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Which of the following muscles is NOT an elevator of the mandible?
Enophthalmos is due to palsy of which muscle?
An 8-year-old boy had an extensive mastoidectomy due to an infection that did not respond to antibiotics. Postoperatively, he developed Bell's palsy (facial paralysis). A feature of this paralysis was the accumulation of saliva in the oral vestibule, leading to dribbling from the corner of his mouth. Which of the following muscles was paralyzed, causing this specific symptom?
Injury to which of the following nerves leads to paralysis of the posterior belly of the digastric muscle?
The anterior ethmoidal nerve is a branch of the nasociliary nerve. Which of the following areas is NOT supplied by the anterior ethmoidal nerve?
A 55-year-old woman has undergone facial surgery for the excision of a malignant parotid tumor. A week postoperatively, marked weakness is seen in the musculature of the patient's lower lip. Which of the following nerves was most likely injured during the parotidectomy?
Ear ossicles articulate with each other through which type of joints?
After extraction of the 3rd molar, paraesthesia occurs over the chin. This is due to the involvement of which nerve?
What is the distance of the promontory from the tympanic membrane?
Ceruminous glands are modified which of the following glands?
Head Indian Medical PG Practice Questions and MCQs
Question 121: Which of the following muscles is NOT an elevator of the mandible?
- A. Temporalis
- B. Medial pterygoid
- C. Masseter
- D. Digastric (Correct Answer)
Explanation: The muscles of mastication are responsible for the movements of the mandible at the temporomandibular joint (TMJ). These movements include elevation (closing the mouth), depression (opening the mouth), protrusion, retraction, and side-to-side movements. ### **Explanation of the Correct Answer** **D. Digastric:** This is the correct answer because the digastric muscle (specifically the anterior belly) acts as a **depressor** of the mandible. When the hyoid bone is fixed by the infrahyoid muscles, the contraction of the digastric pulls the symphysis menti downward, helping to open the mouth. It is not an elevator. ### **Analysis of Incorrect Options (Elevators)** The "elevators" of the mandible are the primary muscles of mastication that close the jaw: * **A. Temporalis:** A fan-shaped muscle that elevates the mandible. Its posterior fibers also act as the primary retractor of the jaw. * **B. Medial Pterygoid:** Often called the "internal masseter," it forms a sling with the masseter to powerfully elevate the mandible. * **C. Masseter:** The most powerful muscle of mastication; its primary action is elevation. ### **High-Yield Clinical Pearls for NEET-PG** * **Innervation Rule:** All four primary muscles of mastication (Masseter, Temporalis, Medial, and Lateral Pterygoids) are supplied by the **Mandibular nerve (V3)**. * **The "Opener":** The **Lateral Pterygoid** is the only primary muscle of mastication that helps depress (open) the mandible. Remember: "Lateral Lowers." * **Digastric Nerve Supply:** This is a common exam favorite. The **Anterior belly** is supplied by the Nerve to Mylohyoid (V3), while the **Posterior belly** is supplied by the Facial Nerve (VII). * **Gravity:** While muscles like the digastric and lateral pterygoid assist, gravity is the primary force for jaw depression in a standing position.
Question 122: Enophthalmos is due to palsy of which muscle?
- A. Levator palpebrae superioris
- B. Superior tarsal muscle
- C. Orbital muscle (Correct Answer)
- D. Inferior tarsal muscle
Explanation: **Explanation:** The correct answer is **Orbital muscle (Müller’s orbital muscle)**. **Why it is correct:** The orbital muscle is a small vestigial layer of smooth muscle that bridges the inferior orbital fissure. It is innervated by **sympathetic fibers**. In humans, its primary function is to maintain the forward position of the eyeball within the orbit. A palsy of this muscle (due to sympathetic denervation, as seen in Horner’s Syndrome) leads to a slight backward displacement of the eyeball, known as **enophthalmos**. While the enophthalmos in Horner’s syndrome is often described as "apparent" (due to the narrowing of the palpebral fissure), the paralysis of the orbital muscle is the classical anatomical explanation for true, albeit subtle, enophthalmos. **Why other options are incorrect:** * **Levator palpebrae superioris (LPS):** This is a skeletal muscle innervated by the **Oculomotor nerve (CN III)**. Its palsy results in complete ptosis, not enophthalmos. * **Superior tarsal muscle:** Also known as Müller’s superior tarsal muscle, this is a smooth muscle innervated by sympathetic fibers. Its palsy causes **partial ptosis** (drooping of the upper eyelid), a hallmark of Horner’s syndrome, but it does not affect the position of the globe. * **Inferior tarsal muscle:** This smooth muscle is located in the lower eyelid. Its palsy leads to "upside-down ptosis" (slight elevation of the lower lid), contributing to the narrowing of the palpebral fissure. **High-Yield Clinical Pearls for NEET-PG:** * **Horner’s Syndrome Tetrad:** Ptosis (partial), Miosis, Anhidrosis, and Enophthalmos. * **Innervation:** Remember that all "Müller’s muscles" (Superior tarsal, Inferior tarsal, and Orbital) are **sympathetically** innervated. * **Enophthalmos Causes:** Apart from sympathetic palsy, the most common clinical cause of enophthalmos is a **Blow-out fracture** of the orbital floor. (Note: No highly relevant textbook citations were found in the provided sources to support the specific anatomical claims of this question.)
