Inlet of larynx is formed by:
Where is Schatzki's Ring present?
Through which meatus is a nasal puncture typically performed?
Which structure prevents spread of infection from middle ear to brain?
All are parts of anterior segment of eye except?
The junction between Retina & Ciliary body is?
Which are the second order neurons in the optic pathway?
What is the longest part of the optic nerve?
Which muscles are responsible for the elevation of the eye?
Yoke muscle for the right superior rectus is:
NEET-PG 2013 - Anatomy NEET-PG Practice Questions and MCQs
Question 91: Inlet of larynx is formed by:
- A. Aryepiglottic fold (Correct Answer)
- B. Vocal cord
- C. False vocal cord
- D. Folds from the base of the tongue to the epiglottis
Explanation: ***Aryepiglottic fold*** - The **inlet of the larynx** is the opening into the laryngeal cavity from the pharynx. - It is bordered anteriorly by the **epiglottis**, laterally by the **aryepiglottic folds**, and posteriorly by the **arytenoid cartilages** and **interarytenoid notch**. *False vocal cord* - The **false vocal cords** (ventricular folds) are located within the laryngeal cavity, inferior to the inlet. - They play a protective role but do not form the boundaries of the laryngeal inlet itself. *Folds from the base of the tongue to the epiglottis* - These folds, including the **glossoepiglottic folds**, connect the tongue to the epiglottis. - They are superior to the laryngeal inlet and are part of the oropharynx, not direct borders of the inlet. *Vocal cord* - The **true vocal cords** are responsible for voice production and are located deeper within the larynx, inferior to the false vocal cords. - They do not form any part of the laryngeal inlet.
Question 92: Where is Schatzki's Ring present?
- A. Upper end of trachea
- B. Lower end of esophagus (Correct Answer)
- C. Upper end of esophagus
- D. Lower end of trachea
Explanation: ***Lower end of esophagus*** - **Schatzki's Ring** is a localized narrowing that can occur at the **gastroesophageal junction**, specifically at the squamocolumnar junction. - This ring is a common cause of intermittent **dysphagia** for solid foods. [2] *Upper end of trachea* - The upper end of the trachea is the **larynx** or a region just below it, which is anatomically distinct from the esophagus. - Constrictions in this area are generally unrelated to Schatzki's Ring and typically involve conditions like **subglottic stenosis**. *Upper end of esophagus* - The upper end of the esophagus contains the **upper esophageal sphincter** (UES), which is a muscular structure. [3] - While strictures can occur here, they are not referred to as Schatzki's Ring. *Lower end of trachea* - The lower end of the trachea **bifurcates into the bronchi** and is part of the respiratory system. [1] - Anatomically, it is separate from the esophagus, and issues here would be related to respiratory conditions, not Schatzki's Ring.
Question 93: Through which meatus is a nasal puncture typically performed?
- A. Superior meatus
- B. Middle meatus
- C. Inferior meatus (Correct Answer)
- D. Sphenoethmoidal recess
Explanation: ---Inferior meatus--- - A nasal puncture for **maxillary sinus irrigation** is typically performed through the **inferior meatus** because it provides direct access to the floor of the nasal cavity and the passage to the maxillary sinus. - The floor of the **inferior meatus** is the thinnest part of the lateral nasal wall, making it an ideal entry point for procedures into the maxillary sinus. *Superior meatus* - The **superior meatus** is associated with the drainage of the **posterior ethmoid cells** and the **sphenoid sinus**. - Puncturing here would not provide access for maxillary sinus irrigation and could risk damage to the **cribriform plate**. *Middle meatus* - The **middle meatus** is where the **maxillary**, **frontal**, and **anterior ethmoid sinuses** primarily drain. - While related to the maxillary sinus, it is not the preferred site for a puncture for irrigation, as it is more complex and less direct than the inferior meatus. *Sphenoethmoidal recess* - The **sphenoethmoidal recess** is located superior to the superior concha and is the drainage site for the **sphenoid sinus**. - This area is too high and posterior to be relevant for a puncture aimed at the **maxillary sinus**.
Question 94: Which structure prevents spread of infection from middle ear to brain?
