Body Cavities Flashcards
Which germ layer forms the neural plate? How is its differentiation induced?
The ectoderm forms the neural plate, which is induced by upregulation of FGFs while the node, notocord, and prechordal mesoderm block BMP 4 activity. -> This combination of increased FGFs and decreased BMP4 activates a neural pathway (fore and midbrain regions only)
What is hindbrain and spinal cord induction depedent on?
FGFs and WNT3a
How does the neural tube form?
The neural plate forms neural folds that elevate and fuse in the midline to form the neural tube = CNS. Crest cells are located at the top of the neural folds - neural crest- migrate to form bones and connective tissue.
The neural folds close in the middle (occipital) region of the plate (and “zipper” toward both ends, leaving the cranial region more open)
List the process of neurulation:
Neural crest cells
Molecular regulation: BMPs, FGF, WNT, PAX2
Placode formation
Closure
Origin
Migratory pathways
List neural tube defects that can occur during neurulation:
Spina bifida - open neural tube anywhere from cervical to lumbosacral (most common) - results from the neural folds failing to close.
Spina bifida occulta - neural tube closes but vertebra do not (covered by skin). Inherited disorder
Anecephaly - cranial neural folds fail to close causing brain tissue to degenerate (death results)
70% of all cases of spina bifida can be prevented by taking folic acid
Folic acid also works to prevent anencephaly
What molecular regulators is the ectoderm involved with?
Noggin, chordin, follistatin, WNT, FGF and RA, and homeobox genes
List the derivatives of the paraxial mesoderm:
Somites, bones, connective tissue, muscles, dermis
scleretome, dermotomes, myotomes
Somitomeres form in head regions and contribute to the skull and muscles of the face
What molecular regulators are involved with the paraxial mesoderm?
Noggin and SHH
List the derivatives of the intermediate mesoderm:
The urogenital structures
List the derivatives of the lateral plate mesoderm:
Parietal or somatic mesoderm - lines body cavities
Splanchnic or visceral mesoderm - surrounds organs
What germ layer is blood and vasculature derived from?
The mesoderm
Describe the difference between vasculogenesis and angiogenesis:
Vasculogenesis - in situ- form blood islands first, then cells coalesce into endothelial tubes to establish major vessels - aorta and cardinal veins
Angiogenesis - new vessels sprout from existing vessels
VEGF and receptors involved in molecular regulation
What does mesenchyme refer to?
Any loose connective tissue regarless of origin
What are the derivatives of the endoderm?
The gut and gut derivatives
Liver, pancrease, lungs…etc.
Decscribe the process of initial folds during body cavity formation:
- Cephalocaudal folding (head and tail folds)
- Lateral folds (one on each side) enclose the gut tube around the umbilical region to make the ventral body wall
-create primitive body cavity
-create gut tube
-Vitelline duct (yolk sac duct) connects gut tube to yolk sac
Decscribe the process of cranial-caudal closures during body cavity formation:
- Gut divided into pharyngeal, fore, mid, and hindgut
- Gut closed at cranial end-buccopharyngeal membrane
- Gut closed at caudal end - cloacal membrane
-Cloaca - expanded portion of hind gut - later forms urogenital sinus and
part of anal canal
Primitive body cavity
Same as intraembryonic cavity (coelom)
What three cavities are derived from space between the two layers of the lateral plate mesoderm?
Cardiac, pleural, and peritoneal cavities
Splanchnic layer
Of caridac, pleural, and peritoneal cavities
Visceral - surrounds gut tube, heart and lungs
Somatic layer
Of caridac, pleural, and peritoneal cavities
Parietal - lines body walls