Head — MCQs

A patient presents with mandibular nerve neuralgia due to herpes zoster infection within the mandibular division of the left trigeminal nerve. The patient experiences difficulty with mandibular protrusion, and the mandible deviates to the left side during protrusion. Which muscle is most probably affected?

Head Indian Medical PG Practice Questions and MCQs

Question 951: Which is the first permanent tooth to erupt?

A. First premolar
B. Second premolar
C. First molar (Correct Answer)
D. Second molar

Explanation: The eruption of permanent teeth is a high-yield topic in Anatomy and Pedodontics. The correct answer is the **First Molar (Option C)**. ### **Explanation of the Correct Answer** The **permanent first molar** is the first permanent tooth to erupt into the oral cavity, typically appearing at **6 years of age**. Because of this timing, it is often referred to as the **"6-year molar."** Crucially, the first molar is **not a succedaneous tooth** (it does not replace a primary tooth). Instead, it erupts posterior to the deciduous second molar. This often leads parents to mistake it for a primary tooth, making it highly susceptible to early dental caries. ### **Analysis of Incorrect Options** * **A & B (Premolars):** Premolars are succedaneous teeth that replace the deciduous molars. The first premolar typically erupts at **10–11 years**, and the second premolar at **11–12 years**. * **D (Second Molar):** The permanent second molar erupts much later, usually around **12–13 years** of age (the "12-year molar"). ### **High-Yield Clinical Pearls for NEET-PG** * **Eruption Sequence:** The general sequence for permanent mandibular teeth is: **1st Molar → Central Incisor → Lateral Incisor → Canine → 1st Premolar → 2nd Premolar → 2nd Molar → 3rd Molar.** * **The "Rule of 6s":** * 6 months: First primary tooth (Lower central incisor). * 6 years: First permanent tooth (First molar). * **Mixed Dentition Period:** This begins with the eruption of the permanent first molar (age 6) and ends when the last primary tooth is shed (usually age 12). * **Calcification:** The permanent first molar is the only permanent tooth that begins to calcify **at birth**.

Question 952: All are true of the mandibular nerve except?

A. Sensory branch arises from the anterior trunk.
B. Muscles of mastication are innervated only by branches of the main trunk. (Correct Answer)
C. Nerve to medial pterygoid arises from the main trunk.
D. Buccal nerve supplies the skin and mucous membrane related to the buccinator.

Explanation: The **Mandibular Nerve (V3)** is the largest branch of the trigeminal nerve and is unique because it contains both sensory and motor fibers. It exits the skull through the **foramen ovale** and divides into a short main trunk, followed by an anterior and a posterior division. ### **Explanation of Options** * **Option B (Correct Answer):** This statement is **false**. The muscles of mastication are supplied by different parts of the nerve: * **Main Trunk:** Supplies the Medial Pterygoid. * **Anterior Division:** Supplies the Masseter, Temporalis, and Lateral Pterygoid. * *Note:* The Nerve to Mylohyoid (from the posterior division) supplies the Mylohyoid and anterior belly of the digastric. * **Option A:** This is **true**. The anterior division is primarily motor, but it gives off one sensory branch: the **Buccal nerve** (Long buccal nerve). * **Option C:** This is **true**. The main trunk gives off two branches before dividing: the **Nervus spinosus** (sensory to dura) and the **Nerve to medial pterygoid** (motor). * **Option D:** This is **true**. The buccal nerve is purely sensory; it pierces the buccinator muscle but does **not** supply it (the buccinator is supplied by the facial nerve). It provides sensation to the skin of the cheek and the internal mucous membrane. ### **High-Yield NEET-PG Pearls** * **Foramen Ovale Contents (MALE):** **M**andibular nerve, **A**ccessory meningeal artery, **L**esser petrosal nerve, **E**missary veins. * **Otics Ganglion:** Topographically related to the mandibular nerve; the nerve to the medial pterygoid passes through it without relaying. * **Auriculotemporal Nerve:** Arises by two roots encircling the **middle meningeal artery**; it carries postganglionic parasympathetic fibers to the parotid gland.