- A. Tegmen tympani (Correct Answer)
- B. Cribriform plate
- C. Fundus tympani
- D. Petrous apex
Explanation: ***Tegmen tympani*** - The **tegmen tympani** is a thin plate of bone forming the roof of the middle ear cavity, separating it from the **middle cranial fossa** and the brain. - Its primary function is to act as a **bony barrier**, preventing upward spread of infection from the middle ear space into the intracranial cavity. *Cribriform plate* - The **cribriform plate** is part of the ethmoid bone, located in the anterior cranial fossa, and is perforated by the **olfactory nerves**. - It does not form a boundary to the middle ear cavity and is not involved in preventing infection spread from the middle ear. *Fundus tympani* - This term is not a standard anatomical landmark. The **floor of the tympanic cavity**, or **fundus tympani**, separates the middle ear from the **internal jugular vein**. - It does not prevent the spread of infection to the brain but rather to structures below the middle ear. *Petrous apex* - The **petrous apex** is the very tip of the petrous part of the temporal bone, which houses the cochlea and vestibule. - While part of the temporal bone, it is not the direct barrier between the middle ear cavity and the brain; its involvement in infection spread is typically due to **petrous apexitis**, a distinct complication.
Question 95: All are parts of anterior segment of eye except?
- A. Lens
- B. Cornea
- C. Aqueous humor
- D. Vitreous (Correct Answer)
Explanation: ***Vitreous*** - The **vitreous humor**, or simply vitreous, is a transparent, gel-like substance that fills the space posterior to the lens and anterior to the retina, making it part of the **posterior segment** of the eye [3]. - Its main function is to maintain the shape of the eye and keep the retina in place. *Lens* - The **lens** is a transparent, biconvex structure located behind the iris and in front of the vitreous, making it a key component of the **anterior segment** [2]. - It works to focus light onto the retina, changing shape to alter the focal length of the eye. *Cornea* - The **cornea** is the transparent, outermost layer of the eye that covers the iris, pupil, and anterior chamber, clearly positioning it within the **anterior segment** [2]. - It plays a crucial role in focusing light into the eye. *Aqueous humor* - The **aqueous humor** is a clear, watery fluid located in the space between the cornea and the lens (the anterior and posterior chambers), which is definitively part of the **anterior segment** [1]. - It nourishes the cornea and lens and maintains intraocular pressure.
Question 96: The junction between Retina & Ciliary body is?
- A. Equator
- B. Pars plicata
- C. Pars plana
- D. Ora serrata (Correct Answer)
Explanation: ***Ora serrata*** - The **ora serrata** represents the **anterior-most jagged edge** of the retina where the sensory retina terminates. [1] - It marks the transition point where the neural retina becomes the **non-photoreceptive ciliary body epithelium**. *Equator* - The **equator** is the imaginary line circling the globe of the eye, approximately equidistant from the anterior and posterior poles. - It is a landmark on the retina itself, indicating the approximate middle of the retina, and not its junction with the ciliary body. *Pars plicata* - The **pars plicata** is the anterior, folded portion of the **ciliary body** that produces aqueous humor. - While part of the ciliary body, it is anterior to the junction with the retina and not the junction itself. *Pars plana* - The **pars plana** is the posterior, relatively flat portion of the **ciliary body**, located between the ora serrata and the pars plicata. - It is a part of the ciliary body immediately adjacent to the ora serrata, but the ora serrata itself is the definitive junction.
Question 97: Which are the second order neurons in the optic pathway?
- A. Bipolar cells (Correct Answer)
- B. Ganglionic cells
- C. Cells of lateral geniculate body
- D. Astrocytes
Explanation: ***Bipolar cells*** - **Photoreceptors** (rods and cones) are first-order neurons, sensing light. [1] - **Bipolar cells** receive input from photoreceptors and transmit signals to retinal ganglion cells, acting as second-order neurons. [1] *Ganglionic cells* - **Ganglion cells** are third-order neurons in the visual pathway. [1] - Their axons form the **optic nerve**, which carries visual information to the brain. [2] *Cells of lateral geniculate body* - The **lateral geniculate nucleus (LGN)** of the thalamus contains fourth-order neurons. [1] - These cells project to the primary visual cortex. [2] *Astrocytes* - **Astrocytes** are a type of glial cell that provides support and protection to neurons in the central nervous system. - They are **not directly involved** in the transmission of visual information in the optic pathway.
