NEET-PG 2013 - Anatomy Practice Questions

Q: All are true regarding the development of T-cells, except?

T-cells are located in mantle layer of spleen. ***T-cells are located in mantle layer of spleen*** - The **mantle layer** (or marginal zone) of the spleen is primarily associated with **B-lymphocytes**, which are involved in antibody production. - While T-cells are present in the spleen, they are predominantly found in the **periarteriolar lymphoid sheath (PALS)**, which is part of the white pulp, rather than the mantle layer. *T-cells are formed in bone marrow* - **Hematopoietic stem cells** in the **bone marrow** are the progenitors of all blood cells, including lymphocytes. - These stem cells differentiate into **lymphoid stem cells**, which then travel to the thymus to become T-cells. *Maturation of T-cells take place in thymus* - **T-cell precursors** migrate from the bone marrow to the **thymus**, where they undergo a complex process of differentiation and selection. - In the thymus, T-cells acquire their **T-cell receptors (TCRs)** and undergo positive and negative selection to ensure they are self-MHC restricted and tolerant to self-antigens. *In lymph nodes, T-cells are found in paracortical area* - The **paracortical area** (or paracortex) of the lymph node is the **T-cell zone**, rich in T-lymphocytes and dendritic cells. - This region is crucial for the interaction between T-cells and antigen-presenting cells, initiating adaptive immune responses.

Q: Which of the following conditions is least likely to cause bilateral recurrent laryngeal nerve palsy?

Aortic aneurysm. ***Aortic aneurysm*** - An aortic aneurysm, especially of the ascending aorta, is **less likely to cause bilateral recurrent laryngeal nerve palsy** because the left recurrent laryngeal nerve typically hooks under the aortic arch, while the right nerve hooks under the subclavian artery. - For **bilateral involvement**, two separate and simultaneous lesions affecting both nerves would be required at different anatomical locations with this etiology, making it a rare cause. *Thyroid carcinoma* - An aggressive **thyroid carcinoma** can directly invade or compress the recurrent laryngeal nerves (RLNs) due to their proximity to the thyroid gland. - If the carcinoma is extensive or multifocal, it can lead to **bilateral involvement** by affecting both nerves. *Lymphadenopathy* - Significant **cervical or mediastinal lymphadenopathy** (e.g., due to metastatic disease or lymphoma) can compress or encase both recurrent laryngeal nerves. - This proximity allows for potential **bilateral compression or damage** to the nerves as they ascend in the tracheoesophageal grooves. *Thyroid surgery* - **Thyroidectomy** is a common cause of recurrent laryngeal nerve injury due to the nerves' close anatomical relationship with the thyroid gland. - **Bilateral recurrent laryngeal nerve palsy** can occur if both nerves are damaged during dissection, often due to surgical misidentification, thermal injury, or traction.

Q: Which structure prevents spread of infection from middle ear to brain?

Tegmen tympani. ***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.

Q: The junction between Retina & Ciliary body is?

Ora serrata. ***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.

Q: Which are the second order neurons in the optic pathway?

Bipolar cells. ***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.

Q: What is the longest part of the optic nerve?

Intraorbital. ***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.

Q: Which muscles are responsible for the elevation of the eye?

SR and IO. ***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].

Q: Downward and outward movement of eye is affected in injury of?

3rd nerve. The 3rd cranial nerve (oculomotor nerve) controls most extraocular muscles including the superior rectus, inferior rectus, medial rectus, and inferior oblique, as well as the levator palpebrae superioris. Injury to the 3rd nerve results in paralysis of these muscles, leaving only the lateral rectus (6th nerve) and superior oblique (4th nerve) functioning. This causes the classic "down and out" position of the eye at rest due to the unopposed action of these two muscles [1]. The eye is pulled downward by the superior oblique and outward by the lateral rectus [1]. Additional features include ptosis (drooping eyelid), dilated pupil, and diplopia (double vision) [1][2]. The patient loses the ability to move the eye upward, downward (via inferior rectus), and medially. Incorrect Option: 4th nerve - The 4th cranial nerve (trochlear nerve) innervates the superior oblique muscle. The superior oblique primarily causes depression (downward), intorsion, and abduction of the eye [1]. However, its action is most effective for downward and INWARD movement when the eye is adducted. - 4th nerve palsy results in vertical diplopia (especially when looking down and inward, like reading or descending stairs), hypertropia (upward deviation), and head tilt to the opposite side. This does NOT produce a "down and out" position. Incorrect Option: 5th nerve - The 5th cranial nerve (trigeminal nerve) provides sensory innervation to the face and motor innervation to the muscles of mastication. It has no role in eye movements. Incorrect Option: 6th nerve - The 6th cranial nerve (abducens nerve) innervates the lateral rectus muscle, responsible for abduction (outward movement) of the eye [1]. 6th nerve palsy causes inability to abduct the eye, resulting in esotropia (inward deviation) and horizontal diplopia.

