Ear Anatomy Quiz: Outer and Middle Ear Structures

Outer Ear Anatomy

• Pinna (auricle) is covered with skin and made of elastic cartilage, consisting of the helix and lobule
• External auditory meatus (ear canal) is lined with skin and ceruminous glands and passes through the temporal bone

Tympanic Membrane

• Separates the outer ear from the middle ear
• Innervated with sensory fibers from the trigeminal and vagus nerves
• Responds to air vibrations or sound waves and transfers energy to the middle ear ossicles

Middle Ear Anatomy

• Consists of three middle ear ossicles: malleus, incus, and stapes
• Malleus (hammer) attaches to the tympanic membrane and is connected to the incus
• Incus (anvil) is connected to the stapes
• Stapes (stirrup) footplate attaches to the oval window of the inner ear, creating ossiculations in the scala vestibuli
• Middle ear muscles: stapedius inserts on the stapes, and tensor tympani inserts on the malleus
• Eustachian tube connects the middle ear to the nasopharynx

Inner Ear Anatomy

• Housed in a maze of temporal bone passages called the bony labyrinth
• Bony labyrinth is filled with perilymph and is lined with periosteum
• Bony labyrinth consists of:
  • Vestibule
  • Cochlea
  • Semicircular canals
• Membranous labyrinth lines inside the bony labyrinth
• Lined with epithelium and is filled with endolymph (high in Na+, K+)

Structures of Hearing

• Cochlea: a spiraling chamber of the bony labyrinth, lined with a membranous labyrinth with 3 separate chambers
  • Scala vestibuli (filled with perilymph) abuts the oval window
  • Cochlear duct (filled with endolymph) contains the organ of Corti
  • Scala tympani (filled with perilymph) abuts the round window
• Organ of Corti: innervated by CN-VIII, the cochlear portion of the VIII pathway to the CNS for hearing

Structures of Equilibrium

• Vestibule houses the saccule and utricle, which each contain a macula that are receptor cells for:
  • Static equilibrium (head position when still)
  • Linear acceleration (head movements in a straight line)
• Semicircular canals are lined with a membranous semicircular duct, with an ampulla at each end containing a crista ampullaris
• Receptors detect:
  • Angular rotation (head rotation)
  • Dynamic equilibrium

The Eye and Vision

• Visual receptors account for ~ 70% of all sensory input in the body
• 40% of the cerebral cortex is involved in processing visual perception
• Eye balls are the sense organs for vision

Accessory Structures of the Eye

• Eyebrows
• Eyelids with tarsal and ciliary glands
• Eyelashes
• Lateral and medial canthus (angles at the corner of the eye)
• Conjunctiva
• Lacrimal apparatus
• Extrinsic eye muscles (6)

Eye Accessory Structures

• Eyelids (palpebrae) protect the eyes from foreign objects and bright light
• Conjunctiva: a transparent mucous membrane covering the inner surface of the eyelids and anterior surface of the eye, but not the cornea

Test your knowledge on the anatomy of the outer and middle ear. Learn about the structures like Pinna, External Auditory Meatus, and Tympanic Membrane. Explore how these components function in hearing and equilibrium.