Transcript 13 - Development_of_the_veins

Development of
the Veins
Dr. Zeenat Zaidi
The veins develop from the three major venous circuits,
vitelline, umbilical and cardinal
Like the arteries they develop in a cephalocaudal direction
The precursors to the veins are never all present at the
same time.
In addition, as new structures develop the course of veins
changes
The formation of the liver and the mesonephric kidney has
profound affects in redirecting blood flow
Most of the venous blood is channeled from the left side
to the right side of the body through the anastomosing
vessels
Development of the Veins
In a 4 weeks embryo, three
paired veins open into the
tubular heart:
 Vitelline veins, returning
deoxygenated blood from
the yolk sac
 Umbilical veins, bringing
oxygenated blood from the
placenta.
 Common cardinal veins,
returning deoxygenated
blood from the body of the
embryo
Vitelline Veins
Pass through the
septum transversum
and drain into the sinus
venosus
In relation to the liver
developing within the
septum transversum,
the vitelline veins are
divided into:
 Pre-hapatic part:
forms anastomosis
around the duodenum
which later on gives
rise to the portal vein
 Hepatic part: interrupted
by the liver cords, forms
an extensive vascular
network called the
hepatic sinusoides
 Post-hepatic part:
 Left vein disappears
 Right vein forms the:
 Hepatic veins &
 Hepatic segment of
inferior vena cava
Umbilical Veins
Bring oxygenated blood
from the placenta
Initially run on each side
of the developing liver
and drain into the sinus
venosus
As the liver grows, the
umbilical veins loose
their connection with
heart and open into the
liver
The right vein
disappears by the end
of the embryonic period.
The left vein persists
A wide channel, the
ductus venosus,
appears through the
substance of liver to
connect the left
umbilical vein with the
inferior vena cava
After birth:
 The left umbilical vein obliterate to form
the ligamentum teres of the liver
 The ductus venosus obliterate to form the
ligamentum venosum
Cardinal Veins
Are responsible to drain the
body of the embryo
 The cranial part of the embryo
is drained by paired anterior
cardinal veins
 The caudal part of the embryo
is drained by paired posterior
cardinal veins
 The anterior & posterior
cardinal veins join to form
common cardinal veins, which
drain into the sinus venosus
Anterior Cardinal Veins
Become connected by an
oblique anastomosis which
shunts blood from left to
right
This anastomosing channel
becomes the left
brachiocephalic vein
Left anterior cardinal vein
 Cranial part: becomes
the left internal jugular
vein
 Caudal part: degenerates
Right anterior cardinal vein
 Cranial part: (cranial to
the 7th intersegmental
vein) becomes the right
internal jugular vein
 Middle part: gives rise to
the right
brachiocephalic vein
 Caudal part of right
anterior cardinal vein
and the right common
cardinal vein form the
superior vena cava
Posterior Cardinal Veins
Drain the caudal part of the
body of embryo including
the developing
mesonephroi and largely
disappear with this
transitory kidneys.
Caudally the two veins get
connected by an
anastomosing channel that
directs the blood from the
left to the right vein
Gradually the
posterior
cardinal veins
are replaced
by two new
veins:
subcardinal &
supracardinal
The adult
derivatives of
the posterior
cardinal veins
are the:
 Root of the
azygos vein
&
 Common
iliac veins
Subcardinal Veins
Appear before the
supracardinal veins
Become connected:
 To each other by the
subcardinal
anastomosis
 With the posterior
cardinal veins
through the
mesonephros
 With supracarinal
veins through
subsupracardinal
anastomosis
The adult derivatives of
the subcardinal veins are
the:
 Stem of the left renal
vein
 Suprarenal veins
 Gonadal veins
 Prerenal segment of
IVC
Supracardinal Veins
Last pair of veins to
develop
Appear lateral to
the supracardinal
veins
Become connected
at both ends, to the
posterior cardinal
veins
Get disrupted in the
region of the kidney
Cranial to the kidney:
 An anastomosis develops
between the two veins
shunting blood from the left to
the right vein
 Anterior connection of the left
vein with the posterior
cardinal vein disappears
 Gives rise to azygos and
hemiazygos veins
Caudal to the kidney:
 Left vein degenerates
 Right vein forms postrenal
segment of IVC
Development of Superior Vena Cava
SVC is derived from
the:
 Caudal part of the
right anterior
cardinal vein
&
 Right common
cardinal vein
Development of Azygos Veins
Azygos vein is derived
from the:
 Cranial part of the right
supracardinal vein &
 Terminal part of the
right posterior cardinal
vein
Hemiazygos vein is
derived from the cranial
part of the left supracardinal vein
Development of Inferior Vena Cava
The IVC develops during a
series of changes in the
primordial veins
Composed of:
 Hepatic segment derived
from the right vitelline vein
 Prerenal segment derived
from the right subcardinal
vein
 Renal segment derived
from the subcardinalsupracardinal anastomosis
 Postrenal segment derived
from the right supracardinal vein
Anomalies of the Venous System
Persistent left SVC (double SVC): is the
most common defect
Left SVC
Absence of IVC
Double IVC
Double Arch
of Aorta
With Double
Superior
Vena Cava
Fetal Circulation
The main features of the
fetal circulation are:
Nonfunctioning lungs
Course of the blood from
the placenta to the heart
Three shunts permitting
the blood to bypass the
liver and lungs:
 Foramen ovale
 Ductus venosus
 Ductus arteriosus
The oxygenated blood
from the placenta reaches
the fetus by umbilical vein
Most of the blood
bypasses the liver
through the ductus
venosus, although little
blood enters the liver
In the inferior vena cava,
the oxygenated blood
mixes with the
deoxygenated blood
arriving from the fetus
IVC opens into the right
atrium. In the right atrium,
the caval blood is guided
into the left atrium through
the foramen ovale.
