Head — MCQs

Head Indian Medical PG Practice Questions and MCQs

Question 1201: Most common wall involved in blow out fracture of orbit is

A. Superior
B. Medial
C. Inferior (Correct Answer)
D. Lateral

Explanation: ***Inferior*** - The **inferior orbital wall** (floor) is the weakest wall due to the presence of the **infraorbital groove and canal**, making it most susceptible to fracture from increased intraorbital pressure. - A fracture here can lead to entrapment of the **inferior rectus** or **inferior oblique muscles**, causing diplopia and enophthalmos. *Superior* - The **superior orbital wall** (roof) is thick and primarily composed of the frontal bone, making it strong and less commonly fractured. - Fractures of the roof are usually associated with severe trauma to the **frontal bone**. *Medial* - The **medial orbital wall** is thin, especially the lamina papyracea, and is the second most common site for blow-out fractures. - However, it is generally stronger than the inferior wall and is covered by the **ethmoid air cells**. *Lateral* - The **lateral orbital wall** is the strongest of the orbital walls due to its composition of the thick frontal process of the zygomatic bone and the greater wing of the sphenoid. - Fractures here are uncommon and typically occur with **high-impact trauma**.

Question 1202: Which intraocular muscle inserts closest to the limbus?

A. Lateral Rectus
B. Superior Rectus
C. Inferior Rectus
D. Medial Rectus (Correct Answer)

Explanation: The medials rectus muscle has the closest insertion point to the limbus, typically inserting about 5.5 mm from it. This muscle is responsible for adduction of the eye (moving the eye inward) [1]. Lateral Rectus - The lateral rectus muscle inserts approximately 6.9 mm from the limbus, which is a greater distance than the medial rectus. - This muscle is responsible for abduction of the eye (moving the eye outward) [1]. Superior Rectus - The superior rectus muscle inserts around 7.7 mm from the limbus, making its insertion further away than both the medial and lateral recti. - It primarily moves the eye upward (elevation) and also contributes to adduction and intorsion [1]. Inferior Rectus - The inferior rectus muscle inserts roughly 6.5 mm from the limbus, placing it further from the limbus than the medial rectus. - This muscle primarily moves the eye downward (depression) and also contributes to adduction and extorsion [1].

Question 1203: Lateral movement of condyle is caused by:

A. Contralateral lateral pterygoid muscle (Correct Answer)
B. Bilateral contraction of lateral pterygoid muscle
C. Both lateral and medial pterygoid muscle
D. Ipsilateral lateral pterygoid muscle

Explanation: ***Contralateral lateral pterygoid muscle*** - The **lateral pterygoid muscle** is primarily responsible for **protrusion** of the mandible and **lateral movements**. - When **one lateral pterygoid contracts unilaterally**, it pulls its condyle **forward and medially**, causing the mandible to deviate to the **opposite side**. - Therefore, for a condyle to move **laterally** (working side), the **contralateral lateral pterygoid** must contract. - Example: **Right lateral pterygoid contraction** → right condyle moves anteromedially → **left condyle** performs lateral excursion. *Bilateral contraction of lateral pterygoid muscle* - **Bilateral contraction** of the lateral pterygoid muscles causes **protrusion** of the mandible, not lateral movement. - This action moves both condyles forward equally, bringing the jaw straight out without deviation. *Both lateral and medial pterygoid muscle* - While both muscles are involved in mastication, the **medial pterygoid primarily elevates and protrudes** the mandible. - The **lateral pterygoid alone** is responsible for lateral deviation through unilateral contraction. - Their combined action does not specifically produce isolated **lateral condylar movement**. *Ipsilateral lateral pterygoid muscle* - Contraction of the **ipsilateral lateral pterygoid** pulls the condyle on the **same side** forward and medially. - This causes the mandible to deviate **away from the contracting muscle** (to the opposite side). - Therefore, ipsilateral contraction would **not** cause that same condyle to move laterally; instead, it moves anteromedially while the opposite condyle performs the lateral excursion.

