CVS development II 8 June 2023.ppt
- 1. DEVELOPMENT OF THE VENTRICLE AND BULBUS CORDIS EN OBIKILI
- 2. In the 4th week of intrauterine life while the primitive atrium is being divided into right and left atria, a muscular septum projects upwards from the midline of the floor of the primitive ventricle. This septum is called the ventricular or interventricular septum
- 3. It is crescent shaped and extends upwards towards the fused atrioventricular cushions (septum intermedium). The opening between the free edge of the interventricular septum and the septum intermedium is called the interventricular foramen
- 4. The left and right ventricles communicate with each other and with the cavity of the bulbus cordis until about the end of the 7th week of intrauterine life when the interventricular foramen closes. The interventricular septum divides the primitive ventricle into left and right ventricles
- 8. Bulbus cordis The bulbus cordis consists of three portions: a proximal third, a middle third called the conus cordis, and a distal third called the truncus arteriosus. In the 5th week of IUL a pair of endocardial swellings appear in the distal end of the truncus arteriosus. These swellings are called the truncal ridges.
- 9. The left and right truncal ridges grow towards each other in a spiral manner. In the 8th week they fuse to form a spiral or aorticopulmonary septum which divides the truncus arteriosus into ascending aorta and pulmonary trunk.
- 11. Aorticopulmonary septum ref. Moore & Persaud
- 12. Similar endocardial swellings appear in the conus cordis and are called the conal or bulbar ridges. They grow towards each other and fuse to form the bulbar septum. The truncal and bulbar ridges are derived mainly from neural crest mesenchyme The conus cordis becomes incorporated into the wall of the ventricle
- 13. The bulbar septum divides the conus cordis into: 1. Anterolateral portion called the conus arteriosus or infundibulum. This is the outflow tract of the right ventricle 2. Posterolateral portion called the aortic vestibule. This is the outflow tract of the left ventricle.
- 14. The proximal third of the bulbus cordis takes part in the formation of the trabeculated portion of the right ventricle
- 15. The bulbar septum grows downwards towards the interventricular septum. The gap between the interventricular septum and the bulbar septum is the interventricular foramen. The foramen is closed by the membranous interventricular septum which is formed by the proliferation and fusion of tissue from the fused atrioventricular endocardial cushions and the left and right bulbar ridges
- 16. The closure of the interventricular foramen not only separates the right and left ventricles but also ensures that the RV communicates with the pulmonary trunk and the LV with the aorta
- 17. Cavities appear in the wall of the ventricles and separate the muscles into bundles. Some of the bundles become trabeculae carneae while others are transformed into papillary muscles and chordae tendinae.
- 19. Pulmonary and aortic valves The pulmonary and aortic valves are derived from the endocardial swellings or cushions that are formed in the wall of the conus cordis close to its junction with the truncus arteriosus . Right and left endocardial swellings appear in the wall of the conus cordis.
- 20. Soon after, two more swellings, anterior and posterior endocardial swellings, also appear in the wall of the cordis cordis. The left and right endocardial swellings approach each other, fuse and become subdivided into two parts. As a result of this subdivision aortic and pulmonary openings have three swellings each
- 21. These swellings become hollowed out (excavated) on the distal surface to form 3 semilunar valves. The pulmonary valve is at first ventral to the aortic valve. Later as a result of rotation it lies ventrolateral and to the left of the aortic valve.
- 22. The aorta has one anterior and two posterior aortic sinuses while the pulmonary trunk has two anterior and one posterior sinuses. The right coronary artery arises from the anterior aortic sinus while the left coronary artery arises from the left posterior aortic sinus
- 23. Formation of pulmonary and aortic valves
- 24. Semilunar valves
- 25. Atrioventricular valves Endocardial swellings also appear at the margins of the atrioventricular orifices. They are invaded by mesenchymal tissue and later become hollowed out on the ventricular side. Three cusps appear in the right atrioventricular orifice while two appear in the left atrioventricular orifice
- 26. The valve of the right atrioventricular orifice is called tricuspid valve because it has three cusps while that of the left has two cusps and is called bicuspid valve. The latter is also called the mitral valve because it looks like the a bishop’s mitre. The cusps enlarge and are attached to the ventricular wall by muscle strands that will form the papillary muscles and the chordae tendinae
- 27. During the IUL the thickness of the LV is about the same as that of the RV. By the 6th month of postnatal life it is about three times the thickness of the RV.
- 28. Formation of the conducting system of the heart Initially a peacemaker lies in the caudal part of the left heart tube. In the 5th week of intrauterine life, it lies in the right wall of the sinus venosus and is called the sinuatrial node When the sinus venosus is incorporated into the atrium the sinuatrial node lies near the opening of the superior vena cava
- 29. The atrioventricular node and the bundle of His are formed in the left wall of the sinus venous and the atrioventricular canal When the sinus venosus is incorporated into the right atrium, the atrioventricular node lies near the interatrial septum
- 30. CONGENITAL ANOMALIES The aetiology or cause of congenital anomalies is unknown in most of the cases. Most of the anomalies are caused by multiple factors Some anomalies are simple and do not require treatment while others are complex and may require surgeries. Some anomalies do not cause a significant
- 31. Common causes of heart anomalies include: A. Genetic factors e.g. Turner’s syndrome, Down syndrome B. Infections e.g. viral infections: TORCH C. Drugs e.g. Ethanol, thalidomide etc.
