Development-of-the-heart.ppt

Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,By:Gan Quan Fu,*,Click to edit Master title style,Content,Introduction,Fusion of Heart Tube,The Bulbus Cordis,The Sinus venosus,Formation of,Atria,Separation of Aorta&Pulmonary Trunk),The Ventricles,The Exterior,of,Heart,Development of Heart Valve,Development of the Heart conducting system,Timeline,Congenital Anomalies of Heart,By:Gan Quan Fu,By:Gan Quan Fu,Introduction,Mesodermal origin,Formed from,angioblastic tissues,that arise from,Splanchnopleuric Mesoderm,(Cardiogenic area).,After formation of the head fold,this tube lies dorsal to pericardial cavity&ventral to foregut.,Tube invaginates pericardial sac from dorsal side,splanchnopleuric mesoderm lining the dorsal side of pericardial cavity proliferates to form a thick layer(,myoepicardial mantle,).,When invagination complete,myoepicardial mantle completely surrounds the heart tube and give rise to,myocardium,and also the,epicardium,.,Parietal layer of pericardium is derived from somatopleuric mesoderm.,By:Gan Quan Fu,Bulbus Cordis,Lies at,arterial end,of heart,Divisible into:,Proximal Part=,Conus,Distal Part=,Truncus arteriosus,Truncus arteriosus continuous distally with aortic sac.,Aortic Sac is continuous distally with right and left pharyngeal arch arteries.,Arteries arch backwards to become continuous with right and left dorsal aortae.,By:Gan Quan Fu,Heart tubes in relation to right and left dorsal aorta,By:Gan Quan Fu,Sinus venosus,Lies at,venous end,of heart,It has,right,and,left horns,(prolongations of sinus venosus),Each Horns are joined by:,One,vitelline vein,(from the yolk sac),One,umbilical vein,(from the placenta),One,common cardinal vein,(from the body wall),By:Gan Quan Fu,By:Gan Quan Fu,Formation of Atria(Sinu-atrial orifice),Sinus venosus and primitive atrial chamber are 1,st,connected by,wide,opening.,Gradually opening becomes,narrow,&,shifts to right,.,Finally becomes a,narrow slit,.(The slit has right&left margins known as right&left venous valves).,Cranially these,2 valve fuse,to form septum spurium.,By:Gan Quan Fu,Formation of Atria(atrioventricular canal),2 thickenings(,atrioventricular cushions,)appear on dorsal and ventral walls.,Grow towards each other and fuse to form,septum intermedium,.,By:Gan Quan Fu,Formation of Atria(Interatrial septum),Atrial chamber undergoes division into right and left by formation of,2 septa,.,Septum Primum,Septa Secundum,By:Gan Quan Fu,Formation of Atria(septum Primum),Arises from roof of atrium towards atrioventricular canal and form,foramen primum,.,Before foramen primum close(Septum primum fuse with septum intermedium),a new gap(,foramen secundum,)is form on upper part of foramen primum by breaking down of upper part of septum primum.,Septum primum now has a free upper edge.,This is to ensure,communication,between left and right atria.,By:Gan Quan Fu,Formation of Atria(septum secundum),Arises downwards from roof of atrial chamber at the,right,of septum primum.,Overlap,with free edge of septum primum and form,foramen ovale,(valvular aperture that allows blood to flow from right to left).,After birth,foramen ovale is obliterated by,fusion,of septum primum and septum secundum.,Annulus ovalis,Lower free edge of septum secundum,Fossa Ovalis,Septum primum,By:Gan Quan Fu,Development of right atrium,Sinus venosus is absorbed into right atrium by great,enlargement,of,sinu-artrial orifice,.,Left horn,Part of coronary sinus,Right common cardinal,Part of superior vena cava,Right vitelline vein,Terminal part,of,inferior vena cava,Right margin of original sinu-atrial orifice(right&left venous valve)expands and divide into:,Crista terminalis,Valve of inferior vena cava,Valve of coronary sinus,Right half of atrioventricular canal is also absorbed into right atrium.,By:Gan Quan Fu,Development of left atrium,During the beginning of formation of septum primum,single,pulmonary vein open into left