Which of the following statements about the lumbrical muscles is correct?
A nerve injured during axillary lymph node dissection leads to loss of sensation in the medial side of the arm. Which nerve is injured?
Azygos vein drains into:
Arch of aorta begins at which vertebral level?
Intercostal nerve is a branch of?
Distance of cricopharynx from incisor teeth
All veins open in sinus venarum except -
Which of the following statements about the atrioventricular groove is true?
Which artery supplies the anterior part of the interventricular septum?
The structure which lies outside the femoral sheath is:
NEET-PG 2015 - Anatomy NEET-PG Practice Questions and MCQs
Question 21: Which of the following statements about the lumbrical muscles is correct?
- A. All lumbricals are supplied by the median nerve
- B. Flex MCP joints and extend IP joints (Correct Answer)
- C. Origin from the tendons of flexor digitorum superficialis
- D. All lumbricals are supplied by the ulnar nerve
Explanation: Flex MCP joints and extend IP joints - The lumbrical muscles are unique in their attachment, originating from tendons and inserting into the extensor hood, allowing them to perform simultaneous metacarpophalangeal (MCP) joint flexion and interphalangeal (IP) joint extension [1]. - This specific action is crucial for fine motor movements of the fingers, particularly in precision grip. All lumbricals are supplied by the median nerve - This statement is incorrect as only the first and second lumbricals (of the index and middle fingers) are typically supplied by the median nerve. - The third and fourth lumbricals are innervated by the ulnar nerve. All lumbricals are supplied by the ulnar nerve - This statement is incorrect because the first and second lumbricals receive innervation from the median nerve. - Only the third and fourth lumbricals are consistently supplied by the deep branch of the ulnar nerve. Origin from the tendons of flexor digitorum superficialis - This statement is incorrect. The lumbricals originate from the tendons of the flexor digitorum profundus, not the superficialis [1]. - They are unique in that they are the only muscles in the human body that originate from a tendon and insert into a tendon (extensor expansion) [1].
Question 22: 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 23: 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 24: 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 25: 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 26: Distance of cricopharynx from incisor teeth
- A. 22 cm
- B. 27 cm
- C. 40 cm
- D. Approximately 15 cm (Correct Answer)
Explanation: ***Approximately 15 cm*** - The **cricopharynx** (upper esophageal sphincter at C6 level), which is the narrowest part of the pharynx, is typically located about **15 cm** from the incisor teeth in adults. - This anatomical landmark is crucial in procedures such as **endoscopy**, **intubation**, and **nasogastric tube insertion** to avoid injury. *22 cm* - This distance corresponds to the level of the **aortic arch** (second physiological narrowing of the esophagus). - This is where the aorta crosses anterior to the esophagus, creating the broncho-aortic constriction. *27 cm* - A distance of 27 cm from the incisor teeth corresponds to the level where the **left main bronchus** crosses the esophagus (third physiological narrowing). - This is well beyond the location of the **cricopharynx** and represents the mid-esophageal region. *40 cm* - This measurement represents the approximate total length of the **esophagus**, reaching the **gastroesophageal junction** at the level of the **diaphragmatic hiatus** (cardia of the stomach). - The **cricopharynx** is at the very beginning of this path, much closer to the incisors.
Question 27: All veins open in sinus venarum except -
- A. SVC
- B. Coronary sinus
- C. Anterior cardiac vein (Correct Answer)
- D. Small cardiac vein
Explanation: ***Anterior cardiac vein*** - The **anterior cardiac veins** are unique in that they drain **directly into the right atrium** through small openings (foramina) in the anterior atrial wall, **bypassing the sinus venarum entirely**. - Unlike other cardiac veins, they do **not** drain into the **coronary sinus** or the **sinus venarum**. - They typically number 2-3 veins and drain the anterior surface of the right ventricle. *SVC* - The **superior vena cava (SVC)** opens directly into the **superior part of the sinus venarum** of the right atrium. - It carries deoxygenated blood from the upper body, head, neck, and upper limbs to the heart. *Coronary sinus* - The **coronary sinus** is the largest venous drainage channel of the heart and opens into the **posteromedial part of the sinus venarum**. - It collects blood from most cardiac veins, including the great cardiac vein, middle cardiac vein, and small cardiac vein. *Small cardiac vein* - The **small cardiac vein** drains into the **coronary sinus**, which then opens into the **sinus venarum**. - It runs along the right atrioventricular (coronary) groove and drains the right atrium and right ventricle.