Question 953: Which of the following muscles is responsible for facial expression during smiling?

A. Zygomaticus major (Correct Answer)
B. Levator labii superioris
C. Levator anguli oris
D. Procerus

Explanation: The muscles of facial expression are unique as they originate from bone or fascia and insert into the skin, all being supplied by the **Facial Nerve (CN VII)**. **Correct Option: A. Zygomaticus major** The Zygomaticus major is known as the **"Laughing muscle"** or the primary muscle of smiling. It originates from the zygomatic bone and inserts into the angle of the mouth (modiolus). Its primary action is to pull the angle of the mouth upward and laterally, creating a smile. **Explanation of Incorrect Options:** * **B. Levator labii superioris:** This muscle elevates the upper lip. It is primarily involved in expressing disdain or sadness, not the broad action of smiling. * **C. Levator anguli oris:** While it helps elevate the corner of the mouth, it is more specifically associated with "sneering" or deepening the nasolabial furrow. * **D. Procerus:** This is a muscle of the nose/forehead region. It pulls the medial angle of the eyebrows down, producing transverse wrinkles over the bridge of the nose, typically seen in expressions of anger or concentration. **High-Yield Clinical Pearls for NEET-PG:** * **The Modiolus:** A chiasma of facial muscles (including zygomaticus major, buccinator, and depressor anguli oris) located at the corner of the mouth; it is crucial for mouth stability. * **Risorius:** Known as the "grinning muscle," it pulls the angle of the mouth laterally but does not elevate it like the zygomaticus major. * **Bell’s Palsy:** Lower motor neuron lesion of the facial nerve leading to paralysis of all these muscles on the ipsilateral side, resulting in the inability to smile or close the eye.

Question 954: Through which foramen does the maxillary nerve transmit?

A. Foramen ovale
B. Foramen rotundum (Correct Answer)
C. Foramen lacerum
D. Foramen spinosum

Explanation: The **Maxillary nerve (V2)** is the second division of the Trigeminal nerve (CN V). It is a purely sensory nerve that originates from the trigeminal ganglion and exits the middle cranial fossa through the **Foramen rotundum** to enter the pterygopalatine fossa. ### **Analysis of Options:** * **Foramen rotundum (Correct):** Located in the greater wing of the sphenoid bone, it specifically transmits the maxillary nerve. A high-yield mnemonic to remember the branches of the Trigeminal nerve and their foramina is **"Standing Room Only"**: * **S**uperior orbital fissure: **O**phthalmic nerve (V1) * Foramen **R**otundum: **M**axillary nerve (V2) * Foramen **O**vale: **M**andibular nerve (V3) * **Foramen ovale:** Transmits the Mandibular nerve (V3), Accessory meningeal artery, Lesser petrosal nerve, and Emissary veins (Mnemonic: **MALE**). * **Foramen lacerum:** In life, this foramen is filled with cartilage. No major structure passes *completely through* it vertically, though the internal carotid artery passes horizontally across its superior aspect. * **Foramen spinosum:** Transmits the **Middle meningeal artery**, middle meningeal vein, and the nervous spinosus (meningeal branch of V3). ### **Clinical Pearls for NEET-PG:** * **Trigeminal Neuralgia:** Often involves the V2 or V3 distributions. Surgical decompression may target these foramina. * **Pterygopalatine Fossa:** The Foramen rotundum is the "entry gate" for V2 into this fossa, where it gives off branches like the zygomatic and infraorbital nerves. * **Skull Base Fractures:** Fractures involving the greater wing of the sphenoid can result in anesthesia over the mid-face (cheek and upper lip) due to V2 injury at the foramen rotundum.

Question 955: Hypophysis cerebri is supplied by which artery?

