10. Breathing and Respiratory Tract (Part 2)

Question 1

What is the visible part of the ear called?

Answer 1

Pinna (auricle)

Question 2

What makes up the external ear?

Answer 2

• Pinna
• External auditory meatus

Question 3

Answer 3

Question 4

What is the pinna made of?

Answer 4

Cartilage and skin that is tightly adhesed

Question 5

What innervates the pinna?

Answer 5

• Auriculotemporal nerve from the mandibular branch of the trigeminal nerve -> Supplies the skin of the auricle anterior to the external auditory meatus.
• Great auricular nerve -> Supplies the back surface of the ear, as well as the helix, antihelix and lobule.

Question 6

What is the external auditory meatus made from?

Answer 6

• Outer 1/3rd -> Cartilage covered with skin that is continuous with the skin of the pinna.
• Inner 2/3rd -> Temporal bone covered with thin skin continuous with the external surface of the tympanic membrane.

Question 7

Summarise the innervation of the external auditory meatus.

Answer 7

• Auriculotemporal nerve (branch of the maxillary branch of the trigeminal nerve)
• Auricular branch of the vagus nerve

Question 8

What separates the external ear from the middle ear?

Answer 8

Tympanic membrane

Question 9

What innervates the tympanic membrane?

Answer 9

Facial nerve (CN 7)

Also the auriculotemporal nerve (branch of the maxillary branch of the trigeminal nerve), vagus nerve and glossopharyngeal nerve.

Question 10

What is the function of the tympanic membrane?

Answer 10

Converts sound waves into physical movement, which is then transmitted to the inner ear via the auditory ossicles of the middle ear.

Question 11

What is notable about the tympanic membrane in children?

Answer 11

It is close to the surface.

Question 12

What does the middle ear contain?

Answer 12

• Ossicles
• Stapedius muscle
• Tensor tympani muscle
• Chorda tympani nerve

Question 13

The ossicles transfer vibrations from … to …

Answer 13

From the tympanic membrane to the oval window.

Question 14

What is the order of the ossicles in the middle ear?

Answer 14

Malleus, Incus, Stapes

Question 15

Which ossicle is this?

Answer 15

Malleus

Question 16

Which ossicle is this?

Answer 16

Incus

Question 17

Which ossicle is this?

Answer 17

Stapes

Question 18

What are the round and oval windows?

Answer 18

• The oval window is the membrane at the start of the inner ear, to which the stapes connects
• The round window is at the “end” of the cochlea, and it vibrates in opposite phase into the middle ear

Question 19

What does the stapedius muscle do?

Answer 19

The stapedius functions to dampen the vibrations of the stapes, controlling the amplitude of sound waves passing to the inner ear.

Question 20

What two places does the middle ear connect to?

Answer 20

• Nasopharynx (at level of inferior nasal concha) -> Via Eustachian tube
• Mastoid air cells -> Via mastoid antrum

Question 21

What is otitis media and what is a complication?

Answer 21

• Also known as a middle ear infection, otitis media is extremely common in childhood and may be caused by either bacterial or viral infection.
• Most children experience a self-limiting illness and complain of earache, tiredness and fever.
• On examination, the eardrum may appear bulging and red.
• In some cases, slow resolution results in chronic inflammation with the accumulation of a glue-like fluid behind an intact tympanic membrane (so called “glue-ear” or otitis media with effusion), which is probably due to Eustachian tube dysfunction. The main symptom is dulled hearing. The fluid often drains away gradually over time, but repeated bouts may require the insertion of grommets into the tympanic membrane to allow drainage.

Question 22

What is otosclerosis?

Answer 22

• A genetic condition affecting the auditory ossicles, resulting in sclerosis of the stapes baseplate in the oval window.
• The condition results in a slowly progressive conductive hearing loss, as sound waves are less effectively conducted from the tympanic membrane to the inner ear.
• Hearing loss can be improved using bilateral hearing aids, whilst surgical stapedectomy can result in significant improvements to hearing.

Question 23

What is conduction deafness?

Answer 23

• Results from blockage or damage to the conducting mechanisms of the external or middle ear: may be due to wax, otosclerosis or damage to the ossicles.
• This is in contrast to sensorineural deafness, which involves damage to the cochlea or its innervation.

Question 24

What are the cartilages of the larynx?

Answer 24

Question 25

What are the three regions of the larynx?

Answer 25

• Supraglottis (vestibule) – from the inferior surface of the epiglottis to the vestibular folds (also called the false vocal cords). These are fixed folds that provide protection to the larynx and underlying vocal folds.
• Glottis – region containing the vocal folds.
• Subglottis – from the base of the glottis to the inferior border of the cricoid cartilage (origin of the trachea).

Question 26

What are the vocal and vestibular folds?

Answer 26

• Vocal folds are just vocal cords
• Vestibular folds (a.k.a. false vocal cords) are formed by the superior layer of infolded membrane and perform a protective function

Question 27

Summarise the innervation of the larynx.

Answer 27

• Sensory above vocal folds -> Internal laryngeal (from superior laryngeal)
• Sensory below vocal folds -> Recurrent laryngeal
• Motor -> Recurrent laryngeal (except cricothyroid, which is external laryngeal, from superior laryngeal)

Question 28

What muscle is this and what is the function?

Answer 28

• Cricothyroid
• Controls pitch of voice
• Its action tilts the thyroid forward to help tense the vocal cords.

Question 29

Describe which muscles open and which close the vocal cords.

Answer 29

• All intrinsic laryngeal muscles adduct the cords (close the glottis)
• Except the posterior crico-arytenoids, which abduct the cords (open the glottis

Question 30

Describe the cough reflex.

Answer 30

• The cough reflex occurs when stimulation of cough receptors in the respiratory tract by dust or other foreign particles produces a cough, which causes rapidly moving air which usually remove the foreign material before it reaches the lungs.
• The cough receptors or rapidly adapting irritant receptors are located mainly on the posterior wall of the trachea, pharynx, and at the carina of trachea, the point where the trachea branches into the main bronchi.
• The receptors are less abundant in the distal airways and absent beyond the respiratory bronchioles.
• Afferent nerve: Internal laryngeal nerve