Development of the cardiovascular
system - 1
Primitive cardiovascular system.
Development of the heart
Institute of Histology and Embryology
Doc. MUDr. Zuzana Jirsová, CSc.
Histology and Embryology – B81402
Lecture – 25. 3. 2014
Note: This presentation is for use by students of the 1st Medical Faculty,
Charles University in Prague – solely for study purposes
EXAM QUESTIONS
Development of the primitive cardiovascular system
Heart development. Aortic arches
and their derivatives
Fetal blood circulation
Development of the primitive
cardiovascular system
Vasculogenesis (blood islands)
Angiogenesis
Development of the primitive heart
Primitive blood circulation:
Extraembryonic circulation: vitelline and umbilical
Intraembryonic circulation
VASCULOGENESIS
Development of the blood vessels begins from the blood
islands which are formed in the extraembryonic
mesoderm of the yolk sac, connecting stalk, and
chorion at the beginning of the third week.
FGF-2 induces differentiation of hemangioblasts,
a comon precursor for vessel and blood cell formation.
Surface cells of blood islands, induced by VEGF,
differentiate into angioblasts – precursors of the
endothelial cells, and inner cells into primitive blood
cells (transitory population of hemopoietic stem cells).
FGF = fibroblast growth factor, VEGF = vascular endothelial growth factor
Proliferation of endothelium stimulated by VEGF leads to the
sprouting of vessels – angiogenesis.
Vessels in the embryo start to develop about two days later in
the lateral plate mesoderm.
A 19-day presomite embryo
Definitive hematopoetic stem
cells are derived from the mesoderm surrounding aorta, gonads
and mesonephros.
Hematopoetic stem cells in the wall
of aorta. Imunocytochemical detection
CD45; a 35-day human fetus.
Scheme: Langman´s Medical Embryology, Sadler, 2004
Photomicrograph: Larsen´s Human Embryology,
Schoenwolf et al., 2009
Development of the primitive heart -1
Progenitor heart cells (located in the epiblast adjacent to the cranial end of the primitive
streak) migrate into the splanchnic layer of the lateral plate mesoderm
(cardiogenic area), where they form a horseshoe-shaped heart field (b). Induced
cells of heart field form blood islands or differentiate into cardiac myoblasts (a).
b
amnion
a
Yolk sac
Blood islands
(heart field)
g
Pericardial cavity
(intraembryonic
coelom)
b
Neural plate
c
f
Wall of thee
yolk sc
Somatic mesoderm (cut edge)
Ektoderm
(cut edge)
Blood islands
Communication
between extraand intraembryonic coelom
A transverse section through 17-day embryo
b = splanchnic mesoderm with progenitor
heart cells, c = extraembryonic splanchnic
Dorsal surface of the late presomite embryo
(ectoderm and somatic mesoderm were removed)
mesoderm, f = intraembryonic coelom,
g = neural plate Scheme: Langman´s Medical Embryology, Sadler, 2004;
Fig.: Human Embryology, Hamilton, Mossman, 1972
Development of the primitive heart - 2
Dorsal aorta
Myocardial
myoblasts
Epicardium
Fig. C: Day-22
Day-18
Paired endothelial tubes
Blood islands unite and form paired endothelial tubes. At the end of the third
week tubes fuse into the endocardial tube surrounded by myoblasts (primitive
myocardium) and epicardium. Heart begins to pump blood into the first aortic
arches at day 22-23.
Position of the heart tube. Initially the cardiogenic area is anterior to the oropharyngeal membrane and the neural plate. Growth of the brain and cephalic folding of embryo
result in the change of the heart position - ventral to the foregut (fig. C) and caudally to the
oropharyngeal membrane. The developing heart tube bulges into the pericardial cavity and
remains attached to the pericardium by dorsal mesocardium, which finally disappers.
