Anatomy
5 questionsAll are infraclavicular branches of brachial plexus except ?
What is the largest branch of the brachial plexus?
Which muscle receives a muscular branch from the ulnar nerve?
How many ossification centers develop at the distal end of the humerus?
Which of the following statements about the mammary gland is false?
NEET-PG 2013 - Anatomy NEET-PG Practice Questions and MCQs
Question 121: All are infraclavicular branches of brachial plexus except ?
- A. Axillary nerve
- B. Thoracodorsal nerve
- C. Long thoracic nerve (Correct Answer)
- D. Ulnar nerve
Explanation: Long thoracic nerve - The long thoracic nerve originates directly from the roots (C5, C6, C7) of the brachial plexus, making it a supraclavicular branch. - It does not arise from the cords of the brachial plexus, which are located infraclavicularly. Ulnar nerve - The ulnar nerve arises from the medial cord of the brachial plexus, which is an infraclavicular structure. - It supplies many intrinsic hand muscles and the ulnar half of the flexor digitorum profundus. Axillary nerve - The axillary nerve is a branch of the posterior cord of the brachial plexus, classifying it as an infraclavicular branch. - It innervates the deltoid and teres minor muscles. Thoracodorsal nerve - The thoracodorsal nerve also originates from the posterior cord of the brachial plexus, making it an infraclavicular branch [1]. - It provides motor innervation to the latissimus dorsi muscle [1].
Question 122: What is the largest branch of the brachial plexus?
- A. Ulnar nerve
- B. Radial nerve (Correct Answer)
- C. Axillary nerve
- D. Median nerve
Explanation: ***Radial nerve*** - The **radial nerve** is considered the largest branch of the brachial plexus due to its extensive innervation of numerous muscles in the posterior compartment of the arm and forearm. - It arises from the **posterior cord** of the brachial plexus and innervates all the extensors of the arm and forearm, including the triceps brachii and supinator. *Ulnar nerve* - The ulnar nerve is a significant branch, but it is **smaller** in cross-sectional area and muscular distribution compared to the radial nerve. - It mainly innervates muscles of the **hand** and some forearm flexors. *Median nerve* - The median nerve is a large and clinically important nerve, formed by contributions from both the **lateral and medial cords**, but it is generally *not* considered the largest in terms of overall bulk or number of muscular branches. - It primarily innervates the **flexor muscles of the forearm** and some muscles of the hand (thenar eminence). *Axillary nerve* - The axillary nerve is one of the **smaller** terminal branches of the brachial plexus. - It primarily innervates the **deltoid** and **teres minor muscles**, and a small area of skin over the shoulder.
Question 123: Which muscle receives a muscular branch from the ulnar nerve?
- A. Both FCU and FDP (Correct Answer)
- B. FCU
- C. None of the options
- D. FDP
Explanation: ***Both FCU and FDP*** - The **flexor carpi ulnaris (FCU)** is solely innervated by the **ulnar nerve** in the forearm. - The **flexor digitorum profundus (FDP)** has dual innervation: the **ulnar nerve** supplies the medial half (tendons to ring and little fingers), while the anterior interosseous nerve (branch of median nerve) supplies the lateral half (tendons to index and middle fingers). - Both muscles receive muscular branches from the ulnar nerve, making this the most complete and accurate answer. *FCU* - While the FCU does receive innervation from the ulnar nerve (and only the ulnar nerve), this option is incorrect because the FDP also receives branches from the ulnar nerve. - Selecting only FCU ignores the dual innervation of FDP and is therefore an incomplete answer when "Both FCU and FDP" is available. *FDP* - While the medial half of FDP does receive innervation from the ulnar nerve, this option is incorrect because FCU also receives innervation from the ulnar nerve. - Selecting only FDP ignores the complete innervation of FCU and is therefore an incomplete answer when "Both FCU and FDP" is available. *None of the options* - This option is incorrect because both the **flexor carpi ulnaris** and the medial portion of the **flexor digitorum profundus** definitively receive muscular branches from the ulnar nerve. - The ulnar nerve provides motor innervation to these specific forearm muscles before continuing into the hand.
Question 124: How many ossification centers develop at the distal end of the humerus?
- A. 2
- B. 3 (Correct Answer)
- C. 5
- D. 4
Explanation: ***3*** - The distal end of the humerus develops **three primary ossification centers**: the capitellum, trochlea, and medial epicondyle [1]. - These centers appear sequentially and their ossification pattern is important for assessing **skeletal maturity** in children using the CRITOE mnemonic [1]. - The capitellum appears at 1 year, medial epicondyle at 5 years, and trochlea at 9 years. *2* - This number is too low and only accounts for the **capitellum and medial epicondyle**, missing the trochlea. - While these are the first two to appear, there is an additional primary ossification center (trochlea) that develops later. *5* - This number is incorrect; there are only **three primary ossification centers** at the distal humerus, not five. - This may cause confusion with other joints or by counting secondary ossification centers. *4* - This number is incorrect; while the lateral epicondyle does ossify, it is not consistently counted as a **primary ossification center**. - The standard anatomical teaching recognizes **three primary centers**: capitellum, trochlea, and medial epicondyle.
