FOM 6.3.2 Flashcards
What are the three derivates of the ectoderm? What signaling contributes to that?
Neuroectoderm (Low BMP4, increased signaling from notochord) Neural Crest (Med BMP4) Non noneural ectoderm (High BMP4)
What are the organ derivatives of the ectoderm?
CNS PNS Sensory epithelium of ear, nose, and eye Epidermis, hair, nails Mammary, pituitary, subcutanous glands NEURAL CREST CELLS
Where is the disc-shaped embryo broadest?
Cranial region
On day 16 the notochord begins to form, what day does does the neural plate begin to form?
Day 19
What are the two main inducers of the neuroectoderm? What molecules do they use for induction?
Notochord and prechordal mesoderm. Dorsalizers (Noggin, chordin, follistatin)
Name the three different portions of the neural plate (their relative position) and corresponding brain region.
Proencephalon - Forebrain (cranial) Mesencephalon- Midbrain Rhombocephalon- Hindbrain (caudal)
Describe the fusion of the neural plate. When?
Birectional (starts at day 22)
How do the somites interact w/ the neural tube? What’s their embryonic origin? What will they eventually form?
Surround the neural tube. Derived from paraxial mesoderm Form vertebrae
What two placodes reside on the anterior portion of the neural tube? What will they eventually form?
Lens placode (lens of eye) Otic placode (inner ear, hearing, balance)
The neuropores, opening of neural tube, close on which days?
Cranial (25 days) Caudal (28 days)
What are two malformations that arise as a result of failure of neuropore closure?
Anencephaly (absent brain) and Spina bifida
What are neural crest cells?
Migratory cell pop. at lateral borders (crest) of neuroectoderm -exit neural tube -multipotent -transient -give rise to diverse cell lineage
What type of transition do neural crest cells undergo as neural folds fuse?
epithelial-to-mesenchymal
What the difference b/t neural crest cell migration in the trunk and cranial region?
Cranial: leave before fusion of neural tube Trunk: leave after fusion
What are some possible lineages of neural crest cells of the trunk?
melanocytes, sensory ganglia, adrenal medulla, enteric neurons, Schwann cells
What is different about cranial neural crest cells as compared to trunk neural crest cells?
Cranial neural crest can form cartilage, bone, and connective tissue along with neurons and ganglia. Trunk neural crest CANNOT form cartilage, bone, nor connective tissue
What are some possible cranio-facial defects associated with neural crest issues?
Treacher collins, Robin sequence, DiGeorge anomaly, Hemifacial microsomia
What do Hox genes code for?
Transcription factors that activate gene cascades regulating segmentation identity.
What are some of the derivatives of the endodermal level?
GI, Respiratory tract, urinary bladder, auditory tube, liver, pancreas, and cloaca
A portion of the amniotic cavity gets sealed in the cranial and caudal regions but remains open in the midgut. What’s the name of this opening?
Vitelline duct
What are the three regions of the endoderm?
Foregut (anterior), midgut, and hindgut (posterior)
What is the most notable feature of the hindgut? And, it’s role in the embryo? (hint: protrudes into the connecting stalk)
Allantois, it contributes to the vascularization
As lateral folding continues and the vitelline duct is eventually sealed off, what embryonic layer surround the embryo and what is it immersed in?
Ectoderm, amniotic cavity
At 10 wks, what is herniated into the yolk sac (within the umbilical cord) and will remain their until 3rd month?
Intestinal loops, herniate due to size constraints
What are some defects of failure to close the ventral body wall after lateral folding?
Ectopia Cordis (ectopic heart) Bladder Exstrophy (failure of pelvic region to close) Gastroschisis (herniation of intestines) Cloacal Exstrophy (failure of pelvic region to close)
When does gut regional specification begin?
When the lateral body wall folding brings 2 sides of the gut tube together
During gut specification: What is released by the gut endoderm? At the same time, what is released by the splanchnic mesoderm?
Gut endoderm: sonic hedgehod (Shh) Splanchnic mesoderm: Hox genes
At day 25, the upper region of the endodermal germ layer begins to form a structure that will give rise to the respiratory system. What is the name of that structure? In comparison to the endodermal germ layer, where will this structure exist?
Respiratory diverticulum, Ventral
During the 3rd to 8th wks, organogenesis is occurring under the influence of various signaling factors. The inhibition of what signaling factor is responsible for neural induction and eventual Neurulation?
BMP4
Gene expression of Hox genes is modulated by retinoic acid. A retinoic acid deficiency will result in what issue in the cephalic region?
Small hindbrain
