Third pharyngeal arch derivatives US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Third pharyngeal arch derivatives. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Third pharyngeal arch derivatives US Medical PG Question 1: During an examination of the cranial nerves, a patient shows inability to move their eye laterally past the midline. Which of the following structures in the cavernous sinus is most likely affected?
- A. Oculomotor nerve
- B. Trochlear nerve
- C. Ophthalmic nerve
- D. Abducens nerve (Correct Answer)
Third pharyngeal arch derivatives Explanation: ***Abducens nerve***
- The **abducens nerve (CN VI)** innervates the **lateral rectus muscle**, responsible for **abduction** (lateral movement) of the eye [1].
- Inability to move the eye laterally past the midline indicates paralysis or weakness of the lateral rectus muscle, directly implicating the abducens nerve [1].
*Oculomotor nerve*
- The **oculomotor nerve (CN III)** controls most **extraocular muscles** (superior, inferior, medial rectus, inferior oblique) and the levator palpebrae superioris, as well as pupillary constriction [1], [2].
- Damage to this nerve would primarily affect **adduction**, elevation, depression, and eyelid opening, not isolated lateral gaze.
*Trochlear nerve*
- The **trochlear nerve (CN IV)** innervates the **superior oblique muscle**, which depresses and internally rotates the eye [1].
- A lesion here typically presents with **vertical diplopia**, particularly when reading or descending stairs, due to impaired eye depression and intorsion.
*Ophthalmic nerve*
- The **ophthalmic nerve (V1)** is one of the three divisions of the trigeminal nerve and is purely **sensory**.
- It provides sensation to the forehead, upper eyelid, cornea, and nose, and does not control any eye movements.
Third pharyngeal arch derivatives US Medical PG Question 2: A 65-year-old male presents to the emergency room complaining of a severe headache. He developed a sudden-onset severe throbbing headache while watching a football game on television. His past medical history is significant for migraines and hypertension; however, he states that this headache is different from his normal migraine headaches. He has a 30 pack-year smoking history. His family history is notable for stroke in his mother and father. His temperature is 98.9°F (37.2°C), blood pressure is 150/90 mmHg, pulse is 100/min, and respirations are 14/min. On examination, he is oriented to person, place, and time. Neck motion is limited due to pain. Strength is 5/5 bilaterally in both the upper and the lower extremities and sensation is grossly intact across all the dermatomal distributions. Patellar, brachioradialis, and Achilles reflexes are 2+ bilaterally. The vessel that is most commonly involved in this patient's likely condition directly branches off which of the following vessels?
- A. Middle cerebral artery
- B. Maxillary artery
- C. Anterior cerebral artery
- D. Posterior cerebral artery
- E. Internal carotid artery (Correct Answer)
Third pharyngeal arch derivatives Explanation: ***Internal carotid artery***
- The patient's presentation with a **sudden-onset, severe "thunderclap" headache**, cervical pain, and normal neurologic examination, particularly in the context of **hypertension and smoking history**, is highly suggestive of a **subarachnoid hemorrhage (SAH)**. SAH is most commonly caused by rupture of a **saccular (berry) aneurysm**.
- Approximately 85% of SAHs result from the rupture of an aneurysm in the **anterior circulation**. The most common site for these aneurysms is the **anterior communicating artery**, which directly branches off the **anterior cerebral artery**. However, the **anterior cerebral artery (ACA)**, the **middle cerebral artery (MCA)**, and the **posterior communicating artery (PCoA)** (which is commonly involved in berry aneurysms) all originate directly or indirectly, through the ACA, from the **internal carotid artery (ICA)**. Therefore, the ICA is the most encompassing and correct option from which the most common aneurysm sites ultimately branch.
*Middle cerebral artery*
- While the **middle cerebral artery (MCA)** is a common location for aneurysms, particularly at its bifurcation, it is generally less common than the anterior communicating artery or the posterior communicating artery.
