Head — MCQs

Head Indian Medical PG Practice Questions and MCQs

Question 621: Which artery supplies the cochlea?

A. Anterior inferior cerebellar
B. Labyrinthine (Correct Answer)
C. Pontine
D. Posterior cerebral

Explanation: **Explanation:** The **labyrinthine artery** (also known as the internal auditory artery) is the primary blood supply to the inner ear, including the cochlea, vestibule, and semicircular canals. It typically arises as a branch of the **Anterior Inferior Cerebellar Artery (AICA)** (85% of cases) or directly from the **basilar artery** (15% of cases). It enters the internal acoustic meatus alongside the vestibulocochlear (CN VIII) and facial (CN VII) nerves [1]. Once it reaches the inner ear, it divides into the common cochlear artery and the vestibular arteries. **Analysis of Incorrect Options:** * **A. Anterior Inferior Cerebellar Artery (AICA):** While the labyrinthine artery usually originates from the AICA, the AICA itself primarily supplies the inferolateral surface of the cerebellum and the lower pons. The labyrinthine artery is the specific terminal branch for the cochlea. * **C. Pontine Arteries:** These are small branches of the basilar artery that supply the pons. They do not extend into the internal acoustic meatus. * **D. Posterior Cerebral Artery (PCA):** This artery supplies the occipital lobe, inferior temporal lobe, and thalamus. It is part of the posterior circulation but does not supply the auditory apparatus. **High-Yield Facts for NEET-PG:** * The labyrinthine artery is an **end artery**, meaning it lacks significant collateral circulation. Occlusion leads to sudden sensorineural hearing loss and vertigo. * **Internal Acoustic Meatus Contents:** CN VIII, CN VIII, and the Labyrinthine artery. * The **Stria Vascularis** (within the cochlear duct) is the only vascularized epithelium in the body and is responsible for producing endolymph.

Question 622: The maxillary sinus achieves its maximum size during which stage of development?

A. Birth
B. Primary dentition
C. Secondary dentition (Correct Answer)
D. Puberty

Explanation: **Explanation:** The maxillary sinus (Antrum of Highmore) is the first paranasal sinus to develop embryologically (around the 3rd month of intrauterine life). However, its growth is biphasic and intimately linked to dental development. **Why Secondary Dentition is Correct:** The floor of the maxillary sinus is initially positioned above the nasal floor. Its most significant expansion occurs during the eruption of **secondary (permanent) dentition**. As the permanent teeth erupt, the alveolar process of the maxilla increases in height, and the sinus undergoes "pneumatization," expanding inferiorly into the space previously occupied by the developing tooth buds. It reaches its maximum adult size and its floor reaches its lowest level (below the nasal floor) only after all permanent teeth have erupted. **Analysis of Incorrect Options:** * **Birth:** At birth, the sinus is merely a small slit-like cavity (approx. 3-4 mm) and is clinically insignificant. * **Primary Dentition:** While the sinus grows during the eruption of milk teeth, it is still limited in size as the maxillary body is occupied by the follicles of permanent teeth. * **Puberty:** While puberty marks the completion of facial skeletal growth, the specific physiological milestone for the maxillary sinus reaching its definitive volume is the completion of permanent tooth eruption. **High-Yield Clinical Pearls for NEET-PG:** * **Drainage:** It drains into the **middle meatus** via the hiatus semilunaris. * **Ostium:** The ostium is located superiorly on the medial wall, making natural drainage difficult in the upright position (prone to sinusitis). * **Relation:** The roots of the **1st and 2nd maxillary molars** are most closely related to the sinus floor; dental infections can lead to maxillary sinusitis, and extractions can occasionally cause oro-antral fistulas.

Question 623: Which of the following statements regarding the muscles of the tongue is FALSE?

A. Palatoglossus arises from the palatine aponeurosis and descends in the palatoglossal arch.
B. Hyoglossus protrudes the tongue forwards.
C. Genioglossus arises from the upper genial tubercle of the mandible and its upper fibers retract the tongue.
D. Styloglossus is inserted onto the dorsum of the tongue. (Correct Answer)

