Embryology of CVS PDF

11 L.E  Fetal circulation Pathway:  Oxygenated blood from placenta →left umbilical vein →liver → ductus venosus →IVC →right atrium  Most of blood pass from right atrium → foramen ovale → left atrium→ Left ventricle →Aorta  Sm...

11 L.E  Fetal circulation Pathway:  Oxygenated blood from placenta →left umbilical vein →liver → ductus venosus →IVC →right atrium  Most of blood pass from right atrium → foramen ovale → left atrium→ Left ventricle →Aorta  Small amount of blood pass from right atrium → right ventricle → pulmonary trunk where small amount pass to lung for nutrition while main amount pass via ductus arteriosus→ descending aorta  The less oxygenated blood pass to placenta through umbilical arteries Sites of mixing blood: 1. Liver: liver sinusoids from blood of portal circulation 2. IVC: blood from lower half of the body 3. Right atrium: blood from SVC from upper half of the body 4. Left atrium: blood from pulmonary veins which is non oxygenated 5. Aorta: distal to the ductus arteriosus. Immediately after birth: 1) Functional closure of foramen ovale due to:  ↑ pressure in left atrium (due to established pulmonary circulation)  ↓ pressure in right atrium (due to stoppage blood from placenta) 2) Functional closure of ductus arteriosus: due to strong contraction of the muscle layer in the ductus arteriosus Changes after birth:  Left umbilical vein: form Ligamentum teres  Ductus venosus: form Ligamentum venosum  Foramen ovale become become close “septum primiun form fossa ovalis & septum secondum form annulus ovalis”  Ductus arteriosus become ligamentum arteriosum.  Umbilical arteries: distal part form medial umbilical ligament & proximal part form superior vesical artery DR.Hendawy “ CVS embryology” 2  Development of CVS Heart tube Development  Timing:  CVS is the 2nd system to develop after CNS  The 1st time to start beating is at 22th day “4th week”  1st time to be detected by U/S is at 6th week  Origin:  Angioplastic cells & myo-epithelial mantle for cardiogenic mesoderm which is condensed into 2 tubes then fuse forming single tube constrictions appear in the heart tube dividing it to 5 segments “from below upward”: 1. Sinus venosus 2. Primitive atrium 3. Primitive ventricle 4. Bulbus cordis 5. Truncus arteriosus.  Growth of the heart tube, resulting in its bending into S-shape tube with: 1. The right (ventral) limb: formed by truncus arteriosus & bulbus cordis. 2. The transverse limb: formed by primitive ventricle. 3. The left (dorsal) limb: formed by primitive atrium & sinus venosus. DR.Hendawy “embryology CVS” 3 Anomalies 1) Dextro-cardia: heart lies as a mirror image to its normal position. This may occur alone or with reversal of all abdominal organs (situs inversus totalis). 2) Ectopia cordis: the chest wall fail to close making the heart exposed through a defect in the sternum. DR.Hendawy “embryology CVS” 4  Sinus venosus Development:  Formed of body and 2 horns “The right horn enlarge on expense of boy & left horn”  It opens in the atrium by opening guarded by sino-atrial valve  The horns receives 1. umbilical veins carry O2 blood from placenta 2. vitelline veins carry deO2 blood from GIT 3. common cardinal veins receives carry deO2 blood from body  Due to liver development on right side & blood shift from left side to right side the right horn become larger than the left and the sino-atrial valve become vertical Fate:  Right horn: forms posterior smooth part of right atrium  Left horn & Body: form coronary sinus.  left sino-atrial valve: absorbed into interatrial septum  Right sino-atrial valve: forms 1. Crista terminalis 2. Valves of IVC 3. Valve of coronary sinus DR.Hendawy “embryology CVS” 5  Atrio-ventricular canal Development: the atrio-ventricular canal become divided into right & left halves by anterior & posterior cushions Fate 1) The upper part: is absorbed up into the atria 2) The lower part: is absorbed down into ventricles 3) The central part: Share in the formation of tricuspid & mitral valves. 