A. Internal carotid artery. (Correct Answer)
B. External carotid artery.
C. Maxillary artery.
D. Facial artery.

Explanation: The **Hypophysis cerebri (Pituitary gland)** is a vital endocrine organ located in the sella turcica of the sphenoid bone. Its blood supply is derived exclusively from branches of the **Internal Carotid Artery (ICA)** [1]. Specifically, the gland is supplied by: 1. **Superior Hypophyseal Arteries:** Arising from the cerebral (supraclinoid) part of the ICA. They supply the adenohypophysis via the hypophyseal portal system [1]. 2. **Inferior Hypophyseal Arteries:** Arising from the cavernous part of the ICA. They primarily supply the neurohypophysis [1]. **Analysis of Incorrect Options:** * **External Carotid Artery (B):** Supplies the exterior of the cranium, face, and neck. While it has branches that enter the skull (like the middle meningeal), it does not directly supply the pituitary gland. * **Maxillary Artery (C):** A terminal branch of the External Carotid Artery. It supplies deep structures of the face, teeth, and nasal cavity, but not the intracranial endocrine glands. * **Facial Artery (D):** A branch of the External Carotid Artery that supplies the superficial structures of the face. **High-Yield Clinical Pearls for NEET-PG:** * **Hypophyseal Portal System:** The superior hypophyseal artery forms a primary capillary plexus in the median eminence. This system is crucial for transporting hypothalamic-releasing hormones to the anterior pituitary. * **Venous Drainage:** Blood from the pituitary drains into the neighboring **cavernous sinuses**. * **Relation:** The optic chiasm lies superior to the pituitary gland; hence, a pituitary tumor often causes **bitemporal hemianopia** due to upward compression. * **Development:** The anterior lobe (adenohypophysis) develops from **Rathke’s pouch** (ectoderm of the stomodeum), while the posterior lobe (neurohypophysis) develops from the **neuroectoderm** of the forebrain.

Question 956: While giving the releasing incision in a three-cornered flap during third molar surgical removal, which of the following structures is at risk of damage?

A. Facial artery
B. Buccal artery (Correct Answer)
C. Mental nerve
D. Facial lymph node

Explanation: Explanation: In the surgical removal of an impacted mandibular third molar, a **three-cornered flap** (Ward’s incision) is commonly used. This involves a sulcular incision and a **vertical releasing incision** that typically extends from the mesio-buccal corner of the second molar down into the vestibular mucosa. **Why Buccal Artery is the Correct Answer:** The **buccal artery** (a branch of the second part of the maxillary artery) travels along the external surface of the buccinator muscle to supply the cheek and the buccal gingiva of the molar region. During the vertical releasing incision, if the cut is extended too far into the mucobuccal fold or made too posteriorly, the buccal artery or its terminal branches are at direct risk of transection, leading to significant bleeding. **Analysis of Incorrect Options:** * **Facial Artery:** This artery crosses the lower border of the mandible at the anterior border of the masseter. It is located much more anteriorly and inferiorly than the standard site for a third molar incision. * **Mental Nerve:** This nerve exits the mental foramen, typically located between the first and second mandibular premolars. It is far anterior to the third molar surgical site. * **Facial Lymph Node:** These are inconsistent nodes located along the facial artery (e.g., mandibular or buccal nodes). While they exist in the cheek, they are not the primary structure at risk during a controlled intraoral gingival incision. **High-Yield Clinical Pearls for NEET-PG:** * **Lingual Nerve:** This is the structure most at risk during the **distal extension** of the incision (the "distal wedge"). To avoid it, the incision must be directed laterally (buccally) toward the external oblique ridge. * **Incision Rule:** Always place the releasing incision on the **mesial** aspect of the flap to maintain a good blood supply and avoid the mental nerve. * **Flap Design:** A three-cornered flap provides better access than an envelope flap but carries a higher risk of postoperative swelling and potential damage to the buccal vessels.

