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Step1: Embryo
| Question | Answer |
|---|---|
| Urine discharge from umbilicus | Patent urachus, failure of urachus to obliterate + persistant allantois remnant. In the 3rd wk, yolk sac forms allantois, and allantois becomes urachus, duct between bladder and yolk sac. A patent urachus connects bladder to umbilicus. |
| Outpouching of bladder | Vesicourachal diverticulum, failure of urachus to obliterate, persistant allantois remnant. Failure to close the part of urachus adjacent to the bladder. Commonly asymptomatic. |
| Failure to close the distal part of urachus (adjacent to the umbilicus) | Urachal sinus; perimumbilical tenderness, discharge from umbilicus from recurrent infections |
| Failure of central part of urachus to obliterate | Urachal cyst. Fluid filled structure between 2 obliterated ends of the urachus. Commonly asymptomatic. |
| Omphalocele | Imcomplete closure of the anterior abdominal wall during development, presents with a ventral opening at the umbilicus with protruding viscera covered by peritoneum |
| Gastroschisis | Inadequate enlargement of peritoneal cavity, viscera protrude thru the anterior abdominal wall ADJACENT to the umbilicus and are NOT covered by peritoneum |
| Hypospadias | Urethral opening is located on the ventral surface of the penis, associated with downward curvature in the penis, associated with failure of urethral folds to close |
| Epispadias | Abnormal opening of penile urethra on dorsal side of penis, due to faulty positioning of genital tubercle |
| Persistent yolk sac (vitelline duct) | Connects small intestine with the skin at the umbilicus. Incomplete obliteration of the vitelline (OMPHALOMESENTERIC) duct results in Meckel diverticulum |
| Sonic hedgehog gene | Involved in patterning along ANTERIOR - POSTERIOR axis, produced at base of limbs in zone of polarizing activity |
| Wnt-7 gene | Organization along DORSAL - VENTRAL axis, produced at apical ectodermal ridge |
| FGF gene | Stimulates mitosis of underlying mesoderm, providing for lengthening of limbs, produced at apical ectodermal ridge |
| Homeobox genes (HOX) | Hox mutations --> appendages in wrong places, involved in segmental organization of embryo in craniocaudal direction |
| Fetus Day 0 | Fertilization |
| Fetus Week 1 | hCG secretion, after implantation of blastocyst |
| Fetus Week 2 | 2 bilaminar discs - epiblast, hypoblast 2 cavities: amniotic cavity, yolk sac 2 components to placenta: cytotrophoblast, syncytiotrophoblast |
| Fetus Week 3 | 3 germ layers: ectoderm, mesoderm, endoderm --> gastrulation |
| Fetus Weeks 3-8 | Organogenesis. Neural tube closes by wk 4. |
| Fetus Week 4 | 4 heart chambers. 4 limb buds begin to grow. |
| Fetus Week 8 | Fetal pd begins. Fetal movement, starts to look like a baby. |
| Fetus Week 10 | Gentialia have male/female characteristics |
| Neural plate | Gives rise to neural tube and neural crest cells |
| Notochord | Becomes nucleus pulposus of IV disc in adults. |
| Malformation | Intrinsic disruption, occurs during embryonic pd (wk 3-8) |
| Deformation | Extrinsic disruption, occurs after embryonic pd |
| Agenesis | Absent organ, due to absent primordial tissue |
| Aplasia | Absent organ, despite present primordial tissue |
| Hypoplasia | Incomplete organ development, primordial tissue present |
| ACE inhibitors | Renal damage |
| Alkylating agents | Absence of digits, multiple anomalies |
| Aminoglycosides | CN VIII toxicity |
| Carbamazepine | Neural tube defects, craniofacial defects, fingernail hypoplasia, developmental delay, IUGR |
| DES | Clear cell adenocarcinoma of vagina |
| Folate antagonists | Neural tube defects |
| Lithium | Ebstein's anomaly (atrialized right ventricle) |
| Phenytoin | Fetal hydantoins syndrome: microcephaly, cardiac defects, IUGR, mental retardation, dysmorphic craniofacial features, hypoplastic nails |
| Tetracyclines | Discolored teeth |
| Thalidomide | Limb defects ("flipper limbs") |
| Valproate | Inhibition of maternal folate absorption --> neural tube defects |
| Warfarin | Bone deformities, fetal hemorrhage, abortion, opthalmologic abnormalities |
| Alcohol | FAS |
| Cocaine | Placental abruption, abnormal fetal development and fetal addiction |
