Development of Cardiovascular System (Special Embryology)

CARDIOVASCULAR
SYSTEM
HEART
(Page 115)
Dr.Sherif Fahmy

Anatomy of Heart
Dr.Sherif Fahmy

Development of the
Heart
Dr.Sherif Fahmy

2 endocardial
tubes
Dr.Sherif Fahmy

Dorsal aortae
Aortic sac
Heart tube Pharynx
Dr.Sherif Fahmy

Bulbo-ventricular
sulcus
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Sinus Venosus
(Page 117)
Dr.Sherif Fahmy

Absorption of
Pulmonary vein
Dr.Sherif Fahmy

Development of Atria
(Page 119)
Dr.Sherif Fahmy

Right & left atria are developed from:
1- Primitive atrium of the heart tube.
2- Absorption of sinus venosus.
3- Absorption of pulmonary vein.
4- Absorption of atrio-ventricular
canal.
5- Formation of inter-atrial septa.
Dr.Sherif Fahmy

Formation of Interatrial Septa
1- Septum primum.
2- Septum secundum.
3- Septum intermedium.
Dr.Sherif Fahmy

Septum
secundum
Dr.Sherif Fahmy

DEVELOPMENT OF HEART
• Heart primordium:
• Two endocardial tubes are formed in the mesoderm
between buccopharyngeal membrane and cranial part of
intraembryonic coelom (cardiogenic area).
• Fusion between the endocardial tubes to form a single
tube.
• Mesoderm that surrounds the tube is called myo-epicardial
mantle which forms myocardium of the heart.
• After folding, heart tube with the mantle will lies ventral to
pharynx in pericardial bulge.
• The cranial (arterial) end is fixed with arteries of the fetus,
while the caudal (venous) end is fixed to veins of the fetus.
• Elongation of the tube leads to formation of U-shaped
tube.
Dr.Sherif Fahmy

Chambers of the heart tube:
-Three constrictions are formed in the tube will form 4 chambers:
Sinus venosus, Primitive atrium, Primitive ventricle and
Bulbus cordis.
-Elongation of the tube leads to formation of U-shaped tube.
-More elongation of the tube leads to formation of S-shaped tube.
-Sinus venosus comes caudal to primitive atrium which is dorsal
to primitive ventricle. Bulbus cordis on the right of primitive
ventricle.
-Sinus venosus, pulmonary vein and primitive atrium will form the
common atrium which is divided into right and left atria.
Primitive ventricle with proximal part of bulbus cordis will form
right and left ventricles, while distal part (truncus arteriosus) will
form ascending aorta and pulmonary trunk.
Dr.Sherif Fahmy

Sinus Venosus
• It is the cuadal chamber of heart tube that is
formed of body and 2 horns; each horn receives 3
veins (vitelline, umbilical and common cardinal
vein).
• The body joins the back of right side of primitive
atrium by sinu-atrial orifice which is guarded by
right and left valves. While back of left side of
primitive atrium is joined by pulmonary vein.
• Left sinus horn becomes reduced in size due to
degeneration of left vitelline and umbilical veins as
well as shift of blood from left anterior cardinal to
right anterior cardinal by an anastomosis (becomes
left brachiocephalic vein. Left horn remains as
coronary sinus. Dr.Sherif Fahmy

Absorption of body of sinus venosus:
-Body of sinus venosus and right horn are absorbed by
widening of sinu-atrial orifice to form sinus venarum of
right atrium.
-Cranial ends of 2 valves fuse together to form septum
spurium that forms upper part of crista terminalis. Left
valve will fuse with interatrial septum while right valve
forms rest of crista as well as valves of inferior vena
cava and coronary sinus.
-Absorption of pulmonary vein:
-Pulmonary vein has 2 divisions and each has 2 more
divisions. Absorption will form wall of left atrium and 4
pulmonary veins will open separately to the left atrium. It
forms the smooth part of the wall of left atrium.
Dr.Sherif Fahmy

Formation of Interatrial Septum
• 1- Septum primum:
• Crescentic septum that downgrows from the roof of
common chamber.
• It is separated from atrio-ventricular canal by osteum
primum. More downgrowth will close the osteum primum
while the upper part degenerates to form osteum
secundum.
• 2- Septum secundum:
• -Downward growth of crescentic septum secundum to the
right side of septum primum to cover osteum secundum
which becomes foramen ovale.
• 3- Septum intermedium:
• It is formed by fusion between ventral and dorsal atrio-
ventricular cushions to separates between right and left
atrio-ventricular orifices.
Dr.Sherif Fahmy

Development of Right Atrium
• It is developed from:
• -Primitive atrium: forms rough anterior (musculi
pectinati) wall and auricle of right atrium.
• -Sinus venosus: forms posterior smooth wall of
right atrium (sinus venarum).
• -Right ½ of atrio-ventricular canal: forms right
atrioventricular orifice, inside which 3 cusps are
formed (tricuspid valve).
• -Rt & Lt sino-atrial valves remain as crista terminalis
and valves of inferior vena cava and coronary sinus.
Dr.Sherif Fahmy

