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40 Cards in this Set
- Front
- Back
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What are the major events of week three of embryonic development?
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3 layer embryo established
Primitive streak formed Signalling centers established: node, notocord, anterior visceral endoderm L-R asymmetry established Neural induction |
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What two structures does the inner cell mass turn into?
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Hypoblast
Epiblast |
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What does the epiblast give rise to?
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Embryo
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What does the hypoblast give rise to?
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Extraembryonic structures: lining of the yolk sac, embryonic blood
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When does the second lineage decision occur?
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Right before implantation
During the second week |
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What are the three germ layers?
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Ectoderm
Mesoderm Endoderm |
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What tissues does the ectoderm give rise to?
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Skin
Nervous tissue Amnion |
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What tissues does the mesoderm give rise to?
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Muscle
Blood Connective tissue |
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What tissues does the endoderm give rise to?
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Epithelial lining
Gut Lung GU tract Inner linings of everything except for the blood vessels |
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What is the signalling center that patterns the mesoderm?
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Primitive node
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What is the axis for mesoderm development during development?
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Cranial - caudal
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What does the axial mesoderm form? Where does it migrate?
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Notochord
Pre-chordal plate Along the midline |
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What does the paraxial mesoderm form? Where does it migrate?
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Somites
Cartilage Skeletal muscle Dermis Just caudal to node, migrates slightly laterally |
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What does the lateral plate mesoderm form? Where does it migrate?
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Circulatory system
Bones (sternum, etc.) Deep connective tissue Laterally |
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What does the extraembryonic mesoderm form? Where does it migrate?
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Extraembryonic membranes, blood vessels
Laterally |
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What is the function of the primitive node during gastrulation?
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Positioning of the primitive streak
Patterns the mesoderm Induces neural differentiation |
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What is the function of the notochord during gastrulation?:
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Patterns the surrounding tissue: ectoderm (overlying) and endoderm (under)
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What is the function of the anterior visceral endoderm during gastrulation?
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Positions primitive streak in the posterior, pattern overlying mesoderm
Pattern head formation |
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What mechanical event is responsible for the L-R patterning of the embryo?
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Beating of cilia the leftward direction
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What genes are responsible for the turning on of the left-side genes during development
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Sonic hedgehog
FGF-8 |
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What are the "left-sided" genes of gastrulation?
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Nodal
Pitx2 |
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What is one consequence of defective cilia action in gastrulation?
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Organ asymmetry
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What type of drugs could cause an asymmetry in an embryo?
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Monoamine oxidase inhibitors:
Serotonin increases the expression of Shh. If it can't be broken down, you'll get it all over the place, leading to asymmetries |
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What are three potential causes of asymmetry in an embryo?
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Genetic efects within cilia
Mechanical defects within cilia MAO inhibitors |
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What is Kartagener syndrome?
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A defect in cilia
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What is the function of BMP-4 in gastrulation?
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Preventing the ectoderm from becoming the brain
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What signalling center induces neural formation? How?
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Primitive node
Secreting a BMP-4 antagonist |
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What is the "default" tissue of ectoderm?
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Neural tissue
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What is the protein that is responsible for preventing the ectoderm from developing into nervous tissue?
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BMP-4
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What signalling center is responsible for the development of the head?
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AVE
Anterior visceral endoderm |
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What is a consequence of not having an AVE?
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No head!
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What is one example of an AVE defect seen in humans?
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Holoprosencephaly
The brain doesn't cleave at the midline. -No corpus callosum -Eyes are close together (sometimes 1 eye) -One upper incisor |
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What are the symptoms of caudal agenesis?
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VATeR:
Vertebral defects Anal atresia Tracheo-esophageal fistula Renal defects |
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What is a result of an overactive primitive node in a baby?
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Sacrococcageal teratoma
All 3 germ layers |
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What are the three fetal membranes? From where do they arise?
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Chorion: trophoblast
Amnion: epiblast Yolk sac: primitive endoderm |
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Where does hematopoesis first occur in an embryo?
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Yolk sac
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How is the amniotic fluid taken up by the fetus?
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Swallowing
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What are two pathologies related to amniotic fluid equilibrium? What is a consequence of one of them?
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Polyhydramnois: swallowing, gut defect; too much fluid
Oligohydramnios: too little fluid. Clipping off of limb buds |
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What fetal defects are associated with oligohydramnois?
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Amputation of limbs due to ensnaring of limb buds by the amniotic sac
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What is a complication of twinning, possibly?
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Twins share a placenta --> conjoined
One can live, the other dies. |
