First Aid USMLE Step 1:
Reproductive Organ Systems +
Embryology
Sonic Hedgehog Gene - answer:-Produced @ base of limbs in zone of polarizing
activity
Involved in patterning along anterior/posterior axis
*SUMMARY: Anterior/posterior pattern*
Wnt-7 Gene - answer:-Produced @ apical ectodermal ridge (thickened ectoderm @
distal end of each developing limb)
Necessary for organization along dorsal/ventral axis
*SUMMARY: Dorsal/ventral pattern*
FGF Gene - answer:-Produced @ apical ectodermal ridge
Stimulates mitosis of underlying mesoderm --> Lengthening of limbs
Homeobox Genes (Hox genes) - answer:-Involved in segmental organization
Fetal Landmarks 1st week - answer:-Day 0: Fertilazation (~ 3d)
Day 5: Morula stage
*Day 7: Blastocyst stage —> Implantation as blastocyst*
Fetal Landmarks 2nd week - answer:-Bilaminar disk (epiblast and hypoblast)
Epiblast (ectoderm precursor) invaginates to form primitive streak —> Gives rise to both
intraembryonic mesoderm and endoderm
"Rule of 2's" for 2nd week of development - answer:-2 germ layers (epiblast, hypoblast)
2 cavities (amniotic cavity, yolk sac)
2 components of placenta (cytotrophoblast, syncytiotrophoblast)
Fetal Landmarks Week 3 - answer:-Gastrulation —> Primitive streak, notochord, and
neural plate begin to form
,First Aid USMLE Step 1:
Reproductive Organ Systems +
Embryology
"Rule of 3's" for 3rd week of development - answer:-3 germ layers (gastrula): Ectoderm,
mesoderm, endoderm
Fetal Landmarks Week 4 - answer:-Heart begins to beat
Upper and lower limb buds begin to form
"Rule of 4's" for 4th week of development - answer:-4 heart chambers (heart begins to
beat)
4 limb buds grow
Fetal Landmarks Embryonic Period (wks 3-8) - answer:-Neural tube forms,
organogenesis
*Extremely susceptible to teratogens*
Fetal Landmarks Fetal Period - answer:-Week 8 (beginning of fetal period): Fetal
movement, "looks like" a baby
*Week 10: Male/female genitalia*
Alar plate - answer:-Dorsal plate, sensory (same position as spinal cord)
Basal plate - answer:-Ventral plate, motor (same orientation as spinal cord)
Surface Ectoderm Derivatives - answer:-*Adenohypophysis (anterior pituitary)*
Lens of eye
Epithelial linings of oral cavity, eye, and nose
Epidermis
Salivary, sweat, and mammary glands
Neuroectoderm Derivatives - answer:-(Think "CNS + Brain")
Brain: Neurohypophysis (posterior pituitary), CNS neurons, oligodendrocytes,
astrocytes, ependymal cells, pineal gland
Retina
Spinal cord
*Notochord induces ectoderm to form neuroectoderm, postnatally: Becomes nucleus
pulposus of IV disks*
Neural Crest Derivatives (ectoderm) - answer:-ANS
,First Aid USMLE Step 1:
Reproductive Organ Systems +
Embryology
DRG
Cranial nerves
Celial ganglion
*Melanocytes*
*Chromaffin cells of adrenal medulla*
*Enterochromaffin cells*
Parafollicular (C) cells of thyroid
Schwann cells
Bones of skull
Laryngeal cartilage
Pia and arachnoid
Odontoblasts
*Aorticopulminary septum*
Endoderm Derivatives - answer:-Gut tube epithelium and derivatives (e.g. lungs, liver,
pancreas, thymus, parathyroid, thyroid follicular cells)
Mesodermal Derivatives - answer:-Muscle, bone, connective tissue
Serous lining of body cavities
Spleen (derived from foregut mesentery)
CV structures, lymphatics, blood
Urogenital structures, kidneys
Adrenal cortex
Mesodermal Defects - answer:-*VACTERL*
*V*ertebral defects
*A*nal atresia
*C*ardiac defects
*T*racheo-*E*sophageal fistula
*R*enal defects
*L*imb defects (in bone/muscle)
Timing of Teratogens - answer:-Before week 3: All-or-none (teratogens induce abortion)
Weeks 3-8 (embryonic period): Organogenesis period; most susceptible to insults
> Week 8: Affect growth/fxn
Fetal Alcohol Syndrome - answer:-*MOST COMMON* cause of birth defects/congenital
malformations and mental retardation (U.S.)
