embryology

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Author:
peachd
ID:
12771
Filename:
embryology
Updated:
2010-04-01 02:00:40
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embryo
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embryological structures
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  1. Major events: weeks 1 & 2
    • Week 1 = implantation (as a blastocyst)
    • Week 2 = 2 cell types of embryoblast: epiblast (--> amniotic sac) & hypoblast (--> yolk sac). In other words, it's a bilaminar disk.
  2. Week 3
    Gastrulation (3 germ cell layers), neurulation (form notochord, which induces ectoderm to become neuroectoderm --> neural plate). Also, blood islands form from mesodermal (mesenchymal) cells this week.
  3. Week 4
    Heart begins to beat, limb buds form. Pronephros degenerates after Week 4.
  4. Week 8
    Fetal movement; fetus looks like baby.
  5. Week 10
    External genitals look male or female.
  6. Fate of thyroglossal duct, which connects thyroid to tongue -- the location from which thyroid arises (i.e. floor of pharynx)
    • Foramen cecum... or, if not obliterated, then pyramidal lobe of thyroid.
    • If parts of duct persist: thyroglossal duct cyst = moves w/swallowing, unlike persistent cervical sinus.
  7. Primary palate = fusion of the...
    2 intermaxillary segments, medial nasal prominences.
  8. Secondary palate = fusion of the...
    2 palatine shelves (forms the palatine raphe)
  9. Cleft lip
    Failure of primary palate to fuse (more anterior than secondary palate).
  10. Cleft palate
    Failure of secondary palate structures to fuse (further posterior).
  11. Name derivatives: 1st through 6th parts of aortic arch
    • 1 = maxillary A; 2 = stapedial & hyoid A's
    • 3 = common & internal carotid A's
    • 4 = (L) aortic arch & (R) subclavian A
    • 6 = proximal pulmonary arteries, ductus arteriosus (L)
  12. Name the specific beginning & end points of midgut.
    • Begin = duodenum, just past the common bile duct
    • End = after first 2/3 of transverse colon
  13. Upper vs. lower anal canals -- formed from:
    • Upper = urorectal septum separating the cloaca (end of gut tube)
    • Lower = ectoderm
  14. Ventral pancreatic bud
    Forms the: pancreatic head, uncinate process (lower 1/2 of head), & main pancreatic duct.
  15. Extrahepatic biliary atresia
    Occlusion of bile duct (connects the hepatic diverticulum to foregut) --> pale stool, dark urine, jaundice.
  16. Lungs develop from...
    • Endoderm: front wall of foregut.
    • Visceral pleura: from mesoderm covering outside of bronchi
    • Parietal pleura: from mesoderm of body wall
  17. Ureteric bud
    Forms ureters, collecting ducts, calyces, pelvis
  18. Urogenital sinus
    Forms bladder, allantois, urethra.
  19. Potter's syndrome
    Bilateral renal agenesis (b/c malformed ureteric bud) --> oligohydramnios, limb & face malformations b/c fetus is pushed up against uterine wall.
  20. Horseshoe kidney
    Inferior poles of both kidneys fuse. As kidneys ascend upward, they get "stuck" on inferior mesenteric artery & stay low in abdomen... but at least the kidneys function normally.
  21. Ovarian ligament
    Connects ovaries to uterus (the place where fallopian tube meets uterus)
  22. Round ligament
    Connects ovary to labia majora.
  23. Fate of processus vaginalis in men vs. women
    Women = obliterated. Men = becomes tunica vaginalis... if it stays wide open (patent), then congenital inguinal hernia --> intestines can herniate into scrotum or labia majora (less common).
  24. Bicornuate uterus
    Incomplete fusion of paramesonephric ducts. Infertility, urinary tract abnormalities. It could also be true that 1 of the paramesonephric ducts is rudimentary.
  25. Genital tubercle: male & female homologues
    • Male = glans penis, corpus spongiosum
    • Female = clitoris, vestibular bulbs
  26. Urogenital sinus
    • Bladder, urethra, allantois is true for both genders
    • Male = Cowper's glands (bulbourethral), prostate gland
    • Female = Bartholin's glands (greater vestibular), urethral & paraurethral glands
  27. Urogenital folds: male vs female
    • Female = labia minora
    • Male = ventral shaft of penis (underside)
  28. Labioscrotal swelling: male vs. female
    • Female = labia majora
    • Male = scrotum
  29. Hypospadias
    Urethra opens on ventral side (underside) of penis; UTI's. More common than epispadias. Failure of urethral folds to close.
  30. Epispadias
    Pee shoots up to ceiling: urethra opens onto dorsal side of penis, b/c faulty positioning of genital tubercle (responsible for glans penis).
  31. Sonic hedgehog gene: axis
    ZPA --> A-P axis.
  32. Wnt-7 gene
    Controls dorsal --> ventral patterning: DAER (apical ectodermal ridge).
  33. Surface ectoderm derivatives
    Eyes, ears, nose, mouth, skin = epithelial linings. Lens of eye, adenohypophysis. Glands: sweat, saliva, mammary.
  34. Neuroectoderm
    Brain, SC, & optic vesicle --> retina, iris, ciliary body. 2 types of neural cells: neuroblasts & glioblasts (for "everything else").
  35. Neural crest
    Everything associated with brain & SC. PNS, CN's, dorsal root ganglia, pia & arachnoid mater. Also: chromaffin cells of adrenal medulla, parafollicular (C) cells of thyroid, melanocytes, AP septum.
  36. Endoderm
    Epithelium (lining) of gut tube... plus lungs, liver, thymus, parathyroid, pancreas. NOT kidneys.
  37. Mesoderm
    • Kidneys, urogenital structures, adrenal cortex, cardiovascular/blood/lymphatics, spleen (from foregut mesentery).
    • Also: muscle, bone, CT, serious linings of body cavities (ex. peritoneum; sclera, choroid, & anterior chamber for eye).
  38. Kartagener syndrome
    Auto recess. Abnormally motile cilia (or not at all). Bronchiectasis, female infertility, sinusitis, situs inversus. (If cilia don't move at all, then a 50/50 chance of situs inversus.)
  39. Cocaine
    Fetal addiction, developmental defects, placental abruption
  40. DES (diethylstilbestrol)
    Causes clear cell vaginal adenocarcinoma
  41. Iodide (lack or excess)
    Hypothyroidism or goiter
  42. Vitamin A (excess)
    Spontaneous abortion (just like w/measles), cardiac abnorm's & cleft palate
  43. Thalidomide
    Flipper limbs
  44. Smoking
    Placental abnormalities, preterm labor. Also IUGR, ADHD
  45. Tetracycline antibiotics
    Inhibit bone growth, discolored teeth
  46. Warfarin
    Abortion, fetal hemorrhage, bone deformities
  47. Alkylating agents
    Missing fingers (mnemonic: count the diff types of agents on your fingers)
  48. Fetal alcohol syndrome
    • Microcephaly, hydrocephalus, facial abnormalities
    • Limb dislocation, heart & lung fistulas
    • May be abnormal cell migration.
  49. Monochorionic, diamniotic twins
    • The most common setup for identical twins. Separate amniotic sacs, but same chorion & placenta.
    • Vs. Siamese twins: 1 amniotic sac, too

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