NEET-PG 2012 Practice Questions

Q: Primordial germ cells are derived from:

Yolk sac. ***Yolk sac*** - **Primordial germ cells (PGCs)** arise from **epiblast** cells but are first identifiable in the wall of the **yolk sac** during the **3rd week** of development. - From the yolk sac, they migrate during the **4th-6th week** through the dorsal mesentery to reach the developing **genital ridges** (gonads) where they form **gametes** [2]. - The yolk sac is considered the site where PGCs are recognized and begin their journey to the gonads. *Neural crest* - Neural crest cells are multipotent cells that migrate to various locations and differentiate into structures like **neurons**, **glial cells**, **melanocytes**, and **facial cartilage**, not germ cells. - They arise from the dorsal part of the **neural tube** during neurulation. *Genital ridge* - The genital ridge is the embryonic structure that develops into the **gonads** (testes or ovaries) [1]. - Primordial germ cells migrate *to* the genital ridge, but they do not originate *from* it — it is their destination, not their source. *Somatopleuritic mesoderm* - **Somatopleuritic mesoderm** (somatic mesoderm) forms the **parietal layer** of serous membranes, the dermis of the body wall, and the skeletal elements of the limbs. - It does not give rise to **primordial germ cells**.

Q: Where is the neurovascular plane located in the anterior abdominal wall?

Between internal oblique and transversus abdominis. ***Between internal oblique and transversus abdominis*** - This space, often referred to as the **transversus abdominis plane (TAP)**, contains the major neurovascular bundles supplying the anterior abdominal wall [1]. - The nerves here are the lower **thoracic (T7-T11)** and **iliohypogastric/ilioinguinal (L1) nerves**, along with accompanying blood vessels [1]. *Between external oblique and internal oblique* - This fascial plane primarily houses some superficial nerves and vessels but not the main neurovascular supply to the abdominal wall muscles. - The major neurovascular bundles for deeper muscle layers and skin are located deeper to the **internal oblique** [1]. *Below transversus abdominis* - Below the **transversus abdominis** muscle lies the **transversalis fascia**, an extraperitoneal fat layer, and then the **peritoneum**. - This deeper region primarily contains retroperitoneal structures and organs, not the main neurovascular plane for the abdominal wall. *Above external oblique* - The layer above the **external oblique** muscle is primarily subcutaneous tissue and skin. - While superficial nerves and vessels are present here, this is not the main neurovascular plane that supplies the muscles of the anterior abdominal wall.

Q: The thyrocervical trunk is a branch of which part of subclavian artery?

1st part. ***1st part*** - The **thyrocervical trunk** is one of the three primary branches arising from the **first part** of the subclavian artery. - The first part lies medial to the **anterior scalene muscle**. *2nd part* - The **second part** of the subclavian artery gives rise to the **costocervical trunk**. - This part lies posterior to the **anterior scalene muscle**. *3rd part* - The **third part** of the subclavian artery typically has no branches or may give off the **dorsal scapular artery**. - This part lies lateral to the **anterior scalene muscle**. *4th part* - This option is incorrect as the **subclavian artery has only three parts**, divided by their relationship to the anterior scalene muscle. - There is no anatomical fourth part of the subclavian artery.

Q: Which of the following is a true difference between gangliosides and cerebrosides?

Charge difference. ***Charge difference*** - **Gangliosides** contain **sialic acid (N-acetylneuraminic acid)** residues, which are negatively charged, making gangliosides **anionic**. - **Cerebrosides** are **neutral glycosphingolipids** as they lack charged sugar residues. *Specific carbohydrate composition* - While both have carbohydrate components, referring to "specific carbohydrate composition" as the *true difference* is too broad. Both have characteristic sugar groups, but the **presence of sialic acid** in gangliosides is the key differentiator in charge. - Cerebrosides typically contain a single sugar (either glucose or galactose), whereas gangliosides have a more complex oligosaccharide chain including sialic acid. *Presence of glucose* - Both cerebrosides (specifically **glucocerebrosides**) and gangliosides can contain **glucose** in their carbohydrate moieties. - This is not a distinguishing feature; the *type* and *arrangement* of sugars, particularly the presence of sialic acid, are more specific. *Location in the nervous system* - Both gangliosides and cerebrosides are abundant in the **nervous system**, particularly in cell membranes. - Their presence in the nervous system is a similarity, not a differentiating factor.

Q: At which positions does pancreatic lipase hydrolyze the ester linkages of triacylglycerides?

