Clinical Anatomy — MCQs

Clinical Anatomy Indian Medical PG Practice Questions and MCQs

Question 71: When a lumbar puncture is performed to sample cerebrospinal fluid, which of the following external landmarks is the most reliable to determine the position of the L4 vertebral spine?

A. The iliac crests (Correct Answer)
B. The lowest pair of ribs bilaterally
C. The inferior angles of the scapulae
D. The posterior superior iliac spines

Explanation: ***The iliac crests*** - A line drawn between the **highest points of the iliac crests** on both sides typically intersects the L4 vertebral body or the L4-L5 intervertebral space. - This anatomical landmark provides a **safe entry point** for lumbar puncture, avoiding the spinal cord which usually ends at L1-L2. *The lowest pair of ribs bilaterally* - The lowest pair of ribs (12th ribs) corresponds to the **twelfth thoracic vertebra (T12)**, which is much higher than the desired lumbar puncture site. - Using this landmark would place the needle at a level where the **spinal cord is still present**, posing a significant risk of injury. *The inferior angles of the scapulae* - The inferior angle of the scapula typically corresponds to the **seventh thoracic vertebra (T7)**. - This landmark is also too superior for a safe lumbar puncture and does not accurately localize the lumbar spine. *The posterior superior iliac spines* - The posterior superior iliac spines (PSIS) are located at the level of the **S2 vertebra**, which is too far inferior for a standard lumbar puncture at L4-L5. - While they are important pelvic landmarks, they are not used for determining the L4 vertebral spine in this context.

Question 72: Lymph nodes of which area are not easily palpable?

A. Neck
B. Abdomen (Correct Answer)
C. Groin
D. Axilla

Explanation: ***Abdomen*** - **Intra-abdominal lymph nodes** are located deep within the body cavity, often surrounded by organs and fatty tissue, making them difficult or impossible to palpate externally. - Their assessment typically requires **imaging techniques** such as CT scans, MRI, or ultrasound [1]. *Neck* - **Cervical lymph nodes** are superficial and easily accessible for palpation along the jawline, posterior triangle, and anterior neck. - They are routinely examined during physical assessments, especially concerning head and neck infections or malignancies [2]. *Groin* - **Inguinal lymph nodes** are located superficially in the groin region, easily palpable below the inguinal ligament. - They are commonly assessed for signs of infection or malignancy affecting the lower extremities or genital area. *Axilla* - **Axillary lymph nodes** are situated in the armpit and are also relatively superficial, making them readily palpable. - They are crucial in the assessment of breast cancer and infections or malignancies of the upper limb.

Question 73: Which are the most commonly fractured ribs during Cardio Pulmonary Resuscitation?

A. 2nd-7th rib (Correct Answer)
B. 7th-10th rib
C. 10th-12th rib
D. 1st & 2nd rib

Explanation: ***2nd-7th rib*** - The **anterior and lateral aspects of the middle ribs (particularly 3rd-7th, extending to the 2nd rib)** are most commonly fractured during CPR due to their position and the direct forces applied to the sternum and rib cage during chest compressions. - These ribs are relatively thin and fixed to the sternum, making them vulnerable to fracture under sustained mechanical stress from repeated compressions. - **This range encompasses the area where CPR compressions are applied** over the lower half of the sternum. *7th-10th rib* - While these ribs can be fractured, they are **less frequently involved** compared to the more central ribs during typical CPR hand placement. - They are somewhat protected by overlying muscle and the costal margin, and lie below the typical compression point. *10th-12th rib* - These are the **floating ribs** and are **rarely fractured during CPR**. - Their free anterior ends provide considerable flexibility, and they are located lower on the torso, well below the area of sternal compressions. *1st & 2nd rib* - The **first rib is extremely well-protected** by the clavicle, scapula, and thick musculature of the shoulder girdle, making it rarely fractured during CPR. - The **second rib**, while more protected than the middle ribs, can occasionally be involved in the fracture pattern, but is **much less commonly fractured** than ribs 3-7. - Isolated fractures of ribs 1-2 typically require very significant force such as severe blunt trauma.