Q: Which nerve is not involved in superior orbital fissure syndrome?

1st cranial nerve. ***1st cranial nerve*** - The **olfactory nerve (CN I)** is responsible for the sense of smell [2] and passes through the **cribriform plate** of the ethmoid bone, not the superior orbital fissure. - Due to its distinct pathway, it is not affected in **superior orbital fissure syndrome**. *3rd cranial nerve* - The **oculomotor nerve (CN III)** passes through the superior orbital fissure and is frequently involved in the syndrome. - Its involvement leads to ophthalmoplegia, ptosis, and a dilated pupil due to paralysis of most extrinsic ocular muscles [1], [3] and the parasympathetic fibers [1]. *4th cranial nerve* - The **trochlear nerve (CN IV)** also travels through the superior orbital fissure. - Damage to this nerve causes **diplopia** and impaired downward and intorsion movements of the eye due to paralysis of the **superior oblique muscle** [3]. *6th cranial nerve* - The **abducens nerve (CN VI)** enters the orbit via the superior orbital fissure. - Injury to the abducens nerve results in **lateral rectus muscle** palsy, leading to esotropia (medial deviation of the eye) and impaired abduction [3].

Question 1

All are true regarding the development of T-cells, except?

Accepted Answer

T-cells are located in mantle layer of spleen

Answer

T-cells are formed in bone marrow

Answer

In lymph nodes, T-cells are found in paracortical area

Answer

Maturation of T-cells take place in thymus

Question 2

In current medical practice, cephalic index is primarily used for

Accepted Answer

Assessment of craniosynostosis

Answer

Evaluation of skull deformities

Answer

Clinical documentation of head shape

Answer

Neurosurgical planning

Question 3

Which of the following conditions is least likely to cause bilateral recurrent laryngeal nerve palsy?

Accepted Answer

Aortic aneurysm

Answer

Thyroid carcinoma

Answer

Lymphadenopathy

Answer

Thyroid surgery

Question 4

Which structure prevents spread of infection from middle ear to brain?

Accepted Answer

Tegmen tympani

Answer

Cribriform plate

Answer

Fundus tympani

Answer

Petrous apex

Question 5

The junction between Retina & Ciliary body is?

Accepted Answer

Ora serrata

Answer

Equator

Answer

Pars plicata

Answer

Pars plana

Question 6

Which are the second order neurons in the optic pathway?

Accepted Answer

Bipolar cells

Answer

Ganglionic cells

Answer

Cells of lateral geniculate body

Answer

Astrocytes

Question 7

What is the longest part of the optic nerve?

Accepted Answer

Intraorbital

Answer

Intracanalicular

Answer

Intraocular

Answer

Intracranial

Question 8

Which muscles are responsible for the elevation of the eye?

Accepted Answer

SR and IO

Answer

IO and SO

Answer

IR and SR

Answer

SO and IR

Question 9

Downward and outward movement of eye is affected in injury of?

Accepted Answer

3rd nerve

Answer

4th nerve

Answer

5th nerve

Answer

6th nerve

Question 10

Which nerve is not involved in superior orbital fissure syndrome?

Accepted Answer

1st cranial nerve

Answer

3rd cranial nerve

Answer

4th cranial nerve

Answer

6th cranial nerve

NEET-PG 2013 — Anatomy