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DEVELOPMENT OF
THE HEART & VESSELS
(CARDIOVASCULAR SYSTEM)
M. MANSYUR ROMI
Department Anatomy, Embryology and Anthropology
Faculty of Medicine Universitas Gadjah Mada
OUTLINE
1.
2.
3.
4.
5.
Introduction
Early Development of the
Cardiovascular/Circulatory System
Development of the Primitive Heart
Partitioning/Septation of the Heart
Development of the Major Arteries &
Veins
1. INTRODUCTION
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The development of the cardiovascular
system is an early embryological event.
From fertilization, it takes eight weeks
for the human heart to develop into its
definitive fetal structure.
During this period the system develops
so it can 1) supply nutrients and oxygen
to the fetus, and 2) immediately
function after birth.
2. EARLY DEVELOPMENT OF THE
CARDIOVASCULAR SYSTEM
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Blood Islands
Heart tube
Primitive Cardiovascular Circuits
1) extra-embryonic blood vessels
---at the middle of 3rd week, wall of the yolk sac,
body stalk and chorion mesenchyma proliferate
and form isolated cell clusters: angiobalstic
blood islands;
central located cells are detached and develop into
primitive blood cells (hemopoetic/blood stem cells)
peripheral cells become flattened and differentiate
into endothelial cells
to from endothelial tube,
---endothelial tube approach and fuse with
each other to form an endothelial tube
network
---endothelial tube network appears in chorionic
membrane and body stalk, and connect to
vitelline circulation
2) intra-embryonic blood vessels
---by the 18-20th days, endothelial tube network
appears in intraembryonic mesenchyma to
form intraembryonic endothelial tube network
---by the end of 3rd week, intraembryonic and
extraembryonic endothelial tube networks
connect to each other to form a diffuse
endothelial tube network
---endothelial tube networks fuse or disappear
to form primitive cardiovascular system
Heart tube

blood islands from the splanchnic mesoderm
appear and form a plexus of vessels lying deep to
the horseshoe-shaped prospective pericardial
cavity. These small vessels develop into paired
endocardial heart tubes. The splanchnic
mesoderm proliferates and develops into the
myocardial mantle which gives rise to the
myocardium. The epicardium develops from
cells that migrate over the myocardial mantle
from areas adjacent to the developing heart.
Primitive cardiovascular system:
/heart tube: paired by the 4th week which fuse
/arteries:
-dorsal aorta:
-vitelline artery
-umbilical artery
-aortic arch: 6 pairs
/veins:
-anterior cardinal vein
-posterior cardinal vein
-common cardinal vein
-vitelline vein
-umbilical vein
Primitive circuits
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One intraembryonic circuit
Two extraembryonic circuits:
Vitelline (omphalomesenteric, yolk sac)
Umbilical (allantoic, placental)
3. DEVELOPMENT OF
PRIMITIVE HEART
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The earliest major organ to function
is formed from at least 3 sources :
 Angioblastic mesenchyme
 Midline splanchnopleuric coelomic epithelium
 Neural crest cells
First indicated in embryos at 18 or 19 days
Contraction of the heart begin by day 22
Splanchnic mesenchymal cell
(in the cardiogenic area)
Aggregate & arrange side by side
Two longitudinal cellular
strands (CARDIOGENIC
CORDS)
canalized
Two thin-walled endothelial tubes
(ENDOCARDIAL HEART TUBE)
Gradually approach & fuse
A SINGLE TUBE
endocardial heart tube
inner
Internal endothelial
lining of heart
(ENDOCARDIUM)
Mesenchyme around tubes thickens
MYOEPICARDIAL
MANTLE
Muscular wall
(MYOCARDIUM)
Visceral
pericardium
(EPICARDIUM)
HEART DEVELOPMENT

