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39 Cards in this Set
- Front
- Back
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What does the hypoblast form?
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Primary extraembryonic endoderm, which forms the yolk sac endoderm
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Where are the epiblast and hypoblast positioned relative to each other?
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epiblast - dorsal
hypoblast - ventral so yolk sac is under embryo/amnion |
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What does the embryonic epiblast form?
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Forms the Embryonic ectoderm and primitive streak
Primitive streak forms the embryonic endoderm, notochord, mesoderm (embryonic and extraembryonic) |
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What does the trophoblast form?
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Cytotrophoblast --> synctiotrophoblast, extraembryonic mesoderm
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What is the primitive streak?
how does it come about? |
the first morphological marker of the craniocaudal axis
- results from proliferation/migration of cells |
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What is the primitive node?
What is its function? |
the cranial end of the primitive streak proliferates to form a primitive node.
Signaling center |
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What is the primitive groove?
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A depression in the middle of the primitive streak. site along which cells migrate through the epiblast. first, endoderm cells migrate....then mesoderm...then ectoderm.
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How do cells migrate through the streak and node?
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In very specfiic, predictable patterns...stereotyped migration
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What determines developmental cell fate?
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Location/timing of ingression
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What is the organizing center for cranial fates?
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anterior visceral endoderm
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What is BMP4? What expresses it? What does it do if you express BMP4?
(bone morphogenetic protein 4 - a TGF-beta family member) |
Growth factor expressed by cells in the bilaminar disk. Controls dorsal/ventral fates
Along with FGFs, BMP4 ventralizes the mesoderm into intermediate and lateral plate mesoderm. |
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What happens if you inhibit BMP4?
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dorsalizes mesoderm to form notochord and somatic mesoderm (paraxial mesoderm)
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How is BMP4 inhibited?
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node secretes BMP agonists (chordin, noggin). Inhibit BMP, dorsalize the mesodrm.
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Summarize what the node controls.
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dorsal/ventral fates of medosderm cells
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What is notable about the notochord?
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- Defines the body axis
- Defines our phylum (Chordata) - Provides rigidity to embryo - Signaling center ..to induce neural fates - precursor for axial skeleton (vertebrae, head bones) |
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How does the neural tube form?
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dorsal ectoderm becomes neural plate.
lateral edges raise to form neural folds, mid region becomes depressed to form neural groove. Neural folds move together, form neural tube. NT detaches from ectoderm. So NT = made of ectoderm entirely |
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What is neurulation?
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formation of the neural tube
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Where does the NT initially fuse?
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About midway along embryo (5th somite = neck region), then fusion moves in both caudal and cranial directions
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What are the cranial and caudal neuropores? Do they stay there?
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The opening at either end of the neural tube. No, they eventually close up when neurulation is finished.
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When is neurulation finished?
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When the neuropores close up
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What happens if there's incomplete fusion of the neuropores? Give 2 diseases
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spina bifida
anencephaly |
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What are some of the things that interact during the formation of the NT
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Folic acid/cholesterol
Genes (Pax3, sonic hedgehog) |
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where does sonic hedgehog (shh) come from? what does it do?
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Notochord is a source of shh
shh and Bmp's induce neural plate |
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How do Shh/bmp's form the neural tube?
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Shh from notochord induces the floor plate, which becomes a source of Shh.
Shh patterns ventral NT fates Bmp's pattern dorsal NT fates |
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How does the neural crest form?
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During specification of dorsal-ventral NT fates, the dorsal-most part of the NT gives rise to the neural crest.
Cells at the lateral borders of the neurectoderm dissociate, undergo epithelial-to-mesenchymal transformation, and migrrate away from NT. The mesenchymal neural crest migrates through the mesoderm, forms various tissues/organs |
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What is mesenchymal?
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loosely organized embryonic connective tissue
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What are the 4 neural crest cell regions?
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1. cranial neural crest
2. cardiac neural crest 3. Vagal/sacral neural crest 4. trunk neural crest |
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Describe the cranial neural crest
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- migrate dorsolaterally to produce craniofacial mesenchyme.
- Differentiates into cartilage/bone/glia/neurons/connective tissue of the face. - pharyngeal arches, thymus, tooth primordia, middle ear, jaw bones |
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Describe the cardiac neural crest
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- gives rise to outflow tract septum (separates pulmonary/aortic circulations)
- also gives rise to smooth muscle around large arteries arising from heart |
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What does the vagal/sacral neural crest turn into
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Parasympathetic ganglia of the gut
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What does the trunk neural crest turn into?
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dorsolateral migrating trunk neural crest cells: --> melanocytes
ventrolateral --> dorsal root/ganglia |
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What are the 4 regions/types of mesoderm?
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axial/chordamesoderm
paraxial mesoderm intermediate mesoderm lateral plate mesoderm Order from outermost: lateral- intermediate - paraxial - chorda - |
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What does the intermediate mesoderm turn into?
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- urogenital structures
- gonads - Segmental in cervical/thoracic regions --> future nephrotomes - unsegmented in caudal region --> nephrogenic cord |
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What does the lateral mesoderm turn into?
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Parietal mesoderm (somatic): overlying ectoderm forms lateral and ventral body walls, thin serous membranes lining the body cavities
Visceral mesoderm (splanchnic) + endoderm --> form gut wall, thin serous membrane around each organ visceral mesoderm of yoc sac --> angioblasts --> give rise to endothelial cells (lining blood islands/vessels) and blood cells |
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What does the paraxial mesoderm turn into?
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gets segmented into somitomeres
head somite: -sclerotome = cartilage which surrounds the notochord, becomes the cartilage cells of vertebrae, ribs -myotome = skeletal muscle, -- dermatome = dermis |
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What does the chordamesoderm turn into? -
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Notochord
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What are the derivatives of the endoderm?
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GI tract
epithelial lining of lung buds and trachea liver gall bladder pancreas - Anterior foregut (cranial region) and posterior hindgut (caudal region) - connected by a midgut that is attached to a vitelline duct attached to yoc sac |
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How does the embryo fold?
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In horizontal (lateral) and medial (head/tail) planes
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Describe the movement during folding?
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cranial/caudal ends move ventrally
heart moves to ventral surface foregut between heart and oropharyngeal membrane hindgut |
