Transcript Chapter 27 Development of circulatory system

Chapter 27
Development of
circulatory system
1.
Formation of primitive
cardiovascular system
1) extra-embryonic blood vessels
---blood island: at the middle of 3rd week, wall of
the yolk sac mesenchyma proliferate and form
isolated cell clusters, the peripheral cell become
flattened and differentiate into endothelial cell to
from endothelial tube; central located cells are
detached and develop into primitive blood
cells(blood stem cell)
---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
---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
2. Development of heart
1) Formation of primitive heart
---cardiogenic plate: proliferation of splanchnic
mesodermal cell to form a pair of longitudinal
cell cord, then differentiate into cardiac tube
---pericardiac coelom: space in mesoderm
---rapid growth of brain vesicles pulls the
buccopharyngeal
membrane,
the
cardiogenic plate and pericardiac
coelom forward
---lateral folds of the
embryo make the
two cardiac tube
approach and fuse
with each other
---dorsal mesocardium:
cardiac tube
invaginate into
pericardiac coelom
and connect to it by
dorsal mesocardium
---the mesoderm adjacent
to
cardiac
tube
differentiates into the
myoepicardial mantle
---cardiac jelly: gelatinous
substance
between
endothelial wall and
myoepicardial mantle,
then
invaded
by
mesenchymal cell
---heart wall: endocardium;
myocardium
and
epicardium
2) Further development of the heart
---single cardiac tube connected caudally
to the umbilical, vitelline and common
cardinal vein; cephalically connected to
the dorsal aortae by means of aortic
arches
---three dilatations:
/bulbus cordis
/ventricle
/atrium
---sinus venousus: dilatation which receives the
umbilical, vitelline, and common cardinal
veins
---truncus arteriosus: distal part of the bulbus
cordis, connect with aortic sac cephalically
---bulboventricular
loop:
bulboventricular
portion of heart tube
grows rapidly, bends
forming a loop
---“U”-shaped heart;
bulboventricular
loop
bends
in
ventral and caudal
directions
and
slightly to the right
---“S”-shaped heart:
the heart tube
continues to grow
and bend, atrium
shifts in dorsocranial direction;
sinus
venousus
located at caudal
portion of atrium
---atrioventricular canal: atrioventricular junction
remains narrow
---the bulbus cordis divided into three portions:
/distal portion: truncus arteriosus
/midportion: bulbus arteriosus cordis
/proximal portion: develops into the right
ventricle
---primary ventricle develop into the left ventricle
3) Partitioning of the heart chambers
---from 27th day to 37th day
① division of the atrioventricular canal
---endocardiac cushion: develop as thickenings
of subendocardial tissue in the dorsal and
ventral walls of the heart
---the endocardial cushions grow toward each
other and fuse
---lateral
atrioventricular
cushion:
form
atrioventricular valve
② partitioning of the
primitive atrium
---septum primum: a thin
sickle-shaped
membrane appearing
from dorsocranial wall
of atrium
---foramen
primum:
septum primum grows
toward the endocardial
cushions, leaving an
opening between its
lower edge and the
endocardial cushions
---foramen secundum: the upper part of
the septum primum perforated and form
an opening
---septum secundum: another membrane
appears in the ventrocranial wall in the
right of the septum primum
---foramen ovale: oval passage between
atrium, covered by valve of foramen ovale
---before birth, blood can flow from right
atrium toward the left atrium
---after birth, two septums fuse to
separate atrium completely
③partitioning
of
the
primitive ventricle
---muscular
part
of
interventricular septum:
by the end of 4th week,
tissue of ventricular
wall grows toward
endocardial cushions,
but left an opening so
called interventricular
foramen
---membranous part of interventricular
septum: made up of right bulbar ridge,
left bulbar ridge and dorsal endocardial
cushion
④division of truncus arteriosus and bulbus
cordis
---right and left bulbar ridges: two spiral
mesodermal ridges grow from the inner walls
of the truncus arteriosus and bulbus cordis,
twist around each other and fuse to form a
spiral aortico-pulmonary septum
---bulbus arteriosus cordis and truncus
arteriosus are divides into the aorta and
the pulmonary trunk
3. Blood circulation of fetus and
circulatory changes after birth
1) blood circulatio of fetus
umbilical
V→ducts
venosus or hepatic sinus
→inferior vena cava →
right atrium →foramen
ovale →left atrium →left
ventricle →head and
neck region →superior
vena
cava
→right
atrium→right ventrical →
ductus
arteriosus
→
aorta→gut and lower
region
of
the
body→umbilical A →
placenta
2) circulatory changes after birth
a. umbilical V and ducts venousus: constrict
and becomes into ligamentum teres hepatis
and ligamentum venosus
b.umbilical A: becomes into medial umbilical
ligament, but proximal portion persist as
superior vesical arteries
c. ductus arteriosus: constrict and become
arterial ligament
d. foramen ovale closed
4. Congenital malformations
1) atrial septal defect:
---patency of the foramen ovale
---foramen secundum defect
---foramen primum effect
---endocardial cushion defect
2) ventricular septal defect:
---membranous part of the ventricular
septum defect
---muscular part of the ventricular septum
3) abnormalities of the truncus arteriosus and
bulbus arteriosus cordis
---unequal division of truncus arteriosus
---presistent truncus arteriosus
---transposition of the great vessels
4) tetralogy of Fallot:
---unequal division of
truncus arteriosus
---four defects:
/pulmonary stenosis
/overriding aorta
/membranous
part
fails to develop
/hypertrophy of right
ventricle
5) patent ductus arteriosus