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The fate of the arches…

The fate of the arches…. Trisha J. Oura Radiology Resident 9/21/09. But first…. Early embryogenesis: Thickenings of mesenchyme, ecto and endoderm Mesenchyme migrates ventrolaterally  pharngeal bulges Neural and cardiac tissue follow, form concentric hemi-rings.

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The fate of the arches…

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  1. The fate of the arches… Trisha J. Oura Radiology Resident 9/21/09

  2. But first… • Early embryogenesis: • Thickenings of mesenchyme, ecto and endoderm • Mesenchyme migrates ventrolaterally  pharngeal bulges • Neural and cardiac tissue follow, form concentric hemi-rings TW Sadler, Langman’s Medical Embryology, Lippincott, Williams & Wilkins, 2003

  3. Enlarged mesoderm stacks (like donuts) to form bilateral pharyngeal (branchial) arches • Ectoderm  clefts (between donuts) • Endoderm  pouches (within donuts) www.gettyimages.com TW Sadler, Langman’s Medical Embryology, Lippincott, Williams & Wilkins, 2003

  4. Each pharyngeal arch contains: • Aortic arch • Cartilage core • Muscle • Nerves BM Patten, BM Carlson, Foundation of Embryology, McGraw-Hill Publishing Co, 1974 MSA Kumar, Developmental Anatomy, Tufts, 2009.

  5. Where did those aortic arches come from? • Early heart = tube • “S” shaped looping creates cranial truncus arteriosus • Truncus  aortic sac  aortic arches DM Noden and A DeLahunta, The Embryology of Domestic Animals, Williams & Williams, 1985 KL Moore and TVN Persaud, The Developing Human, Clinically Oriented Embryology, Saunders, 2003

  6. Now what? • I, II = disappear early • III = common carotids • IV: • Right: common brachiocephalic trunk (R subclavian a.) • Left: arch of aorta • V: transient • VI: pulmonary a. • Right: no connection to dorsal aorta • Left: ductus arteriosus (ligamentum arteriosus) R L TW Sadler, Langman’s Medical Embryology, Lippincott, Williams & Wilkins, 2003

  7. Vascular ring anomalies:aberrations, anomalies, and…. avians? • Birds: • RIGHTIV arch becomes arch of the aorta (vs. left in mammals) • PRAA (dextroaorta): • mammals = birds • Most common • Poss w/ persistent L CrVC • On radiographs: • DV/VD = trachea often midline or left DM Noden and A DeLahunta, The Embryology of Domestic Animals, Williams & Williams, 1985

  8. PRAA PRAA Normal http://cal.vet.upenn.edu/projects/cardiosf/project/embprs/embprs14.htm

  9. PRAA (Acc 71349)

  10. Aberrant Subclavians Right subclavian a.: • Direct from arch of aorta or w/ the left in bi-subclavian trunk • Esophagus constricted dorsally w/o complete ring • R subclavian crosses left  right, causes indentation/half ring stricture of esophagus Normal Aberrant R. subclavian a.

  11. Normal PRAA Left subclavian a.: • Right IV arch  aortic arch (PRAA) • Left IV arch  L subclavian • Retains connection to dorsal aorta • Crosses retroesophageally on left • L subclavian constricts esophagus at heart base R. subclavian Anomalous L. subclavian a.

  12. Double Aortic Arch • Complete persistence of both sides of the fourth arch  vascular ring anomaly • Fuse distally to form the descending aorta • More caudal compression • ONLY vascular ring anomaly with clinically important tracheal compression • Treatment: ligate smaller aorta Normal R. subclavian L. subclavian Double Aortic Arch

  13. Acc 115803

  14. The end • References: • http://cal.vet.upenn.edu/projects/cardiosf/project/embprs/embprs21.htm • MSA. Kumar, Developmental anatomy syllabus, Tufts, 2009.

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