Final answer:
The transverse sinus is the space in the pericardial cavity through which you can put your finger, located superior to the heart and separating major vessels from the heart chambers.
Step-by-step explanation:
The 'hole' you can put your finger through in the pericardial cavity, superior to the heart, is known as the transverse sinus. The transverse sinus is a space behind the heart that separates the aorta and pulmonary trunk from the superior vena cava and the left atrium. It is not an opening within the heart tissue itself, but rather a passage within the pericardial cavity.
This is different from the foramen ovale, which is an opening in the fetal heart that closes after birth, leaving behind the fossa ovalis, thus separating deoxygenated and oxygenated blood within the heart. The transverse sinus is significant during cardiac surgery, as it allows surgeons to manipulate the great vessels and perform procedures such as coronary artery bypass grafting.