Question 28: Which of the following statements about the atrioventricular groove is true?
- A. Contains left anterior descending coronary artery
- B. Also called coronary sulcus (Correct Answer)
- C. Contains posterior descending artery
- D. Contains left coronary artery
Explanation: ***Also called coronary sulcus*** - The **atrioventricular groove** is a critical anatomical landmark that separates the atria from the ventricles on the external surface of the heart. - This anatomical division is consistently referred to as the **coronary sulcus**, which encircles the entire heart. *Contains left anterior descending coronary artery* - The **left anterior descending (LAD) coronary artery**, also known as the anterior interventricular artery, lies within the **interventricular groove** (or sulcus), not the atrioventricular groove. - The interventricular groove separates the left and right ventricles, distinct from the atrioventricular separation. *Contains left coronary artery* - The **left coronary artery (LCA)** is a short main trunk that almost immediately divides into the **left anterior descending** (LAD) and **circumflex arteries** [1]. - While the **circumflex artery** (a branch of the LCA) runs in the left part of the atrioventricular groove, the main left coronary artery itself is too short to be considered within the groove [1]. *Contains posterior descending artery* - The **posterior descending artery (PDA)**, also known as the posterior interventricular artery, lies within the **posterior interventricular groove**, separating the ventricles posteriorly. - The PDA is a branch of either the right coronary artery (in most people) or the circumflex artery, but it follows the interventricular septum, not the atrioventricular border.
Question 29: Which artery supplies the anterior part of the interventricular septum?
- A. Right coronary artery
- B. Posterior descending coronary artery
- C. Left anterior descending artery (LAD) (Correct Answer)
- D. None of the options
Explanation: ***Left anterior descending artery (LAD)*** - The **LAD** is a branch of the **left main coronary artery** and is also known as the "widowmaker" due to its critical supply to a large portion of the left ventricle and the interventricular septum [1]. - It gives rise to **septal branches** that typically supply the anterior two-thirds of the interventricular septum [1]. *Right coronary artery* - The **right coronary artery (RCA)** primarily supplies the **right ventricle**, the right atrium, the SA node (in 60% of people), and the AV node (in 90% of people). - It typically supplies the **inferior wall** of the left ventricle and the posterior one-third of the interventricular septum [1]. *Posterior descending coronary artery* - The **posterior descending artery (PDA)** arises from the **RCA** (in approximately 85% of individuals, known as right dominance) or less commonly from the circumflex artery (in left dominance) [1]. - It supplies the **posterior one-third** of the interventricular septum and typically the inferior wall of the left ventricle [1]. *None of the options* - This option is incorrect because the **LAD** clearly and predominantly supplies the anterior part of the interventricular septum.
Question 30: The structure which lies outside the femoral sheath is:
- A. Genitofemoral nerve
- B. Femoral vein
- C. Femoral artery
- D. Femoral nerve (Correct Answer)
Explanation: ***Femoral nerve*** - The **femoral nerve** lies lateral to the femoral artery and is therefore situated outside the **femoral sheath**, which encloses the femoral artery, femoral vein, and lymphatic vessels [2]. - It originates from the lumbar plexus (L2-L4) and provides motor innervation to the quadriceps femoris and sensory innervation to the anterior thigh and medial leg. *Femoral artery* - The **femoral artery** is a primary content of the **femoral sheath**, occupying the most lateral compartment. - It is a continuation of the external iliac artery and is a major blood supply to the lower limb. *Femoral vein* - The **femoral vein** lies within the **femoral sheath**, positioned medial to the femoral artery. - It is the primary vein responsible for draining blood from the lower limb and eventually becomes the external iliac vein. *Genitofemoral nerve* - The **genitofemoral nerve** typically emerges on the anterior surface of the psoas major muscle and then usually divides into genital and femoral branches [1]. - While its femoral branch supplies sensory innervation to the skin over the femoral triangle, it does not course within the femoral sheath itself but rather anterior to it or outside its immediate vicinity [1].