- Aneurysms of the MCA are also branches of the internal carotid artery.
*Maxillary artery*
- The **maxillary artery** is primarily involved in supplying blood to structures in the deep face, maxilla, and mandible.
- It is not a significant location for intracranial berry aneurysms that lead to subarachnoid hemorrhage.
*Anterior cerebral artery*
- While the **anterior cerebral artery (ACA)** itself can be a site for aneurysms, particularly the **anterior communicating artery** (AComA) which connects the two ACAs, it is a branch off the internal carotid artery.
- The AComA is the single most common site for berry aneurysms; however, the question asks for the vessel from which the commonly involved vessel *directly branches off*. The ACA itself directly branches off the ICA.
*Posterior cerebral artery*
- The **posterior cerebral artery (PCA)** is part of the posterior circulation, originating from the basilar artery.
- Aneurysms in the posterior circulation (vertebrobasilar system) are less common causes of SAH than those in the anterior circulation.
Third pharyngeal arch derivatives US Medical PG Question 3: A 45-year-old patient presents with difficulty speaking and swallowing following a stroke. MRI reveals an infarct in the medulla. Which of the following cranial nerve nuclei is most likely affected?
- A. Vestibulocochlear nucleus
- B. Trigeminal nerve nucleus
- C. Facial nerve nucleus
- D. Nucleus ambiguus (Correct Answer)
Third pharyngeal arch derivatives Explanation: ***Nucleus ambiguus***
- The **nucleus ambiguus** is located in the **medulla** and contains motor neurons that innervate muscles involved in **speaking** and **swallowing**, specifically those of the pharynx, larynx, and soft palate via cranial nerves IX, X, and XI [1].
- An infarct in the medulla causing difficulty speaking and swallowing strongly implicates damage to this nucleus, leading to **dysarthria** and **dysphagia** [1].
*Vestibulocochlear nucleus*
- This nucleus is primarily involved in **hearing** and **balance**, which would manifest as dizziness, hearing loss, or nystagmus, not directly difficulty speaking and swallowing.
- While located in the brainstem, damage to this nucleus typically does not cause the specific symptoms of dysarthria and dysphagia described.
*Trigeminal nerve nucleus*
- The trigeminal nerve is responsible for sensory innervation of the face, and motor innervation for **mastication** (chewing).
- Damage would primarily affect facial sensation or jaw movement, not the act of deglutition or phonation.
*Facial nerve nucleus*
- This nucleus, located in the **pons**, controls the muscles of **facial expression** and taste for the anterior two-thirds of the tongue.
- Damage would lead to facial weakness or paralysis, not the profound difficulty with speaking and swallowing affecting pharyngeal and laryngeal function.
Third pharyngeal arch derivatives US Medical PG Question 4: A 47-year-old man presents to you with gradual loss of voice and difficulty swallowing for the past couple of months. The difficulty of swallowing is for both solid and liquid foods. His past medical history is insignificant except for occasional mild headaches. Physical exam also reveals loss of taste sensation on the posterior third of his tongue and palate, weakness in shrugging his shoulders, an absent gag reflex, and deviation of the uvula away from the midline. MRI scanning was suggested which revealed a meningioma that was compressing some cranial nerves leaving the skull. Which of the following openings in the skull transmit the affected cranial nerves?
- A. Jugular foramen (Correct Answer)
- B. Foramen rotundum
- C. Foramen spinosum
- D. Foramen ovale
- E. Foramen lacerum
Third pharyngeal arch derivatives Explanation: ***Jugular foramen***
- The symptoms described—loss of voice, difficulty swallowing, loss of taste on the posterior third of the tongue, absent gag reflex, and uvula deviation—point to impairment of **cranial nerves IX (glossopharyngeal), X (vagus), XI (accessory)**, which all exit the skull via the **jugular foramen**.
