In the context of human anatomy, the auricle can refer to either one of two distinct body parts: the outer ear or an internal “pouch” or protective layer in the heart. These parts aren’t related except for their shared name. With respect to the ear, the term basically describes everything that’s visible outside the head. People don’t often realize that the ear is more than just the outward protrusion at the side of the face, but internally it’s quite complex. When it comes to the heart, the auricle is part of the atrium, which is actually two chambers — one on the left and one on the right — and the term refers to the muscular pouch-like cover that protects each of these spaces. As such, each person usually has two, one for each atrium.
Most people, and especially children, think of the auricle when they refer to the ear. In truth the ear is much more complex than what’s seen externally. In most cases it’s made up of three parts: the outer ear, which is visible and is where sound is collected; the middle ear, where sound is processed; and the inner ear, where that sound is actually reverberated and translated by the brain into something intelligible. The outer portion is sometimes also called the pinna.
How the External Ear Works
Different people can have slightly different shaped and sized outer ears, and a lot of this is determined by genetics. Just the same, in nearly all cases the basic shape is the same. This part of the ear is made of flexible cartilage, and it’s protruding, layered shape is designed to not only amplify sound, but to filter it as well. To achieve this perhaps seemingly simple task, eleven different parts work together to reflect and channel sound vibrations from the environment. Noises are amplified and directed from outside of the person and into the auditory canal.
The outer ear works differently depending on the frequency of a sound. Low frequencies are directed toward the auditory canal, but there is an extra phase of noise processing for high-pitch sounds, which makes the filtering function even more valuable. People who have degenerative hearing problems or who suffer from progressive hearing loss often first notice the issue when they aren’t able to hear sounds in certain ranges, particularly those that are very high. Over time and after constant exposure to loud sounds, the filtering function of the outer ear can break down.
In the Heart
When referencing the heart, the auricle typically describes part of either the left of the right atrium. The human heart is made up of four main chambers, two ventricles and two atria, one each on the left and right sides. Atria typically sit just above the ventricles and help process blood as it pumps. In decades past, medical experts often referred to the atria as the left and right auricles, but this reference isn’t usually made anymore. Today, the term is typically used to refer to the small, cone-shaped, muscular pouch that projects from the atrium, insulating and in some ways protecting it. These pouches help the atria hold more blood, and in this respect they essentially serve as reservoirs.
Differences from Left to Right
The right pouch, also commonly called the “right auricular appendix,” is typically larger than the left one, which is also known as the “left atrial appendage.” Similarly, the right atrium is larger than the left atrium. They’re both located at the receiving end of the cavities, though, and the difference is largely due to the different functions of the atria themselves. The right atrium accepts de-oxygenated blood that is returning to the heart from the upper body via the superior vena cava and from the lower body via the inferior vena cava. By contrast, the left atrium receives oxygenated blood returning to the heart from the lungs via the pulmonary vein. Different volumes and pressures of blood are needed to execute these different functions.