UNoxygenated blood enters theatrium on the rightside of the heart. Unoxygenated blood comes infrom the top of the body through the superior vena cava. Unoxygenated blood comes in from the lower body though theinferior vena cava.
While theunoxygenatedblood is in the right atrium, the tricuspidvalve is closed to keep the blood from flowing down to the ventricle.
The atriumcontracts and the tricuspid valve opens, forcingthe blooddown into theventricle.
The tricuspid valve closes again so that blood cannot move back upinto the atrium.
The ventricle contracts. This forces theunoxygenatedblood through the pulmonaryvalve and into the pulmonary arteries.
The right pulmonary artery takes theunoxygenated blood to the right lung. The left pulmonary artery takes theunoxygenated blood to the left lung. THE PULMONARYARTERIES ARE THE ONLY ARTERIES THAT CARRYUNOXYGENEATED BLOOD.
In the lungs, the carbondioxide in the blooddiffuses into the alveoli.The oxygenin the lungsdiffuses into the blood. This is called gas http://www.webmd.com/hw/health_guide_atoz/tp10237.asp exchange.
Oxygenated blood from thelungs enters theheart through the left atrium. The mitral valveis closed to keep the blood from going into the ventricle.
Oxygenated blood from the right lungreturns to the heart through the right pulmonary vein. Oxygenated blood from the left lungreturns to the heart through the left pulmonary vein.THE PULMONARY VEINS ARE THEONLY VEINS THAT CARRY OXYGENATED BLOOD.
The left atrium contracts. This forces the oxygenatedblood through the mitralvalve into theLeft ventricle.
The mitralvalve closesagain. This keeps theoxygenated blood frommoving back up into the atrium.
Oxygenatedblood is forced into the aorta to be carried to the rest of the body.
Oxygenated blood is carriedto all body cells where oxygendiffuses into thecells and carbondioxide diffuses into the blood.Blood carryingcarbon dioxidethen returns to the heart.
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
• The heart tube begins to bulge into primitive heart chambers and undergoes right ward looping• Followed by proper valve positioning and chamber formation
CYANOSIS a physical sign causing bluish discoloration of the skin and mucous membranes. caused by a lack of oxygen in the blood. associated with cold temperatures, heart failure, lung diseases, and smothering. It is seen in infants at birth as a result of heart defects, defects respiratory distress syndrome, or lung and breathing problems.
• The blue discoloration of cyanosis is seen most readily in the beds of the fingernails and toenails, and on the lips and tongue.• It often appears transiently as a result of slowed blood flow through the skin due to the cold. As such, it is not a serious symptom.• However, in other cases cyanosis is a serious symptom of underlying disease.
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
o Small VSDs may close on their own and usually does not cause major problems. o These are the kinds that can close at any time during childhood. o A membranous VSD is found in the upper portion of the interventricular septum. o A muscular VSD is found in the lower part of the septum.o Medium and large sized VSDs are unlikely to close spontaneously. o Surgery or other interventional procedures may be required to close these defects. Inlet and Outlet VSDs are less common types and are present where the blood enters or leaves the ventricles.
VSD Signs and Symptoms• Heart murmur• Difficulty maintaining weight• Increased breathing rate• Lower energy and easy tiring Ventricular Septal Defect - Animation http://www.medindia.net/animation/Ventricular_Septal_Defec
• Some of the infants may show poor weight gain, shortness of breath or even bluish discoloration of the lips, nails or skin.• Most of the small VSDs may go unnoticed.• A murmur can be heard with a stethoscope when the baby is a few weeks old.• Untreated moderate to large VSDs may lead to severe complications in a child.• Heart failure may result from the constant overload of the right ventricles.• Arrhythmias and Pulmonary hypertension can also be an outcome of the high volume of blood flowing through the right ventricle.• It is rare that these defects can go unnoticed and so complications are rather rare.