Ear

Question 1

Divisions of the Ear

Answer 1

External Ear, Middle Ear, Internal Ear

Question 2

External Ear

Answer 2

Auricle (aka Pinna, visible portion of external ear) consists of elastic cartilage covered with skin. Its function is to collect sound waves and pass them to external auditory meatus. Consists of Helix, Lobule, Tragus, External Acoustic Meatus, and Tympanic membrane

Question 3

Helix

Answer 3

Outer rim of the visible external ear

Question 4

Lobule

Answer 4

Inferior fleshy portion of the visible external ear. Consists of fibrofatty tissue

Question 5

Tragus

Answer 5

Portion of the visible external ear, elevation anterior to the meatus

Question 6

External Auditory

Answer 6

Extends from auricle to the tympanic membrane. Approx 1.25 inches in length. Canal is lined with skin, which contains modified sweat glands (Ceruminous glands) which produce waxy material. Lateral 1/3 of canal is cartilaginous, medial 2/3rds is bony.

Question 7

Nerve supply to the External Acoustic Meatus

Answer 7

Auriculotemporal Nerve and Vagus Nerve

Question 8

Blood Supply to External Acoustic Meatus

Answer 8

Deep auricular branch of maxillary artery

Question 9

Ceruminous Glands

Answer 9

Modified sweat glands in the skin of the external acoustic meatus that produce waxy material

Question 10

Tympanic Membrane

Answer 10

Approx 1cm in diameter; separates the external ear from the middle ear. Placed obliquely at the medial end of the external auditory meatus. The membrane is a a connective tissue membrane lined on the outside with skin and on the inside with mucus membrane. Biconcave in shape with a depression in the center (the Umbo) which serves for attachment of the handle of the malleus.

Question 11

Umbo

Answer 11

Central depression of TM; serves as point of attachment for Malleus

Question 12

Quadrants of the tympanic membrane

Answer 12

Anterosuperior, anteroinferior (shows very bright on examination, ergo refered to as cone of light), posteroinferior, posterosuperior

Question 13

Nerve supply of Tympanic Membrane

Answer 13

Auriculotemporal nerve (to external side) and tympanic branch of glossopharyngeal nerve (to internal surface)

Question 14

Middle Ear

Answer 14

Cavity of the middle ear is known as the Tympanic cavity and is shaped like a biconcave lens. The cavity is found in the petrous portion of the temporal bone (along with the internal ear) and is lined with mucous membrane. Boundaries of the tympanic cavity include: roof, floor, posterior wall, lateral wall, medial wall, interior wall, and anterior wall. The tympanic cavity itself includes the eustachian tube (aka auditory tube), the ossicles (malleus, incus, stapes), stapedius and tensor tympani, and nerves (chorda tympani and tympanic plexus).

Question 15

Roof of the Tympanic Cavity

Answer 15

Formed by thin layer of temporal bone called Tegman Tympani

Question 16

Tegman Tympani

Answer 16

Thin layer of temporal bone forming the roof of the tympanic cavity

Question 17

Floor of the tympanic cavity

Answer 17

Lies above the carotid canal and the beginning of the internal jugular vein

Question 18

Posterior wall of the tympanic cavity

Answer 18

Provides entrance to mastoid air cells and entrance of the stapedius muscle to attach to the neck of the stapes and the chorda tympani

Question 19

Lateral wall of the tympanic cavity

Answer 19

It’s the tympanic membrane!

Question 20

Medial wall of the tympanic cavity

Answer 20

Separates tympanic cavity from inner ear. Consists of: tympanic plexus, oval window, round window

Question 21

Tympanic Plexus

Answer 21

Tympanic nerve (branch of CN IX) divides into branches which form the tympanic plexus. Found in the medial wall of the tympanic cavity. Provides innervation to the mucosa of the middle ear, along with autonomic parasympathetic fibers that eventually innervate parotid (lesser petrosal)

Question 22

Oval Window

Answer 22

AKA Fenestra Vestibuli. Covered by the footplate of the stapes

Question 23

Round Window

Answer 23

Fenestra Cochleae. Inferior to the oval window. Usually closed by a membrane

Question 24

Anterior Wall

Answer 24

Separates tympanic cavity from carotid canal. Has an opening for the eustachian tube.

Question 25

Eustachian Tube

Answer 25

Aka auditory tube. Part bony, part cartilaginous. Extends from/opens into nasopharynx to/from middle ear (1.5 inches long). Muscles serve to open and close tube. Tube functions to equalize pressure on each side of the tympanic membrane. Cartilage part of the tube remains closed normally; opened by the action of the tensor villi palatini and salpingopharyngeal muscle.

Question 26

Ossicles of the middle ear

Answer 26

Malleus, incus, stapes. Work together to conduct vibrations from the tympanic membrane to the oval window (propogate from external ear to inner ear). Two muscles are attached to the ossicles: tensor tympani and stapedius

Question 27

Malleus

Answer 27

Tensor tympani attaches at the handle of the mallus. Handle of the malleus attached to the umbo of the tympanic membrane

Question 28

Incus

Answer 28

Intermediate bone: articulates between the malleus and the stapes

Question 29

Stapes

Answer 29

Foot bone of stapes fits in the oval window: serves to connect the middle to the inner ear.

Question 30

Tensor Tympani

Answer 30

Attaches to the malleus. Innervated by CNV3 (mandibular)

Question 31

Stapedius Muscle

Answer 31

Attached to neck of stapes. Innervated by CNVII. Smallest voluntary muscle in the body (Fun fact!)

Question 32

Inner Ear

Answer 32

Located in petrous portion of temporal bone (along with tympanic cavity). Consists of an vestibular and auditory portion. Also refered to as the labyrinth due to its complicated series of canals. The labyrinth consists of two main divisions: bony labyrinth and membranous labyrinth.

Question 33

Bony labyrinth

Answer 33

Series of canals of inner ear that exist in bone (petrous bone) and contain fluid (perilymph) similar to CSF. Divided into three areas: Vestibule, cochlea, and semicircular canals

Question 34

Vestibule

Answer 34

Smal oval cavity which communicates anteriorly with the cochlea and posteriorly with semicircular canals. Oval window is in its lateral wall

Question 35

Cochlea

Answer 35

Bony snail like structure about 5mm in height. Coiled 2.25 times around a central structure known as the modiolus

Question 36

Modiolus

Answer 36

Central structure around which the cochlea coils

Question 37

Semicircular canals

Answer 37

There are 3 semicircular canals in the bony labyrinth. Each forms 2/3rds of a circle and communicate with the vestibule

Question 38

Membranous labyrinth

Answer 38

The membranous labyrinth is a membranous duct system that is located WITHIN the bony labyrinth. The membranous labyrinth contains a watery fluid known as endolymph (DIFFERENT FROM PERILYMPH, RESEMBLES INTRACELLULAR FLUID). The membranous labyrinth consists of a cochlear duct, three semicircular ducts and two small sacs (utricle and saccule)

Question 39

Perilymph

Answer 39

Fluid of the bony labyrinth. Resembles CSF

Question 40

Endolymph

Answer 40

Fluid of the membranous labyrinth. Resembles ICF