- The **vagus nerve** (CN X) is responsible for voice and swallowing (via innervation of the pharynx and larynx), the **glossopharyngeal nerve** (CN IX) for taste from the posterior third of the tongue and the gag reflex, and the **accessory nerve** (CN XI) for shoulder shrugging (trapezius and sternocleidomastoid muscles).
- Note: Loss of taste on the palate may involve CN VII (facial nerve) fibers, but the dominant clinical picture with absent gag reflex, uvula deviation, dysphagia, and dysphonia clearly indicates jugular foramen pathology.
*Foramen rotundum*
- The **foramen rotundum** transmits the **maxillary nerve (V2)**, a branch of the trigeminal nerve.
- Damage to V2 would primarily cause sensory deficits in the midface and upper teeth, which are not described in this patient.
*Foramen spinosum*
- The **foramen spinosum** transmits the **middle meningeal artery** and the **meningeal branch of the mandibular nerve (V3)**.
- Injury here would not explain the constellation of symptoms related to voice, swallowing, taste, or shoulder movement.
*Foramen ovale*
- The **foramen ovale** transmits the **mandibular nerve (V3)**, the **accessory meningeal artery**, and occasionally the superficial petrosal nerve.
- Damage to V3 would result in sensory loss to the lower face and motor deficits in the muscles of mastication, which are not reported.
*Foramen lacerum*
- The **foramen lacerum** is filled with cartilage in vivo and does not typically transmit major neurovascular structures directly through its aperture.
- The **internal carotid artery** passes superior to it, and some small nerves may traverse its vicinity, but not the specific cranial nerves indicated by the patient's symptoms.
Third pharyngeal arch derivatives US Medical PG Question 5: A patient undergoes an MRI of the brain that reveals a tumor compressing the facial nerve at the internal acoustic meatus. Which of the following symptoms would most likely be present?
- A. Loss of taste in the posterior third of the tongue
- B. Loss of taste in the anterior two-thirds of the tongue
- C. Decreased salivation
- D. Facial muscle weakness and hyperacusis (Correct Answer)
- E. Decreased lacrimation
Third pharyngeal arch derivatives Explanation: ***Facial muscle weakness and hyperacusis***
- Compression of the **facial nerve (CN VII)** before it branches within the facial canal affects both its motor and special visceral afferent functions. [1]
- **Facial muscle weakness** results from damage to the motor fibers, while **hyperacusis** occurs due to paralysis of the stapedius muscle, innervated by the facial nerve's branch to the stapedius. [1]
*Loss of taste in the posterior third of the tongue*
- **Taste sensation** from the posterior third of the tongue is conveyed by the **glossopharyngeal nerve (CN IX)**, not the facial nerve.
- Therefore, compression of the facial nerve at the internal acoustic meatus would not impact taste in this region.
*Loss of taste in the anterior two-thirds of the tongue*
- While the **chorda tympani nerve** (a branch of the facial nerve) carries taste from the anterior two-thirds of the tongue, this branch typically separates from the facial nerve **distal to the internal acoustic meatus**.
- Compression at the internal acoustic meatus would affect the main trunk before this branching, but other symptoms are more prominent. [1]
*Decreased salivation*
- **Salivation** (specifically from the submandibular and sublingual glands) is mediated by the **chorda tympani nerve**, a branch of the facial nerve. [1]
- Similar to taste, this branch usually separates later, and while salivation can be affected, other symptoms like facial weakness and hyperacusis are more consistently prominent with proximal compression.
*Decreased lacrimation*
- **Lacrimation** is primarily controlled by the **greater petrosal nerve**, which branches off the facial nerve earlier in its course.
- While theoretically possible with very proximal compression affecting all components, compression at the internal acoustic meatus is more commonly associated with the motor and stapedius muscle function impairments first due to the spatial arrangement of fibers.
Third pharyngeal arch derivatives US Medical PG Question 6: Where does the only cranial nerve without a thalamic relay nucleus enter the skull?