Question 957: Elevation of the mandible is primarily caused by all of the following muscles EXCEPT:

A. Masseter
B. Temporalis
C. Medial pterygoid
D. Lateral pterygoid (Correct Answer)

Explanation: ### Explanation The muscles of mastication are a high-yield topic in Head and Neck Anatomy. To answer this question, one must distinguish between the muscles that close the jaw (elevators) and those that open it (depressors). **1. Why Lateral Pterygoid is the Correct Answer:** The **Lateral Pterygoid** is the only muscle of mastication primarily responsible for **depression** (opening) of the mandible. It has two heads; the inferior head pulls the condyle of the mandible forward (protrusion) and downward along the articular eminence, which results in the opening of the mouth. Because it performs the opposite action of elevation, it is the correct "EXCEPT" choice. **2. Why the Other Options are Incorrect:** * **Masseter (A):** The strongest muscle of mastication. Its primary action is the **elevation** of the mandible to close the jaw. * **Temporalis (B):** A fan-shaped muscle. Its anterior vertical fibers **elevate** the mandible, while its posterior horizontal fibers retract it. * **Medial Pterygoid (C):** Often called the "internal masseter," it forms a functional sling with the masseter to **elevate** the mandible. **3. NEET-PG High-Yield Pearls:** * **Innervation:** All four muscles of mastication are supplied by the **Mandibular Nerve (V3)**, specifically the anterior division (except the nerve to medial pterygoid, which comes from the main trunk). * **The "Lateral" Rule:** Remember: **L**ateral pterygoid **L**owers the jaw; **M**edial pterygoid **M**oves it up. * **Protrusion:** Both pterygoids (Lateral and Medial) acting together cause protrusion. * **Side-to-side movements:** Achieved by the alternate contraction of the lateral and medial pterygoids of both sides.

Question 958: What is the sensory supply to the upper part of the right cheek?

A. Ophthalmic nerve
B. Maxillary nerve (Correct Answer)
C. Mandibular nerve
D. Cervical plexus

Explanation: **Explanation:** The sensory innervation of the face is primarily provided by the three divisions of the **Trigeminal Nerve (CN V)**. The face is embryologically derived from the pharyngeal arches, and each division of the trigeminal nerve supplies a specific territory: 1. **Maxillary Nerve (V2) - Correct Answer:** This division supplies the middle third of the face. Specifically, it provides sensory innervation to the **upper cheek**, lower eyelid, side of the nose, and upper lip. The key terminal branch involved here is the **infraorbital nerve**, which emerges through the infraorbital foramen to supply the skin of the cheek. **Analysis of Incorrect Options:** * **Ophthalmic Nerve (V1):** Supplies the upper third of the face, including the forehead, scalp (up to the vertex), and the bridge of the nose. * **Mandibular Nerve (V3):** Supplies the lower third of the face, including the lower cheek (over the mandible), lower lip, and the chin. It also provides motor supply to the muscles of mastication. * **Cervical Plexus:** Branches like the Great Auricular nerve (C2, C3) supply the skin over the angle of the mandible and the parotid gland area, but not the upper cheek. **High-Yield Clinical Pearls for NEET-PG:** * **Trigeminal Neuralgia:** Most commonly involves the V2 and V3 distributions, causing lancinating pain in the cheek or jaw. * **The Angle of the Mandible:** This is a classic "trap" in exams; it is **not** supplied by the Trigeminal nerve but by the **Great Auricular Nerve (C2, C3)**. * **Zygomaticofacial Nerve:** A branch of V2 specifically responsible for the prominence of the cheek.

Question 959: Which branch of the facial nerve conveys the secretomotor impulse involved in lacrimation?