, First Aid USMLE Step 1:
Reproductive Organ Systems +
Embryology
Presentation
- Microcephaly
- Holoprosencephaly
- Facial abnormalities
- Limb dislocation
- Heart and lung fistulas
*SUMMARY*
- *Most common*
- *Micro-, holopresen-*cephaly
ACE-Inhibitors - answer:-Renal Damage
Cocaine - answer:-Abnormal fetal development and fetal addiction
*Placental abruption*
Diethylstilbestrol (DES) (Synthetic nonsteroidal estrogen) - answer:-Vaginal clear cell
carcinoma
Iodide (lack or excess) - answer:-Congenital goiter or hypothyroidism (cretinism)
Vitamin A (excess) - answer:-Extremely high risk for spontaneous abortions and birth
defects (cleft palate, cardiac abnormalities)
Thalidomide - answer:-Limb defects ("flipper" limbs)
Smoking (nicotine + CO) - answer:-Preterm labor
*Placental problems*
*Intra-uterine growth retardation (IUGR)*
ADHD
X-rays, Anticonvulsants - answer:-Multiple anomalies
Warfarin - answer:-Bone deformities
Fetal hemorrhage
Abortion
Reproductive Organ Systems +
Embryology
Sonic Hedgehog Gene - answer:-Produced @ base of limbs in zone of polarizing
activity
Involved in patterning along anterior/posterior axis
*SUMMARY: Anterior/posterior pattern*
Wnt-7 Gene - answer:-Produced @ apical ectodermal ridge (thickened ectoderm @
distal end of each developing limb)
Necessary for organization along dorsal/ventral axis
*SUMMARY: Dorsal/ventral pattern*
FGF Gene - answer:-Produced @ apical ectodermal ridge
Stimulates mitosis of underlying mesoderm --> Lengthening of limbs
Homeobox Genes (Hox genes) - answer:-Involved in segmental organization
Fetal Landmarks 1st week - answer:-Day 0: Fertilazation (~ 3d)
Day 5: Morula stage
*Day 7: Blastocyst stage —> Implantation as blastocyst*
Fetal Landmarks 2nd week - answer:-Bilaminar disk (epiblast and hypoblast)
Epiblast (ectoderm precursor) invaginates to form primitive streak —> Gives rise to both
intraembryonic mesoderm and endoderm
"Rule of 2's" for 2nd week of development - answer:-2 germ layers (epiblast, hypoblast)
2 cavities (amniotic cavity, yolk sac)
2 components of placenta (cytotrophoblast, syncytiotrophoblast)
Fetal Landmarks Week 3 - answer:-Gastrulation —> Primitive streak, notochord, and
neural plate begin to form
,First Aid USMLE Step 1:
Reproductive Organ Systems +
Embryology
"Rule of 3's" for 3rd week of development - answer:-3 germ layers (gastrula): Ectoderm,
mesoderm, endoderm
Fetal Landmarks Week 4 - answer:-Heart begins to beat
Upper and lower limb buds begin to form
"Rule of 4's" for 4th week of development - answer:-4 heart chambers (heart begins to
beat)
4 limb buds grow
Fetal Landmarks Embryonic Period (wks 3-8) - answer:-Neural tube forms,
organogenesis
*Extremely susceptible to teratogens*
Fetal Landmarks Fetal Period - answer:-Week 8 (beginning of fetal period): Fetal
movement, "looks like" a baby
*Week 10: Male/female genitalia*
Alar plate - answer:-Dorsal plate, sensory (same position as spinal cord)
Basal plate - answer:-Ventral plate, motor (same orientation as spinal cord)
Surface Ectoderm Derivatives - answer:-*Adenohypophysis (anterior pituitary)*
Lens of eye
Epithelial linings of oral cavity, eye, and nose
Epidermis
Salivary, sweat, and mammary glands
Neuroectoderm Derivatives - answer:-(Think "CNS + Brain")
Brain: Neurohypophysis (posterior pituitary), CNS neurons, oligodendrocytes,
astrocytes, ependymal cells, pineal gland
Retina
Spinal cord
*Notochord induces ectoderm to form neuroectoderm, postnatally: Becomes nucleus
pulposus of IV disks*
Neural Crest Derivatives (ectoderm) - answer:-ANS
,First Aid USMLE Step 1:
Reproductive Organ Systems +
Embryology
DRG
Cranial nerves
Celial ganglion
*Melanocytes*
*Chromaffin cells of adrenal medulla*
*Enterochromaffin cells*
Parafollicular (C) cells of thyroid
Schwann cells
Bones of skull
Laryngeal cartilage
Pia and arachnoid
Odontoblasts
*Aorticopulminary septum*
Endoderm Derivatives - answer:-Gut tube epithelium and derivatives (e.g. lungs, liver,
pancreas, thymus, parathyroid, thyroid follicular cells)
Mesodermal Derivatives - answer:-Muscle, bone, connective tissue
Serous lining of body cavities
Spleen (derived from foregut mesentery)
CV structures, lymphatics, blood
Urogenital structures, kidneys
Adrenal cortex
Mesodermal Defects - answer:-*VACTERL*
*V*ertebral defects
*A*nal atresia
*C*ardiac defects
*T*racheo-*E*sophageal fistula
*R*enal defects
*L*imb defects (in bone/muscle)
Timing of Teratogens - answer:-Before week 3: All-or-none (teratogens induce abortion)
Weeks 3-8 (embryonic period): Organogenesis period; most susceptible to insults
> Week 8: Affect growth/fxn
Fetal Alcohol Syndrome - answer:-*MOST COMMON* cause of birth defects/congenital
malformations and mental retardation (U.S.)
, First Aid USMLE Step 1:
Reproductive Organ Systems +
Embryology
Presentation
- Microcephaly
- Holoprosencephaly
- Facial abnormalities
- Limb dislocation
- Heart and lung fistulas
*SUMMARY*
- *Most common*
- *Micro-, holopresen-*cephaly
ACE-Inhibitors - answer:-Renal Damage
Cocaine - answer:-Abnormal fetal development and fetal addiction
*Placental abruption*
Diethylstilbestrol (DES) (Synthetic nonsteroidal estrogen) - answer:-Vaginal clear cell
carcinoma
Iodide (lack or excess) - answer:-Congenital goiter or hypothyroidism (cretinism)
Vitamin A (excess) - answer:-Extremely high risk for spontaneous abortions and birth
defects (cleft palate, cardiac abnormalities)
Thalidomide - answer:-Limb defects ("flipper" limbs)
Smoking (nicotine + CO) - answer:-Preterm labor
*Placental problems*
*Intra-uterine growth retardation (IUGR)*
ADHD
X-rays, Anticonvulsants - answer:-Multiple anomalies
Warfarin - answer:-Bone deformities
Fetal hemorrhage
Abortion
