| Question |
Answer |
| what is the most sensitive period for teratogenesis? |
3-8 weeks |
| how does situs inversus happen? |
defective morphogen genes from hensen's node |
| how does caudaldysgenesis happen? |
insufficient mesoderm in caudalmost embryo |
| what is holoprosencephaly? what causes it? |
deficiency of midline craniofacial structures from disruption of forebrain development; fetal alcohol syndrome |
| what is the name for when the neural tube fails to close? |
spinal dysraphism |
| what are the 4 spina bifidas? |
occulta, cystica, meningocele, and meningomyelocele |
| what are the symptoms of meningomyeloceles? |
incontinence, csf leak, flaccid paralysis, and hydrocephaly |
| if the neural tube fails to close in brain vesicles, what happens? |
ancephaly |
| amniocentesis shows what elevation in defects? |
alpha-fetoprotein and acetylcholinesterase |
| Malformations arising during development, produced by environmental, not genetic, insults are what? |
developmental defects |
| disorders present at birth, produced by environmental and/or genetic causes. These can be morphological, behavioral and metabolic: |
Birth Defects, Congenital Anomalies |
| malformations produced over a prolonged period of time due to persistent molding forces, e.g. cranial shape change due to decreased amniotic fluid (oligohydramnios): |
deformation |
| malformations produced after the initial formation of a normal structure, due to abruptly occurring destructive forces, e.g. amniotic band disruption complexes causing in utero amputation: |
disruption |
| morphological anomalies are called what? |
congenital malformations |
| what is an extreme example of caudal dysgenesis? |
sirenomelia |
| spina bifida occulta is a ___ neural tube defect while spina bifida meningomyelocele is a ____ neural tube defect: |
closed; open |
| dysraphism is most common at what points in the neural tube? |
L5 or S1 |
| Hydrocephaly and neurologic deficit is more common with ____ defects, urinary incontinence with ____ defects |
anterior; posterior |
| what is a CSF-filled meningeal sac? |
cranial meningocele |
| what is a CSF-filled meningeal sac that contains brain tissue? |
cranial encephalocele |
| dizygotic twins are what? monozygotic? |
fraternal, identical |
| if dyzygotic blastocysts implant in close proximity, what structures can be fused? |
chorion, placenta |
| what is most common scenario for monozygotic twins, that is, when do they split? |
embryoblast of the blastocyst splits in two |
| in monozygotic twins, if the embryoblast splits in two, what structures become fused? |
chorion, placenta |
| in the case of monozygotic twins, when there is a split in the bilaminar stage just before formation of the primitive streak, what structures are fused? |
chorion, placenta, amnion |
| in monozygotic twins, if the split occurs at the 2-cell embryo stage, what structures will be fused? |
none |
| when a twin resorbs another twin, the mummified body is known as a what? |
fetus papyraceus |
| if the embryoblast or germ disc does not separate completely, what condition develops? |
conjoined twins |
| Conjoined twins are most common in what type of pregnancy? |
monoamniotic |
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