Cardiovascular systemCardiovascular systemEmbryologyEmbryology

20092009

Blood and blood vesselsBlood and blood vessels

Blood islands – Blood islands – vasculogenesisvasculogenesis: : Mesoderm (mesenchyme)Mesoderm (mesenchyme) FGF2 + VEGF induce differentiation to FGF2 + VEGF induce differentiation to

haemangioblasts (haematopoetic stem cells) and haemangioblasts (haematopoetic stem cells) and angioblasts (endothelium)angioblasts (endothelium)

AngiogenesisAngiogenesis

Primary vascular bed is established by Primary vascular bed is established by vasculogenesisvasculogenesis

Existing vessels sprout up = angiogenesis Existing vessels sprout up = angiogenesis (mediated VEGF)(mediated VEGF)

First blood islands appear in the wall of yolk sac First blood islands appear in the wall of yolk sac at the 3at the 3rdrd week of development, and later in week of development, and later in mesoderm in other regions.mesoderm in other regions.

HaematopoesisHaematopoesis

First generation – First generation – blood islandsblood islands - transitory - transitory Second generation of stem cells arise from Second generation of stem cells arise from

intraembryonic mesoderm – aorta-gonad-intraembryonic mesoderm – aorta-gonad-mesonephros region. Stem cells colonize liver mesonephros region. Stem cells colonize liver and spleen: and spleen: hepato-lienal periodhepato-lienal period

Later, stem cells colonize Later, stem cells colonize bone marrowbone marrow – – definitive blood forming tissuedefinitive blood forming tissue

HaemopoesisHaemopoesis

Formation of heart tubeFormation of heart tube

Cardiogenic area – in mesoderm in front of Cardiogenic area – in mesoderm in front of buccopharyngeal membrane and future brainbuccopharyngeal membrane and future brain

Folding of embryonic body – pericardial cavity Folding of embryonic body – pericardial cavity and heart move to cervical region and later to and heart move to cervical region and later to thorax thorax

HeartHeart

Pair of cardiac primordia fuse except for the most Pair of cardiac primordia fuse except for the most caudal reagioncaudal reagion

Longitudinal growth – heart tube bulges into the Longitudinal growth – heart tube bulges into the pericardial cavity, it is attached to the body wall pericardial cavity, it is attached to the body wall by dorsal mesocardium( that disappears later by dorsal mesocardium( that disappears later forming transverse pericardial sinus)forming transverse pericardial sinus)

Heart is fixed to septum transversum and to the Heart is fixed to septum transversum and to the pharyngeal arches (aortal arches)pharyngeal arches (aortal arches)

Cardiac loopCardiac loop

Truncus arteriosusTruncus arteriosus Conus cordisConus cordis Bulbus cordisBulbus cordis VentricleVentricle Atrioventricular canalAtrioventricular canal Common atriumCommon atrium Sinus venosusSinus venosus

Development of heart tubeDevelopment of heart tube

Common atrium = atriumCommon atrium = atrium Bulbus cordis= trabecular part of right ventricleBulbus cordis= trabecular part of right ventricle Conus cordis = outflow tract of both ventriclesConus cordis = outflow tract of both ventricles Bulboventricular sulcus= primary inter-Bulboventricular sulcus= primary inter-

ventricular foramenventricular foramen Ventricle = left ventricleVentricle = left ventricle

Septum formation in common atriumSeptum formation in common atrium

Timing: development starts at the end of 4Timing: development starts at the end of 4 thth week week Septum primum extend toward endocardial cushions of Septum primum extend toward endocardial cushions of

atrioventricular canal – ostium primumatrioventricular canal – ostium primum Closure of ostium primum + formation of ostium Closure of ostium primum + formation of ostium

secundum (cell death).secundum (cell death). Septum secundum – overlap ostium secundumSeptum secundum – overlap ostium secundum The opening left by septum secundum – oval foramenThe opening left by septum secundum – oval foramen Remaining lower part of septum primum = valve of the Remaining lower part of septum primum = valve of the

oval foramenoval foramen

Septum formation in the Septum formation in the atrioventricular canalatrioventricular canal

Atrioventricular endocardial cushionsAtrioventricular endocardial cushions Superior and inferion endocardial cushions fuse – Superior and inferion endocardial cushions fuse –

complete division (5complete division (5thth week) week) Orifice are surrounded by mesenchymal tissue - valveOrifice are surrounded by mesenchymal tissue - valve

Septum formation in the truncus and Septum formation in the truncus and conusconus

Truncus swellings or cushionsTruncus swellings or cushions – twist around – twist around each other – aorticopulmonary septum – septum each other – aorticopulmonary septum – septum spirale – dividing truncus into aortic and spirale – dividing truncus into aortic and pulmonary channelpulmonary channel

