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Formation of the Heart and Heart Defects Michele Kondracki MSII email@example.com Learning Objectives Review anatomy of the heart Formation of the Heart Congenital heart defects Development stages for infants and children Review of Anatomy How does the Heart Form? Formation of the Heart Mesoderm divides into two layers Mesoderm = one of the primary germ cell layers in the early embryo Heart precursor cells come from one of those two mesoderm layers (cardiogenic mesoderm) Heart precursor cells form a single heart tube by day 22 of embryogenesis Formation of the Heart These cells differentiate into the endocardium and myocardium Endocardium = innermost layer that lines the heart chambers and valves valves Myocardium = the muscular layer of the atria and ventricles The heart tube grows and elongates Primitive heart begins to form around day 22-23 Formation of the Heart The heart tube begins to bulge into primitive heart chambers and undergoes right ward looping Followed by proper valve positioning and chamber formation Congenital Heart Defects Abnormalities in heart present at birth Affects 8:1000 live births Examples: Ventricular Septal Defect Atrial Septal Defect Coarctation of the Aorta Tetralogy of Fallot Transposition of the Great Arteries Ventricular Septal Defect (VSD) Most common congenital cardiac anomaly There is a hole between the two ventricles Hole can vary in size and location Oxygenated blood forced through hole from left ventricle to right ventricle then returns to the lungs even though it already carries oxygen Consequences Volume load causes enlargement of both ventricles and the pulmonary artery and exposes right ventricle and pulmonary arteries to high pressures Remember VSD VSD Signs and Symptoms Heart murmur Difficulty maintaining weight Increased breathing rate Lower energy and easy tiring Atrial Septal Defect Hole in the septum between the atria Blood flows through the hole primarily from left to right atria Causes increased blood volume in right atrium so more blood goes to the lungs than normal ASD: Signs and Symptoms Usually no symptoms in children If very large can cause fatigue, poor growth In adulthood can lead to pulmonary hypertension, atrial arrhythmias or congestive heart failure Usually a split S2 (second heart sound) Murmur heard as large amount of blood forced through normal size pulmonary valve Coarctation of the Aorta Common in patients with some chromosomal anomalies (Turner’s syndrome) Due to narrowing of the aorta Left ventricle has to work harder to force blood through narrow aorta Coarctation of the Aorta Coarctation of the aorta: Signs Depends on degree of narrowing Severe – possible heart failure in first days of life Mild – progressive left ventricular hypertrophy (thickening of the muscle) Weak pulses in the legs of the infant (femoral artery pulse) and increased pressure in upper extremities Tetralogy of Fallot Combination of four heart defects Pulmonary stenosis – narrowing of pulmonic valve that impedes blood flow from right ventricle to pulmonary artery VSD Overriding aorta – Aorta is enlarged and appears to arise from both right and left ventricles Right ventricular hypertrophy – due to pumping at high pressure Tetralogy of Fallot Overriding aorta Pulmonary stenosis VSD RV hypertrophy Tetralogy of Fallot: Signs and Symptoms Usually diagnosed in the first few weeks of life Loud murmur Cyanosis due to pulmonary stenosis Rapid breathing in response to low oxygen Transposition of the Great Arteries The aorta and pulmonary artery arise from the wrong ventricle Oxygen poor blood from body to the RA and RV is pumped out of the aorta to the body Oxygen rich blood from the lungs to the LA and LV is sent back to the lungs through the pulmonary artery VSD is common with Transposition of Great Arteries and allows for some blood mixing but not enough to give adequate oxygen to all organs Transposition of the Great Arteries Signs and Symptoms Cyanosis during first hours/days of life Rapid breathing due to lack of oxygen If untreated, 50% will die in the first months of life, and 90% in the first year Helpful Information for Case General guidelines for a child's growth rates include: Weight: 2 weeks - regains birth weight and then gains about 1 1/2 - 2 pounds a month 3 months - gains about 1 pound a month 5 months - doubles birth weight 1 year - triples birth weight and then gains about 1/2 pound a month 2 years - quadruples birth weight and then gains about 4-5 pounds a year 9-10 years - increased weight gain as puberty approaches, often about 10 pounds a year Height: 0-12 months - grows about 10 inches (25 cm) 1-2 years - grows about 5 inches (13 cm) 2-3 years - grows about 3 1/2 inches a year most children will double their birth height by 3-4 years of age 3 years to puberty - grows about 2 inches (5cm) a year Questions?? Thank you!
"Formation of the Heart and Heart Defects"