Question 74: Enophthalmos is caused by fracture of:

A. Lateral wall of orbit
B. Floor of orbit (Correct Answer)
C. Medial wall of orbit
D. Roof of orbit

Explanation: ***Floor of orbit*** - A fracture of the orbital floor allows orbital contents, such as fat and extraocular muscles, to **herniate into the maxillary sinus**, leading to a decrease in orbital volume and thus **enophthalmos**. - This type of fracture is also known as a **blow-out fracture** and can entrap the inferior rectus muscle, causing **diplopia** on upward gaze. *Lateral wall of orbit* - Fractures of the lateral wall of the orbit (involving the **zygoma** or **sphenoid bone**) are less common and typically result in **proptosis** if the orbital volume increases due to hemorrhage, or no significant change in eye position. - While they can be associated with other facial bone injuries, they do not directly cause enophthalmos by way of volume reduction into an adjacent sinus. *Medial wall of orbit* - Fractures of the medial wall, involving the **ethmoid air cells**, can also lead to herniation of orbital contents, potentially causing **enophthalmos**. - However, the orbital **floor** is more commonly fractured in blow-out injuries that specifically lead to significant enophthalmos due to its relative weakness. *Roof of orbit* - Fractures of the orbital roof typically involve the **frontal bone** and are often associated with **intracranial injuries** or **pneumocephalus**. - While they can cause orbital edema or hemorrhage, they usually do not result in enophthalmos; instead, they might cause **proptosis** or a visible deformity.

Question 75: While performing a lumbar puncture, a snap is felt just before entering into the epidural space. This is due to piercing of which structure?

A. Dura mater
B. Posterior longitudinal ligament
C. Ligamentum flavum (Correct Answer)
D. Supraspinous ligament

Explanation: ***Ligamentum flavum*** - The sensation of a "snap" or "pop" during a lumbar puncture just before the epidural space is characteristically felt when the needle penetrates the tough and elastic **ligamentum flavum**. - This ligament connects the laminae of adjacent vertebrae and is the most significant resistance felt by the needle before reaching the epidural space. *Duramater* - The **dura mater** is the outermost meningeal layer, which is pierced after passing through the epidural space. - Penetrating the dura mater provides a second, typically less pronounced, "pop" or "give" sensation as the needle enters the subarachnoid space to access cerebrospinal fluid. *Posterior longitudinal ligament* - The **posterior longitudinal ligament** is located on the posterior surface of the vertebral bodies, within the spinal canal. - It is not typically pierced during a standard posterior approach lumbar puncture and is not associated with the characteristic "snap." *Supraspinous ligament* - The **supraspinous ligament** is the most superficial ligament in the midline posterior to the vertebral column, connecting the tips of the spinous processes. - While it offers initial resistance, the "snap" associated with entering the epidural space comes from the deeper **ligamentum flavum**, not the supraspinous ligament.

Question 76: Axillary Nerve Injury is least likely in:

A. Intramuscular injection
B. Shoulder dislocation
C. Improper use of crutch (Correct Answer)
D. Fracture proximal humerus

Explanation: Improper use of crutch - **Improper crutch usage** primarily affects the **radial nerve** in the axilla due to direct compression against the humerus. - While it can cause nerve damage, the **axillary nerve** is less commonly injured by crutch use as it lies more distally and laterally, protected by the deltoid muscle. *Intramuscular injection* - Injections in the **deltoid muscle** can directly injure the **axillary nerve** due to its superficial course around the surgical neck of the humerus. [1] - This risk is higher with improper technique or very deep injections, leading to **deltoid weakness** and **sensory loss** over the lateral shoulder. *Shoulder dislocation* - **Anterior shoulder dislocations** are a common cause of **axillary nerve injury** due to the stretching or tearing of the nerve as the humeral head displaces. - The nerve wraps around the **surgical neck of the humerus**, making it vulnerable during dislocation. *Fracture proximal humerus* - Fractures of the **surgical neck of the humerus** often lead to **axillary nerve damage** because the nerve lies in close proximity to this region. - The blunt force or displacement of bone fragments can directly compress or lacerate the nerve.

Question 77: In doing phrenic nerve block, it is best to infiltrate

A. Scalenus anterior
B. Scalenus posterior
C. Anterior border of sternomastoid
D. Posterior border of sternomastoid (Correct Answer)