4) The septum intermedium: Shares in inter-atrial & membranous inter-ventricular septa Anomalies 1) Tricuspid stenosis& mitral regurge: septum intermedium deviate to right side 2) Tricuspid regurge & mitral stenosis: septum intermedium deviate to left side 3) Tricuspid atresia 4) Mitral atresia DR.Hendawy “embryology CVS” 6  Inter-atrial septum 1. Mesodermal cushion appears in the AV canal called “septum intermedium” 2. C-shaped membrane appears in the wall of the atrium called “Septum primum” 3. It grows toward the septum intermedium, leaving an opening at its lower edge “ostium primum” 4. Before the ostium primum closes another ostium appears in the septum primum “ostium secondum” 5. Another membrane appears to the right of septum primum called “septum secundum” 6. The septum secondum separated from septumprimium by a passage “foramen ovale” N.B: Inter-atrial septum is formed of:  Septum intermedium  Septum primum  Septum secundum  Left sino-atrial valve  Some neural crest cells N.B: Fate of foramen ovale: After birth  septa premium & secondum fuse to closing foramen ovale  Septum premium will form fossa ovalis  lower edge of septum secondum will form annulus ovalis\ DR.Hendawy “embryology CVS” 7  So the atria are formed of : Right atrium Left atrium Anterior wall 1. Right ½ of primitive atrium 1. Left ½ of primitive atrium 2. Absorbed part of right AV canal 2. Absorbed part of left AV canal Posterior wall Absorbed right horn of sinus venosus Absorbed pulmonary veins Septal wall 1. Septum intermedium 2. septum premium 3. septum secundum 4. left SA valve 5. some neural crest cells DR.Hendawy “embryology CVS” 8 Anomalies : “ASD: atrial septal defect” 1) Persistent ostium primum: In the lower part of the inter-atrial septum. 2) Persistent ostium secundum: In the upper part of the inter-atrial septum. 3) Probe patent foramen ovale: In 20 – 30 % of people. It has no clinical significance 4) Patent foramen ovale: 3rd common cardiac anomaly, Failure of septum premium & secondum to fuse. Blood only pass to left side when pressure ↑ in right atrium on crying or exercise 5) Trilocuar biventricular heart: “rare” failure of septum premium & secondum development 6) Premature closure of foramen ovale during intra-uterine life cause fetal death DR.Hendawy “embryology CVS” 9  Inter-ventricular septum Development  Muscular part: Arises from the floor of primitive ventricle  Membranous part: Arises from septum intermedium & bulbar septum Anomalies: “VSD: ventricular septal defect” 1) Persistent inter-ventricular foramen (Roger disease) It is the 2nd common cardiac anomaly. The defect is in the membranous part 2) Muscular ventricular septal defect: rare 3) Trilocuar bi-atrial heart: “rare” due to failure of inter-ventricular septum development DR.Hendawy “CVS embryology” 10  Bulbus cordis Development 2 bulbar cushions develop& fuse forming septum dividing the bulbus cordis into Right & Left halves. Fate:  The proximal part: Forms muscular parts of right & Left ventricles.  The middle part: forms: infundibulum of right ventricle & vestibule of the left ventricle.  The distal part: forms aortic & pulmonary valves So, right ventricle is formed of:  Rough inflowing part Right ½ of primitive ventricle Absorbed part of right AV canal  Smooth outflowing wall Part of bulbus cordis “form infundibulum of right ventricle” Left ventricle is formed of:  Rough inflowing part Left ½ of primitive ventricle Absorbed part of left AVcanal  Smooth outflowing wall Part of bulbus cordis “form vestibule of left ventricle” DR.Hendawy “CVS embryology” 11  Development of semilunar valve Development  Edocardial cushions develop in the upper part of bulbus cordis  The Right & Left ridges fused dividing the orifice into: pulmonary orifice “anterior” & Aortic orifice “posterior”  The cusps are hollowed out at their upper surface. Anomalies:  Pulmonary stenosis & Aortic stenosis  Pulmonary atresia & Aortic atresia DR.Hendawy “CVS embryology” 12  Truncus Arteriosus Development: o 2 cushions grow in spiral way to form aortico-pulmonary septum dividing truncus arteriosus into pulmonary trunk & ascending aorta o The spiral course of the septum explains relations between ascending aorta & pulmonary trunk;  At first, the pulmonary trunk lies anterior to ascending aorta  Then pulmonary trunk lies to the right of ascending aorta  Finally pulmonary trunk lies posterior to ascending aorta DR.Hendawy “CVS embryology” 13  Anomalies Persistent truncus arteriosus  Failure of aortico-pulmonary septum formation. (PTA)  Accompanied with membranous VSD Transposition of greater vessels  Straight course aortico-pulmonary septum instead of its normal spiral course. (TGA)  Aorta is connected with the right ventricle& pulmonary trunk with the left Ventricle.  