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56 Cards in this Set
- Front
- Back
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What day is morula formed?
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Day 3
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What day is blastocyst implanted?
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Day 6
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What is the embryonic period?
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Weeks 2-8
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What is the cleavage period?
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Weeks 1-2
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What is the fetal period?
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Week 9 to birth
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How many cells comprise a morula?
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16-32 cells
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Until what point are all zygote cells totipotent (important for identical twins)?
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4-8 cell stage.
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Through what process do blastomeres (cells before morula) form the morula?
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Compaction: tight junctions formed b/w cells in outer cell mass, which seals off inner cell mass.
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what glycoprotein is involved in compaction?
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uvomorulin
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What are the 2 cell populations of the blastocyst?
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Inner cell mass and the trophoblast.
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what does the trophoblast form?
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Forms the chorion, which is part of the placenta
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what is the inner cell mass also known as?
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embryoblast
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When does the inner cell mass (embryoblast) segregate into two layers? What are the two layers?
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During implantation the embryoblast segregates into the epiblast and hypoblast.
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During what phase of the menstrual cycle does the blastocyst implant?
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During the progestational (secretory) phase.
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When the blastocyst begins to implant, which inner cell mass layer is closest to the endometrium?
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The epiblast layer is closer to the endometrium than the hypoblast layer.
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How does the amnion form?
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Fluid is secreted between the epiblast and trophoblast cells.
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What moves to surround the amnion during week 2?
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epiblast cells
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What happens to the trophoblast during implantation and where does it happen?
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At the embryonic pole the trophoblast differentiates into the cytotrophoblast and the synctiotrophoblast.
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Is the hypoblast layer dorsal or ventral?
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ventral
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How is the yolk sac formed during week 2?
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Hypoblast cells migrate to line the cytotrophoblast.
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What does the bilaminar embryoblast consist of?
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The cells of the epiblast and hypoblast remaining in contact.
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What are the 3 essential events of Week 2 (from powerpoint slide)?
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-Bilaminar embryoblast forms.
-Differentiation of extraembryonic membranes. -Completion of implantation. |
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Is the synctiotrophoblast mitotically active? What about the cytotrophoblast?
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The synctiotrophoblast is NOT mitotically active. The cytotrophoblast IS mitotically active.
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How does the synctiotriphoblast grow? What forms the primary chorionic villi?
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Cytotrophoblast cells migrate to the synctiotrophoblast. Cytotrophoblast cells also form mounds (primary chorionic villi) that bulge into the synctiotrophoblast
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What first establishes uteroplacental circulation?
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Lacunae of the synctiotrophoblast fuse to form a network that fills with maternal blood.
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How does the trilaminar embryoblast form?
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epiblast cells ingress through the primitive streak to become the endoderm and mesoderm.
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After ingression of epiblast cells into the primitive streak, what do the remaining epiblast cells (ones that didn't ingress) become?
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ectoderm
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What forms from the primitive node?
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The notochordal process.
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What is the cloacal membrane?
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Future site of the anus
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How does the notochord form from the notochordal process?
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The notochordal process is transformed from a tube to a solid rod.
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How is mesoderm organized in the early embryo?
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3 paired populations lateral to the notochord: paraxial mesoderm, intermediate mesoderm, and lateral (plate) mesoderm.
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What begins to form in the lateral mesoderm?
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Coelom
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Where do somites form?
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Paraxial mesoderm
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What three components do somites differentiate into?
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sclerotome (cartilage and bone), myotome (muscle), dermatome (dermis of skin)
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What mesoderm type is involved in formation of the future kidneys and gonads?
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intermediate mesoderm
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What does the coelom divide the lateral mesoderm into?
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The somatic (parietal) layer and the splanchnic (visceral) layer.
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When does neurulation begin?
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Week 3
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What is neural induction?
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The notochord instructs the overlying ectoderm to differentiate into neuroectoderm.
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What eventually happens to the neural plate?
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It folds into the neural tube.
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What do the neural crest cells contribute to?
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The peripheral nervous system and many other structures.
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In what direction does neural induction proceed?
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caudally
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Where does closure of the neural tube begin?
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occipiocervical junction
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What/when completes neural tube closure?
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Anterior neuropore closes ~25 days. The posterior neuropore closes ~26 days.
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What are the 3 essential events of the 3rd week?
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-Endoderm, then mesoderm form from epiblast.
-Notochord and 3 divisions of mesoderm form. -Notochord induces neural plate formation. |
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How does the embryonic disc fold in week 4?
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The cranial, caudal, and lateral extremes of the disc all fold ventrally.
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What are the 3 main results of cranio-caudal folding?
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-foregut, midgut, and hindgut are defined.
-Yolk sac suspended from midgut, creating a narrow vitelline duct. -amnion completely surrounds embryo. |
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what does the surface ectoderm form?
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epidermis, hair, nails, cutaneous glands, enamel.
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What do the two layers of the lateral mesoderm form?
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Somatic layer: limb skeleton, part of body wall.
Splanchnic layer: forms most of the gut, except its lining. |
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what does endoderm form?
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the mucosa and ducts of GI tract, lungs, liver, gall bladder, pancreas, and urinary bladder.
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How does secondary chorionic villi form?
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Somatic mesoderm penetrates core of the primary chorionic villi
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Where/when does angiogenesis initially occur?
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Begins in extraembryonic splanchnic mesoderm around yolk sac on day 17.
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How do angioblasts form and what do they form?
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Extraembryonic mesoderm differentiates into angioblasts. Angioblasts form angiogenic clusters.
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How do endothelial cells of vessels form? How do the endothelial cells form vessels?
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Angioblasts on periphery of angiogenic clusters form endothelial cells. These endothelial cells fuse together to form a vessel.
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Where/when does hematopoiesis begin?
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First occurs within the extraembryonic visceral mesoderm of yolk sac during week 3.
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How are blood cells produced from angiogenic clusters?
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Angioblasts within center of angiogenic cluster give rise to blood cells.
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When is hematopoiesis taken over by embryonic organs?
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week 5
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