half of atrium.,This pulmonary vein divide into left and right branches.,Gradually the parts of pulmonary veins nearest to left atrium are,absorbed,into the atrium resulting in 4 separate veins(2 each side).,By:Gan Quan Fu,Separation of Aorta and pulmonary trunk,Spiral Septum,appears within truncus arteriosus and subdivides it into ascending aorta and pulmonary arteries.,They fuse along the axis of the cylinder extending down towards the ventricles.,Interventricular foramen obliterated by mass of endocardial tissues from interventricular septum,endocardial cushions&,Spiral Septum,.,By:Gan Quan Fu,Development of Ventricles(interventricular septum),Conus of bulbus cordis,merge,with cavity of primitive ventricle.,Interventricular septum,grows upwards from the floor of bulbo-ventricular cavity&divide it into right&left halves.,2 ridges(,right&Left bulbar ridges,)from the wall of the conical part of bulbar cavity(Spiral septum),grows towards each other and fuse form bulbar septum.,The gap between upper edge of interventricular septum and lower edge of bulbar septum,is filled by proliferation of tissues from,atrioventricular cushions,.,By:Gan Quan Fu,Exterior of Heart,Heart tube is suspended from the dorsal wall of the pericardial cavity by 2 layers of percardium which constitude,dorsal mesocardium,.,Mesocardium disappears,and heart tube lies within the pericardial sac.,Caudal part of the heart tube(,atrium,sinus venosus,)is embedded within the,septum transversum,By:Gan Quan Fu,Exterior of Heart,Bulbus cordis and ventricle in pericardial cavity grows rapidly&becomes,folded,to form,U-shape Bulbo-ventricular loop,.,The atrium and sinus venosus freed from septum transversum.(Lie behind and above the ventricle and the heart tube is now S shaped),Arterial and venous ends come closer to each other and the space between them becomes the,transverse sinus of pericardium,.,By:Gan Quan Fu,Exterior of the heart,Till now,bulbus cordis(conus)&ventricle are separated by,deep bulboventricular sulcus,.,Sulcus gradually becomes,narrow,bulbus cordis&ventricle come to form 1 chamber which communicates with truncus arteriosus.,The atrial chamber which lies behind the upper part of ventricle,expands,and,projects forwards,on either side of the truncus.,Finally heart assumes its definitive shape.,By:Gan Quan Fu,Valves of Heart(Mitral&Tricuspid),Formed by,proliferation of connective tissue,under endocardium of left and right atrio-ventricular canals.,By:Gan Quan Fu,Valves of Heart(Pulmonary&Aortic),Derived from,endocardial cushions,formed at junction of,truncus arteriosus,and the,conus,which grows and fuse with each other.,With,separation,of aortic and pulmonary trunk each cushions,are subdivided,into 2 parts(each in each orifice).,2 more,cushions(anterior and posterior),appear,.,3 cushions in each opening which the 3 cusps of the corresponding valve develops.,Pulmonary valve is initially ventral to aortic valve,.Subsequently,rotation,happens and pulmonary valve lie ventral to left aortic valve.,By:Gan Quan Fu,Development of Conducting system of heart,When there are 2 heart tubes,a pacemaker(which later forms sinu-atrial node)lies in,caudal part of left tube,.,After fusion of 2 tubes it lies in,sinus venosus,.,Comes to lie,near to opening of superior vena cava,when sinus venosus is incorporated into right ventricle.,Atrio-ventricular node and atrio-ventricular bundle form in,left wall of sinus venosus,and in,atrio-ventricular canal,.,After sinus venosus is absorbed into right atrium,atrio-ventricular node comes to lie near the interatrial septum.,By:Gan Quan Fu,Timeline on formation of heart,Early 4,th,week,The pair of lateral,endocardial tubes fuse,5,th,to 6,th,week,A pair of septa,Septum Primum&Septum Secundum,separates right&left atria,Development of bicuspid and tricuspid,atrioventricular valve,6,th,week,Muscular ventricular septum,partially separates the ventricles,7,th,&8,th,week,Spiral septum,separates