Explanation: Posterior border of sternomastoid - The phrenic nerve (C3-C5) descends on the anterior surface of the scalenus anterior muscle through the neck. - To block the phrenic nerve as it emerges from the brachial plexus roots, local anesthetic is ideally infiltrated at the posterior border of the sternomastoid muscle at the level of the cricoid cartilage (C6 vertebral level). Scalenus anterior - While the phrenic nerve rests on the anterior surface of the scalenus anterior, infiltrating this muscle directly might not be as effective for a complete block, as the nerve is relatively superficial at the posterior border of the sternomastoid. - Infiltration within the scalenus anterior could potentially lead to a less targeted block or hit other structures within the muscle. Scalenus posterior - The scalenus posterior muscle is located deeper and more laterally in the neck compared to the scalenus anterior. - The phrenic nerve does not have a direct anatomical relationship with the scalenus posterior that would make this an optimal site for a block. Anterior border of sternomastoid - The anterior border of the sternomastoid muscle provides an anatomical landmark for other neck structures, but the phrenic nerve is not readily accessible for blockade at this specific location. - Infiltrating here would be too anterior and medial to where the phrenic nerve emerges from the brachial plexus components.

Question 78: Which is the safest site for intramuscular (IM) injection to avoid injury to vessels and nerves?

A. Upper inner quadrant of buttock
B. Upper outer quadrant of buttock (Correct Answer)
C. Lower part of insertion of deltoid
D. Lower inner quadrant of buttock

Explanation: ***Upper outer quadrant of buttock*** - This site, specifically the **ventrogluteal** or **dorsogluteal** region in the upper outer quadrant, avoids major nerves and blood vessels. - The **gluteus medius** and **gluteus minimus** muscles here are thick enough for medication absorption without risk of injury. *Upper inner quadrant of buttock* - This area is close to the **sciatic nerve** and major **blood vessels** like the superior gluteal artery and vein, increasing the risk of injury. - Injecting here can lead to nerve damage, pain, or hematoma formation. *Lower part of insertion of deltoid* - While deltoid injections are common, the **lower part of the deltoid** near its insertion can be inadequate for larger volumes and is closer to the **radial nerve**, increasing nerve injury risk. - The **mid-deltoid** is usually preferred for smaller volume injections. *Lower inner quadrant of buttock* - This quadrant is in close proximity to the **sciatic nerve** and the **pudendal nerve**, making it highly susceptible to nerve injury. - It also has a thinner muscle mass compared to the upper outer quadrant, increasing the risk of hitting bone or blood vessels.

Question 79: All are pierced in Lumbar Puncture except:

A. Interspinous Ligament
B. Ligamentum Flavum
C. Supraspinous ligament
D. Posterior longitudinal ligament (Correct Answer)

Explanation: ***Posterior longitudinal ligament*** - The **posterior longitudinal ligament** runs along the **posterior surface of the vertebral bodies**, forming the **anterior wall of the spinal canal**. - A lumbar puncture needle **does not reach this ligament** as it enters from the **posterior aspect** of the spinal canal. *Interspinous Ligament* - The **interspinous ligament** is located between the **spinous processes of adjacent vertebrae**. - It is **pierced** during a lumbar puncture as the needle advances through the posterior elements to reach the spinal canal. *Ligamentum Flavum* - The **ligamentum flavum** connects the **laminae of adjacent vertebrae**. - This ligament is **pierced** by the needle just before it enters the epidural space and then the subarachnoid space during a lumbar puncture. *Supraspinous ligament* - The **supraspinous ligament** runs along the tips of the **spinous processes**. - It is the **first ligament pierced** by the needle as it enters the skin and subcutaneous tissue during a lumbar puncture.

Question 80: Winging of scapula is seen in paralysis of which muscle?

A. Infraspinatus
B. Pectoralis major
C. Supraspinatus
D. Serratus anterior (Correct Answer)

Explanation: **Serratus anterior** - The **serratus anterior muscle** is crucial for holding the scapula against the thoracic wall and enabling upward rotation, protraction, and abduction of the arm. - Paralysis of the serratus anterior, typically due to damage to the **long thoracic nerve (of Bell)**, causes the medial border of the scapula to protrude posteromedially, known as **"winging of the scapula."** *Infraspinatus* - The **infraspinatus** is a rotator cuff muscle primarily responsible for **external rotation** of the humerus. - Paralysis of this muscle would lead to weakness in external rotation and potentially some shoulder instability, but not scapular winging. *Pectoralis major* - The **pectoralis major** is a large chest muscle responsible for **adduction, medial rotation, and flexion** of the humerus. - Its paralysis would impair these movements but would not directly cause the scapula to wing. *Supraspinatus* - The **supraspinatus** is another rotator cuff muscle, primarily responsible for initiating **abduction** of the humerus (first 0-15 degrees). - Paralysis would result in difficulty with arm abduction but would not cause scapular winging.

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