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Embryology of the heart and the great vessels

Embryology of the heart and the great vessels. Dr Gerrit Engelbrecht Dept of Radiology UFS. Steps in the embryology of the vascular system. ESTABLISHMENT OF THE CARDIOGENIC FIELD FORMATION AND POSITION OF THE HEART TUBE FORMATION OF THE CARDIAC LOOP

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Embryology of the heart and the great vessels

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  1. Embryology of the heart and the great vessels DrGerritEngelbrecht Dept of Radiology UFS

  2. Steps in the embryology of the vascular system • ESTABLISHMENT OF THE CARDIOGENIC FIELD • FORMATION AND POSITION OF THE HEART TUBE • FORMATION OF THE CARDIAC LOOP • MOLECULAR REGULATION OF CARDIAC DEVELOPMENT • DEVELOPMENT OF THE SINUS VENOSUS • FORMATION OF THE CARDIAC SEPTAE • FORMATION OF THE CONDUCTING SYSTEM OF THE HEART • VASCULAR DEVELOPMENT

  3. ESTABLISHMENT OF THE CARDIOGENIC FIELD

  4. Dorsal view of a late presomite embryo (approximately 18 days) after removal of the amnion. Prospective myoblasts and hemangioblasts reside in the splanchnic mesoderm in front of the neural plate and on each side of the embryo after migrating up from the primitive streak

  5. Transverse section through a similar-staged embryo to show the position of the blood islands in the splanchnic mesoderm layer. • With time, the islands unite and form a horseshoe-shaped endothelial-lined tube surrounded by myoblasts. This region is known as the cardiogenic field • In addition to the cardiogenic region, other blood islands appear bilaterally, parallel and close to the midline of the embryonic shield. These islands form a pair of longitudinal vessels, the dorsal aortae. • 223

  6. Cephalocaudal section through a similar staged embryo showing the position of the pericardial cavity and cardiogenic field.

  7. FORMATION AND POSITION OF THE HEART TUBE 2 processes responsible for positioning of the heart Folding of the embryo in a cephalocaudal direction Simultanous folding laterally

  8. Cephalocaudal folding Figures showing effects of the rapid growth of the brain on positioning of the heart. Initially the cardiogenic area and the pericardial cavity are in front of the buccopharyngeal membrane. A. 18 days. B. 20 days. C. 21 days. D. 22 days

  9. Lateral folding of the embryo

  10. Formation of the cardiac loop

  11. Bulbuscordis

  12. Primitive ventricle

  13. The primitive atrium and sinus venosus

  14. Abnormalities of cardiac looping Dextrocardia, in which the heart lies on the right side of the thorax instead of the left, is caused because the heart loops to the left instead of the right. Dextrocardia may coincide with situs inversus

  15. Molecular regulation of cardiac development • Dependent on the activation of two • transcription factors • NKX2.5 • Specifies cardiogenic field • Septation • Conduction system • TBX5 • Septation

  16. Development of the sinus venosus 4th week receives blood from right and left sinus horns 5th week Obliteration R umbilical vein left vitelline vein

  17. Development of the sinus venosus(2) 10th week left common cardinal vein obliterates

  18. Development of the venous valves

  19. Formation of the cardiac septae • The major septae are formed between the 27 and 37th days of development • It is a simultanuous process if the following areas • Septum formation in the common atrium • Septum formation in the atrioventricular canal • Septum formation in the truncusarteriosus and conuscordis • Septum formation in the ventricles

  20. Septum formation in the common atria At the end of the fourth week, a sickle-shaped crest grows from the roof of the common atrium into the lumen. This crest is the first portion of the septum primum A. 30 days (6 mm). B. Same stage as A, viewed from the right.

  21. Septum formation of the common atria (2) When the lumen of the right atrium expands as a result of incorporation of the sinus horn, a new crescent-shaped fold appears. This new fold, the septum secundum never forms a complete partion in the atrial cavity C. 33 days (9 mm). D. Same stage as C, viewed from the right

  22. Septum formation of the common atria(3) When the upper part of the septum primum gradually disappears, the remaining part becomes the valve of the oval foramen. E. 37 days (14 mm) F. Newborn. G. The atrial septum from the right; same stage as F.

  23. Further differentiation of the atria Coronal sections through the heart to show development of the smoothwalled portions of the right and left atrium. Both the wall of the right sinus horn (blue) and the pulmonary veins (red) are incorporated into the heart to form the smooth-walled parts of the atria.