| Smoking | Preterm labor, placental problems, IUGR, ADHD |
| Maternal diabetes | Caudal regression syndrome - anal atresia to sirenomelia, congenital heart defects, neural tube defects |
| Vit A excess | Cleft palate, cardiac abnormalities, spontaneous abortion |
| Fetal erythropoiesis | 3-8 wk = yolk sac 6-20 wk = liver 9-28 wk = spleen 28 wk + = bone marrow |
| Neural tube defects | Neuropores fail to fuse 4th wk. Persistent connection between amniotic cavity and spinal canal. Associated with LOW folic acid intake during pregnancy. ELEVATED alpha-fetoprotien in amniotic fluid and maternal serum. |
| Telencephalon (forebrain) | Cerebral hemispheres, lateral ventricles |
| Diencephalon (forebrain) | Thalamus, 3rd ventricle |
| Mesencephalon (midbrain) | Midbrain, Aqueduct |
| Metencephalon (hindbrain) | Pons, upper part of 4th ventricle AND Cerebellum |
| Myelencephalon | Medulla, lower part of 4th ventricle |
| Truncus arteriosus ...gives rise to... | Ascending aorta and pulmonary trunk |
| Bulbus cordis ...gives rise to... | Rt ventricle and smooth parts (outflow tract of left and right ventricle) |
| Primitive ventricle ...gives rise to... | trabelculated left and right ventricles |
| Primitive artria ...gives rise to... | Trabeculated left and right atrium |
| Left horn of sinus venosus ...gives rise to... | Coronary sinus |
| Right horn of SV ...gives rise to... | Smooth part of right atrium |
| Right common cardinal vein and right anterior cardinal vein ...gives rise to... | SVC |
| Abnormal neural crest cell migration in heart | Tetralogy of Fallot, transposition of great vessels, persistent TA |
| Endocardial cushion defects | Defects of AV septum. Initially acyanotic, form a L--> R shunt. Over time, pulmonary HTN leads to reversal of blood flow (EISENMENGER) and development of cyanotic symptoms |
| Aortic Arch constriction | Coarctation of the aorta - there is a discrepancy between LE and UE blood pressures |
| Pulmonary HTN | NORMAL IN UTERO. Following birth, resistance drops considerably. |
| Abnormal primitive heart looping | Misplaced inflow and outflow tracts. Leads to severe cardiac malformations. |
| Ductus arteriosis | Derived from 6th aortic arch. PDA can cause a thrill and a continuous murmur on physical exam. Indomethacin can be used to close PDA, while prostaglandins can maintain patency. |
| Hirshsprung's disease | Failure of migration - failure of neural crest cells to migrate to intestinal wall. Leads to absence of myenteric and submucosal plexus. |
| Duodenal atresia | Abnormal apoptosis -- duodenal lumen fails to recanalize during development. See signs of intestinal obstruction. |
| Neural tube defects | FAILED FUSION. increase AFP and acetylcholinesterase in CSF. |
| VACTERL | Group of anomalies typically seen together. Vertebral defects, anal atresia, cardiac defects, tracheo-esophageal fistula, renal defects, limb abnormalities |
| One of most common reasons for elevated AFP | Underestimation of gestational age. |
| Bilateral absence of kidneys | Potter's syndrome - consists of b/l renal aplasia, oligohydraminos (deficiency of amniotic fluid), characteristic fascies, and PULMONARY HYPOPLASIA (cause of death) |
| Lecithin (phosphatidycholine) : Sphingomyelin ration | Lecithin increases more than sphingomyelin (which remains fairly constant) after 30 wks gestation. A ration >2 is indicative of mature lungs. |
| Non fusion of urethral folds in male | HYPOSPADIAS |
| Faulty positioning of the genital tubercle in 5th wk of gestation | EPISPADIAS |
| Pancreas divisum | Improper fusion of dorsal and ventral pancreatic buds |
| Paramesonephric ducts | In females, fuse to form uterine tubes, uterus, cervix, and superior 1/3 of the vagina - failure to fuse can cause a BICORNUATE UTERUS or UTERUS DIDELPHYS |
| Caudal regression syndrome | Condition characterized by sacral agenesis causing LE paralysis and urinary incontinence; associated with POORLY CONTROLLED MATERNAL DIABETES |
| Vessel with highest blood ox saturation in fetus | Umbilical vein, bypasses liver and goes to IVC |
| Horseshoe kidney | Associated with TURNER's. Inferior poles of kidneys fuse |
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