Question 123: An 8-year-old boy had an extensive mastoidectomy due to an infection that did not respond to antibiotics. Postoperatively, he developed Bell's palsy (facial paralysis). A feature of this paralysis was the accumulation of saliva in the oral vestibule, leading to dribbling from the corner of his mouth. Which of the following muscles was paralyzed, causing this specific symptom?
- A. Zygomaticus major
- B. Orbicularis oculi
- C. Buccinator (Correct Answer)
- D. Levator palpebrae superioris
Explanation: ### Explanation **Correct Option: C. Buccinator** The clinical presentation describes **Bell’s palsy** (lower motor neuron facial nerve palsy) following mastoid surgery. The facial nerve (CN VII) is at risk during mastoidectomy as it traverses the facial canal in the petrous temporal bone. The **buccinator** muscle, supplied by the buccal branch of the facial nerve, forms the muscular substance of the cheek. Its primary functional role during mastication is to flatten the cheek against the teeth and gums. This action prevents food and saliva from accumulating in the **oral vestibule** (the space between the teeth/gums and the cheeks/lips) and directs it back toward the occlusal surfaces of the teeth. Paralysis of the buccinator leads to a loss of cheek tone, causing saliva and food boluses to pool in the vestibule, resulting in the characteristic dribbling seen in this patient. **Analysis of Incorrect Options:** * **A. Zygomaticus major:** This muscle draws the angle of the mouth upward and backward (smiling). While paralyzed in Bell’s palsy, it does not control the accumulation of fluids in the vestibule. * **B. Orbicularis oculi:** This muscle is responsible for closing the eyelids. Paralysis leads to *lagophthalmos* (inability to close the eye), not oral symptoms. * **D. Levator palpebrae superioris:** This muscle elevates the upper eyelid and is supplied by the **Oculomotor nerve (CN III)**. It is not affected in facial nerve palsy. **High-Yield Clinical Pearls for NEET-PG:** * **Hyperacusis:** Occurs in facial nerve palsy if the nerve to the **stapedius** is involved (loss of dampening of sound). * **Chorda Tympani involvement:** Leads to loss of taste (ageusia) on the anterior 2/3rd of the tongue and reduced salivation (submandibular/sublingual glands). * **Mastoid Surgery Risk:** The facial nerve is most commonly injured in its **tympanic (horizontal)** or **mastoid (vertical)** segments during middle ear surgeries.
Question 124: Injury to which of the following nerves leads to paralysis of the posterior belly of the digastric muscle?