Question 125: Which of the following statements about the mammary gland is false?
- A. Is a modified sweat gland
- B. Extends from 2nd to 6th rib vertically
- C. Supplied by internal mammary artery
- D. Nipple is supplied by 6th intercostal nerve (Correct Answer)
Explanation: ***Nipple is supplied by 6th intercostal nerve*** - The **nipple and areola** are primarily supplied by branches of the **4th intercostal nerve**. - The 6th intercostal nerve supplies the lower part of the breast and is not the primary innervation for the nipple. *Is a modified sweat gland* - The mammary gland, or breast, is indeed a **modified apocrine sweat gland**. - This embryological origin explains its glandular structure and function of milk production. *Extends from 2nd to 6th rib vertically* - The vertical extent of the mammary gland typically ranges from the **2nd to the 6th rib**. - This anatomical positioning is consistent with its location on the anterior thoracic wall. *Supplied by internal mammary artery* - The **internal mammary artery (internal thoracic artery)** is a major blood supply to the medial aspect of the breast [2]. - Other significant arteries include the lateral thoracic and thoracoacromial arteries for the lateral aspect. The mammary gland is embedded in subcutaneous fat, although fat is absent beneath the nipple and areola [1]. Mature resting breasts lie between the skin and the pectoralis major muscle, supported by Cooper's ligaments [3].
Biochemistry
1 questionsWhat is the process of Hofmann elimination in organic chemistry?
NEET-PG 2013 - Biochemistry NEET-PG Practice Questions and MCQs
Question 121: What is the process of Hofmann elimination in organic chemistry?
- A. E1 elimination reaction favoring tertiary substrates
- B. E2 elimination reaction producing the least substituted alkene (Correct Answer)
- C. SN1 substitution reaction with carbocation intermediate
- D. SN2 substitution reaction with inversion of configuration
Explanation: ***E2 elimination reaction producing the least substituted alkene*** - **Hofmann elimination** is a type of **E2 elimination** reaction where a **quaternary ammonium salt** is heated in the presence of a strong base. - Unlike most E2 reactions which follow **Zaitsev's rule** (producing the most substituted alkene), Hofmann elimination follows the **Hofmann rule**, leading to the formation of the **least substituted (least stable) alkene**. *SN1 substitution reaction with carbocation intermediate* - **SN1 reactions** involve the formation of a **carbocation intermediate** and are typically substitution reactions, not elimination. - Hofmann elimination is an elimination reaction and does not proceed through a carbocation intermediate. *E1 elimination reaction favoring tertiary substrates* - **E1 reactions** are a two-step process involving a **carbocation intermediate** and generally favor **tertiary substrates** and produce the **Zaitsev product**. - Hofmann elimination is a concerted, one-step E2 mechanism and does not involve carbocations. *SN2 substitution reaction with inversion of configuration* - **SN2 reactions** are **bimolecular nucleophilic substitution** reactions that occur in a single step with **inversion of configuration** at the carbon center. - Hofmann elimination is an elimination process resulting in an alkene, not a substitution product, and does not involve inversion of configuration at a stereocenter.
Internal Medicine
2 questionsWhat is the most common location of gastrinoma?
Autoimmune thyroiditis is associated with all except which of the following?
NEET-PG 2013 - Internal Medicine NEET-PG Practice Questions and MCQs
Question 121: What is the most common location of gastrinoma?
- A. Pancreas
- B. Duodenum (Correct Answer)
- C. Jejunum
- D. Gall bladder
Explanation: ***Duodenum*** - The **duodenum** is the most common site for gastrinomas, accounting for over **half of all cases**, particularly in sporadic gastrinoma and Zollinger-Ellison syndrome. - These tumors are often **small** and **multiple** in the duodenum, making them challenging to locate. *Pancreas* - Pancreatic gastrinomas are also common, representing approximately **25-40% of cases**, but are less frequent than duodenal gastrinomas. - Pancreatic gastrinomas tend to be **larger** and more amenable to surgical resection when compared to duodenal gastrinomas. *Jejunum* - Gastrinomas found in the jejunum are **rare**, accounting for only a small percentage of cases. - The small intestine distal to the duodenum is an **uncommon site** for primary gastrinoma formation. *Gall bladder* - The **gallbladder** is not a typical location for gastrinoma development. - Gastrinomas are neuroendocrine tumors that arise from **gastrin-producing cells**, which are not found in the gallbladder.
Question 122: Autoimmune thyroiditis is associated with all except which of the following?
