Ear muscles-1

We hear with the ears. Ears also help in balancing our body. Thus the ear acts as a double sense organ for hearing and equilibrium - statoacoustic in function.

Our ears have 3 parts anatomically - the outer, middle, and inner ear. The outer and middle ear are involved in hearing alone but the inner ear helps in hearing as well as in balancing of the body.

Outer ear is the pinna or auricle. Only the mammals (like humans, cats, dogs, rats, elephants) have the pinna. The other vertebrate classes like Pisces (fish), amphibia like frogs and toads, reptiles like the lizards and snakes, and aves (birds) do not have any pinna.

The pinna in elephant is huge while that in a mouse is tiny. Pinna of an elephant is used for an additional special purpose. The elephants lose heat through their pinnae.

When air around them is very warm their pinnae get more blood supply and less blood goes to the pinnae when it is cold. Also, the elephants flap their ears more when they want to lose heat. If wind is blowing they flap their pinnae less.

A cat's ear can pivot in180 degrees. They have some 30 muscles in each ear. They use nearly a dozen muscles to control the movement of their pinna.

Whales, dolphins, sea-cows, walruses have no pinna though they all are mammals.

The pinna of the external ear, in humans is composed of the outer flap of skin and elastic type of cartilage. It collects air-bone sound waves and funnels them to the ear canal to the eardrum. It rejects to some extent sounds coming from behind the ear. The pinna has intrinsic muscles, such as the - helicis major, helicis minor (helix being the rim of pinna) tragicus, antitragicus transverse and obliques auriculae, these small muscles help maintain or alter the shape of the pinna to some extent.

The extrinsic muscles are the muscles that attach the auricle i.e. pinna to skull and scalp. They are - auriculares anterior (smallest) which has flat tendon that pulls the ear forwards upwards, auriculares superior (largest) that elevates the pinna and auriculares posterior which draws back - cats, dogs, cattle, deer, elephants etc. have binaural audition and can locate source of sound by turning ears.

Many mammals, like dogs, can droop or raise and move their pinna in different directions so as to catch more sound waves and locate their prey or predator.

Go To Page: 1 2