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Development of the Heart and Congenital Heart diseases SESSION 6

Development of the Heart and Congenital Heart diseases SESSION 6. Development of the heart. Week 3 Cardiogenic region appears Overlying mesoderm differentiate into myoblasts and blood islands Horseshoe region at cephalic end Lateral Folding:

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Development of the Heart and Congenital Heart diseases SESSION 6

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  1. Development of the Heart and Congenital Heart diseases SESSION 6

  2. Development of the heart • Week 3 • Cardiogenic region appears • Overlying mesoderm differentiate into myoblasts and blood islands • Horseshoe region at cephalic end • Lateral Folding: • Brings the two endocardial tubes together in the midline • Primitive heart tube • Cephalocaudal folding: • Brings tube into the thoracic region

  3. Primitive heart tube

  4. Looping • Day 23 – day 28 • Cephalic portion • Ventrally • Caudally • Right • Caudal portion • Dorsally • Cranially • Left

  5. What does looping achieve? • Primordium of RV closest to outflow tract • Primordium of LV closest to inflow tract • Inflow is dorsal to outflow • Forms transverse pericardial sinus

  6. Two septums grow down towards the endocardial cushions • The first is the septum primum • Ostiumprimum(temporary gap between septum and endocardial cushion) • Ostiumsecundum(hole in the septum primum) • The second is the septum secundum • Foramen ovale(hole in septum secundum) AtrialSeptation

  7. 2 components: • Muscular portion • Membranous portion • Muscular portion • Forms most of the septum • Grows upwards • Membranous portion • Connective tissue • Grows down from endocardial cushions • They meet and fuse • Defects usually occurs in the membranous parts. Ventricular septation

  8. Septation of the outflow tracts • Endocardial cushions appear in Truncusarteriosus • Requires neurocrest cells migrating into the heart • Staggered appearance • They twist around each other as they grow • Forming a spiral septum

  9. Arches of the aorta • Arterial systems develop from bilaterally symmetrical systems of arched vessels • 5 arches – 1,2,3,4,6 • 5th one regresses • 4th Arch • RIGHT arch right subclavian artery • LEFT arch arch of the aorta • 6th Arch • RIGHT arch pulmonary artery • LEFT arch pulmonary artery & ductusarteriosus

  10. Recurrent Laryngeal Nerve • Each arch of the aorta has a corresponding nerve • 6th arch recurrent laryngeal nerve • Laryngeal nerve shifts caudally into thorax • Left larygneal nerve descends to T5- hooks around ductusarteriosus • Right laryngeal nerve descends to T1/T2 • Laryngeal nerves both loop back up to innervate the larynx

  11. Fetal Circulation

  12. Fetus v. Baby

  13. Congenital Heart Diseases

  14. Pressures in the heart Aorta Diastole: 60-90mmHg Systole: 100-140mmHg Pulmonary Artery Diastole: 4-12mmHg Systole: 15-30mmHg 0-8mmHg 1-10mmHg Diastole: 1-10mmHg Systole: 100-140mmHg Diastole: 0-8mmHg Systole: 15-30mmHg

  15. Congenital Heart Diseases • Atrial Septal Defects • Ventricular Septal Defects • Coarctation of the aorta • Tetralogy of Fallot • Transposition of the great vessels

  16. Left to right shunt • Blood in left heart enters the right heart • Requires a hole between right and left heart • The right heart is at lower pressure than left • If there is an opening  blood flows from left to right • Acyanotic • Examples • Atrial Septal Defect • Ventricular Septal Defect • Patent DuctusArteriosus

  17. Atrial Septal Defect • Left to right shunt • Hole atrial septum • Blood move from the left atria to the right atria • Caused by failure of closure of: • foramen ovale • Ostiumsecundum • Ostiumprimum • Leads to: • Pulmonary hypertension • Right ventricle overload • RIGHT HEART FAILURE

  18. Ventricular Septal Defect • Left to right shunt • Hole in intraventricular septum • Blood moves from left ventricle into the right ventricle • Caused by: failure of the membranous part of the ventricular septum to develop • Leads to: • Pulmonary hypertension • Right ventricular hypertrophy • Pulmonary venous congestion • Dyspnoea • LEFT HEART FAILURE

  19. Coarctation of the aorta • Narrowing of the aorta usually occurring near the attachment of the ductusarteriosus • Leads to: • volume overload in the heart • congestive heart failure • Signs and symptoms: • Tachypnoea • Dyspnoea • RADIAL- RADIAL DELAY

  20. Right to left shunt • Blood bypassing the lungs • This requires a Hole and a Distal Obstruction. • The right heart is usually at a lower pressure than the left • However a distal obstruction in the right heart  pressure in right heart > left heart • Leading to blood flowing from the left to the right • Cyanosis • Blue discolouration arising due to the presence of deoxygenated blood in the arteries • Examples • Tetralogy of Fallot

  21. Tetralogy of fallot • Overriding aorta 2. Ventricular septal defect (HOLE) 3. Pulmonary stenosis (DISTAL OBSTRUCTION) 4. Right ventricular hypertrophy

  22. Transposition of the great vessels • The aorta and pulmonary artery are reversed • RVaorta • LV pulmonary artery • Not viable unless the 2 circuits communicate via: • patent ductusarteriosus • patent foramen ovale • VSD or ASD. • Allows adequate mixing of blood to: • deliver enough oxygenated blood to the body • Treat • Englarging the septal defect and increasing the mixing of blood

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