Case 1 Flashcards
When does gastrulation begin?
3rd week of embryology
What triggers the start of gastrulation?
Formation of primitive streak and primitive node (cranial end)
What is gastrulation?
Formation of trigeminal gastrula - ectoderm, mesoderm, endoderm
What is does each trigeminal gastrulation layer form?
Surface Ectoderm- epidermis,hair, nails, lens of eyes
Mesoderm- muscle, bones, cartilage, adipose tissue, circulatory system
Endoderm- colon,stomach,bladder, pancreas
What is the prechordal plate?
Thickening of the hypoblast and epiblast; forms the mouth and helps to determine cephalic from caudal end
What is the notochord?
Layer of cells from primitive node that forms between the ectoderm and endoderm, and surrounded by mesoderm
It signals the formation of ectoderm neural plate
What does the notochord form?
Nucleus pulposus
When does neurulation begin?
Day 22
What happens during neurulation?
Neural plate forms > neural groove > neural folds elevate to fuse > neural tube
When does the anterior and posterior neuropores close?
Day 24/25 and 27/28
What are neural crest cells?
Cells from the neural folds that go on to make a range of body cells - PNS, adrenal medulla, and dentin of teeth
What are Somites?
Form from mesoderm along the length of neural tube from rostral to caudal end
Total of 44pairs
What do somites form?
Vertebrae, ribs, skeletal muscles, dermis, cartilage and tendons
What are the 3 primary vesicles?
Prosencephalon, Mesencephalon, Rhombencephalon
What are the three flexures?
Cephalic, Pontine and cephalic flexures
What are the secondary vesicles?
Prosencephalon - Telencephalon (cerebrum, basal ganglia and hippocampus) and Diencephalon (thalamus, uvea, retina)
Mesencephalon - mesencephalon (midbrain)
Rhombencephalon - Metencephalon (cerebellum + pons) and myelencephalon (medulla)
What is the development of the spinal cord?
Neural tube > neuroepithelial cells > neuroblast form mantle layer - grey matter > marginal cells form white matter cells
What divides the alar and basal plate?
Sulcus limitans
Where do the neural crest arise?
Dorsal neural tube along the whole length of spinal cord
How do neuronal migration in PNS occur?
Neuroepithelial cells express Snail1/2 > repress adhesion molecules > epithelial to mesenchymal transition > mesenchymal to destination and cease Snail1/2 expression
This is guided by somites
How is a Dorsoventral Axis developed?
TGF-beta (BMP) and SHH morphogens gradient
TGF - dorsal neural tube and SHH notochord and floor plate
The gradients activates Transcription factors that regulate differentiation of sensory and motor neurons
How is an Anterior-Posterior Axis Developed?
Retinoic acid from somites into anterior acid of neural tube (cephalic end)
FGF from stem zone cells into posterior axis of neural tube (caudal end)
Gradient of these two leads to different cell differentiation from the middle (anterior differentiate - posterior undifferentiated)
homeotic genes (HOX) express in clusters and the combination of genes determines the identity of block of tissue
Shh and FGF set up left and right hemisphere, brain and brain stem
What is neurogenesis?
Differentiation of progenitor cells into their programmed cells
How does the progenitor cell know which is apical and basal end?
Par complex at the tip of the cell
What are the two type of progenitor cell division?
Symmetrical = 2 daughter progenitor cells
Assymmetrical = 1 daughter progenitor and 1 neuronal cell
What does Shh do in neurogenesis?
It’s a mitogen for proliferation of progenitor cells