- 32. 1. Acardia. This is congenital absence of the heart. It may be seen in conjoint twins. 2. Anomalies of position a) Ectopia cordis. The heart is exposed partially or completely on the chest wall due to defective development of the sternum and the pericardium. The sternal halves are widely separated from each other
- 33. b) Dextrocardia. The apex of the heart is located on the right side of the chest instead of the left. It is as a result of reversal of the endocardial heart loop. It may occur alone or may be associated with other anomalies such as situs inversus in which there is transposition of some or all of the thoraco-abdominal viscera: the structures that normally lie on the left side are on the right side and vice versa.
- 34. 3. Anomalies of atrial septum: Atrial septal defect. There are various forms of atrial septal defect a) Probe patency of foramen ovale. At birth the foramen ovale usually closes functionaly and later physically. In 20-25% of adults the foramen does not close physically after birth.
- 35. A narrow oblique cleft is left between the right and left atria. A probe can be passed from the right atrium to the left atrium. This anomaly is usually asymptomatic.
- 37. b) Ostium primum defect: the septum primum fails to fuse with the atrioventricular endocardial cushions and the ostium primum persists. The defect is located in the most inferior aspect of the atrial septum: at the level of the tricuspid and mitral vlaves
- 39. c) ostium or foramen secundum defect: It is the most common type of atrial septal defect. It is as result of by either excessive resorption of septum primum, poor development of septum secundum or enlarged foramen ovale The opening between the LA and the RA is large. Depending on the size of the opening, oxygenated blood from the LA passes to the RA. This leads to right sided heart failure as a result of overloading of the right side of the
- 40. d) Common atrium: It is a rare form of atrial septal defect. There is complete absence of the atrial septum as a result of non-development of the septum primum and septum secundum. It is a very serious condition and is usually associated with other defects.
- 41. e) Premature closure of foramen ovale. Closure of the foramen ovale before birth results in hypertrophy of the right side of the heart (RA and RV) and atrophy of the LA and LV. Death occurs within the uterus
- 42. 4. Anomalies of the atrioventricular canal. Non fusion of the atrioventricular endocardial cushions results in: a) Persistent atrioventricular canal: there is a single atrioventricular orifice b) Atrial septal defect c) Ventricular septal defect
- 43. 5. Ventricular septal defects. Ventricular septal defects (VSD) are more common in females than males. In VSD, the defect may be in the membranous or muscular part of the ventricular septum. In membranous VSD the opening is in the superior part of the ventricular septum, near the aortic and tricuspid valves. It is more common than the muscular VSD
- 44. The size of the defect varies. Blood passes from the LV to the RV and leads to enlargement of the RV. Complete absence of the ventricular septum gives rise to a three-chambered heart called cor triloculare biatriatum
- 45. Anomalies of bulbus cordis a) Tetralogy of Fallot. It is due to unequal division of the conus cordis by the bulbar septum. It is usually characterized by 4 defects i) Stenosis of the pulmonary trunk: narrowing of RV outflow tract) ii) Large VSD iii) Hypertrophy of the RV iv) iii) Overriding aorta: the aorta overrides the free edge of the ventricular septum and
- 48. b) Persistent or patent truncus arteriosus. The aorticopulmonary septum fails to develop and divide the truncus arteriosus into aorta and pulmonary trunk. There is only one arterial trunk. The pulmonary trunk originates from this single trunk some distance above its origin
- 49. Persistent truncus arteriosus is always accompanied by VSD. In aorticopulmonary septal defect there is an oval or round window between the aorta and the pulmonary trunk. This window is called the aortic window. Blood from the aorta flows into the pulmonary artery, and as a result too much blood flows to the lungs and causes pulmonary
- 51. c) Transposition of the great arteries: This is due to maldescent of aorticopulmonary septum; the septum descends straight downwards instead of in a spiral manner. The aorta is anterior to the pulmonary artery and originates from the RV while the pulmonary trunk originates from the LV. Transposition of the great arteries may be associated with a defect in the membranous part of the ventricular septum, etc.
- 52. Transposition of great vessels
- 54. 7. Defects of the aortic valve a) Aortic atresia. There is complete obstruction of the aorta or its valve b) Aortic valvular stenosis. The aortic valves are thickened and deformed. The edges of the valves fuse to form a dome with a narrow opening.
- 55. c) Subvalvular aortic stenosis It is usually caused by a ring or band of fibrous tissue just below the aortic valve. It encircles the outflow tract of the LV. There is narrowing of the left ventricle below the level of the aortic valve
- 57. 8. Defects of pulmonary valve a) Pulmonary atresia. The pulmonary valve is not properly formed. The cusps of the pulmonary valve are fused to form a solid sheet of tissue. The pulmonary artery does not have a lumen. It may be due to unequal division of the truncus arteriosus
- 58. b) Pulmonary valve stenosis. The cusps of the pulmonary valve are fused together to form a dome with a central perforation. If the fusion is complete the pulmonary trunk becomes atretic. The foramen ovale becomes the only outlet of blood from the RV
- 59. c) Infundibular pulmonary stenosis. This occurs when the conus cordis is underdeveloped. There is obstruction of the outflow tract of the RV
- 60. 9. Defects of atrioventricular valves. a) Tricuspid atresia. The right atrioventricular valve is absent or poorly developed. Tricuspid stenosis: there is narrowing of the tricuspid valve opening. b) Mitral atresia: The left atrioventricular valve is absent or poorly developed. Mitral stenosis: there is narrowing of the mitral valve opening.
- 61. Tetralogy of Fallot Patent ductus arteriosus