- A. Superior orbital fissure
- B. Internal auditory meatus
- C. Foramen rotundum
- D. Jugular foramen
- E. Cribriform plate (Correct Answer)
Third pharyngeal arch derivatives Explanation: ***Cribriform plate***
- The **olfactory nerve (CN I)** is the only cranial nerve that does not have a thalamic relay nucleus before reaching the cerebral cortex.
- It passes through the **cribriform plate** of the ethmoid bone to reach the olfactory bulbs.
*Superior orbital fissure*
- This opening transmits the **oculomotor (CN III), trochlear (CN IV), ophthalmic division of trigeminal (CN V1)**, and **abducens (CN VI)** nerves.
- These nerves all have sensory or motor components that relay through the thalamus, directly or indirectly.
*Internal auditory meatus*
- This canal transmits the **facial (CN VII)** and **vestibulocochlear (CN VIII)** nerves.
- The vestibulocochlear nerve's auditory pathway involves a thalamic relay in the **medial geniculate nucleus**.
*Foramen rotundum*
- The **maxillary division of the trigeminal nerve (CN V2)** passes through the foramen rotundum.
- Sensory information carried by CN V2 relays through the **thalamus**.
*Jugular foramen*
- This opening transmits the **glossopharyngeal (CN IX), vagus (CN X)**, and **accessory (CN XI)** nerves.
- Sensory components of these nerves, particularly taste and visceral sensation, involve thalamic nuclei.
Third pharyngeal arch derivatives US Medical PG Question 7: A 61-year-old man sustains an intracranial injury to a nerve that also passes through the parotid gland. Which of the following is a possible consequence of this injury?
- A. Changes in hearing (Correct Answer)
- B. Horner's syndrome
- C. Paralysis of lateral rectus muscle
- D. Loss of taste from posterior 1/3 of tongue
- E. Loss of general sensation in anterior 2/3 of tongue
Third pharyngeal arch derivatives Explanation: ***Changes in hearing***
- The **facial nerve (CN VII)** is the only cranial nerve that has both an **intracranial course** and passes **through the parotid gland**.
- The facial nerve gives off the **nerve to stapedius muscle** within the facial canal (before it exits the stylomastoid foramen).
- Damage to this nerve can lead to **hyperacusis** (increased sensitivity to sound), as the stapedius normally dampens excessive sound vibrations.
- **Note**: Facial nerve injury would also cause facial paralysis (the most prominent feature), loss of taste from anterior 2/3 of tongue via chorda tympani, and decreased lacrimation/salivation, but these are not among the answer choices.
*Horner's syndrome*
- This syndrome results from damage to the **sympathetic pathway** (hypothalamus → spinal cord → superior cervical ganglion → eye).
- Characterized by **ptosis**, **miosis**, and **anhidrosis**.
- Not related to facial nerve injury.
*Paralysis of lateral rectus muscle*
- The **lateral rectus muscle** is innervated by the **abducens nerve (CN VI)**.
- CN VI does not pass through the parotid gland.
*Loss of taste from posterior 1/3 of tongue*
- Taste from the **posterior 1/3 of the tongue** is carried by the **glossopharyngeal nerve (CN IX)**.
- CN IX does not pass through the parotid gland.
- **Note**: The facial nerve actually carries taste from the **anterior 2/3** of the tongue via the chorda tympani branch.
*Loss of general sensation in anterior 2/3 of tongue*
- **General sensation** (touch, pain, temperature) from the **anterior 2/3 of the tongue** is carried by the **lingual nerve** (branch of CN V3).
- The lingual nerve does not pass through the parotid gland.
Third pharyngeal arch derivatives US Medical PG Question 8: A 2850-g (6-lb 5-oz) newborn is delivered at term to a 19-year-old primigravid woman via normal spontaneous vaginal delivery. The mother has had no prenatal care. Examination of the newborn in the delivery room shows malformed external ears, facial nerve palsy, and absence of the stapes bone on audiological testing. This patient's condition is most likely caused by abnormal development of the structure that also gives rise to which of the following?