  24. Septum formation of the atrioventricular canal At the end of the fourth week, two mesenchymal cushions, the atrioventricular endocardial cushions, appear at the superior and inferior borders of the atrioventricular canal, two additional lateral cushions appear at the left and right borders. At the end of the fifth week there is complete fusion of the superior and inferior cushions with complete division of the canal into left and right orifices.

  25. Atrioventricular valves Formation of the atrioventricular valves and chordae tendineae. The valves are hollowed out from the ventricular side but remain attached to the ventricular wall by the chordae tendineae.

  26. Clinical correlatesHeart defects • Largest category of birth defects • Multifactorial ( viruses, medicines, alchohol, diabetes, hypertension. • Genetic syndromes: DiGeorge and Downs • TBX5 gene defect: Holt –Oram syndrome( ASD + pre axial abnormalities. • ASD • Premature closure of the oval foramen • Endocardial cushion defects AV canal( persistent AV canal) • Tricuspid atresia

  27. ASD

  28. Persistent common AV canal

  29. Tricuspid atresia

  30. Septum formation of the truncusarteriosus and conuscordis Fifth week, pairs of opposing ridges appear in the truncus and conus cordis

  31. Septum formation of the truncusarteriosus and conuscordis • Proliferations of the right and left conus cushions, combined • with proliferation of the inferior endocardial cushion, close the interventricular foramen and form the membranous portion of the interventricular septum. • 6 weeks(12 mm). • B. Beginning of the seventh week (14.5 mm). • C. End of the seventh week • (20 mm).

  32. Septum formation of the ventricles End of the fourth week the two primitive ventricles start to expand. The medial walls of the expanding ventricles become apposed and gradually merge, forming the muscular interventricular septum

  33. Semilunar valves When partitioning of the truncus is almost complete, primordia of the semilunar valves become visible as small tubercles found on the main truncus swellings. •One of each pair is assigned to the pulmonary and aortic channels, respectively •A third tubercle appears in both channels opposite the fused truncus swellings. •Gradually the tubercles hollow out at their upper surface, forming the semilunar valves. •Recent evidence shows that neural crest cells contribute to formation of these valves.

  34. Longitudinal section through the semilunar valves 6 weeks seven weeks 9 weeks

  35. Clinical correlatesVSD related defects • Isolated lesion • Conotruncal lesions : Tetralogy of Fallot • Persistent truncusarteriosus • Transposition of the great vessels • Pulmonarvalvular atresia • Aorta valvular stenosis and artresia

  36. Isolated VSD

  37. Tetralogy of Fallot

  38. Persistent truncusarteriosus

  39. Transportation of the great vesselsPulmonarvalvular atresia

  40. Aortic valvular stenosis and atresia

  41. Formation of the conducting system of the heart • Sinu atrial node • Initially the pacemaker for the heart lies in the caudal part of the left cardiac tube. • Later the sinus venosus assumes this function, and as the sinus is incorporated into the right atrium, pacemaker tissue lies near the opening of the superior vena cava. Thus, the sinuatrial node is formed. • Atrioventricular node • The atrioventricular node and bundle (bundle of His) are derived from • two sources: • cells in the left wall of the sinus venosus • (b) cells from the atrioventricular canal. • Once the sinus venosus is incorporated into the right atrium, these cells lie in their final position at the base of the interatrial septum.

  42. Vascular development Arterial system Venous system

  43. Arterial system • Aortic arches • Vitelline and umbilical arteries

  44. Aortic archesKey facts • Arise from the aortic sac(truncusarteriosus ) to pharyngeal arches • ( 4-5 weeks) • Terminate in the left and right dorsal aorta • These arches and vessels appear in a cranial to caudal sequence and • not all simultanously • The aortic sac also forms left and right horns which give rise • to the brachiocephalic artery and proximal arch respectively

  45. Aortic arches

  46. Aortic arches

  47. Ductusarteriosus

  48. Vitelline and umbilical arteries • Vitelline arteries fuse and form the Coeliac, SMA and IMA • Umbilical arteries • Initially paired ventral branches of the aorta • Fourth week acquire a secondary connection with the aorta • the common iliac artery • After birth the proximal part persist as the internal iliac and • internal iliac and superior vesical and the distal part obliterate • to form the medial umbilical ligaments.

  49. Clinical correlatesArterial system defects • Patent ductusarteriosus • Coarctation of the aorta ( preductal and post ductal) • Abnormal origin of the right subclavian artery • Right aortic arch • Interrupted aortic arch

  50. Coarctation of the aorta

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