Reproductive Flashcards – First Aid for the USMLE STEP 1

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  • what are the important genes of embryogenesis?
    1. Sonic hedgehog gene 2. Wnt-7 gene 3. FGF gene 4. Homeobox (hox) genes
  • Sonic hedgehog gene is produced where?
    at base of limbs in zone of polarizing activity
  • sonic hedgehog gene is involved in what?
    patterning along anterior-posterior axis CNS development
  • matuation in sonic hedgehog gene can cause what?
    holoprosencephaly
  • Wnt-7 gene is produced where?
    at apical ectodermal ridge
  • what is the apical ectodermal ridge?
    thickened ectoderm at distal end of each developing limb
  • Wnt-7 gene is necessary for what?
    proper organization along dorsal-ventral axis
  • FGF gene is produced where?
    at apical ectodermal ridge
  • FGF gene does what?
    "stimulates underlying mesoderm, providing for lengthening of limbs"
  • Hox genes are involved in what?
    segmental organization of embryo in a cranial caudal direction.
  • Hox mutations lead to what?
    appendages in wrong locations
  • what happens at day 0 of early fetal development?
    "fertilization by sperm forming zygote, initiating embryogenesis"
  • what happens within week 1 of early fetal development?
    hCG secretion begins after implantation of blastocyst
  • what happens within week 2 of early fetal development?
    "bilaminar disc (epiblast, hypoblast). 2 weeks= 2 layers"
  • what happens within week 3 of early fetal development?
    "1. trilaminar disc. 3 weeks = 3 layers. 2. gastrulation 3. Primitive streak, notochord, mesoderm and its organization, and neural plate begins to form"
  • what happens between weeks 3-8 (embryonic period)?
    1. neural tube formed by neuroectoderm and closes by week 4. 2. organogenesis 3. extremely susceptible to teratogens
  • what happens during week 4 of early fetal development?
    1. heart begins to beat 2. upper and lower limb buds begin to form. 3. 4 weeks = 4 limbs
  • what happens during week 8? (start of fetal period)?
    "fetal movement, fetus looks like a baby"
  • what happens during week 10 of early fetal development?
    genitalia have male/female characteristics
  • what is gastrulation?
    "process that forms the trilaminar embryonic disc. establishes the ectoderm, mesoderm, and endoderm germ layers."
  • gastrulation starts with what?
    the epiblast invaginating to form the primitive streak
  • what are the 3 types of ectoderm?
    1. surface ectoderm 2. neuroectoderm 3. neural crest
  • surface ectoderm gives rise to what?
    "1. adenohypophysis (from Rathke's pouch) 2. lens of the eye 3. epithelial linings of oral cavity, sensory organs of ear, and olfactory epithelium 4. epidermis 5. anal canal below the pectinate line 6. parotid, sweat, and mammary glands"
  • what is a Craniopharyngioma?
    "benign rathke's pouch tumor with cholesterol crystals, calcifications"
  • neuroectoderm gives rise to what?
    "1. brain (neurohypophysis, CNS neurons, oligodendrocytes, astrocytes, ependymal cells, pineal gland) 2. retina and optic nerve 3. spinal cord Neuroectoderm think CNS"
  • Neural crest gives rise to what?
    "1. PNS (dorsal root ganglia, cranial nerves, celiac ganglion, Schwann cells, ANS) 2. melanocytes 3. chromaffin cells of the adrenal medulla 4. parafollicular (C) cells of the thyroid 5. Schwann cells 6. Pia ... (for more info refer to your books)"
  • mesoderm gives rise to what?
    1. muscle 2. bones 3. connective tissue 4. serous linings of the body cavities (periotneum) 5. spleen (derived from foregut mesentery) 6. cardiovascular structures 7. lymphatics 8. blood 9. wall of gut tube (for more info refer to your books)
  • notochord induces ectoderm to form what?
    neuroectoderm
  • the only post natal derivative of the notochord is what?
    nucleus pulposus of the intervertebral disc
  • what are the mesodermal defects?