Question 1204: Valve of Hasner is present at

A. Common bile duct
B. Maxillary Sinus
C. Naso lacrimal duct (Correct Answer)
D. Stenson's duct

Explanation: ***Naso lacrimal duct*** - The **Valve of Hasner** (also known as the **plica lacrimalis** or **Hasner's fold**) is located at the **inferior opening of the nasolacrimal duct** into the nasal cavity, specifically at the inferior meatus. - Its primary function is to **prevent retrograde flow** of nasal secretions into the lacrimal drainage system. - This valve is particularly important in newborns; congenital blockage can lead to dacryostenosis. *Common bile duct* - The common bile duct contains the **sphincter of Oddi** at its distal end, which regulates bile flow into the duodenum. - It is part of the biliary system and is not associated with the lacrimal drainage system. *Maxillary Sinus* - The **maxillary sinus** is a paranasal sinus that drains into the middle meatus of the nasal cavity via its ostium. - It has no valve structure and is not associated with the lacrimal drainage system. *Stenson's duct* - **Stenson's duct** (parotid duct) is the excretory duct of the parotid gland, opening into the oral vestibule opposite the upper second molar. - It is part of the salivary system and is not associated with the Valve of Hasner or the nasolacrimal system.

Question 1205: Point of entry of inferior division of oculomotor nerve in the orbit is-

A. Foramen Rotundum
B. Inferior Orbital fissure
C. Foramen Lacerum
D. Superior Orbital fissure (Correct Answer)

Explanation: Superior Orbital fissure - The superior orbital fissure is the primary gateway for several cranial nerves, including the oculomotor nerve (CN III), to enter the orbit. - Both the superior and inferior divisions of the oculomotor nerve pass through this fissure to innervate the extraocular muscles. Foramen Rotundum - The foramen rotundum transmits the maxillary nerve (V2), a branch of the trigeminal nerve, and is not involved with the oculomotor nerve. - It opens from the middle cranial fossa into the pterygopalatine fossa. Inferior Orbital fissure - The inferior orbital fissure transmits structures like the zygomatic nerve, infraorbital nerve, and inferior ophthalmic vein, but not the oculomotor nerve. - It connects the orbit with the pterygopalatine fossa and infratemporal fossa. Foramen Lacerum - The foramen lacerum is a bony opening at the base of the skull, primarily covered by cartilage in life and usually only transmits the internal carotid artery across its superior margin. - It does not serve as a direct entry point for the oculomotor nerve into the orbit.

Question 1206: Endolymphatic duct connects which structure?

A. Scala tympani to subarachnoid space
B. Scala tympani to cochlear aqueduct
C. Utricle and saccule to endolymphatic sac (Correct Answer)
D. Scala vestibule to cochlear aqueduct

Explanation: ***Utricle and saccule to endolymphatic sac*** - The **endolymphatic duct** arises from the **utriculosaccular duct** at the junction of the **utricle and saccule** in the vestibular labyrinth [1]. - It passes through the **vestibular aqueduct** in the petrous part of the temporal bone. - It terminates in the **endolymphatic sac**, which lies in the posterior cranial fossa between two layers of dura mater on the posterior surface of the petrous temporal bone. - The endolymphatic duct plays a crucial role in maintaining **endolymph volume and pressure** within the inner ear by regulating its absorption and secretion. *Scala tympani to subarachnoid space* - This describes the connection via the **cochlear aqueduct (perilymphatic duct)**, NOT the endolymphatic duct. - The cochlear aqueduct connects the **scala tympani** with the **subarachnoid space** and contains **perilymph**. - This pathway helps regulate **perilymphatic pressure** in the inner ear. *Scala tympani to cochlear aqueduct* - This describes the **cochlear aqueduct system** which transmits **perilymph**, not endolymph. - The endolymphatic duct is a completely separate system that carries **endolymph** from the vestibular apparatus. *Scala vestibule to cochlear aqueduct* - The **scala vestibuli** does not directly connect to the cochlear aqueduct. - The scala vestibuli communicates with the scala tympani at the **helicotrema** at the apex of the cochlea. - Both scalae contain **perilymph**, while the endolymphatic duct contains **endolymph** from the vestibular system.

Question 1207: All of the following form the boundary of MacEwen's triangle except:

A. Temporal line
B. Posterosuperior segment of bony external auditory canal
C. Promontory (Correct Answer)
D. Tangent drawn to the external auditory meatus

Explanation: ***Promontory*** - The **promontory** is a bony projection on the medial wall of the **middle ear cavity**, formed by the basal turn of the cochlea. - It is located deep to the tympanic membrane and is **not a boundary of MacEwen's triangle**, which is a superficial external bony landmark on the lateral surface of the temporal bone. - MacEwen's triangle is used surgically to locate the mastoid antrum, while the promontory is an internal middle ear structure. *Temporal line* - The **temporal line** (supramastoid crest, continuation of the posterior root of the zygoma) forms the **superior boundary** of MacEwen's triangle. - This is a key anatomical reference point for mastoid surgery. *Posterosuperior segment of bony external auditory canal* - The **posterosuperior margin of the external auditory meatus** forms the **anterior boundary** of MacEwen's triangle. - This boundary guides surgical dissection during mastoidectomy. *Tangent drawn to the external auditory meatus* - A **tangent drawn to the posterior margin of the external auditory meatus** forms the **posterior boundary** of MacEwen's triangle. - This is one of the three boundaries that define this important surgical landmark, also known as the **suprameatal triangle**.

