What is the largest branch of the brachial plexus?
A person had injury to right upper limb, he is not able to extend fingers but able to extend wrist and elbow. Nerve injured is ?
All are infraclavicular branches of brachial plexus except ?
How many ossification centers develop at the distal end of the humerus?
Which muscle will be paralyzed when the radial nerve is injured just below the spiral groove?
Which of the following statements about the mammary gland is false?
What is the nerve supply to the muscles of the flexor compartment of the arm?
Which muscle receives a muscular branch from the ulnar nerve?
Axillary nerve is accompanied by which artery ?
Which is the primary muscle causing supination of the forearm?
NEET-PG 2013 - Anatomy NEET-PG Practice Questions and MCQs
Question 21: 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 22: A person had injury to right upper limb, he is not able to extend fingers but able to extend wrist and elbow. Nerve injured is ?
- A. Median
- B. Ulnar
- C. Radial
- D. Posterior interosseous (Correct Answer)
Explanation: ***Posterior interosseous*** - This nerve supplies the muscles responsible for **finger extension**, such as the **extensor digitorum**, **extensor indicis**, and **extensor digiti minimi**. - A lesion here would spare wrist and elbow extension because the nerves to the **extensor carpi radialis longus/brevis** and **triceps brachii** branch off the radial nerve proximal to the origin of the posterior interosseous nerve. *Radial* - A more proximal **radial nerve injury** would result in the inability to extend the wrist (leading to **wrist drop**), fingers, and thumb, which is not seen here as wrist extension is preserved. - It also innervates the **triceps brachii**, and a high radial nerve injury would affect elbow extension; this patient can extend their elbow. *Median* - The **median nerve** primarily innervates muscles responsible for **flexion** of the wrist and fingers, as well as **thumb opposition** and **pronation**. - Its injury would not directly lead to an inability to extend the fingers, but rather weakness in flexion and specific thumb movements. *Ulnar* - The **ulnar nerve** innervates most of the **intrinsic hand muscles** and the **flexor carpi ulnaris**, leading to weakness in finger abduction/adduction and flexion of the 4th and 5th digits. - It does not control finger extension, so an injury would not cause this specific deficit.
Question 23: 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 24: 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 25: Which muscle will be paralyzed when the radial nerve is injured just below the spiral groove?
- A. Extensor Digitorum
- B. Extensor Carpi Radialis Brevis (Correct Answer)
- C. Supinator
- D. Abductor Pollicis Longus
Explanation: Extensor Carpi Radialis Brevis - The radial nerve travels in the spiral groove of the humerus and gives off branches in a specific sequence. - Proximal to the spiral groove: Branches to triceps and anconeus - Within/at the spiral groove: Branches to brachioradialis and extensor carpi radialis longus (ECRL) - Just distal to the spiral groove: Branch to extensor carpi radialis brevis (ECRB) [1] - this is the first branch after exiting the spiral groove - More distally: The nerve divides into superficial and deep branches (posterior interosseous nerve) [1] - An injury just below the spiral groove would paralyze ECRB while sparing muscles innervated proximal to or within the groove (triceps, anconeus, brachioradialis, ECRL). Supinator - The supinator is innervated by the deep branch of the radial nerve (posterior interosseous nerve), which branches off more distally in the proximal forearm. - This muscle would only be affected by injuries distal to the bifurcation of the radial nerve into superficial and deep branches, not by an injury just below the spiral groove. Extensor Digitorum - The extensor digitorum is supplied by the posterior interosseous nerve, which is a continuation of the deep branch [1]. - This innervation occurs significantly distal to the spiral groove in the posterior forearm compartment. - It would be affected by posterior interosseous nerve injuries, not by lesions just below the spiral groove. Abductor Pollicis Longus - The abductor pollicis longus is innervated by the posterior interosseous nerve in the distal forearm [1]. - This is the most distal of all the options and would only be affected by posterior interosseous nerve palsy, not by radial nerve injury at the spiral groove level [1].
Question 26: 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].
Question 27: What is the nerve supply to the muscles of the flexor compartment of the arm?
- A. Musculocutaneous nerve (Correct Answer)
- B. Median nerve
- C. Radial nerve
- D. Ulnar nerve
Explanation: ***Musculocutaneous nerve*** - The **musculocutaneous nerve** is the primary nerve supplying all three muscles in the **flexor compartment of the arm**: the **biceps brachii**, **brachialis**, and **coracobrachialis**. - Its motor branches innervate these muscles, allowing for **flexion at the elbow** and **supination of the forearm**. *Median nerve* - The **median nerve** primarily innervates most muscles in the **flexor compartment of the forearm**, not the arm. - It plays a crucial role in **wrist and finger flexion**, as well as movements of the **thenar eminence**. *Radial nerve* - The **radial nerve** is the main nerve for the **extensor compartment of the arm and forearm**. - It is responsible for **elbow, wrist, and finger extension**. *Ulnar nerve* - The **ulnar nerve** primarily supplies intrinsic muscles of the hand and some flexor muscles in the forearm. - It has no motor supply to the muscles of the **flexor compartment of the arm**.
Question 28: 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 29: Axillary nerve is accompanied by which artery ?
- A. Posterior circumflex humeral artery (Correct Answer)
- B. Axillary artery
- C. Subscapular artery
- D. Anterior circumflex humeral artery
Explanation: ***Posterior circumflex humeral artery*** - The **axillary nerve** and the **posterior circumflex humeral artery** both pass through the **quadrangular space** in the axilla. - This anatomical relationship makes them vulnerable to injury together, particularly in cases of **shoulder dislocation** or **fractures of the surgical neck of the humerus**. *Axillary artery* - The **axillary artery** is the main arterial trunk of the axilla, but the axillary nerve is not typically described as directly accompanying the main trunk. - While branches of the axillary artery do supply the region where the axillary nerve travels, the specific artery that accompanies the nerve is a direct branch. *Subscapular artery* - The **subscapular artery** is the largest branch of the axillary artery and gives rise to the circumflex scapular and thoracodorsal arteries. - It does not directly accompany the axillary nerve through the quadrangular space; instead, it mostly supplies muscles like the **subscapularis** and **latissimus dorsi**. *Anterior circumflex humeral artery* - The **anterior circumflex humeral artery** also branches from the axillary artery and wraps around the surgical neck of the humerus. - However, it typically runs anteriorly and does not accompany the axillary nerve as it emerges from the quadrangular space posteriorly.
Question 30: Which is the primary muscle causing supination of the forearm?
- A. Brachioradialis
- B. Anconeus
- C. Biceps brachii
- D. Supinator (Correct Answer)
Explanation: ***Supinator*** - The **supinator muscle** is the **primary muscle** responsible for **supination** of the forearm, rotating the palm anteriorly or superiorly. - It is a deep muscle of the **posterior compartment** of the forearm. - Its action is especially prominent when **supinating against resistance** or in very slow movements, as it works synergistically with the biceps brachii. *Biceps brachii* - While the **biceps brachii** is also a powerful **supinator** of the forearm, especially when the elbow is flexed, it is a **secondary supinator**. - It is primarily a major **flexor** of the elbow, whereas the supinator is dedicated specifically to supination. *Brachioradialis* - The **brachioradialis** is primarily a **flexor** of the forearm at the elbow joint. - It helps to bring the forearm into a **mid-prone or mid-supine position** from either full pronation or full supination, but does not actively supinate. *Anconeus* - The **anconeus** is a small muscle that assists the **triceps brachii** in **extension of the forearm** at the elbow. - It helps to **stabilize the elbow joint** and slightly abducts the ulna during pronation, but has no role in supination.