Primitive cardiovascular system in a 20-day embryo
Extraembryonic circulation: vitelline and umbilical
Intraembryonic circulation
dorsal intersegmental arteries
Umbilical circulation
Chorion, connecting stalk
oxygenated blood
Vitelline circulation
Wall of the yolk sac
Scheme: Moore, Persaud, Before We Are Born, 1993
PRIMITIVE CIRCULATION
Extraembryonic circulation
VILTELLINE CIRCULATION
aa. vitellinae (ventral branches of the dorsal aortae) – capillary
plexus in the wall of the yolk sac – vv. vitellinae (2) - sinus
venosus
UMBILICAL CIRCULATION
aa. umbilicales (branches of the dorsal aortae) – capillary plexus
(in the chorionic villi) – v. umbilicalis (in the connecting stalk);
in the embryo it branches into v. umbilicalis dextra and sinistra –
sinus venosus
Intraembryonic circulation
Truncus arteriosus - aortic arches – dorsal aortae – capillary
plexus in embryo - vv. cardinales anteriores and posteriores –
vv. cardinales communes - sinus venosus
PRIMITIVE CARDIOVASCULAR SYSTEM
(End of the fourth week; only the vessels on the left side of the embryo are shown)
x
Truncus
arteriosus
Common cardinal veins, vitelline, and umbilical veins open into the sinus venosus (x)
Scheme: Langman´s Medical Embryology, Sadler, 2004
Heart tube (day – 22)
neural groove
ectoderm
the first aortic arch
BULBUS
CORDIS
V
pericardial
cavity
BC
V
BC
VENTRICLE
ATRIUM
sinus venosus
Scheme: ÚHIEM
Bending and formation of the cardiac loop
(blue arrows)
Days 23-24
FRONTAL SECTION OF THE HEART of a 28-day embryo
TRUNCUS ARTERIOSUS
CONUS CORDIS
Outflow part of ventricles
Primordium of the left ventricle
Primordium of the right ventricle
Fig.: Hamilton, Mossman, Human Embryology, 1972
FORMATION OF THE CARDIAC SEPTA
(days 27 – 37)
Partitioning of the common atrium and
atrioventricular canal
Formation of the interventricular septum
Septum formation in the truncus arteriosus
and conus cordis
Partitioning of the atrioventricular canal,
primitive atrium, and ventricle
Schemes: Hamilton, Mossman, Human Embryology, 1972
Partitioning of the atrioventricular canal
Endocardial cushions develop in the dorsal
and ventral walls of the atrioventricular (A-V)
canal. These swellings grow toward each other
and fuse dividing canal into right and left A-V
canals.
Partitioning of the common atrium
Caudal attachment
Endocardial cushion
muscular
SP
Septum primum (SP) grows as thinofcrescentthe s. secundum
shaped membrane from the dorsocranial wall
part
of Conus
the atrium
toward the endocardial cushions.
Opening between the free edge of SP and
endocardial cushions is call foramen primum
(FP). Before the fusion of SP with the endocardial cushions, cell death produces perforations
A: obliteration of the
in the upper portion of SP. Coalescence
of these
septovalvular
space
perforations leads to the formation of the foramen secundum (FS). A new crescent-shaped
fold, septum secundum (SS) grows from the
ventrocranial wall of the atrium on the right side
of SP.
Partitioning of the primitive ventricle
When primitive ventricles begin to expand, their
medial walls become apposed and gradually
merge to form muscular septum. The space
above the free rim of interventricular muscular
septum is called interventriculare formamen.
SEPTUM FORMATION IN THE COMMON ATRIUM – OVAL FORAMEN
Scheme: Moore, Persaud, Before We Are Born, 1993
Septum secundum (SS) grows from the
ventrocranial wall of the atrium on the right
side of SP and overlaps FS. Oval opening
in the SS is called foramen ovale (FO).
Remaining part of SP forms valve of the FO.
Before birth FO allows most of the blood to
flow from the right to left atrium
Partitioning of the atrioventricular canal,
primitive atrium, and ventricle
Schemes: Hamilton, Mossman, Human Embryology, 1972
Caudal attachment
of the s. secundum
Further differentiation of the atria
Primitive right atrium enlarges by incorporation of the right sinus horn. Primitive left
atrium is enlarged when the pulmonary vein
and its branches are incorporated into
muscular
atrium, forming its smooth-walled part.
Membranous part ofSPthe interventricular septum is derived from the
Conus part
A: obliteration of the
septovalvular space
conus septum and inferior endocardial
cushion.
Partitioning of the conus cordis
and truncus arteriosus is formed by
fusion of opposing endocardial swellings
(ridges), which twist around each other,
foreshadowing the spiral course of the
future septum. Aorticopulmonary septum
divides truncus arteriosus into ascending
aorta and pulmonary trunc. Conus septum partitions outflow tracts of the left and right ventricle
Partitioning of the conus cordis and truncus arteriosus: conus and aorticopulmonale septa
Position of the
truncal and
bulbar ridges
(swellings):
1 = frontal
2 = saggital
3 = frontal
conus cordis
Endocardial
swellings
(rigdes) contain
the neural crest
derived cells
Spiral course
of the ridges
(180o)
Spiral form of the
septum
Ascending aorta
Ventral aspect of the heart
(A,D)
Transverse section through
the truncus arteriosus and
conus cordis (B, E)
Removed ventral wall of
the heart (C,F)
Schemes: Moore, Persaud, Before We Are Born, 1993
Truncus pulmonalis +
outflow part of the
right ventricle