Question 1208: Name the extraocular muscle which is NOT arising from the apex of orbit?

A. Inferior rectus
B. Superior rectus
C. Superior oblique
D. Inferior oblique (Correct Answer)

Explanation: ***Inferior oblique*** - The **inferior oblique muscle** originates from the orbital floor, specifically near the **nasolacrimal groove**. [1] - Its unique origin allows it to be the only extraocular muscle that does not originate from the **common tendinous ring** at the apex of the orbit. [1] *Inferior rectus* - The **inferior rectus muscle** originates from the lower part of the **common tendinous ring** at the orbital apex. [1] - All four rectus muscles (superior, inferior, medial, lateral) share this common origin at the orbital apex. [1] *Superior rectus* - The **superior rectus muscle** arises from the upper part of the **common tendinous ring** at the orbital apex. [1] - Along with the other rectus muscles, its origin is crucial for its role in eye movement. [1] *Superior oblique* - The **superior oblique muscle** originates from the **sphenoid bone** superior and medial to the common tendinous ring, still within the orbital apex. [1] - It then passes through the **trochlea** (a fibrous pulley) before inserting onto the eyeball.

Question 1209: Stapes rests in

A. Tympanic membrane
B. Basilar membrane
C. Oval window (Correct Answer)
D. Round window

Explanation: ***Oval window*** - The **stapes**, the innermost of the three ossicles, articulates with the **oval window** via its footplate [1]. - This articulation allows the stapes to transmit sound vibrations from the middle ear to the fluid-filled cochlea of the inner ear [1]. *Tympanic membrane* - The **tympanic membrane** (eardrum) is the structure that receives sound vibrations from the external auditory canal [1]. - The **malleus**, not the stapes, is directly attached to the tympanic membrane [1]. *Basilar membrane* - The **basilar membrane** is a structure within the cochlea of the inner ear, crucial for frequency discrimination. - It is not directly contacted by the stapes; rather, the vibrations transmitted by the stapes create fluid waves that stimulate the hair cells on the basilar membrane [1]. *Round window* - The **round window** is another membrane-covered opening in the inner ear, separate from the oval window. - It serves as a pressure relief valve for the fluid movements within the cochlea, accommodating the vibrations transmitted through the oval window.

Question 1210: The ducts of the lacrimal gland open into the:

A. Lacrimal Puncta
B. Inferior fornix of the conjunctiva
C. Superior fornix of the conjunctiva (Correct Answer)
D. Lacrimal Canaliculi

Explanation: ***Superior fornix of the conjunctiva*** - The **lacrimal gland** secretes tears into the conjunctival sac through several small ducts that open into the **lateral part of the superior fornix** of the conjunctiva. - This allows tears to bathe the surface of the eye before being collected by the lacrimal puncta. *Lacrimal Puncta* - The **lacrimal puncta** are small openings located on the medial aspect of the upper and lower eyelids. - They serve as the entry point for tears into the **lacrimal drainage system**, not as the exit point for tears from the lacrimal gland. *Inferior fornix of the conjunctiva* - The **inferior fornix** is the fold between the lower eyelid and the eyeball. - While tears collect and distribute across the entire conjunctival sac, the primary openings of the lacrimal gland ducts are not located in the inferior fornix. *Lacrimal Canaliculi* - The **lacrimal canaliculi** are small tubes that begin at the lacrimal puncta and drain tears into the lacrimal sac. - They are part of the **tear drainage system**, responsible for collecting tears, not for secreting them from the lacrimal gland.

Practice by Chapter

Skull and Facial Bones

Practice Questions

Scalp and Facial Muscles

Practice Questions

Dural Venous Sinuses

Practice Questions

Cranial Cavity

Practice Questions

Orbit and Contents

Practice Questions

Temporal and Infratemporal Regions

Practice Questions

Pterygopalatine Fossa

Practice Questions

Oral Cavity

Practice Questions

Paranasal Sinuses

Practice Questions

Applied Anatomy and Clinical Correlations

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free

Head — MCQs

Head — MCQs

On this page

Practice by Chapter

Want unlimited practice?