Dr. Ahmed Fathalla Ibrahim

EARLY DEVELOPMENT OF HEART in cardiogenic areaSplanchnic mesenchymal cells aggregate in cardiogenic area to form two angioblastic cords two endocardial heart tubesCords canalize to form two endocardial heart tubes After folding:After folding: fuse (cranio-caudally)a single heart tube 1.The 2 tubes approach each other & fuse (cranio-caudally) to form a single heart tube 2.The heart tube becomes caudal to oropharyngeal membrane

EARLY DEVELOPMENT OF HEART

The heart tube elongates & forms: 1.Truncus arteriosus 2.Bulbus cordis 3.Ventricle 4.Atrium 5.Sinus venosus

EARLY DEVELOPMENT OF HEART The trucus arteriosusThe trucus arteriosus is continuous cranially with aortic sac from which aortic arches arise The sinus venosusThe sinus venosus lies in the septum transversum & receives umbilical, vitelline & common cardinal veinsSo: The arterial & venous ends of heart are fixed by pharyngeal arches & septum transversum, respectively

EARLY DEVELOPMENT OF HEART grow fasterThe bulbus cordis & ventricle grow faster than atrium & sinus venosus: U-shaped loop 1.The heart bends upon itself forming a U-shaped loop dorsal 2.The atrium and sinus venosus become dorsal (transverse pericardial sinus)after degeneration of dorsal mesocardium 3.A track is formed between arterial & venous end (transverse pericardial sinus) after degeneration of dorsal mesocardium

PARTITIONING OF ATRIOVENTRICULAR CANAL

(endocardial cushions)At the end of 4 th week, 2 mesenchymal thickening (endocardial cushions) form on the dorsal & ventral walls of atrioventricular canal divide AV canal into right & left canalsThe 2 dorsal & ventral cushions fuse & divide AV canal into right & left canals The 2 cushions contribute to the formation of: 1.AV valves 2.Membranous part of interventricular septum

PARTITIONING OF PRIMORDIAL ATRIUM

Septum primum:Septum primum: a crescent-shaped septum arises from the roof of the atrium & grows toward the endocardial cushions. Foramen primum:Foramen primum: an opening between edge of septum primum & cushions. It disappears when septum primum fuses with cushions

PARTITIONING OF PRIMORDIAL ATRIUM Foramen secundum:Foramen secundum: formed by fusion of many perforations appearing in the central part of septum primum Septum secundum:Septum secundum: a crescent-shaped septum arises from the roof of atrium to the right of septum primum & overlaps foramen secundum

PARTITIONING OF PRIMORDIAL ATRIUM Foramen ovale: a valve for the oval foramenForamen ovale: a defect between primary & secondary septum that allows passage of most of oxygenated blood from right to left atrium. Later on, the cranial part of septum primum degenerates & its remaining part forms a valve for the oval foramen preventing the passage of blood in the opposite direction

PARTITIONING OF PRIMORDIAL ATRIUM AFTER BIRTH: Due to equalization of pressure on both atria, the foramen ovale closes & both septa fuse to form the interatrial septum Fossa ovalis:septum primum (valve of foramen ovale),Fossa ovalis: remnant of septum primum (valve of foramen ovale), marks site of foramen ovale Annulus ovalis:septum secundumAnnulus ovalis: remnant of septum secundum

CHANGES IN SINUS VENOSUS

Initially,Initially, sinus venosus opens into the atrium & is formed of 2 equal horns Right horn incorporated in the wall of right atriumRight horn: enlarges & becomes incorporated in the wall of right atrium The valve between right horn & right atrium:its cranial part its caudal partThe valve between right horn & right atrium: its cranial part forms crista terminalis; its caudal part forms valves of IVC and coronary sinus

CHANGES IN SINUS VENOSUS The valve between left horn & left atrium:The valve between left horn & left atrium: forms part of interatrial septum Left horn:Left horn: remains small & forms the coronary sinus

Primordial pulmonary vein

outgrowth of dorsal atrial wall, to the left of septum primumDevelops as an outgrowth of dorsal atrial wall, to the left of septum primum Divides into two branches then into 4 branches gradually incorporated into the wall of left atriumAs atrium expands, the stem of pulmonary vein & its main branches are gradually incorporated into the wall of left atrium

