NEET-PG 2012 Practice Questions

Q: The thoracic duct crosses from the right to the left at the level of

T4-T5 vertebra. ***T4-T5 vertebra*** - The **thoracic duct** crosses from the right to the left side of the vertebral column at the level of the **T4-T5 vertebrae**, specifically just above the root of the left lung. - This crossover is an important anatomical landmark as it signifies the duct's ascent towards the neck to drain into the left subclavian vein. *T12 vertebra* - The **thoracic duct** originates from the **cisterna chyli** at the level of the L1 or L2 vertebra and ascends into the thorax at or below the T12 vertebra, it does not cross over at this level. - This level primarily marks its entry into the thoracic cavity, not its main crossover point. *T6 vertebra* - While the **thoracic duct** is present in the thorax at this level, it does not undergo its characteristic crossover from right to left at the T6 vertebra. - The duct continues its ascent along the right side of the vertebral column before moving across. *T2 vertebra* - By the level of the T2 vertebra, the **thoracic duct** has already crossed to the left side of the vertebral column and is ascending towards its termination in the neck. - The crossover event occurs more inferiorly, at the T4-T5 level.

Q: Pituicytes are seen in ?

Posterior lobe. ***Posterior lobe*** - **Pituicytes** are specialized glial cells found exclusively in the **posterior pituitary** (neurohypophysis). [1] - They provide structural support and regulation for the nerve terminals that release **antidiuretic hormone (ADH)** and **oxytocin**. [1] *Anterior lobe* - The anterior pituitary, or **adenohypophysis**, consists of glandular epithelial cells that synthesize and secrete various hormones. [2] - It does not contain pituicytes, which are glial cells. [2] *Intermediate lobe* - The intermediate lobe is a rudimentary part of the pituitary gland in humans, primarily producing **melanocyte-stimulating hormone (MSH)**. [1] - While it is part of the pituitary, it does not contain pituicytes. *All of the options* - Pituicytes are specific to the posterior pituitary, so they are not found in all parts of the gland. - Different lobes of the pituitary gland have distinct cellular compositions and functions.

Q: In patients with penile or urethral injury, Colle's fascia prevents extravasation of urine from spreading into which anatomical space?

Ischiorectal fossa. ***Ischiorectal fossa*** - Colle's fascia (superficial perineal fascia) is the membranous layer that defines the boundaries of the **superficial perineal space**. - When urethral injury occurs, urine extravasates into the superficial perineal space but is **prevented from spreading laterally and posteriorly** into the ischiorectal fossa because Colle's fascia fuses with the **ischiopubic rami** laterally and the **perineal membrane** posteriorly [1]. - The ischiorectal fossa is a space lateral to the **anal canal** that is separated from the superficial perineal space by these fascial attachments. *Superficial perineal space* - This is actually the space **into which** urine extravasates when penile or urethral injury occurs, not the space that is protected from extravasation [1]. - Colle's fascia forms the inferior boundary of this space, so urine collects here rather than being prevented from entering. *Abdomen* - Colle's fascia in the perineum is continuous with **Scarpa's fascia** of the anterior abdominal wall. - Due to this continuity, urine can actually **track superiorly** into the anterior abdominal wall along this fascial plane. - Therefore, Colle's fascia does NOT prevent spread to the abdomen. *None of the options* - This option is incorrect because Colle's fascia specifically prevents lateral and posterior spread into the ischiorectal fossa through its anatomical attachments.

Q: Which lymph nodes are involved in the lymphatic drainage of the lateral wall of the nose?

All of the options. ***All of the options*** - The lymphatic drainage from the **lateral wall of the nose** follows a sequential pathway involving **submandibular nodes**, **retropharyngeal nodes**, and ultimately the **deep cervical nodes**. - This question tests understanding of the complete lymphatic drainage pathway, not just the primary drainage site. - All three node groups are anatomically involved in draining lymph from the lateral nasal wall. **Drainage Pathway:** - **Submandibular nodes** (Primary): The anterior and middle portions of the lateral nasal wall drain primarily to the submandibular lymph nodes. - **Retropharyngeal nodes** (Secondary): The posterior portions of the lateral wall and areas near the nasal pharynx drain to retropharyngeal nodes. - **Deep cervical nodes** (Final pathway): Lymph from both submandibular and retropharyngeal nodes eventually drains into the deep cervical chain, particularly the jugulodigastric and juguloomohyoid nodes. *Why not just one node group?* - The lateral wall of the nose has an extensive lymphatic network with multiple drainage routes. - Different regions of the lateral wall have preferential drainage to different node groups. - Understanding the complete drainage pathway is clinically important for assessing spread of infections and malignancies from the nasal cavity.