- A. Accessory nerve
- B. Trigeminal nerve
- C. Ansa cervicalis
- D. Facial nerve (Correct Answer)
Explanation: The digastric muscle is unique because its two bellies arise from different embryological sources, each retaining the nerve supply of its respective branchial arch. **1. Why the Facial Nerve (CN VII) is correct:** The **posterior belly of the digastric** develops from the **second branchial arch**. Therefore, it is innervated by the digastric branch of the **facial nerve**, which arises just after the nerve exits the stylomastoid foramen. Injury to the facial nerve results in paralysis of this belly along with the muscles of facial expression and the stylohyoid muscle. **2. Why the other options are incorrect:** * **Trigeminal nerve (CN V):** The mandibular division ($V_3$) supplies the **anterior belly of the digastric** because it is derived from the **first branchial arch**. * **Accessory nerve (CN XI):** This nerve supplies the sternocleidomastoid and trapezius muscles. It does not innervate the suprahyoid muscles. * **Ansa cervicalis:** This loop of the cervical plexus ($C1-C3$) supplies the **infrahyoid muscles** (omohyoid, sternohyoid, and sternothyroid), except for the thyrohyoid (supplied by $C1$ via the hypoglossal nerve). **High-Yield NEET-PG Pearls:** * **Dual Nerve Supply:** The digastric muscle is a classic example of a muscle with two different nerve supplies ($V_3$ for anterior; $VII$ for posterior). * **Stylohyoid Connection:** Both the posterior belly of the digastric and the stylohyoid are 2nd arch muscles supplied by the facial nerve. * **Action:** The digastric muscle acts to depress the mandible (opening the mouth) or elevate the hyoid bone during swallowing.
Question 125: The anterior ethmoidal nerve is a branch of the nasociliary nerve. Which of the following areas is NOT supplied by the anterior ethmoidal nerve?
- A. Maxillary sinus (Correct Answer)
- B. Interior of the nasal cavity
- C. Dural sheath of the anterior cranial fossa
- D. Ethmoidal air cells
Explanation: **Explanation:** The **anterior ethmoidal nerve** is a terminal branch of the **nasociliary nerve** (a branch of the Ophthalmic division of the Trigeminal nerve, CN V1). Understanding its course is key to identifying its distribution: it leaves the orbit through the anterior ethmoidal canal, enters the anterior cranial fossa, and then descends into the nasal cavity. **Why Maxillary Sinus is the Correct Answer:** The **Maxillary sinus** is primarily supplied by the **Superior Alveolar nerves** (Anterior, Middle, and Posterior) and the **Infraorbital nerve**, all of which are branches of the **Maxillary division (CN V2)**. The anterior ethmoidal nerve (CN V1) does not contribute to its innervation. **Analysis of Incorrect Options:** * **Interior of the nasal cavity:** After passing through the cribriform plate, the nerve divides into internal nasal branches that supply the anterior part of the nasal septum and the lateral nasal wall. * **Dural sheath of the anterior cranial fossa:** As the nerve passes over the cribriform plate, it gives off meningeal branches to the dura mater of the anterior cranial fossa. * **Ethmoidal air cells:** The nerve provides sensory innervation to the **anterior and middle ethmoidal air cells** during its course through the ethmoidal canal. **High-Yield Clinical Pearls for NEET-PG:** * **External Nasal Nerve:** The anterior ethmoidal nerve terminates as the external nasal nerve, supplying the skin of the **tip and bridge of the nose**. * **Hilton’s Law Application:** The nerve supplies the ethmoidal sinuses it traverses. * **Sneeze Reflex:** The anterior ethmoidal nerve is a major afferent pathway for the sneeze reflex triggered by nasal irritants. * **Little’s Area:** While the nerve supplies the anterior septum, remember that the blood supply to this area (Kiesselbach's plexus) involves both ICA and ECA branches.
Question 126: A 55-year-old woman has undergone facial surgery for the excision of a malignant parotid tumor. A week postoperatively, marked weakness is seen in the musculature of the patient's lower lip. Which of the following nerves was most likely injured during the parotidectomy?
- A. Marginal mandibular branch of facial (Correct Answer)
- B. Zygomatic branch of facial
- C. Mandibular division of the trigeminal nerve
- D. Buccal branch of facial
Explanation: **Explanation:** The **facial nerve (CN VII)** provides motor innervation to the muscles of facial expression. After exiting the stylomastoid foramen, it enters the parotid gland and divides into five terminal branches: Temporal, Zygomatic, Buccal, Marginal Mandibular, and Cervical. 1. **Why Option A is correct:** The **Marginal Mandibular branch** supplies the muscles of the lower lip, specifically the *depressor anguli oris*, *depressor labii inferioris*, and *mentalis*. Injury to this nerve during parotid surgery is a known complication that results in drooping of the corner of the mouth and weakness in depressing the lower lip, leading to an asymmetrical smile. 2. **Why other options are incorrect:** * **Zygomatic branch:** Supplies the orbicularis oculi; injury would cause inability to close the eye tightly. * **Mandibular division of Trigeminal (V3):** Provides sensory innervation to the lower face and motor innervation to the muscles of mastication (e.g., masseter), not the muscles of facial expression. * **Buccal branch:** Supplies the buccinator and muscles of the upper lip; injury would affect cheek tension and the ability to whistle or pucker. **High-Yield NEET-PG Pearls:** * **Pes Anserinus:** The "goose's foot" pattern formed by the branching of the facial nerve within the parotid gland. * **Safe Plane:** During parotidectomy, the facial nerve is the critical landmark that divides the gland into superficial and deep lobes. * **Most common nerve injured:** The marginal mandibular nerve is particularly vulnerable because it often dips below the lower border of the mandible before ascending to the lip.