- A. Muscles of mastication (Correct Answer)
- B. Maxillary process
- C. Meckel's cartilage
- D. Palatine tonsil
- E. Trigeminal nerve (CN V)
Third pharyngeal arch derivatives Explanation: ***Muscles of mastication***
- The patient's presentation with **malformed external ears, facial nerve palsy (CN VII), and absence of the stapes** is characteristic of **second pharyngeal arch** abnormalities (seen in conditions like hemifacial microsomia or other branchial arch syndromes).
- The **second pharyngeal arch** (Reichert's cartilage) gives rise to the stapes, muscles of facial expression, styloid process, and is associated with CN VII (facial nerve).
- However, this question asks what else derives from "the structure" causing these findings. Since the **muscles of mastication derive from the first pharyngeal arch**, this appears to test understanding that they are NOT from the same arch as the stapes.
- **NOTE:** If this represents a combined first and second arch syndrome, then muscles of mastication (first arch) could be co-affected, making this the correct answer in that clinical context.
*Maxillary process*
- The maxillary process is derived from the **first pharyngeal arch** and forms the maxilla, zygoma, and part of the temporal bone.
- This is not derived from the second pharyngeal arch, which is primarily affected in this patient based on the stapes absence and facial nerve palsy.
*Meckel's cartilage*
- **Meckel's cartilage** is the cartilaginous component of the **first pharyngeal arch** and gives rise to the malleus, incus, anterior ligament of malleus, and sphenomandibular ligament.
- The **stapes** originates from the **second pharyngeal arch** (Reichert's cartilage), not Meckel's cartilage, making this an incorrect association.
*Palatine tonsil*
- The palatine tonsil develops from the **second pharyngeal pouch** (endoderm), not from the pharyngeal arches (mesoderm).
- Pouch derivatives are distinct from arch derivatives and are not involved in the skeletal and nerve malformations described.
*Trigeminal nerve (CN V)*
- The trigeminal nerve is the nerve of the **first pharyngeal arch** and provides sensory innervation to the face and motor innervation to the muscles of mastication.
- The **facial nerve (CN VII)** is the nerve of the **second pharyngeal arch**, which is the arch primarily affected in this clinical presentation.
Third pharyngeal arch derivatives US Medical PG Question 9: A group of investigators studying embryological defects in mice knock out a gene that is responsible for the development of the ventral wing of the third branchial pouch. A similar developmental anomaly in a human embryo is most likely to result in which of the following findings after birth?
- A. Cleft palate
- B. Discharging neck sinus (Correct Answer)
- C. Carpopedal spasm
- D. Conductive hearing loss
- E. White oral patches
Third pharyngeal arch derivatives Explanation: ***Discharging neck sinus***
- The **ventral wing of the third pharyngeal pouch** gives rise to the **thymus**
- During embryonic development, the thymus descends from the pharynx into the anterior mediastinum via the **thymopharyngeal duct**
- Normally, this duct obliterates completely, but **failure of obliteration** can result in a **cervical thymic cyst** or **persistent thymic tract**
- This presents as a **discharging neck sinus** along the lateral neck (anterior border of sternocleidomastoid), which may drain clear fluid or become infected
- This is a classic presentation of a **third pharyngeal pouch anomaly** affecting the thymic descent pathway
*Carpopedal spasm*
- **Carpopedal spasm** is a sign of **hypocalcemia** due to **hypoparathyroidism**
- The **dorsal wing** (not ventral wing) of the third pharyngeal pouch forms the **inferior parathyroid glands**
- Since the question specifically identifies a defect in the **ventral wing** (thymus), hypoparathyroidism would not result
- A dorsal wing defect would cause absent inferior parathyroid glands and hypocalcemia
*Cleft palate*
- Results from failure of **palatine shelf fusion** during weeks 8-12 of development
- Associated with **maxillary prominence** derivatives (first pharyngeal arch) and secondary palate formation
- Not related to third pharyngeal pouch development
*Conductive hearing loss*
