NEET-PG 2015

1414 Questions — Page 8 of 142

Anatomy

9 questions

Q71

Teres minor is supplied by

Q72

Intercostal nerve is a branch of?

Q73

Arch of aorta begins at which vertebral level?

Q74

Root value of the thoracodorsal nerve

Q75

Which of the following statements is true about the anatomy of the great saphenous vein?

Q76

The sternocleidomastoid muscle is examined by

Q77

Azygos vein drains into:

Q78

A nerve injured during axillary lymph node dissection leads to loss of sensation in the medial side of the arm. Which nerve is injured?

Q79

Which nerve roots are primarily involved in Erb's palsy?

NEET-PG 2015 - Anatomy NEET-PG Practice Questions and MCQs

Question 71: Teres minor is supplied by

A. Suprascapular nerve
B. Lower subscapular nerve
C. Thoracodorsal nerve
D. Axillary nerve (Correct Answer)

Explanation: ***Axillary nerve*** - The **axillary nerve** (C5-C6) innervates both the **teres minor** and the **deltoid muscle**. - It arises from the posterior cord of the brachial plexus and traverses the quadrangular space. *Suprascapular nerve* - The **suprascapular nerve** (C5-C6) primarily supplies the **supraspinatus** and **infraspinatus** muscles. - It plays a crucial role in shoulder abduction and external rotation, but not directly in teres minor function. *Lower subscapular nerve* - The **lower subscapular nerve** (C5-C6) innervates the **subscapularis muscle** and **teres major**. - Teres major and teres minor are anatomically adjacent but have different innervations and functions. *Thoracodorsal nerve* - The **thoracodorsal nerve** (C6-C8) innervates the **latissimus dorsi muscle** [1]. - This nerve is distinct from those supplying the rotator cuff muscles, including teres minor.

Question 72: Intercostal nerve is a branch of?

A. Brachial plexus
B. Dorsal rami of thoracic spinal nerves
C. Ventral rami of thoracic spinal nerves (Correct Answer)
D. Ventral rami of cervical spinal nerves

Explanation: ***Ventral rami of thoracic spinal nerves*** - Intercostal nerves are direct continuations of the **ventral rami of the thoracic spinal nerves** (T1-T11) [1]. - These nerves run within the **intercostal spaces**, providing sensory and motor innervation to the thoracic wall [2]. *Brachial plexus* - The brachial plexus is formed by the **ventral rami of spinal nerves C5-T1**. - It primarily innervates the **upper limb**, not the intercostal spaces. *Dorsal rami of thoracic spinal nerves* - The dorsal rami of thoracic spinal nerves supply the **deep back muscles** and the skin over the back. - They do not contribute to the innervation of the intercostal spaces or the anterior/lateral thoracic wall. *Ventral rami of cervical spinal nerves* - The ventral rami of cervical spinal nerves form the **cervical plexus (C1-C4)** and contribute to the **brachial plexus (C5-T1)**. - They innervate structures in the neck, diaphragm, and upper limb, but not the intercostal region.

Question 73: Arch of aorta begins at which vertebral level?

A. T2
B. T5
C. T3
D. T4 (Correct Answer)

Explanation: ***T4*** - The **arch of the aorta** typically begins at the level of the **upper border of the fourth thoracic vertebra (T4)**. - This anatomical landmark is crucial for understanding the **topography of the mediastinum** and the branching of the great vessels. *T2* - The **T2 vertebral level** is too high; the arch of the aorta does not begin this superiorly. - This level is often associated with structures like the **trachea** and **esophagus** in the superior mediastinum, but not the aortic arch's origin. *T3* - The **T3 vertebral level** is also too high for the typical origin of the aortic arch. - The **manubrium of the sternum** generally extends down to this level, but the aorta's arch begins slightly lower. *T5* - The **T5 vertebral level** is too low; at this point, the arch of the aorta has usually already passed posteriorly and begun its descent as the **descending aorta** [1]. - The **bifurcation of the trachea** typically occurs at the T4/T5 intervertebral disc level. *T2* - The left recurrent laryngeal nerve (RLN) separates from the vagus as it passes anterior to the arch of the aorta [1].

