Download The heart develops from mesoderm,

Dr. Frank CT Voon
The Development of the Heart
26th October 2010
Summary
Mesoderm forms the entire cardiovascular system, beginning from the third week of
development.
The endocardial tube (primitive heart tube) has 4 chambers - the sinus venosus, common
atrium, embryonic ventricle and bulbus cordis.
The common atrium will be divided by an interatrial septum to form the adult right and
left atrium.
The sinus venosus will form the smooth posterior part of the right atrium.
The myoblasts of the common atrium remain as the rough parts of the right and left
atrium.
The embryonic ventricle develops into the adult (definitive) left ventricle.
The proximal one-third of the bulbus cordis develops into the adult right ventricle.
The middle one-third of the bulbus cordis develops into the infundibulum (right ventricle)
and the aortic vestibule (left ventricle).
The distal one-third (truncus arteriosus) of the bulbus cordis gives rise to the pulmonary
trunk and aorta (separated by a spiral aorticopulmonary septum).
The transverse sinus of the heart
The primitive heart tube lies within the pericardial cavity.
As the heart tube enlarges and lengthens within this space, it bends into an S-tube.
The horizontal space posterior to the aorta and pulmonary trunk will remain as the
transverse sinus of the heart in the adult.
The oblique sinus of the heart
The vertical space posterior to the left atrium and bounded by the pulmonary veins will
become the oblique sinus of the heart in the adult.
The right atrium
The smooth part of the right atrium has developed from the sinus venosus.
The rough part of the right atrium is the original musculature derived from myoblasts of
the common atrium.
The interatrial septum is formed by the septum primum and the septum secundum.
Foramen ovale
The foramen ovale is the passage way between the septum primum and the septum
secundum between which blood from the right atrium enters through the foramen
secundum (in the septum primum) into the left atrium.
Crista terminalis
The crista terminalis is a muscular ridge on the internal wall of the right atrium.
It runs vertically between the openings of the superior and inferior vena cava.
It represents the junction between the smooth and rough parts of the right atrium.
It is indicated on the external wall of the right atrium by the sulcus terminalis.
Fossa ovalis
The fossa ovalis is an oval depression on the right side of the interatrial septum.
It is the lower part of the septum primum which formed the valve of the foramen ovale.
Annulus fossa ovalis
The annulus (limbus) fossa ovalis is the rounded upper margin of the fossa ovalis that
was formed by the edge of the septum secundum.
Atrial Septal Defect
The foramen ovale usually closes within the first week after birth. When this opening is
too large, a defect remains and is called an atrial septal defect (ASD).
Ventricular Septal Defect
Deficiencies in the formation of the membranous or muscular parts of the interventricular
septum can result in ventricular septal defects (VSD), for example, failure of fusion of
endocardial tissues which form the membranous part of the interventricular septum.
Incomplete formation of the membranous part of the interventricular septum results in a
ventricular septal defect (VSD).
Ligamentum arteriosum
The ligamentum arteriosum is the obliterated ductus arteriosus.
Coarctation of the aorta
Coarctation of the aorta is a constriction of the arch of the aorta in the region of the
ligamentum arteriosum.
The alternative routes for blood flow (collateral circulation) through the intercostal
arteries leads to enlargement of the subcostal grooves giving rise to notching of the ribs
(in X-rays).