Anatomy - Ear

Question 1

3 parts of the ear and a summary of their functions?

Answer 1

• External: receives sound waves
• Middle: Transmits sound waves from air to bone, and amplifies via bone to bone
• Inner: Sounds waves to nerve impulses, and vestibular organs

Question 2

What is the auricle/pinna?

Answer 2

Visible part of the ear that resides outside of the head

Question 3

Parts of the auricle/pinna?

Answer 3

• Helix
• Triangular area
• Tragus
• Meatus
• Concha
• Antihelix
• Lobule

Question 4

What type of epithelium makes up the auricle?

Where does the elastic cartilage get its blood supply from?

Answer 4

• Stratified keratinized epithelium (skin)

- Gets blood supply from overlying dense CT/perichondrium

Question 5

What are the parts of the external ear canal?

Answer 5

• Lateral 1/3: made of skin and cartilage (glands, wax, hairs)
• Medial 2/3: made of skin and bone (no hairs/cilia or wax)

Question 6

What are ceruminous glands? Where are they?

Answer 6

Modified sweat glands in the lateral 1/3 of the external ear canal - produce wax instead of sweat

(Occur alongside sebaceous glands which produce sebum)

Question 7

Describe cleaning mechanism of external ear canal

Answer 7

Skin of ear grows from ombo of tympanic membrane out, but is constantly being shed.
Gets shed in the lateral 1/3 and trapped as earwax

Question 8

What is otitis externa?

Treatment?

Answer 8

Inflammation of the ear canal, often due to infection (bacterial/fungal)

Treatment usually to clear infection via ear drops

Question 9

What are the layers of the tympanic membrane?

Answer 9

• Outer: continuous with skin of ear canal
• Middle: fibrous layer
• Inner: cuboidal epithelium

(as a whole only about 1/10mm thick)

Question 10

Contents of the middle ear?

Answer 10

• Ossicular chain
• Oval window
• Round window
• Facial nerve
• Eustachian tube opening
• Mastoid air cells

Question 11

What is the oval window?

Answer 11

Membrane covered opening between middle and inner ear

Gets contacted directly by the stapes to conduct sound

Question 12

Role of the ossicles? Names of the bones?

Answer 12

• Conduct sound through to inner ear
• Amplification

Malleus, Incus & Stapes

Question 13

How does hearing work? Simplified steps

Answer 13

• Sound enters
• TM vibrates
• Ossicles vibrate
• Cochlear fluid vibrations via oval window
• Hair cells in organ of corti detect vibrations
• Impulse transmitted to brainstem

Question 14

Functions of the Eustachian tube?

Answer 14

• Pressure equalization

- Mucus drainage

Question 15

What are the muscles of the eustachian tube?

Answer 15

• Levator veli palatini
• Tensor veli palatini

Think they attach to the palate

Question 16

What are the three divisions of the ear? Where does each extend to/from?

Answer 16

• external ear: from auricle to eardrum
• Middle ear: eardrum (TM) to oval window
• Inner ear: oval window & inside (cochlea / hair cells)

Question 17

Describe the composition of the external acoustic meatus

Answer 17

1. Lateral 1/3: surrounded by cartilage

2. Medial 2/3: surrounded by bone

Question 18

What are the components of the inner ear?

Answer 18

• Semicircular canals (balance & rotational movements)
• Cochlea (hearing - hair cells)
• Vestibule (detect changes in gravity and linear acceleration)

Question 19

What nerve innervates the inner ear? Where does it insert on the brainstem?

Answer 19

• CNVIII: vestibulocochlear

- Originates at the pons