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Development of the Heart
212 – 2004 – Week 6
Avinash Bharadwaj
Retrospect…
Trilaminar embryo
 Three germ layers
 Head and tail folds

Cardiovascular System
The Heart
 Blood vessels
 Abnormal development
 Correlation

Some Special Features
Early development and function
 Requirements of the foetus
 Non-functional lungs
 Placental circulation
 Planning for postnatal life



Right-left passage essential during foetal life,
obliteration required immediately after birth.
The phylogenetic sequence.
Earliest Development

Angiogenic cell
clusters or Blood
Islands

Blood cells and
endothelium
Cardiogenic Area
Flat embryo
 Position of
cardiogenic area

Head Fold
Cardiac area
 Gut formation
 Pericardium and
heart tube

Later…
The Heart Tube
Venous and arterial ends
 Regions defined






Bulbus cordis
Ventricle
Atrium
Sinus venosus
Conus and Truncus…?
The Tube Bends
V
B
D
A
V
SV
The Chambers
A
A
A
V
BVL
Left
Front
The Interior
A-Ar
R and L atria
 Atrioventricular
canal : common
 Outflow
 Aortic arches

LA
RA
AVC
Left – Right Partitioning






Interatrial septum
Interventricular septum
Spiral (aortico-pulomonary septum
Endocardial cushions (A-V cushions)
Functional requirements
There must always be a right to left passage!
Interatrial septum

Partitioning

Right to left passage

Mechanism for closing the passage
A
V
Septum Primum

AVC
V
This is a sagittal
section seen from the
right.
Foramen Primum

Foramen primum :
Between
the septum and
the AV Cushions
Passage is a Must!

Foramen secundum

Foramen primum
about to disappear
Septum Secundum

To the right of primum

Foramen primum has
disappeared
Foramen ovale

F. Ovale –
In septum secundum

Further…

The ‘Valve’

Two septa

Two foramina
Sinus Venosus
Originally a symmetrical structure
 Right and left “horns”
 Venous return more to the right
 Left horn becomes smaller
 Opening shifts to the right
 Later – part of right atrium

Left Atrium
Four pulmonary veins
 Common opening
 “Absorption” of veins into atrium
 Rough part - auricle

The Ventricular Septum
Three Parts
 Interventricular septum
 AV Cushions
 Spiral Septum
The Ventricular Septum
R
Membranous
Muscular
Spiral
(Aorticopulmonary)
Foetal Circulation

Very little pulmonary flow

Placental Circulation

Right to Left Passages

IVC :
Blood from
placenta
 Ductus
venosus

F. ovale

Ductus
arteriosus
Changes At Birth

Closure of interatrial septum

Closure of ductus arteriosus

Closure of ductus venosus
Congenital Heart Disease
Septal Defects – Atrial and Ventricular
 Endocardial cushion defects
 Aorticopulmonary defects
 PDA
 Others
