dr. ahmed fathalla ibrahim. early development of heart in cardiogenic areasplanchnic mesenchymal...

Dr. Ahmed Fathalla Ibrahim

EARLY DEVELOPMENT OF EARLY DEVELOPMENT OF HEARTHEART

• Splanchnic mesenchymal cells aggregate in cardiogenic areain cardiogenic area to form two angioblastic cords

• Cords canalize to form two endocardial two endocardial heart tubesheart tubes

• After folding:After folding:1. The 2 tubes approach each other & fuse fuse

(cranio-caudally)(cranio-caudally) to form a single heart tubea single heart tube2. The heart tube becomes caudal to

oropharyngeal membrane


The heart tube elongates & forms:

1.1. Truncus arteriosusTruncus arteriosus

2.2. Bulbus cordisBulbus cordis

3.3. VentricleVentricle

4.4. AtriumAtrium

5.5. Sinus venosusSinus venosus


• 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 veins

So:So:• The arterial & venous ends of heart are

fixed by pharyngeal arches & septum transversum, respectively


• The bulbus cordis & ventricle grow fastergrow faster than atrium & sinus venosus:

1. The heart bends upon itself forming a U-U-shaped loopshaped loop

2. The atrium and sinus venosus become dorsaldorsal

3. A track is formed between arterial & venous end (transverse pericardial sinus)(transverse pericardial sinus) after degeneration of dorsal mesocardiumafter degeneration of dorsal mesocardium

PARTITIONING OF PARTITIONING OF ATRIOVENTRICULAR CANALATRIOVENTRICULAR CANAL

PARTITIONING OF PARTITIONING OF ATRIOVENTRICULAR CANALATRIOVENTRICULAR CANAL

• At the end of 4th week, 2 mesenchymal thickening (endocardial cushions)(endocardial cushions) form on the dorsal & ventral walls of atrioventricular canal

• The 2 dorsal & ventral cushions fuse & divide AV canal into right & left canalsdivide AV canal into right & left canals

• The 2 cushions contribute to the formation of:

1.1. AV valvesAV valves2.2. Membranous part of interventricular Membranous part of interventricular

septumseptum

PARTITIONING OF PRIMORDIAL PARTITIONING OF PRIMORDIAL ATRIUMATRIUM


• 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


• 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


• Foramen ovale:Foramen 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 foramena valve for the oval foramen preventing the passage of blood in the opposite direction


AFTER BIRTH: AFTER BIRTH: • Due to equalization of pressure on both

atria, the foramen ovale closes & both septa fuse to form the interatrial septum

• Fossa ovalis:Fossa ovalis: remnant of septum primum septum primum (valve of foramen ovale),(valve of foramen ovale), marks site of foramen ovale

• Annulus ovalis:Annulus ovalis: remnant of septum septum secundumsecundum

CHANGES IN SINUS VENOSUSCHANGES IN SINUS VENOSUS


• Initially,Initially, sinus venosus opens into the atrium & is formed of 2 equal horns

• Right hornRight horn: enlarges & becomes incorporated in the wall of right atriumincorporated in the wall of right atrium

• The valve between right horn & right The valve between right horn & right atrium:atrium: its cranial partits cranial part forms crista terminalis; its caudal partits caudal part forms valves of IVC and coronary sinus


• The valve between left horn & left The valve between left horn & left atrium:atrium: forms part of interatrial septum

• Left horn:Left horn: remains small & forms the coronary sinus

Primordial pulmonary veinPrimordial pulmonary vein

Primordial pulmonary veinPrimordial pulmonary vein

• Develops as an outgrowth of dorsal outgrowth of dorsal atrial wall, to the left of septum primumatrial wall, to the left of septum primum

• Divides into two branches then into 4 branches

• As atrium expands, the stem of pulmonary vein & its main branches are gradually incorporated into the wall of gradually incorporated into the wall of left atriumleft atrium

SUMMARY OF DEVELOPMENT SUMMARY OF DEVELOPMENT OF RIGHT ATRIUMOF 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 SUMMARY OF DEVELOPMENT OF LEFT ATRIUMOF 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 PARTITIONING OF PRIMORDIAL VENTRICLEVENTRICLE