SUMMARY OF DEVELOPMENT OF RIGHT ATRIUM Muscular part:Muscular part: primordium atrium Smooth part:Smooth part: right horn of sinus venosus Fossa ovalis:Fossa ovalis: part of septum primum Annulus ovalis:Annulus ovalis: part of septum secundum Crista terminalis:Crista terminalis: cranial part of right sinuatrial valve Valves of IVC & coronary sinus:Valves of IVC & coronary sinus: caudal part of right sinuatrial valve Interatrial septum:Interatrial septum: fused septum primum & secundum + left sinuatrial valve Coronary sinus:Coronary sinus: left horn of sinus venosus

SUMMARY OF DEVELOPMENT OF LEFT ATRIUM Left auricle:Left auricle: primordium atrium Rest of left atrium (smooth part):Rest of left atrium (smooth part): stem of pulmonary vein & its main branches

PARTITIONING OF PRIMORDIAL VENTRICLE

Muscular part of interventricular septum:Muscular part of interventricular septum: a crescentic fold with a concave cranial edge arises from the floor of ventricle (near its apex) & grows toward fused endocardial cushions

PARTITIONING OF PRIMORDIAL VENTRICLE Interventricular foramen: closed fusion ofInterventricular foramen: an opening between muscular part of septum & cushions. It is closed (7 th week) as a result of fusion of : right & left bulbar ridges + endocardial cushions

PARTITIONING OF PRIMORDIAL VENTRICLE Membranous part of interventricular septum: endocardial cushionMembranous part of interventricular septum: derived from an extension from right side of endocardial cushion

PARTITIONING OF BULBUS CORDIS & TRUNCUS ARTERIOSUS

During 5 th weekmesenchyme derived from neural crest cells bulbar & truncal ridgesDuring 5 th week, mesenchyme derived from neural crest cells proliferate to form bulbar & truncal ridges that are continuous with each other spirally orientedRidges are spirally oriented Bulbus cordisconus arteriosus (infundibulum)aortic vestibuleBulbus cordis is divided into conus arteriosus (infundibulum) & aortic vestibule Truncus arteriosus pulmonary trunkascending aortaTruncus arteriosus is divided into: pulmonary trunk & ascending aorta

SUMMARY OF DEVELOPMENT OF RIGHT VENTRICLE Muscular part: primordium ventricleMuscular part: primordium ventricle Infundibulum: bulbus cordisInfundibulum: bulbus cordis

SUMMARY OF DEVELOPMENT OF LEFT VENTRICLE Muscular part: primordium ventricleMuscular part: primordium ventricle Aortic vestibule: bulbus cordisAortic vestibule: bulbus cordis

DEVELOPMENT OF VALVES Develop as swellings arising from localized proliferations of tissue: (AV valves) 1.Around AV canals (AV valves) (semilunar valves) 2.Around orifices of aorta & pulmonary trunk (semilunar valves) Swellings are hollowed out & reshaped to form the cusps

CONGENITAL HEART DEFECTS commonAre common ( %) Caused byCaused by genetic abnormalities, rubella virus or by environmental factors Some are with unknown cause

DEXTROCARDIA Most frequent positional abnormalityMost frequent positional abnormality Cause:Cause: heart tube bends to the left Results:Results: heart is displaced to the right Occurrence:Occurrence: isolated or with situs inversus

ATRIAL SEPTAL DEFECT femalesMore frequent in females Most common form:patent foramen ovaleMost common form: patent foramen ovale (due to incomplete adhesion between septum primum & secundum)

ATRIAL SEPTAL DEFECT Other forms: 1.Ostium secundum defect: 1.Ostium secundum defect: due to defect in one or both septa 2.Endocardial cushions defects with ostium primum: 2.Endocardial cushions defects with ostium primum: septum primum does not fuse with cushions resulting in a patent forament primum 3.Sinus venosus defect: 3.Sinus venosus defect: incomplete absorption of sinus venosus 4.Common atrium: 4.Common atrium: failure of both septa to develop

VENTRICULAR SEPTAL DEFECT Most common typeMost common type of congenital heart diseases 1.Membranous VSD(most common): 1.Membranous VSD (most common): incomplete closure of IV foramen due to failure of membranous part of septum to develop 2.Muscular VSD 3.Common ventricle: 3.Common ventricle: absence of whole IV septum

ECTOPIA CORDIS Very rareVery rare partly or completely exposed on the surface of thoraxHeart is partly or completely exposed on the surface of thorax Usually associated with separated halves of sternum & open pericardial sac Cause:Cause: faulty development of sternum & pericardium due to failure of complete fusion of lateral folds in formation of thoracic wall