First Aid USMLE 2012 p124 Flashcards
Fx of neural tube and notochord during Neural development
- Notochord induces overlying ectoderm to differentiate into neuroectoderm and form the neural plate.
- Neural plate gives rise to the neural tube and neural crest cells.
- Notochord becomes nucleus pulposus of the intervertebral disk in adult.
What are the derivatives of the Endoderm?
Gut tube epithelium (including anal canal above the pectinate line) and derivaties (lung, liver, pancreas, thymus, parathyroid, thyroid follicular cells)
What are the Fetal Landmarks?
Day 0: Fertilization
Within week 1: hCG
Within week 2: Bilaminar disk (epiblast, hypoblast)
Within week 3: Trilaminar disk. Gastrulation
Weeks 3-8: Neural tube formed by neuroectoderm closes by week 4. Organogenesis. Extremely susceptible to teratogens.
Week 4: Rule of 4: Heart chambers & limb buds
Week 8 (fetal period): Fetal movement
Week 10: Genitalia
Alar plate (dorsal): Sensory
Basal plate (ventral): Motor
What are the Rules of Early Development?
Rule of 2’s for 2nd week:
2 germ layers (bilaminar disk) : epiblast,
hypoblast.
2 cavities: amniotic cavity, yolk sac.
2 components to placenta : cytotrophoblast,
syncytiotrophoblast.
Rule of 3’s for 3rd week: 3 layers of gastrula: endoderm, mesoderm, ectoderm
Rule of 4’s for 4th week
4 heart chambers.
4 limb buds grow.
What are the derivatives of the Ectoderm?
- surface ectoderm: Adenohypophysis (from Rathke’s pouch); lens of eye; epithelial linings of oral cavity, sensory organs of ear, and olfactory epithelium; epidermis; anal canal below the pectinate line; salivary, sweat, and mammary glands.
- Neuroectoderm: Brain (neurohypophysis, CNS neurons,
oligodendrocytes, astrocytes, ependymal cells, pineal gland), retina, spinal cord.
Neural crest: ANS, dorsal root ganglia, cranial nerves,
celiac ganglion, melanocytes, chromaffin
cells of adrenal medulla, parafollicular (C) cells of thyroid, Schwann cells, pia and arachnoid, bones of the skull, odontoblasts,
aorticopulmonary septum.
What are the derivatives of the Mesoderm?
Muscle, bone, connective tissue, serous linings of body cavities (e.g., peritoneum), spleen (derived from foregut mesentery), cardiovascular structures, lymphatics, blood, bladder, urethra, vagina, eustachian tube, kidneys, adrenal cortex, ski n derm is, testes, ovaries. Notochord induces ectoderm to form neuroectoderm (neural plate). Its postnatal derivative is the nucleus pulposus of the intervertebral disk.
Fx of Shh?
Produced at base of limbs in zone of polarizing activity. Involved in patterning along A-P axis.
Fx of Wnt-7 gene?
Produced at apical ectodermal ridge (thickened ectoderm at distal end of developing limbs). Necessary for proper organization along D-V axis.
Fx of FGF gene?
Produced at apical ectodermal ridge. Stimulating mitosis of underlying mesoderm, providing for lengthening of limbs.
Fx of Hox genes?
Involved in segmental organization of embryo in craniocaudal direction. Hox mutations=appendages in wrong locations.
Teratogen: Ace inhibitors
renal damage
Teratogen:Alkylating agemts
absence of digits, multiple anomalies
Teratogen: Aminoglycosylides (A MEAN GUY hit the baby in the ear)
CN VIII toxicity
Teratogen: Carbamazepine
Neural tube defects, craniofacial defects,
fingernail hypoplasia, developmental delay,
IUGR
Teratogen: Diethylstilbesterol
Vaginal clear cell adenocarcinoma
Teratogen: Folate antagonists
Neural tube defects
Teratogen: Lithium
Ebstein’s anomaly (atrialized right ventricle)
Teratogen: Phenytoin
Fetal hydantoin syndrome: microcephaly,
dysmorphic craniofacial features, hypoplastic
nails and distal phalanges, cardiac defects,
IUGR, mental retardation
Teratogen: Tetracyclines
Discolored teeth
Teratogen: Thalidomide
limb defects (flipper limbs)
Teratogen: Valproate
Inhibition of maternal folate absorption - neural tube defects
Teratogen: Warfarin (Do not wage warfare on the baby; keep it heppy with heparin (does not cross placenta)
Bone deformities, fetal hemmorhage, abortion, opthalmologic abnormalities
Birth defects of Maternal Diabetes?
Caudal regression syndrome (anal atresia to sirenomelia), congenital heart defects, neural tube defects.
Birth defects of Vit. A excess?
Extremely high risk for spontaneous abortions and birth defects (cleft palate, cardiac abnormalities)
Birth defects of X-rays?
Microcephaly, mental retardation
Fetal component: Cytotrophoblast
inner layer of chorionic villi. Cyto makes Cells.
Fetal component: Syncytiotrophoblast
outer layer of chorionic villi; secretes hCG (structurally similar to LH; stimulates corpus luteum to secrete progesterone during first trimester).
Maternal component: Decidua basalis
derived from the endometrium. Maternal blood in lacunae.
UMBILICAL CORD: Properties of Umbilical arteries (2)?
Return deoxygenated blood from fetal internal iliac to placenta; single umbilical artery associated with congenital & chromosomal anomalies.
UMBILICAL CORD: Properties of umbilical vein (1)?
Supplies oxygenated blood from placenta to fetus; drains into IV; Umbilical arteries and veins derived from Allantois
Urachal Duct abnormalities?
3rd week: yolk sac forms allantois, which extends into urogenital sinus. Allantois becomes Urachus, a duct between bladder and yolk sac.
Failure of urachus to obliterate:
1. PATENT URACHUS: urine discharge from umbilicus.
2. VESICOURACHAL DIVERTICULUM: outpouching of bladder
Vitelline duct abnormalities?
7th week: Obliteration of vitelline duct (omphalomesenteric duct), which connects yolk sac to midgut lumen.
- VITELLINE FISTULA: failure of duct to close -> meconium discharge from umbilicus.
- MECKEL’S DIVERTICULUM: partial closure with patent portion attached to ileum. May have ectopic gastric mucosa -> melena and periumbilical pain.
Heart Embryology: Truncus Arteriosus(TA) gives rise to:
Ascending Aorta and pulmonary trunk
Heart Embryology: Bulbos cordis gives rise to:
Right ventricle and smooth parts (outflow tract) of left and right ventricle.
Heart Embryology: primitive ventricle gives rise to:
Trabeculated left and right ventricles
Heart Embryology: Primitive atria gives rise to:
Trabeculated left and right atrium
Heart Embryology: Left horn of sinus venosus (SV) gives rise to:
Coronary sinus
Heart Embryology:Right Horn of SV gives rise to:
Smooth part of right atrium
Heart Embryology: Right common cardinal vein and right anterior cardinal vein gives rise to:
SVC