1 and 3. **Correct: 1 and 3** - Pancreatic lipase specifically targets the **ester bonds at the sn-1 and sn-3 positions** (primary alcohol positions) on the glycerol backbone of triacylglycerides. - This positional specificity results in the formation of **2-monoacylglycerol (2-MAG)** and **two free fatty acids**. - This is the characteristic action of pancreatic triacylglycerol lipase during fat digestion in the intestinal lumen. *Incorrect: 1 and 2* - Hydrolysis at positions 1 and 2 would produce a 3-monoacylglycerol and free fatty acids, which is not the physiological product of pancreatic lipase. - The enzyme's positional specificity favors the outer sn-1 and sn-3 positions, not the middle sn-2 position. *Incorrect: 2 and 3* - Hydrolysis at positions 2 and 3 would yield a 1-monoacylglycerol and free fatty acids, which does not reflect pancreatic lipase activity. - The enzyme specifically spares the sn-2 position due to its structural specificity. *Incorrect: Only 3* - If only position 3 were hydrolyzed, the product would be a 1,2-diacylglycerol and one free fatty acid. - This represents incomplete hydrolysis; pancreatic lipase typically hydrolyzes **both outer positions (sn-1 and sn-3)** due to its regiospecificity.

Q: What cofactor is required for the proper functioning of glucose-6-phosphate dehydrogenase?

NADP. ***NADP*** - **NADP+** (nicotinamide adenine dinucleotide phosphate) acts as the **electron acceptor** in the **glucose-6-phosphate dehydrogenase (G6PD)** reaction, becoming **NADPH**. - **NADPH** is crucial for maintaining the **redox balance** in cells, particularly in red blood cells, by reducing **oxidative stress**. *NAD* - **NAD+** (nicotinamide adenine dinucleotide) is a primary cofactor for many **dehydrogenase reactions** in catabolic pathways like **glycolysis** and the **Krebs cycle**. - It primarily functions as an electron acceptor in pathways that generate **ATP**, distinct from the role of **NADPH** in reductive biosynthesis and antioxidant defense. *FAD* - **FAD** (flavin adenine dinucleotide) is a coenzyme derived from **riboflavin (vitamin B2)** that is involved in various redox reactions, often in the form of **flavoproteins**. - Enzymes like **succinate dehydrogenase** in the electron transport chain utilize **FAD** as an electron acceptor, which is not the case for G6PD. *FMN* - **FMN** (flavin mononucleotide) is another coenzyme derived from **riboflavin**, structurally similar to FAD but lacking the additional adenosine monophosphate. - It participates in electron transfer reactions, particularly within **complex I** of the **electron transport chain**, but is not a cofactor for G6PD.

Q: What is the most common cause of dissecting hematoma?

Hypertension. ***Hypertension*** - **Chronic hypertension** is the most frequent cause of dissecting hematoma (aortic dissection) due to the constant high pressure stressing the arterial wall [1]. - It leads to **medial degeneration** and predisposition to intimal tear, allowing blood to enter the arterial wall [1]. *Marfan syndrome* - While Marfan syndrome is a significant risk factor for aortic dissection due to **connective tissue weakness** (cystic medial necrosis), it is much less common than hypertension [1]. - It primarily affects younger individuals with a genetic predisposition to **fibrillin-1 mutations**. *Iatrogenic causes* - These include complications from medical procedures like **cardiac catheterization** or surgery [1]. - Though a possible cause, iatrogenic dissection is relatively rare compared to spontaneous dissection due to hypertension [1]. *Kawasaki disease* - Kawasaki disease primarily causes **coronary artery aneurysms** in children. - It is not a common cause of aortic dissecting hematoma in adults.

Q: Cystic medial necrosis is seen in?

Marfan syndrome. ***Marfans syndrome*** - Cystic medial necrosis is a prominent feature of Marfan syndrome, leading to **aortic dilation** and increased risk of dissection [1] [2]. - It is associated with **connective tissue abnormalities**, specifically affecting elastic fibers in the aorta [2]. *Kawasaki disease* - Primarily affects children, leading to **vasculitis** of medium-sized arteries, especially the coronary arteries. - Does not characteristically cause **cystic medial necrosis** in the aorta. *Friedrichs ataxia Pattern* - An autosomal recessive disorder characterized by degeneration of spinal cord and peripheral nerves, not related to cystic medial necrosis. - Presents with **ataxia**, **scoliosis**, and **diabetes**, lacking cardiovascular changes associated with cystic medial necrosis. *Downs syndrome* - A genetic condition resulting from **trisomy 21**, associated with various congenital anomalies but not specifically with cystic medial necrosis. - Includes features like **heart defects** but does not involve the aortic changes seen in Marfan syndrome. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 511-512. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 153-154.

Q: Which of the following conditions can lead to pulmonary infarction?