ascending aorta&pulmonary trunk,Swellings within truncus arteriosus give rise to,semilunar valves of aorta&pulmonary trunk,Complete ventricular septation,By:Gan Quan Fu,cONGENITal Anomalies of Heart,Anomalies of Position,Atresia or Stenosis,Abnormal Growth,Defective Formation of Septa,Anomalies of Relationship of Chambers to Great Vessels,By:Gan Quan Fu,Anomalies of position,Dextrocardia,Chambers and blood vessels of heart are,reversed,from side to side(i.e.all structures that normally lie on right side are on left and vice versa),Maybe a part of the condition called,situs inversus,(Organs are transposed),If not part of situs inversus,usually accompanied by anomalies of heart chambers and great vessels.,Ectopia Cordis,Heart lies,exposed,on front of the chest and can be seen from outside,due to defective development of chest wall.,By:Gan Quan Fu,Atresia or stenosis,Too narrow opening(,stenosis,)or no opening(,atresia,)of the orifices of heart.,Aortic and pulmonary passages may also show,supravalvular,or,subvalvular,stenosis.,Alternately,the openings may be too large and valves becomes incompetent.,In pulmonary stenosis,foramen ovale and ductus arteriosus remain patent.,In aortic stenosis ductus arteriosus is patent and blood flows into aorta through it.,By:Gan Quan Fu,Abnormal Growth,There maybe acessory cusps in the valves,Congenital tumors may be formed,Left atrium may be partially subdivided by a transverse septum.,Myocardium may be poorly developed(hypoplasia).,By:Gan Quan Fu,Defective Formation of Septa,INTERATRIAL,SEPTAL DEFECTS,Osteum,Primum,Defect,(image A),S,eptum,primum,fail,to,reach,atrio-ventricular endocardial cushions,F,oramen,primum persist.,Osteum,Secundum,Defect,(image B),S,eptum secundum,fail to develop,foramen secundum remains wide open,.,Patent,Foramen,Ovale,(image C),Septum,Primum and Secundum may develop normally but the,Oblique,valvular passage between them may remain patent.,By:Gan Quan Fu,Defective Formation of Septa,Interventricular Septal Defects,(image D),Maybe seen either in the membranous or muscular part of the septum,Most common congenital anomalies of the heart.,Patent Truncus Arteriosus,Defects of the spiral septum,Spiral Septum may not be formed at all.Partial absence of the septum leads to communications(shunts)between the aorta and pulmonary trunk.,Atrio-ventricular canal defect/Persistent atrio-ventricular canal,Defective formation of AV cushions,4 chambers of heart may intercommunicate.,By:Gan Quan Fu,Combined defects,Tetralogy of Fallot,Interventricular septal Defect,Aorta overriding the free upper edge of ventricular septum,Pulmonary Stenosis,Hypertrophy of the Right Ventricle,By:Gan Quan Fu,Anomalies of Relationship of Chambers to Great Vessels,Transposition of Great Vessels,The aorta arises from the right ventricle and the pulmonary trunk from the left ventricle.,Taussig-Bing Syndrome,The aorta arises from the right ventricle and pulmonary trunk overrides both the right and left ventricle.,Interventricular defect,The Superior Vena Cava may end in the Left Atrium,Pulmonary Veins may end in the Right Atrium or one of its tributaries.,By:Gan Quan Fu,Summary,Heart primodium forms in a horseshoe-shape region of,splanchnopleuric mesoderm,at cranial end of germ disc(,Cardiogenic Region,).,In response to signals from underlying endoderm,angioblastic cords,in this region coalesce to form,a pair of lateral heart tube,.,Early of 4,th,week,they fuse to form,primitive heart tube,.,Between weeks 5 and 8,primitive heart tube undergoes process of,looping,remodelling,and,septation,that transform its single lumen into 4 chambers,thus laying down the basis for separation of pulmonary and systemic circulation,By:Gan Quan Fu,References,Larsen,W.J.(1997)Human Embryology,2,nd,edn.Hong Kong;Churchill Livingstone.,Singh,I.&Pal,G.P.(1976)Human Embryology,7,th,edn.India;Macmillan.,By:Gan Quan Fu,Q&a Session!,By:Gan Quan Fu,THANK YOU!,By:Gan Quan Fu,