    VACTERL: Vertebral defects Anal atresia Cardiac defects Tracheo-Esophageal fistula Renal defects Limb defects (muscle and bone)
  • Endoderm gives rise to what?
    "1. Gut tube epithelium (including anal canal above the pectinate line) 2. luminal epithelial derivatives (lungs, liver, gallbladder, pancreas, eustachian tube, thymus, parathyroid, thyroid follicular cells)"
  • what are the 5 types of errors in organ morphogenesis?
    1. agenesis 2. aplasia 3. deformation 4. hypoplasia 5. malformation
  • what is agenesis?
    absent organ due to absent primordial tissue
  • what is aplasia?
    absent organ despite present primordial tissue
  • what is deformation?
    extrinsic disruption; occurs after embryonic period
  • what is hypoplasia?
    incomplete organ development; primordial tissue present
  • what is malformation?
    intrinsic disruption; occurs during the embryonic period
  • when is susceptibility to teratogens highest?
    3-8 weeks (embryonic period- organogenesis).
  • what happens if teratogens are present before week 3?
    all or none effects
  • what happens if teratogens are present after week 8?
    growth and function affected
  • what are the teratogenic effects of ACE inhibitors?
    renal damage
  • what are the teratogenic effects of alkylating agents?
    "absence of digits, multiple anomalies"
  • what are the teratogenic effects of aminoglycosides?
    CN VIII toxicity A mean guy hit the baby in the ear
  • what are the teratogenic effects of carbamazepine?
    1. neural tube defects 2. craniofacial defects 3. fingernail hypoplasia 4. developmental delay 5. IUGR
  • what are the teratogenic effects of diethylsilbesterol (DES)?
    "vaginal clear cell adenocarcinoma, congenital Mullerian abnormalities"
  • what are the teratogenic effects of folate antagonists?
    neural tube defects
  • what are the teratogenic effects of lithium?
    Ebstein's anomaly (atrialized right ventricle)
  • what are the teratogenic effects of phenytoin?
    Fetal hydantoin syndrome: 1. microcephaly 2. dysmorphic craniofacial features 3. hypoplastic nails and distal phalanges 4. cardiac defects 5. IUGR 6. mental retardation
  • what are the teratogenic effects of tetracyclines?
    discolored teeth
  • what are the teratogenic effects of thalidomide?
    limb defects (flipper limbs)
  • what are the teratogenic effects of valproate?
    inhibition of maternal folate absorption--> NTD
  • what are the teratogenic effects of warfarin?
    "bone deformities, fetal hemorrhage, abortion, ophthalmologic abnormalities"
  • what are the teratogenic effects of alcohol?
    leading cause of birth defects and mental retardation; fetal alcohol syndrome
  • what are the teratogenic effects of cocaine?
    1. abnormal fetal development and fetal addiction 2. placental abruption
  • what are the teratogenic effects of smoking?
    1. preterm labor 2. placental problems 3. IUGR 4. ADHD
  • what are the teratogenic effects of iodide (lack or excess)?
    congenital goiter or hypothyroidism (cretinism)
  • what are the teratogenic effects of maternal diabetes?
    1. caudal regression syndrome (anal atresia to sirenomelia) 2. congenital heart defects 3. NTD
  • what are the teratogenic effects of Vit A excess?
    "extremely high risk for spontaneous abortions and birth defects (cleft palate, cardiac abnormalities)"
  • what are the teratogenic effects of X-ray?
    microcephaly MR
  • what is the leading cause of congenital malformations in the USA?
    fetal alcohol syndrome
  • newborns of mothers who consumed a significant amount o alcohol during pregnancy have an increased incidence of what?
    congenital abnormalities including: 1. mental retardation 2. pre and post natal developmental retardation 3. microcephaly 4. holoprosencephaly 5. facial abnormalities 6. limb dislocation 7. heart and lung fistulas
  • what are dizygotic twins?
    "2 eggs that are separately fertilized by 2 different sperm (always 2 zygotes), and will have 2 separate amniotic sacs and 2 separate placentas (chorions)"
  • what are monozygotic twins?