Explanation: ### Explanation The tongue muscles are categorized into extrinsic (change position) and intrinsic (change shape). Understanding their specific attachments and actions is crucial for NEET-PG. **1. Why Option D is the Correct (False) Statement:** The **Styloglossus** arises from the styloid process and inserts into the **side (lateral aspect)** of the tongue, interdigitating with the hyoglossus. It does not insert onto the dorsum. Its primary action is to **retract and elevate** the tongue (e.g., during swallowing). **2. Analysis of Other Options:** * **Option A (True):** The **Palatoglossus** is unique as it is the only tongue muscle arising from the palate (palatine aponeurosis) and is supplied by the **Cranial Nerve X** (via the pharyngeal plexus), unlike all others supplied by CN XII. * **Option B (True):** The **Hyoglossus** is a thin, quadrilateral muscle that primarily **depresses** the tongue. While its main role is depression, its fibers also assist in retraction; however, in the context of standard anatomy, it is often tested against the genioglossus (protrusion). *Note: Some texts emphasize its role in depression/retraction.* * **Option C (True):** The **Genioglossus** is the "safety muscle" of the tongue. It arises from the **superior genial tubercle**. Its lower fibers protrude the tongue, while its **upper fibers** (which insert into the tip) act to **retract** the tip. **Clinical Pearls for NEET-PG:** * **Safety Muscle:** Genioglossus prevents the tongue from falling back and obstructing the oropharynx. * **Nerve Supply:** All muscles (intrinsic and extrinsic) are supplied by the **Hypoglossal nerve (CN XII)** EXCEPT the Palatoglossus (CN X). * **Hypoglossal Nerve Injury:** On protrusion, the tongue deviates **towards the side of the lesion** (due to the unopposed action of the contralateral genioglossus).

Question 624: The facial nerve is classified as which of the following?

A. Mixed nerve (Correct Answer)
B. Sensory nerve
C. Motor nerve
D. Parasympathetic nerve

Explanation: **Explanation:** The **Facial Nerve (CN VII)** is classified as a **Mixed Nerve** because it contains both sensory and motor fibers, performing four distinct functional roles: 1. **Special Visceral Efferent (SVE):** The "Motor" component. It supplies the muscles of facial expression, the posterior belly of the digastric, stylohyoid, and stapedius muscles. 2. **General Visceral Efferent (GVE):** The "Parasympathetic" component. Via the nervus intermedius, it provides secretomotor supply to the lacrimal, submandibular, and sublingual glands. 3. **Special Visceral Afferent (SVA):** The "Sensory" component. It carries taste sensations from the anterior two-thirds of the tongue via the chorda tympani. 4. **General Somatic Afferent (GSA):** A minor sensory component providing cutaneous sensation to a small part of the external auditory meatus. **Why other options are incorrect:** * **Sensory nerve:** While it carries taste (SVA), it is not purely sensory (unlike CN I, II, or VIII). * **Motor nerve:** Although its primary clinical presentation involves facial movement, it carries significant autonomic and sensory fibers, making "Mixed" the more accurate classification. * **Parasympathetic nerve:** It *carries* parasympathetic fibers, but this is only one of its four functional components. **NEET-PG High-Yield Pearls:** * **Nucleus Ambiguus vs. Facial Nucleus:** The motor fibers originate from the facial nucleus in the pons, which loops around the abducens nucleus (Internal Genu). * **Nervus Intermedius (of Wrisberg):** This is the part of the facial nerve that specifically carries the sensory and parasympathetic fibers. * **Clinical Correlation:** Lesions at the **Stylomastoid Foramen** (Bell’s Palsy) result in pure motor loss, whereas lesions within the **Facial Canal** can affect taste (chorda tympani) and lacrimation (greater petrosal nerve).

Question 625: Loss of lacrimation occurs due to injury of which nerve?

A. Nasocilliary nerve
B. Greater petrosal nerve (Correct Answer)
C. Anterior ethmoidal nerve
D. Supraorbital nerve

Explanation: ### Explanation The correct answer is **Greater petrosal nerve**. **1. Why the Greater Petrosal Nerve is correct:** Lacrimation (tear production) is controlled by the **parasympathetic nervous system**. The pathway begins in the **lacrimatory nucleus** (pons), with fibers traveling via the facial nerve (CN VII). These fibers branch off at the geniculate ganglion as the **greater petrosal nerve**. This nerve carries preganglionic parasympathetic fibers to the **pterygopalatine ganglion**, where they synapse. Postganglionic fibers then travel via the maxillary nerve (V2), the zygomatic nerve, and finally the lacrimal nerve to reach the lacrimal gland. Injury to the greater petrosal nerve interrupts this secretomotor pathway, leading to a dry eye (xerophthalmia). **2. Why the other options are incorrect:** * **Nasociliary nerve (A):** A branch of the ophthalmic nerve (V1) that provides sensory innervation to the eyeball and ethmoidal sinuses. It does not carry secretomotor fibers for lacrimation. * **Anterior ethmoidal nerve (C):** A branch of the nasociliary nerve providing sensation to the nasal cavity and the skin of the bridge of the nose. * **Supraorbital nerve (D):** A branch of the frontal nerve (V1) providing sensory innervation to the forehead and upper eyelid. **3. NEET-PG High-Yield Pearls:** * **Schirmer’s Test:** Used clinically to evaluate lacrimation. * **Crocodile Tears Syndrome:** Occurs during recovery from Bell’s Palsy when regenerating gustatory fibers (intended for the submandibular gland) are misdirected into the greater petrosal nerve, causing tearing while eating. * **Deep Petrosal Nerve:** Carries sympathetic fibers (vasoconstrictive) and joins the greater petrosal nerve to form the **Nerve of the Pterygoid Canal (Vidian nerve)**.

