FOM 6.3.2

Question 1

What are the three derivates of the ectoderm? What signaling contributes to that?

Answer 1

Neuroectoderm (Low BMP4, increased signaling from notochord) Neural Crest (Med BMP4) Non noneural ectoderm (High BMP4)

Question 2

What are the organ derivatives of the ectoderm?

Answer 2

CNS PNS Sensory epithelium of ear, nose, and eye Epidermis, hair, nails Mammary, pituitary, subcutanous glands NEURAL CREST CELLS

Question 3

Where is the disc-shaped embryo broadest?

Answer 3

Cranial region

Question 4

On day 16 the notochord begins to form, what day does does the neural plate begin to form?

Answer 4

Day 19

Question 5

What are the two main inducers of the neuroectoderm? What molecules do they use for induction?

Answer 5

Notochord and prechordal mesoderm. Dorsalizers (Noggin, chordin, follistatin)

Question 6

Name the three different portions of the neural plate (their relative position) and corresponding brain region.

Answer 6

Proencephalon - Forebrain (cranial) Mesencephalon- Midbrain Rhombocephalon- Hindbrain (caudal)

Question 7

Describe the fusion of the neural plate. When?

Answer 7

Birectional (starts at day 22)

Question 8

How do the somites interact w/ the neural tube? What’s their embryonic origin? What will they eventually form?

Answer 8

Surround the neural tube. Derived from paraxial mesoderm Form vertebrae

Question 9

What two placodes reside on the anterior portion of the neural tube? What will they eventually form?

Answer 9

Lens placode (lens of eye) Otic placode (inner ear, hearing, balance)

Question 10

The neuropores, opening of neural tube, close on which days?

Answer 10

Cranial (25 days) Caudal (28 days)

Question 11

What are two malformations that arise as a result of failure of neuropore closure?

Answer 11

Anencephaly (absent brain) and Spina bifida

Question 12

What are neural crest cells?

Answer 12

Migratory cell pop. at lateral borders (crest) of neuroectoderm -exit neural tube -multipotent -transient -give rise to diverse cell lineage

Question 13

What type of transition do neural crest cells undergo as neural folds fuse?

Answer 13

epithelial-to-mesenchymal

Question 14

What the difference b/t neural crest cell migration in the trunk and cranial region?

Answer 14

Cranial: leave before fusion of neural tube Trunk: leave after fusion

Question 15

What are some possible lineages of neural crest cells of the trunk?

Answer 15

melanocytes, sensory ganglia, adrenal medulla, enteric neurons, Schwann cells

Question 16

What is different about cranial neural crest cells as compared to trunk neural crest cells?

Answer 16

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

Question 17

What are some possible cranio-facial defects associated with neural crest issues?

Answer 17

Treacher collins, Robin sequence, DiGeorge anomaly, Hemifacial microsomia

Question 18

What do Hox genes code for?

Answer 18

Transcription factors that activate gene cascades regulating segmentation identity.

Question 19

What are some of the derivatives of the endodermal level?

Answer 19

GI, Respiratory tract, urinary bladder, auditory tube, liver, pancreas, and cloaca

Question 20

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?

Answer 20

Vitelline duct

Question 21

What are the three regions of the endoderm?

Answer 21

Foregut (anterior), midgut, and hindgut (posterior)

Question 22

What is the most notable feature of the hindgut? And, it’s role in the embryo? (hint: protrudes into the connecting stalk)

Answer 22

Allantois, it contributes to the vascularization

Question 23

As lateral folding continues and the vitelline duct is eventually sealed off, what embryonic layer surround the embryo and what is it immersed in?

Answer 23

Ectoderm, amniotic cavity

Question 24

At 10 wks, what is herniated into the yolk sac (within the umbilical cord) and will remain their until 3rd month?

Answer 24

Intestinal loops, herniate due to size constraints

Question 25

What are some defects of failure to close the ventral body wall after lateral folding?

Answer 25

Ectopia Cordis (ectopic heart) Bladder Exstrophy (failure of pelvic region to close) Gastroschisis (herniation of intestines) Cloacal Exstrophy (failure of pelvic region to close)

Question 26

When does gut regional specification begin?

Answer 26

When the lateral body wall folding brings 2 sides of the gut tube together

Question 27

During gut specification: What is released by the gut endoderm? At the same time, what is released by the splanchnic mesoderm?

Answer 27

Gut endoderm: sonic hedgehod (Shh) Splanchnic mesoderm: Hox genes

Question 28

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?

Answer 28

Respiratory diverticulum, Ventral

Question 29

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?

Answer 29

BMP4

Question 30

Gene expression of Hox genes is modulated by retinoic acid. A retinoic acid deficiency will result in what issue in the cephalic region?

Answer 30

Small hindbrain