- Associated with **first and second pharyngeal arch** derivatives affecting the middle ear structures
- First arch: malleus, incus (in part); Second arch: stapes (in part)
- The **third pharyngeal pouch** does not contribute to auditory structures
*White oral patches*
- Typically represent **mucosal lesions** (leukoplakia, candidiasis, lichen planus)
- Not associated with embryological defects of the pharyngeal apparatus
- Unrelated to third pharyngeal pouch derivatives
Third pharyngeal arch derivatives US Medical PG Question 10: A 25-year-old woman gives birth to a male child at 30 weeks of gestation. Pregnancy was complicated by polyhydramnios diagnosed on ultrasonography at 26 weeks of gestation. The baby is born vaginally weighing 1.2 kg (2.64 lb). Because he does not cry immediately after birth, endotracheal intubation is attempted to secure the airway. However, the vocal cords cannot be visualized because there is only a single opening corresponding to the esophagus. He is transferred to the NICU under bag and mask ventilation, where intubation is attempted once again by passing the endotracheal tube in the visualized opening, after which his oxygen saturation begins to improve. His temperature is 37.0ºC (98.6°F), pulse is 120/min, and respiratory rate is 42/min. On physical examination, no abnormalities are noted. Chest radiography is suggestive of respiratory distress syndrome. Which of the following most likely failed to develop in this patient?
- A. Second branchial arch
- B. Mesonephric duct
- C. Fourth and sixth branchial arches (Correct Answer)
- D. First branchial arch
- E. Third branchial arch
Third pharyngeal arch derivatives Explanation: ***Fourth and sixth branchial arches***
- The clinical presentation of **inability to visualize the vocal cords** and the presence of only a **single opening** suggests **laryngeal atresia** or severe laryngotracheal malformation. While the laryngotracheal structures primarily develop from the laryngotracheal diverticulum (an outgrowth of the foregut), the **fourth and sixth pharyngeal arches** are critical for the development of **laryngeal cartilages** and **innervation**:
- **Fourth arch**: Contributes to the thyroid cartilage, cricothyroid muscle, and superior laryngeal nerve
- **Sixth arch**: Forms the cricoid cartilage, arytenoid cartilages, and provides the recurrent laryngeal nerve (innervating all intrinsic laryngeal muscles except cricothyroid)
- Failure of proper development of these arches results in **absence or malformation of the larynx**, preventing normal vocal cord formation and airway development.
- The **polyhydramnios** occurs because the fetus cannot swallow amniotic fluid effectively due to airway obstruction.
*Second branchial arch*
- The **second branchial arch** (hyoid arch) contributes to the **stapes**, styloid process, stylohyoid ligament, lesser horn and upper body of the hyoid bone, and muscles of facial expression (via facial nerve).
- Defects in this arch typically lead to conditions like **Treacher Collins syndrome** or hemifacial microsomia, not laryngeal agenesis.
*Mesonephric duct*
- The **mesonephric duct (Wolffian duct)** is an embryonic structure crucial for the development of male internal reproductive organs including the **epididymis**, vas deferens, seminal vesicles, and ejaculatory duct.
- Failure of this duct to develop would result in male reproductive anomalies, not respiratory tract malformations.
*First branchial arch*
- The **first branchial arch** (mandibular arch) gives rise to the **maxilla, mandible, malleus, incus**, muscles of mastication, and trigeminal nerve branches.
- Malformations of this arch are associated with conditions like **Pierre Robin sequence** or mandibulofacial dysostosis, presenting with micrognathia and facial abnormalities, which are not described in this case.
*Third branchial arch*
- The **third branchial arch** forms the **greater horn and lower body of the hyoid bone**, stylopharyngeus muscle, and glossopharyngeal nerve.
- Anomalies of this arch may present with swallowing difficulties or glossopharyngeal nerve deficits, but do not cause the complete absence of laryngeal structures described in this scenario.
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