Question 626: The posterior belly of the digastric muscle is attached to which bony landmark?

A. Styloid process
B. Hyoid bone
C. Mastoid notch (Correct Answer)
D. Thyroid cartilage

Explanation: **Explanation:** The **digastric muscle** is a unique suprahyoid muscle consisting of two bellies connected by an intermediate tendon. The **posterior belly** originates from the **mastoid notch** (digastric fossa), which is a deep groove located on the medial aspect of the mastoid process of the temporal bone. From here, it passes downwards and forwards toward the hyoid bone. **Analysis of Options:** * **A. Styloid process:** This is the origin of the *stylohyoid* muscle. While the posterior belly of the digastric passes deep to the stylohyoid, it does not attach to this process. * **B. Hyoid bone:** Both bellies of the digastric are connected to the hyoid bone via an intermediate tendon held by a fibrous pulley, but the hyoid is the *insertion* area, not the specific origin point of the posterior belly. * **D. Thyroid cartilage:** No part of the digastric muscle attaches to the thyroid cartilage; muscles attaching here include the thyrohyoid and sternothyroid. **High-Yield NEET-PG Pearls:** 1. **Dual Nerve Supply:** This is a classic exam favorite. The **anterior belly** is derived from the 1st branchial arch (**Nerve to Mylohyoid**, a branch of CN V3), while the **posterior belly** is derived from the 2nd branchial arch (**Facial Nerve**, CN VII). 2. **Relations:** The posterior belly serves as a key surgical landmark; the **occipital artery** runs along its lower border, and it forms the posterosuperior boundary of the **carotid triangle**. 3. **Action:** It depresses the mandible when the hyoid is fixed and elevates the hyoid during swallowing.

Question 627: Which structure does not traverse the parotid gland?

A. Superficial temporal artery
B. Posterior auricular artery
C. External carotid artery
D. Internal carotid artery (Correct Answer)

Explanation: The parotid gland is a major salivary gland that acts as a "crossroad" for several important neurovascular structures. Understanding the relationship between these structures is high-yield for NEET-PG. ### **Explanation** The **Internal Carotid Artery (ICA)** does not traverse the parotid gland. After its origin at the carotid bifurcation, the ICA ascends deep to the parotid gland and the styloid process to enter the skull via the carotid canal. It is separated from the gland by the styloid process and its associated muscles. ### **Analysis of Options** * **External Carotid Artery (ECA):** This is the deepest structure traversing the gland. It enters the lower part of the gland, ascends, and divides into its two terminal branches (Maxillary and Superficial Temporal arteries) within the parotid substance. * **Superficial Temporal Artery:** As one of the terminal branches of the ECA, it arises within the parotid gland and emerges from its superior border. * **Posterior Auricular Artery:** This is a branch of the ECA that typically arises within or just deep to the parotid gland before heading posteriorly. ### **High-Yield NEET-PG Pearls** 1. **Order of structures (Deep to Superficial):** * **Deep:** External Carotid Artery (and its branches). * **Middle:** Retromandibular Vein (formed by the union of Maxillary and Superficial Temporal veins). * **Superficial:** Facial Nerve (CN VII) and its five terminal branches. 2. **Facial Nerve:** It enters the gland through the posteromedial surface and divides the gland into a "superficial" and "deep" lobe (separated by the **Plane of Patey**). 3. **Stensen’s Duct:** Opens into the vestibule of the mouth opposite the **crown of the upper second molar tooth**.

Question 628: Which of the following is true regarding the palatine tonsil?

A. It lies on the middle constrictor muscle.
B. It drains into the submandibular lymph nodes.
C. It is supplied by the facial artery. (Correct Answer)
D. It is innervated by the pharyngeal plexus.

