08 Heart

Heart development

Embryonic + fetal blood + gas supply

placenta

• lungs still developing

Post-natal blood + gas supply

lungs

• regular cardiovascular system works

cardiogenic area

horse-shoe area @ cephalic end where cells induced by endoderm form cardiac myoblasts + blood islands

• starts @ gastrulation

• forms primary + secondary heart fields

Primary heart field (PHF) derivatives

atria + L ventricle

Secondary heart field (SHF) derivatives

atria + R ventricle + outflow tracts

cardiac progenitor cells origin

from epiblast into splanchnic mesoderm

Heart tube segments

• bulbus cordis

  • truncus arteriosus

  • conus cordis

  • primitive right ventricle

• primordial ventricle

• primordial atrium

• sinus venosus

Truncus arteriosus derivatives

Proximal outflow tracks

• proximal aorta

• pulmonary trunk

Conus cordis derivatives

Ventricle outflow

• conus arteriosus/ infundibulum

Primitive right ventricle derivative

right ventricle

Primordial ventricle derivative

left ventricle

Primordial atrium derivatives

parts of left + right atrium

Sinus venosus derivatives

• coronary sinus

• sinus venarum

• oblique vein of left atrium

Steps for cardiac loop

1. elongation of heart tube from SHF

2. cephalic + caudal portion of tube bends

   • cephalically: ventrally + caudally + right

   • caudally: dorsally + cranially + left

Foramen ovale

embryonic opening btwn atria that will become fossa ovalis post-natally

Atrioventricular endocardial cushions origin

cardiac mesoderm

Atrioventricular endocardial cushion development

right + left atrioventricular canals → AV valves + AV chamber septum

Sinus venosus bilateral venous blood donors + development

Venous structures

• vitelline (VIT)

  • from yolk sac

• Umbilical (UV)

  • from placenta

• Common cardinal (CCV)

  • anterior + posterior cardinal

  • from embryo proper

Development

• sinuatrial junction shifts right

• obliterate vessels

  • right umbilical vein

  • left vitelline vein

  • left common cardinal vein

Later development of Sinus Venosus

• right sinus horn enlarges → right atrium

• formation of IVC valve + valve of coronary sinus

• crista terminalis divides trabeculated right atrium vs sinus venarum

Draw + explain

• septum primum

• foramen primum

• foramen secundum

• septum secundum

• foramen ovale

• septum primum: descends towards endocardial cushions to separate R vs L atrium //SEPTUM

• foramen primum: allows shunt of blood btwn R to L atrium

  • aka allows blood to go from R atrium to L atrium + bypass pulmonary circuit

• foramen secundum: perforations in septum primum that eventually come together

• septum secundum: another septum next to septum primum that will divide R vs L atrium

• foramen ovale: opening in septum secundum

  • cranial septum primum regresses

  • caudal septum primum becomes valve of foramen ovale

Fossa ovalis

closure of foramen ovale after birth from pressure reversal

R sinuatrial valve derivative

valve of inferior vena cava + valve of coronary sinus

Portions of interventricular septum

Membranous portion

• endocardial cushions

• conotruncal septum

Muscular portion

• cardiac myocytes

Mesenchyme at AV junction derivative

AV valves

Ventricular septal defect (VSD)

opening btwn R + L ventricle

• muscular portion problem

  • Common type of VSD

  • usually spontaneously closes up during embryonic development

• membranous portion problem

  • less likely to close spontaneously → more clinical intervention needed = more common clinical VSD presentation

  • may lead to high pressure on right side

  • more serious

Mechanism for septation + valves of outflow tracts

1. truncus arteriosus swells + grows distally from heart tube

2. R + L conotruncal ridges spiral and fuse together

• invaded by neural crest cells to form valves

3. Conotruncal ridges separate and mesenchymal tubercles appear bc of neural crest cells

Tetralogy of Fallot

deficiency in neural crest cells bc of migration or malalignment

• pulmonary stenosis

• right ventricle hypertrophy

• overriding aorta

• ventricular defect

Conotruncal defects

• tetralogy of Fallot

• transposition of the great vessels

• persistent truncus arteriosus

Persistent truncus arteriosus

• conotruncal ridges do not fuse

• Interventricular septal defect

  • truncus gets blood from both ventricles

Transposition of great vessels

the septum that normally divides aorta vs pulmonary trunk does not form properly

Atrial septal defect + types/etiologies

defects in endocardial cushions

• ostium secundum ASD

• Ostium primum ASD

• sinus venosus defect near entrance of SVC

• common atrium

• patent foramen ovale

Ostium secundum ASD

excessive absorption of septum primum or poor development of septum secundum

Ostium primum ASD

lack of closure of ostium primum

• occurs near AV valves

• commonly associated w valvular problems or VSD

Cor triloculare biventriculare

absence of an atrial septum resulting in a 3-chambered heart

Premature closure of oval foramen S/S

• hypertrophy of right atrium + ventricle

• hypotrophy of left atrium + ventricle

Pt typically dies shortly after birth

Dextrocardia

heart tube bends to left side and heart becomes displaced to right side

Kartagener Syndrome S/S

• situs inversus

• bronchiectasis

• recurrent sinusitis

Ebstein anomaly

• improper formation of tricuspid valve

  • valves partially fused to ventricular wall

• tricuspid regurgitation

• cyanosis + heart failure