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


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


• Membranous part of Membranous part of interventricular septum: interventricular septum: derived from an extension from right side of endocardial endocardial cushioncushion

PARTITIONING OF BULBUS CORDIS PARTITIONING OF BULBUS CORDIS & TRUNCUS ARTERIOSUS& TRUNCUS ARTERIOSUS

PARTITIONING OF BULBUS CORDIS PARTITIONING OF BULBUS CORDIS & TRUNCUS ARTERIOSUS& TRUNCUS ARTERIOSUS

• During 5During 5thth week week, mesenchyme derived from mesenchyme derived from neural crest cellsneural crest cells proliferate to form bulbar bulbar & truncal ridges& truncal ridges that are continuous with each other

• Ridges are spirally orientedspirally oriented• Bulbus cordisBulbus cordis is divided into conus conus

arteriosus (infundibulum)arteriosus (infundibulum) & aortic vestibuleaortic vestibule• Truncus arteriosusTruncus arteriosus is divided into:

pulmonary trunkpulmonary trunk & ascending aortaascending aorta

SUMMARY OF DEVELOPMENT SUMMARY OF DEVELOPMENT OF RIGHT VENTRICLEOF RIGHT VENTRICLE

• Muscular part: Muscular part: primordium ventricleprimordium ventricle

• Infundibulum: Infundibulum: bulbus cordisbulbus cordis

SUMMARY OF DEVELOPMENT SUMMARY OF DEVELOPMENT OF LEFT VENTRICLEOF LEFT VENTRICLE

• Muscular part: Muscular part: primordium ventricleprimordium ventricle

• Aortic vestibule: Aortic vestibule: bulbus cordisbulbus cordis

DEVELOPMENT OF VALVESDEVELOPMENT OF VALVES

• Develop as swellings arising from localized proliferations of tissue:

1. Around AV canals (AV valves)(AV valves)

2. Around orifices of aorta & pulmonary trunk (semilunar valves)(semilunar valves)

• Swellings are hollowed out & reshaped to form the cusps

CONGENITAL HEART DEFECTSCONGENITAL HEART DEFECTS

• Are commoncommon (0.6 -0.8%)

• Caused byCaused by genetic abnormalities, rubella virus or by environmental factors

• Some are with unknown cause

DEXTROCARDIADEXTROCARDIA

• 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 DEFECTATRIAL SEPTAL DEFECT

• More frequent in femalesfemales

• Most common form:Most common form: patent patent foramen ovaleforamen ovale (due to incomplete adhesion between septum primum & secundum)

ATRIAL SEPTAL DEFECTATRIAL SEPTAL DEFECT

• Other forms:1.1.Ostium secundum defect:Ostium secundum defect: due to defect

in one or both septa2.2.Endocardial cushions defects with Endocardial cushions defects with

ostium primum:ostium primum: septum primum does not fuse with cushions resulting in a patent forament primum

3.3.Sinus venosus defect:Sinus venosus defect: incomplete absorption of sinus venosus

4.4.Common atrium:Common atrium: failure of both septa to develop

VENTRICULAR SEPTAL DEFECTVENTRICULAR SEPTAL DEFECT

• Most common typeMost common type of congenital heart diseases

1.1. Membranous VSDMembranous VSD (most common):(most common): incomplete closure of IV foramen due to failure of membranous part of septum to develop

2.2. Muscular VSDMuscular VSD3.3. Common ventricle:Common ventricle: absence of whole

IV septum

ECTOPIA CORDISECTOPIA CORDIS

• Very rareVery rare• Heart is partly or completely exposed on partly or completely exposed on

the surface of thoraxthe 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

dr. ahmed fathalla ibrahim. early development of heart in cardiogenic areasplanchnic mesenchymal...

Documents

septum primum septum

interventricular septum

foramen primum

septum primum fuses

edge of septum primum

sinus venosus slide

septum secundumannulus

crescentshaped septum