitive streak.
Define germ layer
A layer from which other developed tissues originated from
Define ectoderm
Outermost germ layer of cells
What does the ectoderm become?
Epidermis
Nerve tissue
Retina of eye
Define endoderm
Innermost germ layer of cells
What does the endoderm become?
GI lining
Glands associated with gut
Define dorsal surface
The outermost surface during early development
Define ventral surface
The innermost surface during early development
Define mesoderm
Middle germ layer of cells
What does the mesoderm become?
Muscle Bone Cartilage Blood vessels Urogenital tract
Define primitive streak
A narrow groove that develops on the dorsal surface of the Epiblast. It has an important role in the orientation of the embryo, determining the front and the back.
Define gastrulation
The reorganisation of the germ layers into the ectoderm, mesoderm and endoderm and hence establishing the origin of all tissues
Define trilaminar disk
The three germ layers. Ectoderm, mesoderm and endoderm.
What is the first step in gastrulation?
Appearance of the primitive streak
Which surface does the primitive streak form on?
Dorsal
Which end of the primitive streak is the primitive node at?
Cranial end
Which end of the primitive streak is the primitive pit at?
Caudal end
When does the primitive streak regress?
As gastrulation proceeds and the 3 germ layers are produced
Which direction does development go in?
Cranial to caudal
How is the trilaminar disc formed?
Cells on the epiblast migrate to the primitive streak
Invaginate into the epiblast and displace the hypoblast to create the mesoderm
Why are there 2 gaps in the mesoderm layer?
One is for the future mouth and the other is for the future anus
What is the notochord?
Basis for the axial skeleton
Drives formation of the nervous system
Defines the midline
Important signalling role
The notochord regresses, where is it in the adult?
Nucleus pulposus of the intervertebral discs
What is the primitive node responsible for?
Molecular signals which control patterning and orientation (axes)
