Two additional passageways are present in the fetal heart

Two additional passageways are present in the fetal heart -...

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Two additional passageways are present in the fetal heart:  The foramen ovale is an opening across the interatrial septum. It allows blood to  bypass the right ventricle and the pulmonary circuit while the nonfunctional fetal lungs are  still developing. The opening, which closes at birth, leaves a shallow depression called the  fossa ovalis in the adult heart. The ductus arteriosus is a connection between the pulmonary trunk and the aorta.  Blood that enters the right ventricle is pumped out through the pulmonary trunk. Although  some blood enters the pulmonary arteries (to provide oxygen and nutrients to the fetal  lungs), most of the blood moves directly into the aorta through the ductus arteriosus. The coronary circulation consists of blood vessels that supply oxygen and nutrients to the tissues of  the heart. Blood entering the chambers of the heart cannot provide this service because the 
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Unformatted text preview: endocardium is too thick for effective diffusion (and only the left side of the heart contains oxygenated blood). Instead, the following two arteries that arise from the aorta and encircle the heart in the artioventricular groove provide this function: • The left coronary artery has the following two branches: the anterior interventricular artery (left anterior descending, or LAD, artery) and the circumflex artery. The right coronary artery has the following two branches: the posterior interventricular artery and the marginal artery. Blood from the coronary circulation returns to the right atrium by way of an enlarged blood vessel, the coronary sinus. Three veins, the great cardiac vein, the middle cardiac vein, and the small cardiac vein, feed the coronary sinus....
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