    1 fertilized egg that splits into 2 zygotes in early pregnancy.
  • the degree of separation between monozygotic twins depends on what?
    when the fertilized egg splits into 2 zygotes
  • what happens when a zygote splits at 0-4 days?
    splits between 2 cell stage and morula. --> fused placenta or separate placenta = dichorionic diamniotic
  • what happens when a zygote splits between 4-8 days?
    splits between morula and blastocyst stage: --> monochorionic diamniotic
  • what happens when a zygote splits between 8-12 days?
    splits between blastocyst and formation of embryonic disc: --> monochorionic monoamniotic
  • what happens when a zygote splits after 13 days?
    splits after embryonic disc formation --> monochorionic monoamniotic conjoined twins
  • what is the relative prevalence of the different types of twins?
    dizygotic = 80% monozygotic = 20% - dc/da= 25% - mc/da= 75% - mc/ma= <1%
  • what is the 1st site of nutrient and gas exchange between mother and fetus?
    placenta
  • what is cytotrophoblast?
    inner layer of chorionic villi
  • cytotrophoblast makes what?
    cells
  • what is syncitiotrophoblast?
    outer layer of chorionic villi; secretes hCG
  • function of hCG?
    stimulates corpus luteum to secrete progesterone during first trimester
  • hCG is structurally similar to what?
    LH
  • what are the fetal components of the placenta?
    cytotrophoblast syncytiotrophoblast
  • what are the maternal components of the placenta?
    1. decidua basalis
  • decidua basalis is derived from what?
    endometrium. maternal blood in lacunae
  • how many umbilical arteries are there?
    2
  • what is the function of the umbilical arteries?
    return deoxygenated blood from internal iliac arteries to placenta
  • how many umbilical veins are there?
    1
  • function of the umbilical vein?
    supplies oxygenated blood from placenta to fetus; drains via ductus venosus into IVC
  • single umbilical artery is associated with what?
    congenital and chromosomal anomalies
  • umbilical arteries and veins are derived from what?
    allantois
  • what are the structures that make up allantois?
    1. allantoic duct 2. amniotic epithelium 3. umbilical arteries 4. umbilical vein 5. Wharton's jelly
  • how does urachal duct develop?
    "3rd week- yolk sac forms allantois, which extends into urogenital sinus. allantois becomes urachus"
  • what is the urachus?
    a duct between the bladder and the yolk sac
  • what are the consequences of failure of urchus to obliterate?
    patent urachus- urine discharge from umbilicus vesicourachal diverticulum- outpouching of the bladder
  • what is the other name for the vitelline duct?
    omphalo-mesenteric duct
  • what does the vitelline duct do?
    connects yolk sac to midgut lumen
  • when does obliteration of the vitelline duct occur?
    7th week
  • what are the consequences of failure of vitelline duct to close?
    "vitelline fistula--> meconium discharge from umbilicus meckel's diverticulum- partial closure, with patent portion attached to ileum. may have ectopic gastric mucosa--> melena, periumbilical pain, ulcer"
  • the aortic arch derivatives develop into what?
    the arterial system
  • what are the derivatives of the 1st aortic arch?
    part of maxillary artery (branch of external carotid) 1st arch is maximal
  • what are the derivatives of the 2nd aortic arch?
    stapedial artery and hyoid artery second=stapedial
  • what are the derivatives of the 3rd aortic arch?
    Common Carotid artery and proximal part of internal Carotid artery C is 3rd letter of the alphabet
  • what are the derivatives of the 4th aortic arch?
    "on left, aortic arch on right, proximal part of right subclavian artery"
  • what are the derivatives of the 6th aortic arch?
    proximal part of pulmonary arteries an (on left only) ductus arteriosus 6th arch= pulmonary and the pulmonary to systemic shunt
  • branchial apparatus is also called what?
    pharyngeal apparatus
  • branchial apparatus is composed of what?
    "branchial clefts, arches, and pouches CAP covers outside from inside: Clefts= ectoderm Arches= mesoderm Pouches= endoderm"
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