The fetal heart differs from and adult heart because there is a hole or foramen in the wall separating the atria that allows blood to pass through. Its purpose is to allow the fetus to receive oxygenated blood and in essence bypass the pulmonary circuit, by allowing blood to enter from the right atrium into the left atrium. Also, the fetal circulatory system includes the ductus arteriosus, which shunts blood from the pulmonary trunk to the aorta, again bypassing the pulmonary circuit. Both of these structures close at birth, once the newborn's lungs have been exposed to air. The ductus arteriosus is subsequently called the ligamentum arteriosus.

The average (normal) blood pressure is approximately . The first number represents the systolic pressure which is caused when the blood is forced out of the left ventricle and the aortic valve opens. The second number is the diastolic pressure and it occurs when the aortic valve closes and the ventricles. The device used to measure blood pressure is called a sphygmomanometer.  

The average (normal) blood pressure is approximately 120/80. The first number represents the systolic pressure which is caused when the blood is forced out of the left ventricle and the aortic valve opens. The second number is the diastolic pressure and it occurs when the aortic valve closes and the ventricle relaxes. The device used to measure blood pressure is called a sphygmomanometer.

The P wave represents the depolarization of the atria which leads to atrial contraction. The QRS complex represents depolarization of the ventricles and leads to ventricular contraction. The T wave represents depolarization of the ventricles.  

Although the bundle of His is part of the cardiac conduction system, it is not one of the internodal tracts.

Because systemic vascular resistance increases, to a point, as the child matures, the myocardium of the left ventricle hypertrophies. The concomitant decrease in pulmonary vascular resistance decreases the thickness of the right ventricle wall. The foramen ovale and ductus arteriosus are pulmonary circuit-bypasses. Since the fetus does not have functioning lungs until birth, these structures close in infancy.

The P wave represents atrial depolarization. The QRS complex represents ventricular depolarization, the T wave represents repolarization, and the U wave (if present) represents late ventricular repolarization (e.g. repolarization of bundle branches). There are no X waves on an EKG.

The heart has four chambers. During diastole the atria contract to push blood into the ventricles, which are relaxed, but during systole the atria relax to fill with blood while the ventricles contract. This alternating contraction moves blood through the heart, the pulmonary circulatory path, and eventually out of the heart.

When the atria contract during diastole, blood is moving into the right ventricle and also into the left ventricle. During systole when the ventricles contract, blood is moving from the right ventricle towards the pulmonary circuit and from the left ventricle to the rest of the body.

The pathway starts with sinoatrial (SA) node. It is the pacemaker of the heart and when a person has an artificial pacemaker installed it usually because of a malfunction at this node. The SA node releases electrical impulse regularly which spread in waves. Upon reaching the atrioventricular node, there is a small delay in reaction to allow for blood to be emptied from the atria. After they do empty, the impulse travels through the bundle of His and splits into the left and right bundles, which then lead to Purkinje fibers. These bundles split the signal to the left and right sides of the heart and the Purkinje fibers end in the walls of the ventricles.

Cardiac outflow from the left side of the heart is the systemic blood flow. Cardiac flow from the right side of the heart is the pulmonary blood flow. Blood flows along the following course: from the lungs to the left atrium (LA) via the pulmonary vein. From the LA to the left ventricle (LV) through the mitral valve. From the LV to the aorta through the aortic valve. From the aorta to the systemic arteries and systemic tissues (i.e., cerebral, coronary, renal, skeletal muscle, and skin). From the tissues to the systemic veins and vena cava. From the vena cava (mixed venous blood) to the right atrium (RA). From the RA to the right ventricle via the tricuspid valve. From the RV to the pulmonary artery through the pulmonic valve. From the pulmonary artery to the lungs for oxygenation.