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Ear Anatomy

January 5, 2016 0 Comments

Hi, it’s Reg here again with Ear Anatomy as part of the Body Systems module for Health Care Studies.

Anatomy of the Ear

Sound is brought to the brain via a complex ear system

The ear is made up of the:

  • external ear,
  • middle ear, and
  • inner ear

The External Ear

The external ear is made up of the:

Pinna (aka the auricle). The pinna is that bit that sticks out of the side of your head… the part my mother used to grab whenever I was a precocious child (back in those days when such things were socially acceptable!). It is made from cartilage and is covered with skin. The pinna collects and directs sounds towards the ear canal. The ingenious twists and folds of the pinna serve a purpose. High pitched sounds are intensified and the formation also assists you with working out which direction a sound came from. Did you know that a sound originating from the front and sides are slightly enhanced? It only makes sense then that sounds originating from behind you are less pronounced.

The pinna is made up of two sections – the helix (upper portion) and the ear lobe (and I’m sure you know where that is). Even I know – and I’m a skeleton who is, you could say, quite pinna-challenged!

Now the earlobe may appear to be lacking in purpose – apart from a platform for some shiny bling – but it has a large blood supply and may actually assist in warming the ears and helping one to maintain balance. Also, some conjecture has it that “earlobes developed as an additional erogenous zone to facilitate the extended sexuality necessary in the evolution of human monogamous pair bonding”. (Sourced: “The Naked Ape” by the zoologist, Desmond Morris).

External Auditory Canal. This is a canal that leads from the pinna to the eardrum. It is also where all that ear wax forms. This wax is actually created by your body to deter foreign objects from entering the canal! Yet, why are so many people determined to gouge it out, thrusting earbuds aka qtips (definitely foreign objects) into their ears with great gusto!

Eardrum. This is made from a fibrous connective tissue.

The Middle Ear

The Middle Ear begins on the other side of the eardrum. It is a cavity filled with air – please, no puns about being an ‘air head’ – and contains three tiny bones called Ossicles.

These Ossicles are:

  • the malleus (hammer),
  • the incus (anvil), and
  • the stapes (stirrups). The stapes is the tiniest of the three bones. It is also the tiniest bone in your body! It attaches to another membrane that is known as the oval window, separating the middle and inner ear.

To give you an even better idea of how small we are talking when it comes the ear anatomy, the oval window is around 30 times smaller than the eardrum.

The middle ear is connected to the nasopharynx (the upper part of the throat behind the nose) via the eustachian tube. The nasopharynx (that kind of word that one drops during a cocktail party conversation to impress others) is 2 – 3cm wide and 3 – 4cm in length. It also connects the nose to the mouth so you can breathe through your nose. The eustachian tubes can be a pathway for infections from the nose and throat to the ear.

The Inner Ear

The inner ear has two parts:

  • the bony labyrinth, and
  • the membranous labyrinth which runs inside of the bony labyrinth.

This labyrinth structure contains:

  • the vestibule,
  • the cochlea, and
  • the semi-circular canals

This where we hit the basics of sound being delivered to the brain for interpretation…

These labyrinths contain fluid and the organ of Corti (aka the spiral organ). These are found in the cochlea as a flap within the middle of three fluid filled tubes. The flap covers rows of tiny hair-like cells. When these hair cells are stimulated (through vibration, eg. sound) they send signals to the brain via the auditory nerve.

How cool is that! It’s like domino’s! One part affects another, so the process of hearing begins as:

1. sound enters the ear canal,
2. it hits the eardrum,
3. the eardrum vibrates,
4. the vibration causes the ossicles to move or shake,
5. the movement of the ossicles causes the oval window to vibrate,
6. this causes the vibration to intensify,
7. the fluid within the cochlea tubes now begin to move or ripple sending waves of fluid over the flap within the organ of Corti,
8. the hair cells are stimulated by this fluid,
9. the hair cells respond by sending signals to the brain that a sound has been heard,
10. the brain interprets what that sound is.

et Voila! We have hearing!

Filed in: Care Studies, Reg Talks

About the Author:

Reg, while being the perfect specimen of the human body, is the man of the hour when it comes to studying ‘Body Systems’. He is committed to improving your understanding of the body’s structure and functions, and is excited to share articles on the subject in his own unique and quirky manner.

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