100+ Free FC ORL(SA) Part I Practice Questions

Explanation: The labyrinthine segment of the facial nerve is the narrowest portion of the Fallopian canal, measuring approximately 0.68 mm in diameter. Because it lacks a rich vascular collateral network and possesses a tight fibrous sheath, edema of the nerve within this narrow segment leads to ischemic entrapment, making it the primary site of compression in Bell's palsy.

Explanation: The posterior cricoarytenoid (PCA) muscle is the only vocal fold abductor in the larynx. It originates from the posterior surface of the cricoid lamina and inserts into the muscular process of the arytenoid cartilage, pulling the muscular process medially and rotating the vocal process laterally to open the glottis.

Explanation: The stapes is the innermost ossicle whose footplate (base of stapes) fits into the oval window and is held in place by the annular ligament. Movement of the stapes footplate transfers acoustic vibrations into fluid waves within the perilymph of the scala vestibuli.

Explanation: General somatic sensation (pain, touch, temperature) to the anterior two-thirds of the tongue is conveyed by the lingual nerve, a branch of the mandibular division of the trigeminal nerve (CN V3). Special taste sensation to the same area is carried by the chorda tympani nerve (CN VII).

Explanation: The internal branch of the superior laryngeal nerve (a branch of CN X) pierces the thyrohyoid membrane alongside the superior laryngeal artery to provide sensory innervation to the laryngeal mucosa extending from the epiglottis down to the level of the true vocal cords (supraglottis).

Explanation: The medial wall (labyrinthine wall) of the middle ear cavity separates it from the inner ear. Its prominent central feature is the promontory, a rounded bulge produced by the basal turn of the cochlea, which is covered by the tympanic plexus of nerves (CN IX).

Explanation: The marginal mandibular branch of the facial nerve runs along or up to 1-2 cm below the inferior border of the mandible, superficial to the deep cervical fascia and crossing anterior/superficial to the facial artery and vein. It must be identified and protected during submandibular gland surgery to prevent ipsilateral lower lip weakness (depressor anguli oris paralysis).

Explanation: The parapharyngeal space is divided into pre-styloid and post-styloid compartments by an imaginary coronal plane running from the styloid process and its attached muscles (stylohyoid, styloglossus, stylopharyngeus) and aponeurosis (tensor veli palatini fascia/styloid diaphragm). The pre-styloid space contains fat and minor salivary tissue, while the post-styloid space contains the carotid sheath (carotid artery, internal jugular vein, CN IX-XII, and sympathetic chain).

Explanation: The natural ostium of the maxillary sinus opens into the ethmoid infundibulum, a curved channel located in the middle meatus bounded medially by the uncinate process and laterally by the lamina papyracea and ethmoid bulla.

Explanation: Dorello's canal is a small fibro-osseous space situated at the tip of the petrous apex bounded by the petrosphenoidal ligament (Grüber's ligament) and the petrous bone. The abducens nerve (CN VI) traverses Dorello's canal to enter the cavernous sinus; compression here due to petrous apicitis causes CN VI palsy (a classic component of Gradenigo's syndrome).