Blockage of 2nd and 3rd generation end arteries. ***Blockage of 2nd and 3rd generation end arteries*** - These are **true end arteries** beyond the reach of **bronchial collateral circulation**, making pulmonary infarction more likely when blocked. - The **dual blood supply** (pulmonary and bronchial arteries) is compromised at this level, leading to tissue necrosis and infarction. *Saddle embolus at bifurcation* - A **saddle embolus** typically causes **sudden death** or **acute cor pulmonale** rather than pulmonary infarction. - The **main pulmonary artery bifurcation** is proximal enough that **bronchial collateral circulation** can still maintain tissue viability. *Arterioles being blocked* - **Arterioles** are small vessels that can be compensated by the **dual blood supply** from both pulmonary and bronchial circulations. - The **bronchial artery collaterals** can provide adequate perfusion to prevent infarction at this level. *None of the above* - This option is incorrect as **blockage of 2nd and 3rd generation end arteries** does cause pulmonary infarction. - The lung's **dual circulation** protects against infarction except when **true end arteries** are involved.

Q: What is the appropriate treatment for an incidentally detected appendicular carcinoid tumor measuring 2.5 cm?

Right hemicolectomy. ***Right hemicolectomy*** - An appendiceal carcinoid tumor **larger than 2 cm** (or with **mesoappendix invasion, positive margins, or high-grade features**) warrants a right hemicolectomy due to a significantly higher risk of lymph node metastasis (20-30%). - This 2.5 cm tumor clearly exceeds the 2 cm threshold, making right hemicolectomy the standard of care. - This procedure ensures adequate oncological margins and removal of regional lymph nodes, which is crucial for complete treatment. *Limited resection of the right colon* - This option is insufficient for an appendiceal carcinoid of this size, as it may not remove all regional lymph nodes or provide adequate oncological margins. - Limited resection lacks the systematic lymphadenectomy required for tumors exceeding 2 cm. *Total colectomy* - This is an **overly aggressive** and unnecessary procedure for an isolated appendiceal carcinoid tumor, even one of this size. - Total colectomy is typically reserved for diffuse colonic involvement, multifocal tumors, or specific genetic syndromes, which is not indicated here. *Appendicectomy* - An appendicectomy alone is only appropriate for very small appendiceal carcinoid tumors, typically **less than 1 cm** in size, with negative margins and without evidence of mesoappendix invasion or aggressive features. - For a 2.5 cm tumor, the risk of regional lymph node involvement (20-30%) is too high for appendicectomy to be considered adequate oncological treatment.

Question 1

Primordial germ cells are derived from:

Accepted Answer

Yolk sac

Answer

Neural crest

Answer

Genital ridge

Answer

Somatopleuritic mesoderm

Question 2

Where is the neurovascular plane located in the anterior abdominal wall?

Accepted Answer

Between internal oblique and transversus abdominis

Answer

Between external oblique and internal oblique

Answer

Below transversus abdominis

Answer

Above external oblique

Question 3

The thyrocervical trunk is a branch of which part of subclavian artery?

Accepted Answer

1st part

Answer

2nd part

Answer

3rd part

Answer

4th part

Question 4

Which of the following is a true difference between gangliosides and cerebrosides?

Accepted Answer

Charge difference

Answer

Specific carbohydrate composition

Answer

Location in the nervous system

Answer

Presence of glucose

Question 5

At which positions does pancreatic lipase hydrolyze the ester linkages of triacylglycerides?

Accepted Answer

1 and 3

Answer

1 and 2

Answer

2 and 3

Answer

Only 3

Question 6

What cofactor is required for the proper functioning of glucose-6-phosphate dehydrogenase?

Accepted Answer

NADP

Answer

NAD

Answer

FAD

Answer

FMN

Question 7

What is the most common cause of dissecting hematoma?

Accepted Answer

Hypertension

Answer

Marfan syndrome

Answer

Iatrogenic causes

Answer

Kawasaki disease

Question 8

Cystic medial necrosis is seen in?

Accepted Answer

Marfan syndrome

Answer

Friedreich's ataxia

Answer

Down syndrome

Answer

Kawasaki disease

Question 9

Which of the following conditions can lead to pulmonary infarction?

Accepted Answer

Blockage of 2nd and 3rd generation end arteries

Answer

Saddle embolus at bifurcation

Answer

Arterioles being blocked

Answer

None of the above.

Question 10

What is the appropriate treatment for an incidentally detected appendicular carcinoid tumor measuring 2.5 cm?

Accepted Answer

Right hemicolectomy

Answer

Limited resection of the right colon

Answer

Total colectomy

Answer

Appendicectomy

NEET-PG 2012

Anatomy

Biochemistry

Internal Medicine

Pathology

Surgery