Question 127: Ear ossicles articulate with each other through which type of joints?
- A. Synostosis
- B. Synovial (Correct Answer)
- C. Synchondrosis
- D. Syndesmosis
Explanation: The ear ossicles (Malleus, Incus, and Stapes) are connected to one another by **synovial joints**, which allow for the precise movement and transmission of sound vibrations from the tympanic membrane to the oval window [1]. ### **Why Synovial is Correct:** There are two primary articulations between the ossicles: 1. **Incudomalleolar Joint:** A **saddle-type** synovial joint between the head of the malleus and the body of the incus [1]. 2. **Incudostapedial Joint:** A **ball-and-socket** synovial joint between the lentiform process of the incus and the head of the stapes [1]. These joints are lined with hyaline cartilage and contained within a fibrous capsule, facilitating the mechanical amplification of sound. ### **Why Other Options are Incorrect:** * **Synostosis (A):** This refers to the bony fusion of two bones (e.g., skull sutures in adults). If ossicles fused, it would lead to conductive hearing loss. * **Synchondrosis (C):** A primary cartilaginous joint (e.g., growth plates). Ossicular joints are mobile, not rigid cartilaginous connections. * **Syndesmosis (D):** A fibrous joint connected by ligaments (e.g., distal tibiofibular joint). While the **stapes base** is attached to the oval window by a fibrous "tympanostapedial syndesmosis," the articulations *between* the ossicles themselves are synovial [1]. ### **High-Yield Clinical Pearls for NEET-PG:** * **Otosclerosis:** Often involves the fixation of the stapes footplate (syndesmosis), leading to conductive deafness. * **Muscle Protection:** The **Tensor Tympani** (supplied by CN V3) and **Stapedius** (supplied by CN VII) dampen excessive ossicular movement to protect the inner ear from loud noises (Acoustic Reflex) [1]. * **Development:** Malleus and Incus are derived from the **1st Pharyngeal Arch** (Meckel’s cartilage), while the Stapes is derived from the **2nd Pharyngeal Arch** (Reichert’s cartilage).
Question 128: After extraction of the 3rd molar, paraesthesia occurs over the chin. This is due to the involvement of which nerve?
- A. Inferior alveolar nerve. (Correct Answer)
- B. Lingual nerve.
- C. Buccal nerve.
- D. All of the above.
Explanation: The extraction of a mandibular third molar (wisdom tooth) is a common surgical procedure that carries a risk of nerve injury due to the close anatomical proximity of specific branches of the mandibular nerve ($V_3$). ### Why Option A is Correct The **Inferior Alveolar Nerve (IAN)** runs within the mandibular canal, which is located immediately inferior to the roots of the third molar. During extraction, the nerve can be compressed or damaged. The IAN eventually exits the **mental foramen** (near the premolars) as the **mental nerve**. The mental nerve provides sensory innervation to the **skin of the chin**, the lower lip, and the labial gingiva. Therefore, damage to the IAN results in paresthesia (numbness or tingling) over the chin. ### Why Other Options are Incorrect * **B. Lingual Nerve:** This nerve lies on the lingual (tongue) side of the third molar. Injury to this nerve would cause loss of sensation and taste to the **anterior 2/3 of the tongue** and the floor of the mouth, but not the skin of the chin. * **C. Buccal Nerve:** This nerve provides sensory innervation to the **cheek** (buccal mucosa). It does not supply the chin. * **D. All of the above:** Incorrect because the sensory distribution of the lingual and buccal nerves does not include the mental region. ### High-Yield Clinical Pearls for NEET-PG * **Mental Nerve:** It is the terminal branch of the IAN. Remember: **IAN $\rightarrow$ Mental Nerve $\rightarrow$ Chin/Lower Lip.** * **Radiographic Sign:** On an OPG (Orthopantomogram), if the mandibular canal is diverted or the roots of the 3rd molar appear darkened/nicked, there is a high risk of IAN injury. * **Nerve most commonly injured:** While IAN injury is common, the **Lingual nerve** is also frequently at risk during the surgical flap reflection for 3rd molar surgery. Always distinguish between "numbness of the tongue" (Lingual) vs. "numbness of the chin" (IAN).
