Embryology Parts I And II questions Flashcards
The blastocysts contain which 2 parts
- inner cell mass
- trophoblast
Cells in the ICM differentiate into…
- epiblast which gives rise to the embryo proper (dorsal-back)
- hypoblast which gives rise to the primary (extraembryonic) endoderm that forms the yolk sac (ventral-belly)
What is the primitive streak?
First marker of the craniocaudal axis. It occurs on the dorsal side of the epiblast and near the caudal end of the epiblast. The cranial end of the streak proliferates the become the primitive node and results from proliferation and migration of cells
How do we turn the 2 layer disc into a 3 layer disc
Through gastrulation. There is a depression in the primitive streak called the primitive groove and it is the site along which the cels migrate through the epiblast. The first cells to migrate (ingress) through the epiblast form the endoder (and displace hypoblast cells). Later cells form the mesoderm, and non-ingressing cells form the ectoderm. Two populations of cells that migrate through the streak generate the 3 layer disc from the 2 layer disc
What is gastrulation
Process by which the three germ layers are formed through cell migration
What are the 3 ways in which cells can migrate through the epiblast and why is that important
- Through the node
- Near the node
- Away from the node
It is important because they create three different cell fates. Where you migrate through the primitive streak helps to determine your fate
How is the neural tube formed
Dorsal ectoderm becomes the neural plate. Lateral edges become elevated to form neural folds and mid region becomes depressed and form the neural groove. Neural fold moves toward each other and fuse to become the neural tube. Neural tube then detaches from the overlying ectoderm
What does the nonneural ectoderm become
The skin
What does the neural ectoderm become
The brain and spinal cord (CNS)
What germ layer does the notochord derive from
Mesoderm
What is neurlation
Formation of the neural tube
How do cells fuse during neurulation
Cells in the middle of the neural folds fuse first and zippers both anteriorly and posteriorly at the same time
What are cranial and caudal neuropores
Transient openings at either end of the neural tube after zippering of the neural folds occur
How dour the defects or neural tube defects occur? How should women avoid neural tube defects?
- when the nuropores do not close correctly
- consume more folic acid
What are the functions of the notochord
- transient structure that defines the body axis
- provides rigidity to the embryo
- functions as a signaling center to, at least, induce neural fates such as which neural cells become dorsal or ventral
- precursor for the axial skeleton
Which germ layer forms the neural crest
Ectoderm
What are the neural crest cells
Migratory cells that are ectoderm-derived and migrate throughout the body to give rise to a diverse number of cell fates
What are the 4 regions of the mesoderm
- axial (chordamesoderm)
- Parasail mesoderm
- Intermediate mesoderm
- Lateral plate mesoderm
Axial (chordamesoderm)
Gives rise to the notochord
Paraxial mesoderm
Gives rise to somites, adjacent to the neural tube
Intermediate mesoderm
Gives rise to the kidney/gonads
Lateral plate mesoderm
Gives rise to the lining of the organ cavities
What are the derivatives of the endoderm
Gives rise to the GI tract, epithelial lining of lung buds and trachea, liver, gall bladder, and pancreas