- A. DM
- B. Myasthenia gravis
- C. SLE
- D. Psoriasis (Correct Answer)
Explanation: ***Psoriasis*** - Psoriasis is generally not associated with **autoimmune thyroiditis**, which is more commonly linked to other autoimmune disorders [1]. - Autoimmune thyroiditis does not typically result in the **skin changes** seen in psoriasis, distinguishing them clinically. *Sly* - Sly syndrome, while a genetic disorder, is not directly connected to **autoimmune thyroiditis**. - Conditions like Sly syndrome are metabolic and do not involve the autoimmune pathways typically seen in thyroiditis. *Myasthenia gravis* - Myasthenia gravis is an **autoimmune neuromuscular disorder** that can occur concurrently with thyroid diseases, particularly **thyroiditis** [1]. - Both conditions arise from **autoimmune processes**, making their association plausible [1]. *DM* - Diabetes Mellitus (DM), particularly Type 1, is often linked with other autoimmune diseases, including **autoimmune thyroiditis** [2]. - They share a common **autoimmune pathway**, making them more likely to co-occur than psoriasis [2].
Pathology
2 questionsDonath-Landsteiner antibody is seen in?
Gastric carcinoma is associated with all of the following EXCEPT:
NEET-PG 2013 - Pathology NEET-PG Practice Questions and MCQs
Question 121: Donath-Landsteiner antibody is seen in?
- A. PNH
- B. Waldenstrom's macroglobulinemia
- C. Malaria
- D. Paroxysmal cold hemoglobinuria (Correct Answer)
Explanation: ***Paroxysmal cold hemoglobinuria*** - **Donath-Landsteiner antibody** is a **biphasic IgG autoantibody** that binds to red blood cells in the cold and causes **hemolysis** upon warming, characteristic of paroxysmal cold hemoglobinuria. - This antibody has **anti-P specificity**, meaning it targets the P antigen on red blood cells, leading to complement activation and cell lysis. *PNH* - **Paroxysmal nocturnal hemoglobinuria** (PNH) is characterized by a deficiency in **GPI-anchored proteins** on red blood cells, notably **CD55** and **CD59**, making them susceptible to complement-mediated lysis. - It is not associated with the Donath-Landsteiner antibody; rather, it is identified by **flow cytometry** showing absence of CD55/CD59. *Waldenstrom's macroglobulinemia* - This is a **B-cell lymphoma** characterized by the overproduction of **monoclonal IgM antibodies**, leading to hyperviscosity syndrome and other symptoms. - It does not involve Donath-Landsteiner antibodies or cold-induced hemolysis in the same manner as paroxysmal cold hemoglobinuria. *Malaria* - **Malaria** is caused by **Plasmodium parasites** that infect and destroy red blood cells, leading to hemolytic anemia and fever. - While it causes **hemolysis**, it is not mediated by the Donath-Landsteiner antibody; the destruction is primarily due to parasitic replication and immune responses against infected cells.
Question 122: Gastric carcinoma is associated with all of the following EXCEPT:
- A. Over expression of C-met
- B. Inactivation of p53
- C. Over expression of C-erb
- D. Activation of RAS (Correct Answer)
Explanation: ***Activation of RAS*** - **RAS mutations** are relatively uncommon in gastric carcinoma compared to other gastrointestinal malignancies. While KRAS mutations can occur in approximately 10-15% of gastric cancers (particularly intestinal type), they are **far less frequent** than in **pancreatic adenocarcinoma** (~90%) or **colorectal carcinoma** (~40%). - In the context of gastric carcinoma, RAS pathway alterations are **not considered a major oncogenic driver** compared to the other molecular changes listed, making this the **LEAST characteristically associated** alteration. *Inactivation of p53* - **Inactivation of the p53 tumor suppressor gene** is one of the most frequent molecular events in gastric carcinoma, occurring in approximately **50-60% of cases**. - Loss of p53 function leads to genomic instability, uncontrolled cell proliferation, and resistance to apoptosis, contributing significantly to **tumorigenesis** and **poor prognosis**. *Over expression of C-met* - **Overexpression of C-MET**, a receptor tyrosine kinase for hepatocyte growth factor (HGF), is commonly observed in gastric carcinoma (30-40% of cases) and is strongly linked to **tumor growth**, **invasion**, and **metastasis**. - C-MET amplification and overexpression promote cell proliferation, survival, migration, and angiogenesis, making it an important **therapeutic target** in advanced gastric cancer. *Over expression of C-erb* - **Overexpression of C-erbB-2 (HER2/neu)** is found in approximately **10-20% of gastric adenocarcinomas**, particularly the intestinal type. - HER2 amplification or overexpression is a significant **prognostic and predictive biomarker**, and is specifically targeted by **trastuzumab** (Herceptin) therapy in HER2-positive advanced gastric cancer, improving survival outcomes.