Development of Left Atrium
• It is developed from:
• 1- Primitive atrium: forms rough part of
left atrium in the left auricle (musculi
pectinati).
• 2- Pulmonary trunk: absorped to form
the smooth wall of the left atrium.
• 3- Left ½ of atrio-ventricular canal: forms
the left atrio-ventricular orifice in which 2
cusps are developed. Dr.Sherif Fahmy

Anomalies of Interatrial Septum:
1- Patent foramen ovale.
2- Premature closure of foramen ovale.
3- Probe patent foramen ovale.
4- Osteum secondum defect.
5- Agenesis of interatrial septum.
Anomalies of atrio-ventricular canal:
1- Persistent A-V canal.
2- Osteum primum defect.
3- Tricuspid atresia.
Dr.Sherif Fahmy

Development of
Ventricles
(Page 125)
Dr.Sherif Fahmy

Anatomy of Ventricles and
Related Arteries
Dr.Sherif Fahmy

Infundibulum
Inflow part
Pulmonary valve
Tricuspid valve
Dr.Sherif Fahmy

Muscular part
Membranous part
Dr.Sherif Fahmy

Development of Ventricles:
Sources:
1- Primitive ventricle form most of left
ventricle and inlet of right ventricle.
2- Proximal portion of bulbus cordis
forms most of right ventricle.
3- Midportion (Conus Cordis) of bulbus
cordis forms the outflow parts of both
ventricles.
Dr.Sherif Fahmy

Upper crescentic margin of
intermuscular septum
Right auricle
Inferior A/V endocardial
cushion
Conus septum
Lt. ventricle
Rt Ventricle
Dr.Sherif Fahmy

Steps of Formation of Ventricles
• Bulbus cordis lies to the right of primitive
ventricle then becomes ventral to it.
• -Proximal part of bulbus cordis enlarges to
form right ventricle. The mid-prtion will
form outflow part of each ventricle. The
distal part forms truncus arteriosus
(ascending aorta and pulmonary trunk).
• -Conus cordis is divided by Conus septum
which is formed by fusion between right &
left bulbar ridges.
Dr.Sherif Fahmy

Formation of interventricular septum:
1- Muscular part developed by:
-Upward growth from floor by proliferation of
myoblasts.
-Dilatation of both ventricles.
2- Membranous part: developed by
migrated cells from:
-Atrio-ventricular cushions.
-Lower part of bulbar ridges.
Anomalies of interventricular septum:
1- Septal defect in muscular or membranous part.
2- Complete absence of the septum.Dr.Sherif Fahmy

Fate of bulbus cordis
1- Proximal part: forms most of right
ventricle.
2- Mid-portion (Conus cordis): forms
outflow parts of both ventricles.
3- Distal part (truncus arteriosus):
forms orifices and main parts of
ascending aorta and pulmonary trunk.
Dr.Sherif Fahmy

Conus septum
Rt Ventricle
Aortico-pulmonary
septum
Truncus Arteriosus
Muscular part of
interventricular septum
Dr.Sherif Fahmy

Formation of Aortico-
pulmonary Septum
Dr.Sherif Fahmy

Spiral aortico-
pulmonary septum
Upper crescentic margin of
intermuscular septum
Dr.Sherif Fahmy

Anomalies of Bulbus Cordis
Fallot’s Tetralogy: due to anterior displacement of
aortico-pulmonary septum. is manifested by pulmonary
stenosis, overriding aorta, ventricular septal defect and
hypertrophy of right ventricle.
Persistant truncus arteriosus: due to failure of
formation of bulbar cushions. It is usually accompanied
with membranous ventricular septal defect.
Transposition of great arteries (TGA): Aorta arise
from right ventricle while pulmonary trunk arises from
left ventricle due to loss of spiral shape of the septum.
Dr.Sherif Fahmy

Cardiac valves: (Page 129)
1- Aortic & Pulmonary: from
Subendocrdial swelling developed from
migrated neural crest cells. Hollow up to
those swellings lead to formation of
semilunar valves.
2- Tricuspid & Mitral: At A/V canal by
formation subendocardial swellings
(cushions).
Dr.Sherif Fahmy

Anomalies in the valves
Pulmonary and aortic stenosis:
-Narrowing of aortic and pulmonary
orifices due to fusion of their cusps.
Tricuspid atresia:
-Tricuspid atresia due to fused cusps.
Dr.Sherif Fahmy

Anomalies of position of heart
-Ectopia cordis: defective
formation of chest wall with
external exposure of the heart.
-Dextrocardia: The heart is
rotated to the right.
Dr.Sherif Fahmy

Anomalies of the
Heart
Dr.Sherif Fahmy

Anomalies of interventricular septum:
1- Septal defect in muscular or membranous part.
2- Complete absence of the septum.
Dr.Sherif Fahmy

Development of Cardiovascular System (Special Embryology)

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