Question 74: Root value of the thoracodorsal nerve

A. C6, C7, C8 (Correct Answer)
B. T1, T2
C. C5, C6, C7
D. C6, T1

Explanation: ***C6, C7, C8*** - The **thoracodorsal nerve**, also known as the middle subscapular nerve, originates from the **posterior cord of the brachial plexus**. - Its specific root values are **C6, C7, and C8**, which supply motor innervation to the **latissimus dorsi muscle** [1]. - This nerve is one of the three subscapular nerves arising from the posterior cord [1]. *C5, C6, C7* - While these roots contribute to the **posterior cord**, the thoracodorsal nerve specifically arises from **C6, C7, C8**. - **C5** primarily contributes to the **upper and middle trunk** and is more associated with nerves like the **suprascapular** and **axillary nerves**. *C6, T1* - These root values contribute to various nerves of the **brachial plexus**, but not specifically the thoracodorsal nerve. - **T1** contributes mainly to the **medial cord** and its branches like the **ulnar nerve**, not the posterior cord from which the thoracodorsal nerve arises. *T1, T2* - These are typical root values for **intercostal nerves** and contribute to the **sympathetic trunk**, not the **brachial plexus** or its branches like the thoracodorsal nerve. - The brachial plexus predominantly arises from **C5 to T1 spinal nerve roots**, and **T2** is not part of the brachial plexus.

Question 75: Which of the following statements is true about the anatomy of the great saphenous vein?

A. Ends at the femoral vein 2.5 cm below the inguinal ligament.
B. Ascends anterior to the medial malleolus. (Correct Answer)
C. Starts as a continuation of the medial marginal vein.
D. There are usually more than 5 valves below the knee.

Explanation: ***Ascends anterior to the medial malleolus.*** - The **great saphenous vein (GSV)** originates on the dorsum of the foot and passes **anterior to the medial malleolus** to ascend the medial side of the leg [1]. - This anatomical landmark is **consistently present** and crucial for identifying the vein during clinical procedures such as venous cutdown and physical examination [1]. - The GSV continues to ascend along the medial aspect of the leg and thigh to terminate at the saphenofemoral junction. *Ends at the femoral vein 2.5 cm below the inguinal ligament.* - The GSV terminates by joining the **femoral vein** at the **saphenofemoral junction** in the femoral triangle. - This junction is located approximately **3-4 cm below and lateral to the pubic tubercle**, not simply 2.5 cm below the inguinal ligament. - The precise location varies among individuals. *Starts as a continuation of the medial marginal vein.* - The GSV is formed by the union of the **dorsal vein of the great toe** and the **dorsal venous arch** of the foot. - While the **medial marginal vein** is part of the superficial venous system of the foot and contributes to the dorsal venous arch, it is not accurate to say the GSV is a direct continuation of the medial marginal vein alone. *There are usually more than 5 valves below the knee.* - While this statement might seem plausible, there is **significant individual variation** in valve numbers. - The GSV typically has **5-10 valves below the knee**, meaning some individuals have exactly 5, while others have more. - The phrase "usually more than 5" is **imprecise** and not universally true, making it an incorrect statement for exam purposes. - In contrast, the anterior position relative to the medial malleolus is a **constant anatomical feature** [1].

Question 76: The sternocleidomastoid muscle is examined by

A. Shrugging of shoulder
B. Overhead abduction
C. Turning the head towards the same side to assess the muscle on that side
D. Turning the head towards the opposite side to assess the muscle on that side (Correct Answer)

Explanation: ***Turning the head towards the opposite side to assess the muscle on that side*** - The **sternocleidomastoid muscle** unilaterally acts to rotate the head to the **contralateral side**. - To palpate or visually inspect the right sternocleidomastoid, the patient would turn their head to the left, making the right muscle prominent. *Turning the head towards the same side to assess the muscle on that side* - Turning the head towards the same side primarily engages the **ipsilateral deep neck flexors** and **splenius capitis**, not the sternocleidomastoid. - This action would relax the sternocleidomastoid on the side towards which the head is turned, making it difficult to assess. *Shrugging of shoulder* - Shrugging the shoulder is primarily an action of the **trapezius** and **levator scapulae muscles**. - The sternocleidomastoid does not contribute significantly to shoulder elevation. *Overhead abduction* - Overhead abduction of the arm is primarily performed by the **deltoid muscle** and assisted by the **supraspinatus**. - This movement is entirely unrelated to the function of the sternocleidomastoid muscle.