Question 98: What is the longest part of the optic nerve?
- A. Intracanalicular
- B. Intraorbital (Correct Answer)
- C. Intraocular
- D. Intracranial
Explanation: ***Intraorbital*** - The **intraorbital segment** is the **longest portion** of the optic nerve, measuring approximately **25-30 mm**. - It extends from the posterior pole of the eyeball to the **optic canal** and is characterized by a curved, **S-shaped course** within the orbit. - This excess length (approximately 8 mm more than the distance it spans) allows for **free eye movements** without putting tension on the nerve. *Intracranial* - The **intracranial portion** extends from the **optic canal** to the **optic chiasm**, measuring approximately **10-16 mm**. - While often mistakenly thought to be the longest, it is actually the **second longest segment**. - This segment is crucial for the formation of the **optic chiasm** where partial decussation of fibers occurs. *Intracanalicular* - The **intracanalicular portion** passes through the **optic canal** within the sphenoid bone, measuring approximately **4-10 mm**. - This segment is relatively short and constricted, making it vulnerable to compression in conditions like optic nerve gliomas or meningiomas. *Intraocular* - The **intraocular portion** (optic disc) is the **shortest segment**, measuring only about **1 mm**. - It passes through the **lamina cribrosa** of the sclera and is visible on fundoscopy as the optic disc.
Question 99: Which muscles are responsible for the elevation of the eye?
- A. SR and IO (Correct Answer)
- B. IO and SO
- C. IR and SR
- D. SO and IR
Explanation: ***SR and IO*** - The **superior rectus (SR)** muscle primarily elevates the eye, especially when the eye is **abducted** [1]. - The **inferior oblique (IO)** muscle also contributes to elevation, particularly when the eye is **adducted** [1]. *IO and SO* - While the **inferior oblique (IO)** elevates the eye, the **superior oblique (SO)** muscle is responsible for **depression** and **intorsion**, not elevation [1]. - Therefore, this combination does not exclusively perform elevation. *IR and SR* - The **superior rectus (SR)** muscle elevates the eye, but the **inferior rectus (IR)** muscle is responsible for **depression** of the eye, not elevation [1]. - This pair has opposing primary actions in vertical movement. *SO and IR* - Both the **superior oblique (SO)** and **inferior rectus (IR)** muscles are primarily involved in **depression** of the eye [1]. - The superior oblique also causes **intorsion**, and the inferior rectus causes **extorsion** [1].
Question 100: Yoke muscle for the right superior rectus is:
- A. Left Inferior Oblique (Correct Answer)
- B. Left Lateral Rectus
- C. Left Superior rectus
- D. Left Inferior rectus
Explanation: ***Left Inferior Oblique*** - Yoke muscles are pairs of synergistic muscles, one in each eye, that act together to produce conjugate eye movements in the same direction of gaze. - The **right superior rectus** and **left inferior oblique** are yoke muscles that work together during **upward and rightward gaze** (dextro-elevation) [1]. - Right SR elevates the **adducted** right eye, while left IO elevates the **abducted** left eye, producing coordinated upward-right movement [1]. - This follows **Hering's Law of Equal Innervation**, where yoke muscles receive equal and simultaneous innervation. *Left Superior rectus* - The left superior rectus is the **contralateral homologous muscle**, not a yoke muscle for the right superior rectus. - Both superior recti work together for **upward gaze in primary position**, but they are versional muscles, not yoke pairs. - Yoke muscles produce conjugate movements in oblique directions, not straight up. *Left Inferior rectus* - The left inferior rectus depresses the left eye and is an antagonist to elevation. - It would pair with the **right superior oblique** for downward-left gaze (levo-depression), not with the right superior rectus. *Left Lateral Rectus* - The left lateral rectus is responsible for **abduction** of the left eye (leftward gaze). - Its yoke muscle is the **right medial rectus** for leftward horizontal gaze (levoversion), not for upward-right gaze.