Special Embryology 5 - Speaker Deck

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CARDIOVASCULAR SYSTEM HEART (Page 73) Dr.Sherif Fahmy

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Anatomy of Heart Dr.Sherif Fahmy

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Dr.Sherif Fahmy

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Rt. Atrium Rt. auricle S.V.C I.V.C Rt. Ventricle Lt. ventricle Lt. auricle Pulmonary trunk Ascending aorta Dr.Sherif Fahmy

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Lt Atrium Rt. Atrium Lt. ventricle Rt. ventricle 4 pulmonary veins Inf. Vena cava Sup. Vena cava Coronary sinus Dr.Sherif Fahmy

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Crista terminalis Anterior rough wall (pectinate muscle) Fossa ovalis Sinus venarum Tricuspid valve Rt. auricle Semilunar valves of IVC & coronary sinus Internal of right atrium Limbus fossa ovalis Dr.Sherif Fahmy

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Smooth outflow part Rough inflow part Right ventricle Dr.Sherif Fahmy

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Smooth Lt atrium Left ventricle (rough inflow part) Smooth outflow part Rough left auricle Dr.Sherif Fahmy

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Development of the Heart (Page 73) Dr.Sherif Fahmy

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DEVELOPMENT OF HEART • Heart primordium: • Two endocardial tubes are formed in the mesoderm between buccopharyngeal membrane and cranial part of intraembryonic coelom (cardiogenic area). • Fusion between the endocardial tubes to form a single tube. • Mesoderm that surrounds the tube is called myo-epicardial mantle which forms myocardium of the heart. • After folding, heart tube with the mantle will lies ventral to pharynx in pericardial bulge. • The cranial (arterial) end is fixed with arteries of the fetus, while the caudal (venous) end is fixed to veins of the fetus. • Elongation of the tube leads to formation of U-shaped tube. Dr.Sherif Fahmy

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2 endocardial tubes Fusion Single heart tube Dr.Sherif Fahmy

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Chambers of the heart tube: -Three constrictions are formed in the tube will form 4 chambers: Sinus venosus, Primitive atrium, Primitive ventricle and Bulbus cordis. -Elongation of the tube leads to formation of U-shaped tube. -More elongation of the tube leads to formation of S-shaped tube. -Sinus venosus comes caudal to primitive atrium which is dorsal to primitive ventricle. Bulbus cordis on the right of primitive ventricle. -Sinus venosus, pulmonary vein and primitive atrium will form the common atrium which is divided into right and left atria by interatrial septum. -Primitive ventricle with proximal and middle parts of bulbus cordis will form right and left ventricles, while distal part (truncus arteriosus) will form ascending aorta and pulmonary trunk.

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Bulbus cordis Primitive ventricle Primitive atrium Sinus venosus Arterial end Venous end Dr.Sherif Fahmy

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Dorsal aortae Aortic sac Heart tube Pharynx Dr.Sherif Fahmy

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Dr.Sherif Fahmy

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Sinus Venosus • It is the cuadal chamber of heart tube that is formed of body and 2 horns; each horn receives 3 veins (vitelline, umbilical and common cardinal vein). • The body joins the back of right side of primitive atrium by sinu-atrial orifice which is guarded by right and left valves. While back of left side of primitive atrium is joined by pulmonary vein. • Left sinus horn becomes reduced in size due to degeneration of left vitelline and umbilical veins as well as shift of blood from left anterior cardinal to right anterior cardinal by an anastomosis (becomes left brachiocephalic vein. Left horn remains as coronary sinus. Dr.Sherif Fahmy

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Absorption of body of sinus venosus: -Body of sinus venosus and right horn are absorbed by widening of sinu-atrial orifice to form sinus venarum of right atrium. -Cranial ends of 2 valves fuse together to form septum spurium that forms upper part of crista terminalis. Left valve will fuse with interatrial septum while right valve forms rest of crista as well as valves of inferior vena cava and coronary sinus. Absorption of pulmonary vein: -Pulmonary vein has 2 divisions and each has 2 more divisions. Absorption will form wall of left atrium and 4 pulmonary veins will open separately to the left atrium. It forms the smooth part of the wall of left atrium. Dr.Sherif Fahmy