Question 77: Azygos vein drains into:

A. Right subcostal vein
B. Right ascending lumbar vein
C. Superior vena cava (Correct Answer)
D. Brachiocephalic

Explanation: ***Superior vena cava*** - The **azygos vein** is a major venous channel that drains the walls of the thorax and abdomen, emptying directly into the **superior vena cava (SVC)**. [1] - This connection is crucial for venous return from the posterior thoracic wall, pericardium, and bronchi, especially bypassing the inferior vena cava if it's obstructed. [1] *Right subcostal vein* - The right subcostal vein is a tributary that helps form the **azygos vein**; it does not receive drainage from the azygos vein. - It contributes to the initial formation of the azygos system, not its termination. *Brachiocephalic* - The **brachiocephalic veins** are formed by the union of the internal jugular and subclavian veins, and they merge to form the **superior vena cava**. - The azygos vein drains into the superior vena cava, not directly into the brachiocephalic veins. *Right ascending lumbar vein* - The **right ascending lumbar vein** is a major tributary that contributes to the formation of the **azygos vein** in the lumbar region. - It drains into the azygos system, illustrating its origin rather than its termination.

Question 78: A nerve injured during axillary lymph node dissection leads to loss of sensation in the medial side of the arm. Which nerve is injured?

A. Long thoracic nerve
B. Intercostobrachial nerve (Correct Answer)
C. Medial pectoral nerve
D. Accessory nerve

Explanation: ***Intercostobrachial nerve*** - The **intercostobrachial nerve** (T2) is the nerve most commonly injured during **axillary lymph node dissection** - It provides **sensory innervation to the medial side of the upper arm**, specifically the skin over the medial and posterior aspects of the arm [1] - This nerve arises from the **lateral cutaneous branch of the second intercostal nerve** and crosses the axilla to reach the arm [1] - Injury during axillary surgery results in **numbness or paresthesia** in the medial upper arm region, which is a well-recognized complication of breast cancer surgery with axillary node dissection [1] - Studies show **30-80% of patients** undergoing axillary dissection experience intercostobrachial nerve injury *Long thoracic nerve* - The **long thoracic nerve** (C5-C7) innervates the **serratus anterior muscle**, which is crucial for scapular protraction and rotation - Damage to this nerve causes **"winged scapula"**, where the scapula protrudes posteriorly - This is a **motor nerve**, not sensory, so injury does not result in sensory deficits in the arm *Medial pectoral nerve* - The **medial pectoral nerve** (C8-T1) primarily innervates the **pectoralis major** and **pectoralis minor** muscles [1] - This is a **motor nerve** playing a role in muscle function rather than sensation [1] - Injury would result in weakness of these muscles, not sensory loss *Accessory nerve* - The **accessory nerve** (cranial nerve XI) innervates the **sternocleidomastoid** and **trapezius muscles** - This nerve is located in the **posterior triangle of the neck**, not in the axilla - Injury would lead to weakness in shrugging the shoulders or turning the head, not sensory loss in the arm during axillary dissection

Question 79: Which nerve roots are primarily involved in Erb's palsy?

A. C5, C6 (Correct Answer)
B. C4, C5
C. C5, C7
D. C6, C8

Explanation: C5, C6 - **Erb's palsy** primarily involves injury to the **upper trunk of the brachial plexus**, which is formed by the ventral rami of **C5 and C6** spinal nerves. - This lesion results in a characteristic "waiter's tip" posture due to paralysis of muscles supplied by these nerve roots, including the **deltoid**, **biceps**, and **brachialis**. *C4, C5* - While C5 is involved, **C4** is typically associated with the **phrenic nerve** and diaphragm function, and its primary involvement is not characteristic of Erb's palsy. - Injury to C4 and C5 alone would not produce the comprehensive motor deficits seen in Erb's palsy involving shoulder and elbow flexion. *C5, C7* - This option includes C5 but also **C7**, which is more commonly associated with the **middle trunk** of the brachial plexus. - While C7 can be involved in extended brachial plexus injuries, its primary involvement alone is not the classic presentation of Erb's palsy. *C6, C8* - This combination includes C6 but introduces **C8**, which is part of the **lower trunk** of the brachial plexus. - Injuries involving C8 and T1 are characteristic of **Klumpke's palsy**, affecting intrinsic hand muscles and causing a "claw hand" deformity, which is distinct from Erb's palsy.

Physiology

1 questions

Q71

Stapedius pulls stapes in which direction?