A. Chorda tympani nerve
B. Deep petrosal nerve
C. Greater petrosal nerve (Correct Answer)
D. Lesser petrosal nerve

Explanation: ### Explanation The **Greater Petrosal Nerve (GPN)** is the first branch of the facial nerve (CN VII), arising from the geniculate ganglion. It carries **preganglionic parasympathetic (secretomotor)** fibers destined for the lacrimal gland. #### Why the Correct Answer is Right: The pathway for lacrimation is a high-yield sequence: 1. **Origin:** Lacrimatory nucleus (Pons). 2. **Course:** Fibers travel via the Nervus Intermedius to the geniculate ganglion, exiting as the **Greater Petrosal Nerve**. 3. **Relay:** The GPN joins the deep petrosal nerve to form the **Nerve of the Pterygoid Canal (Vidian nerve)**, which synapses in the **Pterygopalatine ganglion**. 4. **Target:** Postganglionic fibers hitchhike along the Maxillary nerve (V2) → Zygomatic nerve → Lacrimal nerve (V1) to reach the **Lacrimal gland**. #### Why Other Options are Wrong: * **Chorda tympani nerve:** Carries taste from the anterior 2/3 of the tongue and secretomotor fibers to the submandibular and sublingual salivary glands. * **Deep petrosal nerve:** Carries **sympathetic** (vasoconstrictor) fibers from the internal carotid plexus; it does not have a secretomotor function. * **Lesser petrosal nerve:** A branch of the **Glossopharyngeal nerve (CN IX)** via the tympanic plexus, carrying secretomotor fibers to the **parotid gland** (synapsing at the Otic ganglion). #### NEET-PG High-Yield Pearls: * **Schirmer’s Test:** Used clinically to assess GPN function by measuring tear production. * **Crocodile Tears Syndrome (Bogorad’s Syndrome):** Occurs due to misdirected regeneration of nerve fibers after facial nerve injury, where GPN fibers grow toward the submandibular ganglion (or vice versa), causing lacrimation while eating. * **Vidian Nerve:** Formed by GPN (Parasympathetic) + Deep Petrosal (Sympathetic).

Question 960: A patient presents with mandibular nerve neuralgia due to herpes zoster infection within the mandibular division of the left trigeminal nerve. The patient experiences difficulty with mandibular protrusion, and the mandible deviates to the left side during protrusion. Which muscle is most probably affected?

A. Lateral pterygoid on the right side
B. Medial pterygoid on the left and Lateral pterygoid on the left
C. Medial pterygoid on the right and Lateral pterygoid on the left
D. Lateral pterygoid on the left side (Correct Answer)

Explanation: ### Explanation **1. Why the Correct Answer is Right:** The **Lateral Pterygoid** is the primary muscle responsible for the **protrusion** of the mandible. It acts by pulling the condyle and the articular disc forward. * **Mechanism of Deviation:** Under normal conditions, the bilateral contraction of both lateral pterygoids results in symmetrical protrusion. If the **left** lateral pterygoid is paralyzed (due to mandibular nerve involvement), the **right** lateral pterygoid acts unopposed. * As the right muscle pushes its side of the mandible forward and toward the midline, the paralyzed left side remains stationary, causing the mandible to **deviate toward the side of the lesion** (the left). **2. Why the Other Options are Wrong:** * **Option A:** If the right lateral pterygoid were affected, the mandible would deviate to the *right* side during protrusion. * **Options B & C:** While the medial pterygoid assists in protrusion, its primary role is elevation (closing the jaw). The lateral pterygoid is the "prime mover" for protrusion. Furthermore, the question specifies a unilateral deviation; involving muscles on both sides (Option C) or multiple muscles unnecessarily (Option B) does not fit the classic clinical presentation of a unilateral nerve lesion. **3. NEET-PG High-Yield Pearls:** * **Rule of Deviation:** In cranial nerve lesions, the **Tongue** (CN XII) and the **Jaw** (CN V3) always deviate **TOWARD** the side of the lesion. (In contrast, the Uvula deviates *away* from the side of a CN X lesion). * **Lateral Pterygoid Anatomy:** It is the only muscle of mastication that **opens** the jaw (depresses the mandible). All others (medial pterygoid, masseter, temporalis) close it. * **Innervation:** All muscles of mastication are supplied by the **mandibular division of the trigeminal nerve (V3)**, specifically the anterior division (except for the nerve to the medial pterygoid, which arises from the main trunk).

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