Explanation: The palatine tonsil is a collection of lymphoid tissue located in the tonsillar fossa of the lateral oropharyngeal wall. **Correct Answer: C. It is supplied by the facial artery.** The primary arterial supply to the palatine tonsil is the **tonsillar artery**, which is a direct branch of the **facial artery**. This is the most significant vessel providing blood to the tonsil. Other contributors include the ascending pharyngeal, lingual (dorsal lingual branches), and palatine (descending and ascending) arteries. **Explanation of Incorrect Options:** * **A. It lies on the middle constrictor muscle:** The tonsillar bed is primarily formed by the **superior constrictor** muscle and the styloglossus. The middle constrictor lies inferior to this region. * **B. It drains into the submandibular lymph nodes:** Lymphatic drainage of the palatine tonsil passes through the superior constrictor to the **jugulodigastric node** (also known as the "tonsillar node"), which belongs to the deep cervical group. * **C. It is innervated by the pharyngeal plexus:** The sensory nerve supply is primarily via the **glossopharyngeal nerve (CN IX)** and the lesser palatine nerves. This explains why tonsillitis often presents with referred ear pain (via the tympanic branch of CN IX). **High-Yield Clinical Pearls for NEET-PG:** * **Tonsillar Bed:** The **external palatine vein** (paratonsillar vein) is the most common cause of hemorrhage during tonsillectomy. * **Internal Carotid Artery:** Lies approximately 2.5 cm posterolateral to the tonsil and is generally safe during surgery unless tortuous. * **Waldeyer’s Ring:** The palatine tonsils form the lateral components of this protective lymphoid ring.

Question 629: The crus commune is a part of which structure?

A. Cochlea
B. Middle ear
C. Semicircular canal (Correct Answer)
D. Vestibule

Explanation: ### Explanation **Correct Option: C (Semicircular canal)** The **crus commune** (common limb) is a specific anatomical feature of the bony and membranous labyrinth of the internal ear. There are three semicircular canals: anterior (superior), posterior, and lateral. While the lateral canal has two independent openings into the vestibule, the **medial end of the anterior canal** and the **upper end of the posterior canal** fuse together to form a single common duct—the crus commune [1]. This structure then opens into the medial wall of the vestibule. **Analysis of Incorrect Options:** * **A. Cochlea:** This is the snail-shaped organ responsible for hearing. It consists of the scala vestibuli, scala tympani, and scala media, but does not contain a crus commune. * **B. Middle Ear:** This is an air-filled cavity containing the ossicles (malleus, incus, stapes) [1]. The crus commune is a part of the internal ear (inner ear), not the middle ear. * **D. Vestibule:** While the crus commune *opens into* the vestibule, it is developmentally and structurally considered a part of the semicircular canal system. The vestibule itself contains the utricle and saccule [1]. **NEET-PG High-Yield Pearls:** * **Total Openings:** There are 3 semicircular canals, but they only have **5 openings** into the vestibule (instead of 6) because of the crus commune. * **Ampulla:** Each semicircular canal has one dilated end called the ampulla, which contains the **crista ampullaris** (sensory organ for kinetic balance) [1]. * **Innervation:** The semicircular canals are supplied by the vestibular nerve (CN VIII) [2]. * **Orientation:** The lateral semicircular canal is tilted backwards at an angle of **30 degrees** to the horizontal plane.

Question 630: Which of the following muscles are innervated by the facial nerve?

A. Risorius, Anterior belly of digastric, Zygomaticus
B. Anterior belly of digastric, Lateral pterygoid, Auricular muscles
C. Zygomaticus, Risorius, Auricular muscles (Correct Answer)
D. Auricular muscles, Risorius, Lateral pterygoid

Explanation: The **Facial Nerve (CN VII)** is the nerve of the **second pharyngeal arch**. It provides motor innervation to all muscles of facial expression, the posterior belly of the digastric, stylohyoid, and the stapedius muscle. **Why Option C is Correct:** * **Zygomaticus (Major & Minor):** Muscles of facial expression (elevators of the angle of the mouth). * **Risorius:** A muscle of facial expression (retracts the angle of the mouth). * **Auricular muscles (Anterior, Superior, Posterior):** Vestigial muscles that move the auricle, all derived from the second arch and supplied by the facial nerve. **Why Other Options are Incorrect:** * **Anterior belly of digastric (Options A & B):** This muscle is derived from the **first pharyngeal arch** and is therefore supplied by the **nerve to mylohyoid** (a branch of the mandibular nerve, V3). Only the *posterior* belly is supplied by the facial nerve. * **Lateral pterygoid (Options B & D):** This is a muscle of mastication, derived from the **first pharyngeal arch**, and is supplied by the **mandibular nerve (V3)**. **High-Yield Clinical Pearls for NEET-PG:** * **The "Two-Belly" Rule:** The Digastric and Digastric-like muscles have dual innervation. The **Anterior belly of digastric** and **Tensor tympani** (1st arch) are supplied by CN V3; the **Posterior belly of digastric** and **Stapedius** (2nd arch) are supplied by CN VII. * **Extracranial Course:** After exiting the **stylomastoid foramen**, the facial nerve gives off the posterior auricular nerve before entering the parotid gland to divide into its five terminal branches (Temporal, Zygomatic, Buccal, Marginal Mandibular, Cervical). * **Clinical Sign:** In **Bell’s Palsy** (LMN lesion), all muscles of facial expression on the ipsilateral side are affected, including the inability to wrinkle the forehead.

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