The external ear (outer) is made up of the auricle, ear canal and lateral surface of the tympanic membrane. Its function is to trap sound waves (auricle) and transmit it to the inner ear by passing down the canal and causing the eardrum to vibrate.
Picture of the Human Ear from Wikimedia Commons
The outer shell-shaped part of the external ear is known as the pinna or auricle. It traps sounds waves in the surroundings and directs it into the ear canal. The auricle is composed of elastic cartilage covered by a thin layer of skin. The lower part known as the lobule (common name ~ ear lobe) is made up of fibrous tissue, fat and blood vessels.
The outer margin of the ear is known as the helix and the inner elevated margin is the antihelix. The deepest depression which leads to the ear canal is known as the concha. The tragus is the small cartilaginous flap that can be pushed down to block the opening to the ear canal.
The ear canal runs from the concha to the ear drum (lateral side of the tympanic membrane) and is known as the external acoustic meatus. It runs inward through the temporal bone of the skull (tympanic part) and is about 2 to 3 centimeters long,
The ear canal is an S-shaped tunnel. The outer one-third is made up of cartilage lined with skin that is similar to the skin of the auricle. Sebaceous and ceruminous glands in this outer one-third produces earwax (cerumen). The inner two-thirds are bony and lined with a thinner skin.
The eardrum (tympanic membrane) divides the external ear from the middle ear. It is a thin membrane that is about 1 centimeter in diameter. The lateral part of the tympanic membrane which faces the ear canal is lined with thin skin that is continuous with the skin of the inner two-thirds of the ear canal.
The best description for the eardrum is that it looks like a satellite dish. It is concave so through the ear canal it looks like the back of a satellite dish, with a central depression known as the umbo.
The tympanic membrane moves inward and outward in response to vibration, similar to speaker. Due to the auditory ossicles, which are attached to the medial surface of the eardrum, the movement of membrane transmits force to the internal ear where it can be converted into electrical impulses and passed to the brain.
Article reviewed by Dr. Greg. Last updated on October 6, 2010