Question 129: What is the distance of the promontory from the tympanic membrane?
- A. 2 mm (Correct Answer)
- B. 5 mm
- C. 6 mm
- D. 7 mm
Explanation: The **middle ear (tympanic cavity)** is a narrow, air-filled space shaped like a biconcave disc [1]. Its narrowest dimension is the distance between the lateral wall (tympanic membrane) and the medial wall (labyrinthine wall). 1. **Why 2 mm is correct:** The medial wall of the middle ear features a rounded projection called the **promontory**, which is formed by the basal turn of the cochlea. Because the tympanic membrane is "tented" inwards (at the umbo), the distance between the umbo and the promontory is the narrowest part of the cavity, measuring approximately **2 mm**. 2. **Why other options are wrong:** * **5 mm:** This is the approximate distance at the floor (hypotympanum) of the middle ear. * **6 mm:** This represents the vertical and anteroposterior diameters of the tympanic cavity, but not the width. * **7 mm:** This is the approximate distance at the roof (epitympanum) of the middle ear. **High-Yield NEET-PG Pearls:** * **Dimensions of the Middle Ear:** Remember the "2-4-6" rule for the width of the cavity: 2 mm at the center (level of the promontory), 4 mm at the floor, and 6 mm at the roof. * **Promontory:** It is covered by the **tympanic plexus** (formed by the tympanic branch of the Glossopharyngeal nerve, CN IX). * **Clinical Significance:** In cases of **Glomus Jugulare** or **Glomus Tympanicum**, a "red flush" may be seen behind the tympanic membrane over the promontory (Rising Sun sign). * **Anatomy:** The promontory lies between the **fenestra vestibuli** (oval window) above and the **fenestra cochleae** (round window) below and behind.
Question 130: Ceruminous glands are modified which of the following glands?
- A. Eccrine glands
- B. Apocrine glands (Correct Answer)
- C. Sebaceous glands
- D. Holocrine glands
Explanation: The **ceruminous glands** are specialized sudoriferous (sweat) glands located in the subcutaneous layer of the external auditory canal. They are histologically classified as **modified apocrine glands**. 1. **Why Apocrine is Correct:** These glands produce a secretion that mixes with the oily sebum from sebaceous glands to form **cerumen (earwax)**. Like other apocrine glands (found in the axilla and groin), they secrete by budding off a portion of the apical cytoplasm. Their primary role is to lubricate the canal and provide a protective barrier against foreign bodies, insects, and microbes. 2. **Analysis of Incorrect Options:** * **Eccrine glands:** These are the common sweat glands found all over the body (especially palms and soles) involved in thermoregulation. They secrete via exocytosis without loss of cell cytoplasm. * **Sebaceous glands:** These are holocrine glands that secrete sebum into hair follicles. While they contribute to earwax, the ceruminous glands themselves are not modified sebaceous glands. * **Holocrine glands:** This refers to a mode of secretion where the entire cell disintegrates (e.g., sebaceous glands). Ceruminous glands do not function this way. **High-Yield Clinical Pearls for NEET-PG:** * **Location:** Ceruminous glands are found only in the **outer cartilaginous 1/3rd** of the external auditory canal. The inner 2/3rd (bony part) lacks these glands. * **Function of Cerumen:** It has an acidic pH (approx. 6.1) which inhibits bacterial and fungal growth (otomycosis). * **Other Modified Apocrine Glands:** **Moll’s glands** (eyelids) and **Mammary glands** are also important examples of modified apocrine glands frequently tested in exams.
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Skull and Facial Bones
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Scalp and Facial Muscles
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Orbit and Contents
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Temporal and Infratemporal Regions
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Pterygopalatine Fossa
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Oral Cavity
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Paranasal Sinuses
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Applied Anatomy and Clinical Correlations
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