The human body contains various passages and openings. Understanding their open or closed state, known as “patency,” is fundamental in anatomy. Patency refers to a biological structure being open, unobstructed, or unclosed. This concept applies broadly to tubular passages, called canals, and natural openings, called foramina. Canals are tubular passages or channels that facilitate the movement of fluids, nerves, or other substances. Foramina are natural openings, often in bone or membrane, that allow passage for structures such as nerves, blood vessels, or other tissues. Recognizing whether these pathways remain patent or close as expected is important for bodily function.
Anatomical Canals
A notable example of a canal is the ductus arteriosus, a temporary blood vessel present during fetal development. This canal connects the aorta, the body’s main artery, to the pulmonary artery, which carries blood to the lungs. During fetal life, the ductus arteriosus serves an important role by allowing blood to bypass the developing lungs, which are not yet functional for oxygen exchange. Oxygenated blood from the placenta is shunted directly into the systemic circulation.
After birth, as the infant begins breathing and the lungs become functional, this canal typically closes within the first few days or weeks of life. When the ductus arteriosus fails to close, it remains “patent,” a condition known as a Patent Ductus Arteriosus (PDA). This continued openness alters normal blood flow patterns.
Anatomical Foramina
A common example of a foramen is the foramen ovale, located within the heart. During fetal development, this opening in the atrial septum, the wall separating the heart’s upper chambers, functions as a critical opening. This allows blood to flow directly from the right atrium to the left atrium, bypassing the fetal lungs.
Like the ductus arteriosus, the foramen ovale closes shortly after birth as pressure changes within the heart occur with the onset of breathing. When this opening does not fully close, it is termed a Patent Foramen Ovale (PFO). While PFOs are common and often asymptomatic, their continued patency means a small flap of tissue in the atrial septum remains unfused.
The Significance of Patency
The persistence of normally temporary patent structures, such as the ductus arteriosus or foramen ovale, can have various physiological implications. For a Patent Ductus Arteriosus, the continued connection between the aorta and pulmonary artery allows oxygenated blood from the higher-pressure aorta to flow back into the lower-pressure pulmonary artery. This additional blood flow to the lungs can lead to increased pressure within the pulmonary arteries and potentially strain the heart over time. The heart may have to work harder to pump blood, which can contribute to chamber enlargement.
For a Patent Foramen Ovale, a concern arises from the potential for blood to shunt directly from the right side of the heart to the left side, particularly during moments of increased pressure, such as coughing or straining. While usually small, this opening could allow small blood clots originating in the venous system to bypass the lungs and enter the arterial circulation. These clots could then travel to various parts of the body, including the brain, potentially leading to a stroke or other embolic events. The clinical significance of PFOs varies widely among individuals, with many remaining without symptoms throughout their lives.