The commonest cyanotic heart disease  Anterior displacement of aortico- pulmonary septum Fallout’s tetralogy  Accompanied with patent ductus arteriosus “blood passes from aorta to pulmonary”  Marked by: pulmonary stenosis, right ventricular hypertrophy, VSD & Overriding aorta N.B: Fallot’s Pentalogy: Fallout’s tetralogy +ASD DR.Hendawy “CVS embryology” 14  Development of arteries th th  During 4 & 5 weeks of development, the aortic sac (lies distal to the truncus arteriosus)  Aortic sac has right and left horns  Horns are continuous with 1st aortic arch  1st aoric arches grow dorsal to the gut forming dorsal arotae  2 dorsal aortae fuse to form common dorsal aorta  Other 5 aortic arches develop cranio-caidally between aortic sac & dorsal aortae DR.Hendawy “ CVS embryology” 15 Fate of: Aortic sac :  Stem :form aortic arch proximal to brachiocephalic artery  Right horn: form brachiocephalic artery  Left horn: form aortic arch between brachiocephalic artery & Left common carotid Aortic arches :  1st aortic arch: forms Maxillary artery  2nd aortic arch: forms Stapedial artery  3rd aortic arch: forms Common carotid & Proximal part of Internal carotid N.B: External carotid “appear as bud”  4th aortic arch:  Right one: forms part of right subclavian  Left one: forms Aortic arch between left common carotid & left subclavian  5th aortic arch: degenerates  6th aortic arch: forms  Pulmonary artery from its proximal part while the distal part degenerates on the right side  Pulmonary artery from its proximal part while the distal part form ductus arteriosus on the left side N.B: course to recurrent laryngeal nerve At First, RLN hooks around the distal part of 6th arch.  Right RLN hooks around 4th arch which form right subclavian as the distal part of 6th & 5th arch degenerate  Left RLN hooks around ligamentum arteriosum “the distal part of 6th arch” Dorsal aorta :  Cranial to 3rd aortic arch: form distal part of internal carotid  Between 3rd & 4th aortic arch degenerate Right side Left side th th  From 4 to 6 aortic arch Right subclavian Arch of aorta distal to subclavian th th  Distal to 6 aortic arch Right subclavian till 7 ISA Descending aorta th Degenerate distal to 7 ISA DR.Hendawy “ CVS embryology” 16 Arch of aorta is formed of: 1. stem of aortic sac “form part from origin to brachiocephalic artery” 2. left horn of aortic sac “form part from brachiocephalic to left common carotid” 3. Left 4th aortic arch “form part from left common carotid to left subclavian” 4. Left dorsal aorta “form part distal to left subclavian artery” Subclavian artery is formed of: 1. Left subclavian: is formed of left 7th inter-segmental artery 2. Right subclavian:  Right 4th aortic arch  Right dorsal arota between 4th aortic arch & Right 7th inter-segmental artery  Right 7th inter-segmental artery DR.Hendawy “ CVS embryology” 17  Anomalies Patent ductus arteriosus:  It is a common potential cyanotic heart disease.  The duct between the left branch of pulmonary artery and aortic arch remains patent  May be accompanied with other diseases such as Fallot’s tetralogy Aortic coarctation: Constriction of aorta distal to origin of left subclavian It occurs in 10 % of cases of congenital heart diseases There are 2 types: Pre-ductal Post-ductal Coarctation is proximal Coarctation is distal to entrance of ductus arteriosus to entrance of ductus arteriosus The ductus remains open The ductus usually closes Collateral circulation develops. DR.Hendawy “ CVS embryology” 18