Clusters of angiogenic cells form a "horseshoeshaped" cluster anterior and lateral to the brain
plate.
The cardiac tube folds under the gut
tube……
THE EARLY DEVELOPMENT OF THE HEART - 1
B
A
DORSAL AORTA
GUT TUBE
ENDODERM
CARDIAC TUBE
PERICARDIAL CAVITY
CARDIAC PRIMORDIUM
(SPLANCHNIC MESODERM)
The cardiac primordia are established in the
early gastrula as regions of splanchnic
mesoderm ahead of the embryo itself. As a
result of the head fold, this region ends up
beneath the pharynx.
VITELLINE VEINS
The heart is a U-shaped tube at this stage and
the forming blood vessels are initially
unconnected
HEART DEVELOPMENT
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Following cardiac mesoderm involution
during gastrulation, the two
endocardial tubes fuse along the
embryonic midline.
The single tubular heart develops
many constrictions outlining future
structure
HEART DEVELOPMENT
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Prior to looping the heart tubes forms constrictions
defining separate components of the heart
(cranial to caudal):
 Bulbus Cordis
 Ventricle
 Atrium
The primitive atrium is still paired and connects
caudally to the paired sinus venosus.
The heart tube will bend ventrally, caudally and
slightly to the right.
HEART DEVELOPMENT
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At this stage the paired sinus venosus
extend laterally and give rise to the
sinus horns.
As the cardiac looping is developing the
paired atria form a common chamber
and move into the pericardial sac.
Sinus venosus
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a large venous sinus
Receives :
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The umbilical vein from the chorion
(primitive placenta)
Vitelline vein from yolk sac
Common cardinal vein from embryo
HEART DEVELOPMENT
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The arterial and venous end of the heart tube
are fixed by :
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The branchial arches
The septum transversum
Bulbus cordis & ventricel grow faster than
other region, the heart bends upon itself,
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forming a U-shaped bulboventricular loop
Later an S-shaped heart
4. PARTITIONING
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During the second month, the heart
begins to septate into two atria, two
ventricles, the ascending aorta and
the pulmonary trunk.
Partitioning of the atrioventricular canal , the
atrium and the ventricle
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begins around the middle of the fourth week
essentially complete by the end of the fifth week
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Endocardial cushions develop in the
dorsal (inferior) and ventral (superior)
walls of the heart. These grow toward
each other as the cardiac jelly
mesenchyme proliferates deep to the
endocardium. These cushions fuse and
divide the common AV canal into the
left and right AV canals.
Atrial Partitioning
SAO = Sinoatrial
oriface
SS = Septum
spurium
S1 = Septum
primum
Perf =
Perforations
O1 = Ostium
primum
EC = Endocardial
cushions
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At the same time there is a developing
septum from the dorsocranial atrial wall
that grows toward the cushions. This is
the septum primum, and the
intervening space is called the
foramen primum. As the septum
reaches the endocardial cushions
closing foramen primum, a second
opening, foramen secundum appears
in septum primum.

As foramen secundum enlarges, a
second septum, septum secundum
forms to the right of septum primum.
Septum secundum forms an incomplete
partition (lying to the right of foramen
secundum) which leaves an opening,
the foramen ovale. The remaining
portions of septum primum become the
valve of foramen ovale.
Atrial Partitioning
O1 = Ostium
primum
S1 = Septum
primum
FO = Foramen
ovale
S2 = Septum
secundum
Ventricular septation
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The muscular interventricular (I.V.)
septum grows as a ridge of tissue from
the caudal heart wall toward the fused
endocardial cushions. The remaining
opening is the interventricular
foramen. The IV foramen is closed by
the conal ridges, outgrowth of the
inferior endocardial cushion, the right
tubercle, and connective tissue from the
muscular interventricular septum.
5. Development of the Major
Arteries & Veins
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The six pairs of aortic arches, develop
in a cephalocaudal direction and
interconnect the ventral aortic roots
and the dorsal aorta.
Of the six pairs of aortic arches, most of
the first, second and fifth arches
disappear.
The veins develop from the three major
vascular circuits.
The Circulatory System
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Functioning circulatory by the end of
the first month of life.
is vital for sustaining life because it
nourishes tissues with oxygen-rich
blood and removes waste products from
the body.
Second month
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Throughout the second month of gestation
the two atria are formed first, while there still
remains just one large ventricle.
At this point, the atria are only partially
separate, joined by a hole called the foramen
ovale.
The ventricles are slightly slower to separate,
and their separation marks the end of the
development of the fetal heart.
the end of the second month
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the fetal heart has
 four chambers
 four valves
begun to beat, about 148 beats per minute
the fetal lungs have formed but are not yet
functioning
Instead, the fetus receives oxygen-rich blood
from its mother through a vein in the
umbilical cord attached to the placenta
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This oxygen-rich maternal blood enters the right
atrium through the inferior vena cava, where it
mixes with oxygen-poor fetal blood returning
from the upper body through the superior vena
cava.
Some of the blood then travels to the left atrium
through the foramen ovale — a normal prenatal
hole in the wall between the upper chambers of
the heart (atria).
The blood in the right atrium is thus a mixture of
oxygen-rich and oxygen-poor blood.
The blood travels from the upper to the lower
chambers of the heart
(the ventricles).
Before birth
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The left ventricle pumps the blood out
through the aorta to nourish the upper body.
The right ventricle pumps the blood through
the pulmonary artery (which will one day
carry blood to the lungs), through a prenatal
passageway called the ductus arteriosus and
out through the aorta to nourish the lower
body.
The ductus arteriosus is responsible for
bypassing the fetal lungs, which are not yet
functioning.
Before birth
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Waste products from the developing
fetus are carried in the blood back to
the placenta via two arteries in the
umbilical cord.
These waste products diffuse into the
mother’s blood and are carried away
and excreted by the maternal
circulation.
After Birth
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During and immediately after birth,
changes take place in the fetal heart
that prepare it for independent life.
1st: the foramen ovale closes, which
prevents blood from freely mixing
between the left and right atria.
2nd: after birth, the baby draws its first
breath, and the lungs go to work for
the first time.
After Birth
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In healthy newborns, the lungs expand with
air, and oxygen sensors in the ductus
arteriosus muscles detect the rising levels of
oxygen.
This causes the ductus arteriosus muscles to
contract, squeezing the ductus arteriosus
(connects the pulmonary artery to the aorta)
 closed.