Eye and Ear

Middle ear consists of

1. Tympanic cavity

2. Ossicles → malleus, incus, and stapes

3. Pharyngotympanic/Eustachian tube

Which bone is attached to the tympanic membrane?

Malleus

Which bone is attached to the round window?

Stapes

External ear canal is also called

External auditory/acoustic meatus

Inner ear is made of

Cochlea, semicircular canals, and vestibule

Vestibule consists of

Utricle and saccule

What part of the inner ear helps with equilibrium/balance?

Vestibular complex, which is made of:

→ Vestibule (Utricle and saccule)

→ Semicircular canals

Which muscle protects ear drum from loud sounds?

Tensor tympani muscle

→ Attaches to malleus

→ When it contracts, it tenses the tympanic membrane, reducing vibration and dampening loud sounds

Why are children more common to get otitis media?

Eustachian tube is more horizontal in children

Bony labyrinth is filled with

Filled with perilymph

Membranous labyrinth is filled with

Filled with endolymph

Extra-ocular muscles and their movements

1. Superior rectus → Up

2. Inferior rectus → Down

3. Medial rectus → In

4. Lateral rectus → Out

5. Superior oblique → Downward and outward

6. Inferior oblique → Upward and outward

Three tunics of the eye

1. Fibrous

2. Vascular

3. Nervous

Fibrous tunic of the eye

Sclera → Cornea

Vascular tunic of the eye

Choroid → Ciliary body → Iris

Nervous tunic of the eye

Retina

Two layers of nervous tunic

1. Pigmented outer layer

2. Neural inner layer

Types of photoreceptors

1. Rods → night vision

2. Cones → color vision

Cavities of the eye

Anterior cavity

→ Anterior chamber

→ Posterior chamber

→ Filled with aqueous fluid

Posterior cavity

→ Vitreous chamber

→ Filled with vitreous fluid

What are the three ducts found within the cochlea, and what are they filled with?

1. Vestibular duct → Perilymph

2. Cochlear duct → Endolymph

3. Tympanic duct → Perilymph

Smallest muscle in the body

Stapedius muscle

Stapedius muscle is innervated by

Facial nerve (CN VII)