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Sinus Venosus (Page 117) Dr.Sherif Fahmy

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Sinus venosus Sino-atrial orifice with lt & rt valves Primitive atrium A-V canal Ventral & dorsal A/V cushions Ant. Cardinal vein Posterior cardinal vein Pulmonary vein Lt vitelline & umbilical veins Primitive ventricle Left horn Rt horn Common cardinal vein Dr.Sherif Fahmy

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Anastomosis Lt anterior cardinal vein Rt anterior cardinal vein Shrunken left horn Degenerated umbilical and vitelline veins 2 pulmonary veins Primitive atrium A/V canal Dr.Sherif Fahmy

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Common atrium Absorbed sinus venosus in right side of back of primitive atrium Absorbed pulmonary veins Sinus venarum (smooth posterior of right atrium) Smooth wall of left atrium S.V.C Septum intermedium Azygos vein Primitive ventricle Left brachio-cephalic vein Dr.Sherif Fahmy

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Development of Atria (Page 119) Dr.Sherif Fahmy

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Development of Right Atrium • It is developed from: • Primitive atrium: forms rough anterior (musculi pectinati) wall and auricle of right atrium. • Sinus venosus: forms posterior smooth wall of right atrium (sinus venarum). • Right ½ of atrio-ventricular canal: forms right atrioventricular orifice, inside which 3 cusps are formed (tricuspid valve). • Rt & Lt sino-atrial valves remain as crista terminalis and valves of inferior vena cava and coronary sinus. Dr.Sherif Fahmy

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Development of Left Atrium • It is developed from: • 1- Primitive atrium: forms rough part of left atrium in the left auricle (musculi pectinati). • 2- Pulmonary trunk: absorped to form the smooth wall of the left atrium. • 3- Left ½ of atrio-ventricular canal: forms the left atrio- ventricular orifice in which 2 cusps are developed. Dr.Sherif Fahmy

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Formation of Interatrial Septum

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Formation of Interatrial Septum 1- Septum primum. 2- Septum secundum. 3- Septum intermedium. Dr.Sherif Fahmy

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Formation of Interatrial Septum 1- Septum primum: • Crescentic septum that downgrows from the roof of common chamber. • It is separated from atrio-ventricular canal by osteum primum. More downgrowth will close the osteum primum while the upper part degenerates to form osteum secundum. 2- Septum secundum: • Downward growth of crescentic septum secundum to the right side of septum primum to cover osteum secundum which becomes foramen ovale. 3- Septum intermedium: • It is formed by fusion between ventral and dorsal atrio-ventricular cushions to separates between right and left atrio-ventricular orifices. Dr.Sherif Fahmy

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Septum primum Osteum primum Roof Developing septum intermedium Crescentic lower margin of septum primum Dr.Sherif Fahmy

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Degenerated upper part of septum primum (osteum secondum) Fusion between lower margin of septum primum and septum intermedium Septum primum Dr.Sherif Fahmy

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Foramen ovale Septum secundum Septum primum Crescentic lower margin Dr.Sherif Fahmy

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Development of Ventricles (Page 125) Dr.Sherif Fahmy

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Anatomy of Ventricles and Related Arteries Dr.Sherif Fahmy

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Rt. Atrium Rt. auricle Rt. Ventricle Lt. ventricle Lt. auricle Pulmonary trunk Ascending aorta Dr.Sherif Fahmy

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Infundibulum (smooth outflow) Rough Inflow part Pulmonary valve Tricuspid valve Dr.Sherif Fahmy

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Muscular part Membranous part Interventricular septum Dr.Sherif Fahmy

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Formation of Bulbo-ventricular Chamber Dr.Sherif Fahmy

