Embryology
DEVELOPMENT OF THE HEART 7 ECTO ALL IMAGES ON THIS PAGE ARE OF A TRANSVERSE VIEW Somatic Splanclinic o > MESO LATERALA SENDO MESO PARAXIAL MESO INTERMEDIATE MESO • heart tube develops from splanchnic layer of the lateral plate mesoderm • endoderm secretes vascular endothelial growth factors that (VEGFs) influence splanchnic layer of the mesoderm • VEGFs stimulate lateral mesoderm to start differentiating and specialising: outer core (angioblast cells) becomes blood vessels & heart tubes, inner core (haemocytoblast) will form blood cells • From lateral plate mesoderm, mesoderm forms cavities, outer = heart tubes, inner = pericardial cavities MESODERM > Angioblast Hemocytu - PERICARDIAL CAVITIES HEART TUBES DORSAL MESOCARDIUM -1 PERICARDIAL 1 HEART TUOF lateral folding fuses together each germ layer: • 2 heart tubes form 1 heart tube · 2 pericardial cavities form 1 pericardial cavity • endoderm forms epithelial lining of GI tract • some mesoderm connects the suspended pericardium to heart tube via the dorsal mesocardium (formed from endocardium, cardiac jelly and myocardium) • endocardium formed from endothelial cells that are derived from angioblasts, myocardium formed from cardiac myocytes, myocytes secrete cardiac jelly ENDOCARDIUM -CARDIAC JELLY MYOCARDIUM
Craniocaudal folding (SAGITTAL VIEW) 5 est - ECTO SENDO > HEART TURE > PERICARDIAL CAVITY € R. HORN AS TA BC PV PP CRANIO CAUDAL FOLDING • As craniocaudal folding takes place: heart tube moves inwards, in front of the face, in front the neck, into the thorax (heart tube is pulled caudally) • during craniocaudal folding, heart tube gets "stuffed" into pericardial cavity O AORTIC SAC - DORSAL AORTAE O TRUNCUS ARTERIOSUS L. P. TRUNK + AORTIC ARCH C BUBUS CORDES 4 R.V. + OUTFLOW TRAUT'S PRIMITIVE VENTRICLE GL.V. IMAGES BELOW AND TO THE LEFT ARE IN THE CORONAL VIEW L. HORN 0 PRIMITIVE ATRIA LOLA + RA OSINUS VENOSUS O COMMON CARDINAL VEINS o umbilical veins o Vitelline veins Cardiac looping 1) +A Be PV PA absence of dyneins - improper looping, heart bends to right (dextrocardia/situs inversus) TA + BC MOVE DOWN TO THE RIGHT 2) PV moves to the left of the midline TA Bc PA 50