Swelling in conus fuse together and with truncalSwelling in conus fuse together and with truncal Neural crest cells (hindbrain)- contribution to the Neural crest cells (hindbrain)- contribution to the

formation of the septum – abnormal migration = formation of the septum – abnormal migration = malformationmalformation

Formation of interventricular septumFormation of interventricular septum

Muscular interventricular septum – muscular wall Muscular interventricular septum – muscular wall of ventriclesof ventricles

Interventricular foramenInterventricular foramen Conus septum, inferior endocardial cushion and Conus septum, inferior endocardial cushion and

top of interventricular septum fuse forming top of interventricular septum fuse forming membranous part of the interventricular septummembranous part of the interventricular septum

Development of the arterial systemDevelopment of the arterial system

Ventral aortaVentral aorta Dorsal aortaDorsal aorta Aortic archesAortic arches Vitelline arteriesVitelline arteries Umbilical arteriesUmbilical arteries

Aortic archesAortic arches

I. Terminal part of maxillary arteryI. Terminal part of maxillary artery II (Stapedial artery)II (Stapedial artery) III. Common carotid artery IV. Arch of aorta and right subclavian artery VI. Pulmonary artery and ductus arteriosus VI. Pulmonary artery and ductus arteriosus

Vitelline and umbilical arteriesVitelline and umbilical arteries Arteries supplying yolk sac (number of paired Arteries supplying yolk sac (number of paired

arteries) – vitelline arteriesarteries) – vitelline arteries They develop in vascular supply of gut – celiac, They develop in vascular supply of gut – celiac,

superior mesenteric, and inferior mesenteric superior mesenteric, and inferior mesenteric artery artery

Umbilical arteries – paired branches of dorsal Umbilical arteries – paired branches of dorsal aorta – to placenta (allantois) in embryonic stalk aorta – to placenta (allantois) in embryonic stalk or later in umbilical cordor later in umbilical cord

It persist as internal iliac and superior vesical It persist as internal iliac and superior vesical arteries (medial umbilical ligaments)arteries (medial umbilical ligaments)

Venous systemVenous system

Vitelline veinsVitelline veins Umbilical veinsUmbilical veins Common cardinals veinsCommon cardinals veins

Vitelline veinsVitelline veins

Vitelline veins form plexus surrounding duodenum – Vitelline veins form plexus surrounding duodenum – pass septum transversum - sinusoids in liverpass septum transversum - sinusoids in liver

Reduction of left sinus horn – blood flow enter right side Reduction of left sinus horn – blood flow enter right side of heart – right hepatocardiac channel – hepatocardiac of heart – right hepatocardiac channel – hepatocardiac portion of the inferior vena cavaportion of the inferior vena cava

Network around duodenum – portal vein Network around duodenum – portal vein Left vitelline vein except for hepatic part disappearsLeft vitelline vein except for hepatic part disappears Right vitteline vein – superior mesenteric vein Right vitteline vein – superior mesenteric vein

Umbilical veinsUmbilical veins

Initially pass along liver, then enter liver participating Initially pass along liver, then enter liver participating on sinusoids formationon sinusoids formation

Proximal part of both and right left umbilical vein Proximal part of both and right left umbilical vein disappeardisappear

Peripheral part of left umbilical vein - in umbilical cordPeripheral part of left umbilical vein - in umbilical cord Anastomosis with vena cava (right hepatocardial duct) – Anastomosis with vena cava (right hepatocardial duct) –

ductus venosusductus venosus After birth- ligamentum teres hepatis (from artery) and After birth- ligamentum teres hepatis (from artery) and

ligamentum venosum (from duct)ligamentum venosum (from duct)

Cardinal veinsCardinal veins

Anterior cardinal veins – drain cephalic part of Anterior cardinal veins – drain cephalic part of embryoembryo

Posterior cardinal veins - drain the rest of embryoPosterior cardinal veins - drain the rest of embryo Common cardinal veins enter sinus horns Common cardinal veins enter sinus horns

Anterior cardinal veinsAnterior cardinal veins

Anastomosis between anterior cardinal veins – Anastomosis between anterior cardinal veins – left brachiocephalic vein – blood from the left left brachiocephalic vein – blood from the left side is moved to rightside is moved to right

Superior vena cavaSuperior vena cava is formed from right common is formed from right common cardinal vein and proximal part of the right cardinal vein and proximal part of the right anterior cardinal veinanterior cardinal vein

Inferior vena cavaInferior vena cava develops from many different develops from many different regions and venous systemsregions and venous systems