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• Bulbus cordis lies to the right of primitive ventricle then becomes ventral to it. • Proximal part of bulbus cordis enlarges to form right ventricle. The mid-prtion will form outflow part of each ventricle. The distal part forms truncus arteriosus (ascending aorta and pulmonary trunk). • Conus cordis is divided by conus septum which is formed by fusion between right & left bulbar ridges. Dr.Sherif Fahmy

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Sources of Ventricles 1- Primitive ventricle form most of left ventricle and inlet of right ventricle. 2- Bulbus cordis ➢Proximal portion of forms most of right ventricle. ➢Midportion (Conus Cordis) forms the outflow parts of both ventricles. Dr.Sherif Fahmy

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Fate of bulbus cordis 1- Proximal part: forms most of right ventricle except inlet from primitive ventricle. 2- Mid-portion (Conus cordis): forms outflow parts of both ventricles. 3- Distal part (truncus arteriosus): forms orifices and main parts of ascending aorta and pulmonary trunk. Dr.Sherif Fahmy

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Formation of Interventricular Septum Dr.Sherif Fahmy

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1- Muscular part developed by: -Upward growth from floor by proliferation of myoblasts. -Dilatation of both ventricles. 2- Membranous part: developed by migrated cells from: -Inferior atrio-ventricular cushions. -Lower part of bulbar ridges. Anomalies of interventricular septum: 1- Septal defect in muscular or membranous part. 2- Complete absence of the septum. Dr.Sherif Fahmy

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Dr.Sherif Fahmy

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Ventral & Dorsal A/V cushions Atrio-ventricular orifices Muscular part of interventricular septum

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Dr.Sherif Fahmy

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Distal part (truncus arteriosus) Middle part (conus arteriosus) Proximal part Parts of bulbus cordis Dr.Sherif Fahmy

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Upper crescentic margin of intermuscular septum Right auricle Inferior A/V endocardial cushion Conus septum Lt. ventricle Rt Ventricle Dr.Sherif Fahmy Bulbar ridges

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Bulbo-ventricular sulcus Dr.Sherif Fahmy

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Formation of Aortico-pulmonary Septum Dr.Sherif Fahmy

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Dr.Sherif Fahmy

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Spiral aortico- pulmonary septum Upper crescentic margin of intermuscular septum Dr.Sherif Fahmy

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Dr.Sherif Fahmy

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Source & Time of Formation of Cardiac Septa And Valves Source: Neural crest cells. Time: Start formation at the 5th week and complete formation at 7th or 8th week.

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Anomalies of the Heart Dr.Sherif Fahmy

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Anomalies of Interatrial Septum: 1- Patent foramen ovale. 2- Premature closure of foramen ovale. 3- Probe patent foramen ovale. 4- Osteum secundum defect. 5- Agenesis of interatrial septum. Anomalies of atrio-ventricular canal: 1- Persistent A-V canal. 2- Osteum primum defect. 3- Tricuspid atresia. Dr.Sherif Fahmy

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Anomalies of interventricular septum: 1- Septal defect in muscular or membranous part. 2- Complete absence of the septum. Dr.Sherif Fahmy

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Anomalies of Bulbus Cordis Fallot’s Tetralogy: due to anterior displacement of aortico- pulmonary septum. is manifested by pulmonary stenosis, overriding aorta, ventricular septal defect and hypertrophy of right ventricle. Persistant truncus arteriosus: due to failure of formation of bulbar cushions. It is usually accompanied with membranous ventricular septal defect. Transposition of great arteries (TGA): Aorta arise from right ventricle while pulmonary trunk arises from left ventricle due to loss of spiral shape of the septum. Dr.Sherif Fahmy

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Anomalies in the valves Pulmonary and aortic stenosis: -Narrowing of aortic and pulmonary orifices due to fusion of their cusps. Tricuspid atresia: -Tricuspid atresia due to fused cusps. Dr.Sherif Fahmy

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Anomalies of position of heart -Ectopia cordis: defective formation of chest wall with external exposure of the heart. -Dextrocardia: The heart is rotated to the right. Dr.Sherif Fahmy