In Spanish there are two words that are frequently used for ears la oreja and el oído. The former is the external part of the ear. Oído is the inner part of the ear or sense of hearing.

Parts of the ear:
El estribo – stirrup
El lóbulo – ear lobe
El martillo – hammer
El oído externo – external ear
El oído medio – the middle ear
El tímpano – eardrum This word also refers to a percussion instrument called the kettledrum
La trompa de Eustaquio –eustachain tube
El yunque – anvil

El otorrinolaringólogo or médico de oídos, nariz y garganta – Nose ears and throat specialist. Note: there are two ways to say it in Spanish

Hear are some expressions using the word ear:
Agachar las orejas – to let someone dominate you.
Aguzar el oído – to be attentive or prick one’s ear
Arder las orejas – to believe or think that someone is talking or gossiping about you
Con las orejas gachas – to be dejected
De oído – to play by ear like some musicians do
Dumbo – a person with big ears like the cartoon character. Also the nickname the ticos fondly call Oscar Arias.
Enseñar la oreja – to show one’s true colors or intention
Jalarle las orejas – to pull one’s ears or to scold someone
Oreja – the fleshy outer ear or a person who spies on someone
Oreja de mercader – a deaf ear
Orejear – to eaves drop
Orejón – a person with big ears
Las paredes tienen orejas or las paredes oyen – the walls have ears
Parar la oreja – to listen or pay attention
Planchar la oreja – to sleep (iron one’s ear). Planchar means to iron clothers. In Costa Rica you will often hear aplanchar used instead of planchar.
Prestarle a alguien la oreja – to lend someone your ear (to listen)
Ser todo oídos – to be all ears
Verle las oreja al lobo –to see trouble coming