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Heart development -I


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Heart development -I

  1. 1. Development of CVS-I MBBS first year Dr. Laxman Khanal Assistant professor Department of anatomy BPKIHS, Dharan 23-04-2017
  2. 2. Introduction • The vascular system appears in the middle of the third week, when the embryo is no longer able to satisfy its nutritional requirements by diffusion alone. • Basically heart (with coverings) develops from four sources 1. Splanchnic layer of lateral plate mesoderm 2. Somatic layer of lateral plate mesoderm 3. Septum transverusm 4. Neural crest cells (spiral septum)
  3. 3. Bilaminar disc with epiblast and hypoblast Progenitor heart cells lie adjacent to the cranial end of primitive streak.
  4. 4. Process of ‘Gastrulation’- formation of three germ layers 1. Ectoderm 2. Mesoderm 3. Endoderm
  5. 5. Parts of mesoderm 1. Paraxial mesoderm 2. Intermediate mesoderm 3. Lateral plate mesoderm
  6. 6. Lateral plate mesoderm 1. Splanchnic layer 2. Somatic layer Cardiac progenitor cells migrate to the splanchnic layer of mesoderm. Primary heart field (PHF) Secondary heart field (SHF) Heart fields are located cranial to the oropharyngeal membrane. Finally heart fields form the bilateral two heart tubes.
  7. 7. Oropharyngeal membrane
  8. 8. Inner to outer layers of heart
  9. 9. Oropharyngeal membrane Parietal layer of pericardium Fibrous pericardium
  10. 10. During the lateral folding of embryo, two heart tubes fuse to form single heart tube. Direction of blood flow
  11. 11. Fusion of heart tubes during lateral folding of embryo.
  12. 12. Cephalo-caudal folding- Position of heart tube changes.
  13. 13. See how heart tube is changing its position during folding of embryo. • Anterior to foregut • Superior to septum transverusm • Posterior to pericardial cavity • Inferior to oropharyngeal membrane
  14. 14. Bulbous cordis Primitive ventricle Primitive atrium Sinus venosus B-V sulcus A-V canal TA Conus L 1/3rd Body Right Horn Left Horn
  15. 15. Ascending aorta Pulmonary trunk
  16. 16. The dorsal aorta form independently and then grow to meet the ventral output from the heart in the aortic arches. FUSED DORSAL AORTA 1ST AORTIC ARCH (R) ORAL PLATE ATRIUM VENTRICLE
  17. 17. Mature shape of heart Anterior view Posterior view
  18. 18. Cardiac looping • Cardiac looping start from the day 23 and completed by day 28. • What is it ?? – it is continuous process of growth of heart tube due to change in cell shape result in bending of straight tube into adult form of heart. • Why ?? – to accommodate the components of heart in the pericardial cavity. Abnormality lead to Dextrocardia
  19. 19. Cardiac looping: cephalic portion bends ventrally, caudally and toward right side. Caudal end loops in exactly opposite direction. • From day 23 to 28
  20. 20. Right ventricle left ventricle Left/right atrium Cardiac looping to correct the developmental error !!!
  21. 21. Fate of Sinus venosus
  22. 22. #Left horn: only remains are left # Right horn: it has right to persist : Right choice for right atrium
  23. 23. Development of right atrium
  24. 24. Incorporation of SV into right atrium
  25. 25. Incorporation of SV into right atrium
  26. 26. Development of left atrium
  27. 27. Right atrium – rough part by primitive atrium and smooth part by right sinus horn. Left atrium- rough part by primitive atrium and smooth part by absorption of pulmonary veins.
  28. 28. Division of A-V canal Common A-V canal divide into right and left halves by the thickenings of AV cushion that appear on its dorsal and ventral walls. Fusion of cushions form the septum intermedium.
  29. 29. Defect in A-V canal division • Risk factor is Lithium intake by mother • Definition- it is atrialization of right ventricle Ebstein’s anomaly
  30. 30. Right ventricle (T) left ventricle (T) Left/right atrium (T) Right atrium (S) Rt/Lt ventricle (S) Coronary sinus Oblique V of left atrium B-V sulcus primary interventricular foramen Fate of BC and primitive ventricle # T Vs S Atria Vs ventricle
  31. 31. Conclusion • On day 16 progenitor cell from epiblast migrate to the splanchnic layer of mesoderm to for PHF and SHF, which later form the endocardial heart tube. • Cardiac looping causes heart to fold itself to assume the normal position in left part of thorax. • Right horn of sinus venosus and pulmonary veins absorb to form smooth part of Rt and Lt atrium respectively.