The heart is the first FUNCTIONAL organ in
vertebrate embryos
Beats spontaneously by WEEK 4 of development
Heart morphogenesis: Primary heart tube loops to establish LEFT-RIGHT
Cardiac looping polarity = Begins at 4th WEEK OF GESTATION
Defect in left-right dynein [Involved in L/R
asymmetry] can lead to dextrocardia = Kartagener
syndrome [Primary ciliary dyskinesia]
1. Septum primum grows
toward endocardial cushions,
narrowing foramen primum
2. Foramen secundum forms in
septum primum [Foramen
primum disappears]
3. Septum secundum develops
as foramen secundum
maintains RIGHT-LEFT SHUNT
4. Septum secundum expands
Septation of the
and covers most of the
chambers
foramen secundum
5. REMAINING PORTION OF
SEPTUM PRIMUM FORMS
VALVE of FORAMEN OVALE
6. Septum secundum and
septum primum fuse to form
the atrial septum
7. Foramen ovale usually closes
soon after birth because of an
increase in LA pressure
When and how does Foramen ovale usually closes soon after birth
foramen ovale close? because of an increase in LA pressure
What fuses for form the Septum secundum and septum primum fuse to form
atrial septum? the atrial septum
Caused by failure of the septum primum and
septum secundum to fuse AFTER birth
Most are left untreated
Patent foramen ovale
Can lead to PARADOXICAL EMBOLI [Venous
thromboemboli that enter systemic arterial
circulation] - Similar to those resulting in ASD
1. Muscular ventricular septum forms [Opening =
Interventricular foramen]
2. Aorticopulmonary septum rotates and fuses with
muscular ventricular contraction, closing the
Ventricular Formation interventricular foramen
3. Growth of endocardial cushion separate atria
from ventricles and contributes both atrial septation
and membranous portion of the interventricular
septum
What separates separate Endocardial cushion
atria from ventricles and
contributes to both atrial
septation and
membranous portion of
the interventricular
septum?
Where are most Membranous septum
ventricular septal defects
[VSD] located?
Truncus arteriosus rotates
Neural crest and endocardial cushion migrates
Outflow tract formation Leads to truncal and bulbar ridges that spiral and
fuse to form aorticopulmonary septum
Leads to ascending aorta + pulmonary trunk
1. Transposition of great vessels
Conotruncal
2. Tetralogy of Fallot
abnormalities
3. Persistent truncus arteriosus
Aortic/pulmonary = Derived from endocardial
cushions of outflow tract
Valve development
Mitral/Tricuspid = Fused endocardial cushions of the
AV canal
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