From the inferior vena cava, the blood enters the right atrium, then passes through the foramen ovale into the left atrium; from there it moves into the left ventricle and out through the aorta, which pumps the oxygenated blood to the head and upper extremities.
Each spinal nerve exits the vertebral canal through an opening called the intervertebral foramen.
The obturator enters the thigh through the obturator foramen; motor branches proceed to the obturator internus and gracilis muscles as well as the adductor muscles, while sensory branches supply the articular capsule of the knee joint.
The most common such defect is persistence of the foramen ovale, an opening in the atrial septum that is normal before birth and that should close at birth or shortly thereafter.
The partition between the atria in mammalian embryos remains incomplete, so that blood returning from the body and from the placenta enters into the right half of the heart but is shunted (through the interatrial foramen) into the left half of the heart and thence again into general circulation.
Formed by the joining of ventral and dorsal divisions of the plexus, it passes through the greater sciatic foramen and descends in back of the thigh.
Just outside the intervertebral foramen, two branches, known as the gray and white rami communicantes, connect each spinal nerve with the sympathetic trunk.
The medulla oblongata is connected by the pons to the midbrain and is continuous posteriorly with the spinal cord, with which it merges at the opening (foramen magnum) at the base of the skull.
The inner end of the stapes abuts against a small opening (the foramen ovale) to the cavity in the skull containing the inner ear.
Defects in the atrial septum may be small or large and occur most commonly in the midportion in the area prenatally occupied by the aperture called the foramen ovale.
At birth, however, the interatrial foramen is closed by a membraneous flap, and oxygen-depleted blood from the body enters the right atrium, is channelled into the right ventricle, and thence to the lungs for oxygenating.