However, little blood
remains in the right atrium,
which mixes with the blood
arriving through the
superior vena cava.
In the left atrium also, the
oxygenated blood mixes
with deoxygenated blood
arriving from the lungs.
Blood enters the left ventricle
and then into the ascending
aorta. Thus the heart and the
brain receive better oxygenated
blood.
The blood from the right atrium
enters into the right ventricle,
and from there into the
pulmonary artery.
Most of the blood from the
pulmonary artery enters into the
aorta through the ductus
arteriosus.
From the aorta, the blood is
distributed to body tissues and
flows through the umbilical
arteries into the placenta.
The blood circulating in
the fetal arterial system
is not fully oxygenated
There is mixing of
oxygenated and
deoxygenated blood in
the:
I. Liver sinusoids
II. Inferior vena cava
III. Right atrium
IV. Left atrium
V. Descending aorta.
V
IV
III
II
I
What happens at birth?
Oh… let me take a
deep breath… and
then everything
will be OK
At birth, dramatic changes occur in the
circulatory pattern.
The changes are initiated by baby’s first
breath.
 Fetal lungs begin to function
 Placental circulation ceases
 The three shunts that short-circuited the
blood during the fetal life cease to
function
Neonatal Circulation
1. The infant’s lungs begin to function:
 The lungs inflate, which tends to draw blood from the
right ventricle.
 Oxygenated blood from the lungs passes through
pulmonary veins to left atrium. The increased
pressure in the left atrium results in closure of the
foramen ovale. effectively separating the two atria.
 This also increases blood flow to the lungs as
blood entering the right atrium can no longer bypass
the right ventricle, which pumps it into the pulmonary
artery and on to the lungs.
2. The placental circulation ceases.
 Umbilical vessels are no longer needed. They
become obliterated
 Occlusion of the placental circulation causes fall of
blood pressure in the inferior vena cava and right
atrium
3. The shunts stop to function:
 Within a day or two of birth, the ductus arteriosus
closes off, preventing blood from the aorta from
entering the pulmonary artery
 The ductus venosus closes off so that all blood
entering the liver passes through the hepatic
sinusoids.
Adult Derivatives of Fetal Vascular
Structures
Ductus venosus becomes the ligamentum venosum,
attached to the inferior vena cava.
Ductus arteriousus becomes ligamentum arteriousum
Foramen ovale closes shortly after birth, fuses completely in
first year and becomes fossa ovalis
The intra-abdominal portions of the umbilical arteries become
the medial umbilical ligaments
The intra-abdominal portion of the umbilical vein becomes
the ligamentum teres. (the umbilical vein remains patent for a long
time and may be used for exchange transfusions during early infancy.
The lumen of the umbilical vein usually does not disappear completely;
hence, the ligamentum teres can be cannulated in adults for the injection
of contrast medium or chemotherapeutic drugs).
Persistence of Fetal Circulation
Patent ductus arteriosus
and patent foramen ovale
each characterize about 8%
of congenital heart defects.
Both cause a mixing of
oxygen-rich and oxygenpoor blood
Blood reaching tissues is
not fully oxygenated and
can cause cyanosis.
Many of these defects go
undetected until child is at
least school age.