Q: All are lateral branches of the abdominal aorta, EXCEPT which of the following?

Celiac trunk. ***Celiac trunk*** - The **celiac trunk** is an anterior branch of the abdominal aorta, supplying the foregut derivatives. - It arises from the ventral aspect of the aorta, distinguishing it from lateral branches. *Right testicular artery* - The **testicular arteries** (gonadal arteries) are paired lateral branches of the abdominal aorta. - They arise inferior to the renal arteries and descend to supply the testes in males. *Left renal artery* - The **renal arteries** [1] [3] are large paired lateral branches of the abdominal aorta. - They supply the kidneys [2] and typically arise just inferior to the superior mesenteric artery. *Middle suprarenal artery* - The **middle suprarenal arteries** are paired lateral branches, typically arising directly from the abdominal aorta. - They supply the suprarenal (adrenal) glands [2].

Q: The cofactor vitamin B12 is required for the following conversion:

Methyl malonyl CoA to succinyl CoA. ***Methyl malonyl CoA to succinyl CoA*** - **Vitamin B12**, in its active form **adenosylcobalamin**, is a crucial cofactor for the enzyme **methylmalonyl-CoA mutase**, which catalyzes the isomerization of **methylmalonyl-CoA to succinyl-CoA**. - This conversion is vital for the metabolism of **odd-chain fatty acids** and certain **amino acids**, allowing their entry into the **Krebs cycle**. *Dopamine to Norepinephrine* - This conversion is catalyzed by **dopamine beta-hydroxylase**, which requires **vitamin C** (ascorbate) and **copper** as cofactors, not vitamin B12. - It is a key step in the synthesis of **catecholamines** within the nervous system. *Propionyl CoA to methyl malonyl CoA* - This conversion is catalyzed by **propionyl-CoA carboxylase** and requires **biotin** as a cofactor, not vitamin B12. - This reaction is the first step in the metabolic pathway that leads to succinyl-CoA from odd-chain fatty acids. *Homocysteine to cysteine* - This conversion occurs via the **transsulfuration pathway** and requires **vitamin B6** (pyridoxal phosphate) as a cofactor, not vitamin B12. - The enzymes involved are **cystathionine β-synthase** and **cystathionine γ-lyase**, both B6-dependent. - Vitamin B12 is involved in the **remethylation** of homocysteine to methionine (not in transsulfuration to cysteine).

Q: Renal vein thrombosis is associated with all of the following conditions except:

Trauma. **Trauma** - While trauma to the abdomen can cause **renal injury** and other vascular issues, isolated **renal vein thrombosis** is not a common direct association or complication [1]. - Renal vein thrombosis typically results from conditions that lead to a **hypercoagulable state** or local vascular stasis. *Sickle cell anemia* - Individuals with **sickle cell anemia** are prone to **vaso-occlusive crises** from sickled red blood cells obstructing blood flow [2]. - This can lead to **renal medullary ischemia** and infarction, making them highly susceptible to **renal vein thrombosis**. *Nephrotic syndrome* - **Nephrotic syndrome** is a significant risk factor for **renal vein thrombosis** due to the urinary loss of **antithrombin III**, a natural anticoagulant. - This loss creates a **hypercoagulable state**, increasing the likelihood of thrombus formation in renal veins. *Dehydration* - Severe **dehydration** leads to **hemoconcentration** (increased blood viscosity) and reduced blood flow. - These factors promote a **hypercoagulable state**, increasing the risk of thrombotic events, including **renal vein thrombosis**, especially in vulnerable populations like infants or the elderly.

Q: What is the most common bacterial cause of multiple sinus tracts resulting from an infection of the great toe?

Actinomyces. ***Actinomyces*** - **Actinomycosis** is known for causing **chronic suppurative infections** with **multiple draining sinus tracts** and characteristic **sulfur granules**. - The causative organism is **Actinomyces israelii**, an anaerobic, gram-positive, filamentous bacterium. - While rare, it can affect bones, leading to **osteomyelitis**, especially in the feet, presenting with these multifocal sinus tracts. *Tuberculosis* - **Tuberculosis of bone** is typically a **monoarticular affection**, often affecting larger joints, and does not commonly present with multiple draining sinus tracts like actinomycosis. - It is more common in the spine (**Pott's disease**) and large weight-bearing joints, rather than solely the great toe with multiple sinuses. *Staphylococcus aureus* - **Staphylococcus aureus** is the most common cause of **acute osteomyelitis** and can lead to draining sinuses. - However, it typically causes **single or localized sinus tracts** rather than the extensive, multiple sinus formation associated with actinomycosis. *Pseudomonas aeruginosa* - **Pseudomonas aeruginosa** is often associated with **osteomyelitis following puncture wounds** through footwear. - While it can cause chronic infections, it is not primarily known for forming the characteristic **multiple, long-standing sinus tracts** seen with Actinomyces.

