Human Ear
The ear isn’t just the hearing organ. It is a complex system of parts that not only allows humans to hear, but also makes it possible for humans to walk.
How big are human ears?
Ears come in many shapes and sizes. Typically, men’s ears are larger than women’s, according to a study in the journal Plastic and Reconstructive Surgery. Researchers also found that the average ear is about 2.5 inches (6.3 centimeters) long, and the average ear lobe is 0.74 inches (1.88 cm) long and 0.77 inches (1.96 cm) wide. They also noted that the ear does indeed get larger as a person ages.
For instance, researchers in Germany reported in 2007 in the Anthropologischer Anzeiger: Journal of Biological and Clinical Anthropology that women’s ears increased in size less than men’s ears did. Whereas the maximum ear length for a 20-year-old woman in the study was 2.4 inches (6.1 cm), it reached up to 2.8 inches (7.2 cm) for women older than 70. For men, those lengths were 2.6 inches (6.5 cm) at age 20 and 3 inches (7.8 cm) for individuals over 70.
Another study at Texas Tech University confirmed this observation. The study found that as people age, the ear’s circumference increases on average 0.51 millimeters per year, likely due to aging changes of collagen. A correlation between age and ear circumference can be put into an equation: Ear circumference in mm = 88.1 + (0.51 x subject’s age). Conversely, a person’s age can therefore be calculated by the size of a person’s ear, using the equation: Subject’s age = 1.96 x (Ear circumference in mm – 88.1)
How do ears function?
The ear has three main parts: external ear, middle ear and inner ear. They all have different, but important, features that facilitate hearing and balance.
How hearing works
The external ear, also called the auricle or pinna, is the loop of cartilage and skin that is attached to the outside of the head. It works much like a megaphone. Sound waves are funneled through the external ear and piped into the external auditory canal, according to Nebraska Medicine. The auditory canal is the part of the ear hole that can easily be seen when looking at an ear up-close.
The sound waves pass through the auditory canal and reach the tympanic membrane, better known as the eardrum. Just like when a drum is hit by a drumstick, the thin sheet of connective tissue vibrates when sound waves strike it.
The vibrations pass through the tympanic membrane and enter the middle ear, also called the tympanic cavity. The tympanic cavity is lined with mucosa and filled with air and the auditory ossicles, which are three tiny bones called the malleus (hammer), incus (anvil), and stapes (stirrup), according to Encyclopedia Britannica.
As the bones vibrate, the stapes pushes a structure called the oval window in and out, according to the National Library of Medicine (NLM). This action is passed on to the inner ear and the cochlea, a fluid-filled, spiral-shaped structure that contains the spiral organ of Corti, which is the receptor organ for hearing. Tiny hair cells in this organ translate the vibrations into electrical impulses that are carried to the brain by sensory nerves.
How ears help with balance
The Eustachian tube, or pharyngotympanic tube, equalizes air pressure in the middle ear with the air pressure in the atmosphere. This process helps humans retain their balance.
The vestibular complex, in the inner ear, is also important to balance because it contains receptors that regulate a sense of equilibrium. The inner ear is connected to the vestibulocochlear nerve, which carries sound and equilibrium information to the brain.
