Heart Development Flashcards
Primitive hematopoietic stem cells
Make erythrocytes, megakaryocytes and macrophages
Meet immediate needs of the early embryo
Definitive hematopoietic stem cells
Programmed from hemogenic endothelial cells found in the aortic-gonadal-mesonephric (AGM) region
Appear at day 27, seed the liver at day 30
Generate full spectrum of myeloid and lymphoid cell lineages
Without AGM, you never get definitive hematopoietic stem cells
Sites of hematopoiesis
Yolk sac mesoderm- day 17-60: source of early RBCs and macrophages
Liver primordia: beginning day 23, continues to birth
AGM dorsal aorta: colonizes liver
Lymph organs
Bone marrow
AGM region vasculogenesis
Hematopoiesis is coupled to vasculogenesis, which is different from the rest of the embryo
Mesodermal cells directly turn into endothelial cells and form blood vessels in most other areas
Angiogenesis vs vasculogenesis
Vasculogenesis is de novo formation of blood vessels, while angiogenesis is the sprouting of new vessels from existing ones
Intussusception
Taking an existing blood vessel and splitting it in half
Angioma
Abnormal blood vessel and lymphatic capillary growth via vasculogenesis
Capillary hemangioma- excessive formation of capillaries
Cavernous hemangioma- excessive formation of venous sinuses
Primary heart field
Splanchnic mesoderm- precardiomyocytes
Endoderm
Endothelial precursor cells form angiogenic clusters (all though this is a vasculogenic process) which form cardiac crescent and two endocardial tubes
Endocardial tube formation
Splanchnic mesoderm consisting of precardomyocytes continue with the process of body folding and bring the two tubes towards the midline
Fuse into one single tube formed from endocardium and myocardium, and the tube dangles from dorsal mesocardium
Dorsal mesocardium must rupture so the tube can loop
Proepicardial organ
Remnants of dorsal mesocardium that are responsible for forming the epicardium- cardiovasculature, CT and visceral layer of pericardium
Primitive ventricle and proximal portion of outflow
Primitive ventricle forms left ventricle
Proximal portion of outflow forms the right ventricle
Sinus horns
Two horns come together to form sinus venosus, which expands into atrium
Lengthening of the heart tube is due to
Growth of the second heart field
Neural crest cells
Do not add to heart
Regulate GF that comes from endoderm to drive proliferation of precardiac mesenchyme/mesoderm
If NCCs do not migrate to correct place there will be problems with cardiac looping
Heterotaxia
Any symmetry anomaly
Situs inversus- total side reversal of organs
Situs ambiguous- partial reversal of organs
Visceroatrial heterotaxia - right sided heart, normal GI
Ventricular inversion- reverse cardiac looping, right sided left ventricle
Right vitelline vein and Right common cardinal vein
Right vitelline becomes inferior vena cava, right common cardinal becomes superior vena cava
Cushion tissue and separating atria and ventricles
Myocardial cells produce more extracellular matrix which pushes endocardial cells from both sides towards eachother
Endocardial cells are signaled by myocardium to undergo epithelial–>mesenchymal/mesodermal cell transition so the two sides can fuse
This is how AV septum is formed
Valves derived from what tissue
Endocardium which is derived from intraembryonic splanchnic mesoderm
Cushion tissue in outflow tract is derived from
Both endocardium (intraembryonic splanchnic mesoderm) and neural crest cells (ectoderm)
Persistent AV canal
Failure of AV septum fusion
Results in atrial septal defect and ventricular septal defect
Abnormal or agenesis of AV valves
Pulmonary hypertension, exercise intolerance, shortness of breath
Linked with downs syndrome
How does O2 rich blood entering right atrium bypass the pulmonary circuit and get into the systemic side
One-way flutter valve between atria formed by dorsal mesenchymal protrusion
Ductus arteriosus allows blood entering right atrium to travel to left atrium
Early blood flow into right atrium flows through
Goes through foramen ovale, then displaces septum primum from septum secundum and through foramen secundum
Fibrous CT of AV septum is derived from
Endocardium
Foramen primum is filled in by
Cushion tissue