Q: What is the primary physiological effect of increased 2,3-DPG on hemoglobin?

Decreased affinity of hemoglobin to oxygen. ***Decreased affinity of hemoglobin to oxygen*** - **2,3-Diphosphoglycerate (2,3-DPG)** binds to the beta subunits of deoxyhemoglobin, stabilizing the **deoxygenated state** and thus **reducing hemoglobin's affinity for oxygen**. - This is the **primary molecular mechanism** by which 2,3-DPG exerts its effect, facilitating **oxygen unloading** in peripheral tissues. - This decreased affinity manifests graphically as a **right shift** in the oxygen-hemoglobin dissociation curve. *Increased affinity of hemoglobin to oxygen* - This is incorrect because 2,3-DPG specifically works to **decrease hemoglobin's affinity** for oxygen, promoting oxygen release. - Increased affinity would mean oxygen is held more tightly, which is counterproductive for **oxygen delivery** to tissues. *Left shift of oxygen-hemoglobin dissociation curve* - A **left shift** indicates **increased affinity** of hemoglobin for oxygen, meaning oxygen is held more tightly. - Since 2,3-DPG decreases affinity, it causes a **right shift**, not a left shift. *Right shift of oxygen-hemoglobin dissociation curve* - While this is the **graphical representation** of 2,3-DPG's effect, it is a **consequence** of the primary molecular mechanism (decreased affinity). - A right shift signifies that for any given partial pressure of oxygen, hemoglobin is **less saturated** with oxygen, reflecting the decreased affinity caused by 2,3-DPG binding.

Question 1

The thoracic duct crosses from the right to the left at the level of

Accepted Answer

T4-T5 vertebra

Answer

T12 vertebra

Answer

T2 vertebra

Answer

T6 vertebra

Question 2

Pituicytes are seen in ?

Accepted Answer

Posterior lobe

Answer

Anterior lobe

Answer

Intermediate lobe

Answer

All of the options

Question 3

In patients with penile or urethral injury, Colle's fascia prevents extravasation of urine from spreading into which anatomical space?

Accepted Answer

Ischiorectal fossa

Answer

Superficial perineal space

Answer

None of the options

Answer

Abdomen

Question 4

Which lymph nodes are involved in the lymphatic drainage of the lateral wall of the nose?

Accepted Answer

All of the options

Answer

Deep cervical nodes

Answer

Retropharyngeal nodes

Answer

Submandibular nodes

Question 5

What are the main types of cells found in the cerebellar cortex?

Accepted Answer

Purkinje cells, granule cells, and molecular layer interneurons

Answer

Glomus cells

Answer

Principal cells

Answer

Intercalated cells

Question 6

All are lateral branches of the abdominal aorta, EXCEPT which of the following?

Accepted Answer

Celiac trunk

Answer

Right testicular artery

Answer

Left renal artery

Answer

Middle suprarenal artery

Question 7

The cofactor vitamin B12 is required for the following conversion:

Accepted Answer

Methyl malonyl CoA to succinyl CoA

Answer

Dopamine to Norepinephrine

Answer

Propionyl CoA to methyl malonyl CoA

Answer

Homocysteine to cysteine

Question 8

Renal vein thrombosis is associated with all of the following conditions except:

Accepted Answer

Trauma

Answer

Nephrotic syndrome

Answer

Dehydration

Answer

Sickle cell anemia

Question 9

What is the most common bacterial cause of multiple sinus tracts resulting from an infection of the great toe?

Accepted Answer

Actinomyces

Answer

Tuberculosis

Answer

Pseudomonas aeruginosa

Answer

Staphylococcus aureus

Question 10

What is the primary physiological effect of increased 2,3-DPG on hemoglobin?

Accepted Answer

Decreased affinity of hemoglobin to oxygen

Answer

Increased affinity of hemoglobin to oxygen

Answer

Left shift of oxygen-hemoglobin dissociation curve

Answer

Right shift of oxygen-hemoglobin dissociation curve

NEET-PG 2012

Anatomy

Biochemistry

Internal Medicine

Microbiology

Physiology