Functional Anatomy — MCQs
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Voluntary retrusion of the mandible in a closed mouth is done by which muscles?
All are possible during contraction of the tensor fasciae latae muscle except.
The main antagonistic muscle of the rectus abdominis muscle is
Abduction of the thigh is limited by:
A healthy young athlete is sitting at the edge of the table with the knee at 90 degrees of flexion. He then fully extends the knee. What happens to the patella?
Which of the following movements is least permitted in the lumbar region of the vertebral column?
What is the anatomical arrangement of fibers in the masseter muscle that contributes to its strength?
Which muscle paralysis can cause winging of the scapula?
Functional Anatomy Indian Medical PG Practice Questions and MCQs
Question 21: Voluntary retrusion of the mandible in a closed mouth is done by which muscles?
- A. Anterior belly of digastric
- B. Posterior belly of digastric
- C. Deep fibers of masseter
- D. Posterior fibers of temporalis (Correct Answer)
Explanation: The original text does not contain any relevant citations from the provided reference set to include. ***Posterior fibers of temporalis*** - The posterior fibers of the **temporalis muscle** are primarily responsible for **retrusion of the mandible**, pulling it backward. - This action is particularly effective when the mouth is closed, as the muscle's pull retracts the condyle into the glenoid fossa. *Anterior belly of digastric* - The anterior belly of the **digastric muscle** is mainly involved in **depressing the mandible** (opening the mouth) and elevating the hyoid bone. - It does not directly contribute to the retrusion of the mandible. *Posterior belly of digastric* - The posterior belly of the **digastric muscle** functions to **elevate the hyoid bone** and assist in depressing the mandible when the hyoid is fixed. - It does not play a direct role in retracting the mandible. *Deep fibers of masseter* - The **masseter muscle**, including its deep fibers, is a powerful muscle of **mastication** primarily responsible for **elevating the mandible** (closing the mouth). - It also contributes to protraction and only minimally to retrusion, not as a primary mover.
Question 22: All are possible during contraction of the tensor fasciae latae muscle except.
- A. Gluteus medius
- B. Obturator internus
- C. Quadratus femoris (Correct Answer)
- D. Piriformis
Explanation: ***Quadratus femoris*** - The **tensor fasciae latae (TFL)** functions as a **hip flexor**, **abductor**, and **internal rotator**. - The **quadratus femoris** is a powerful **external rotator** of the hip, making it a direct antagonist to TFL's internal rotation action. - During typical TFL contraction, the quadratus femoris would be **inhibited** due to reciprocal innervation, making simultaneous contraction highly unlikely. - This is the **least likely** muscle to contract during TFL activation. *Gluteus medius* - Primary **hip abductor** with anterior fibers assisting in **internal rotation**. - Acts **synergistically** with TFL for both abduction and internal rotation. - **Commonly contracts** simultaneously with TFL during gait and standing. *Obturator internus* - Primarily an **external rotator**, but also functions as a hip **stabilizer**. - Despite being an external rotator, it can contract with TFL in **complex stabilization movements** and postural adjustments. - Its stabilizing role makes simultaneous contraction **possible** in certain functional contexts. *Piriformis* - Functions as an **external rotator** and **abductor** when the hip is flexed. - Can act as a **hip stabilizer** and may contract with TFL during complex movements requiring fine motor control. - While primarily an antagonist, simultaneous contraction is **possible** for stabilization.
Question 23: The main antagonistic muscle of the rectus abdominis muscle is
- A. Psoas major
- B. Latissimus dorsi
- C. Quadratus lumborum
- D. Erector spinae (Correct Answer)
Explanation: ***Erector spinae*** - The **rectus abdominis** flexes the trunk, while the **erector spinae muscles** extend the trunk. [1] - This direct opposition in primary function makes the erector spinae the main antagonist to the rectus abdominis. *Psoas major* - The **psoas major** primarily functions as a **hip flexor** and contributes to lumbar stabilization. - While it has some action on the trunk, its main antagonistic relationship is with hip extensors, not primarily the rectus abdominis. *Latissimus dorsi* - The **latissimus dorsi** is a large muscle of the back that primarily extends, adducts, and internally rotates the arm. - It has a minimal direct antagonistic role to the rectus abdominis, which focuses on trunk flexion. *Quadratus lumborum* - The **quadratus lumborum** acts to laterally flex the trunk and stabilize the lumbar spine. - Its primary actions are distinct from the rectus abdominis's main function of trunk flexion, making it an antagonist for different movements, not directly for trunk flexion/extension.
Question 24: Abduction of the thigh is limited by:
- A. Ischiofemoral ligaments
- B. Pubofemoral ligaments (Correct Answer)
- C. Iliofemoral ligaments
- D. Sacroiliac ligament
Explanation: Abduction of the thigh is limited by: ***Pubofemoral ligaments*** - The **pubofemoral ligament** is positioned anteroinferiorly and becomes taut during **ADDUCTION** and **extension**, limiting these movements. - Note: This ligament primarily limits **adduction**, not abduction. Some sources suggest it may provide minimal limitation to abduction in certain hip positions, but its primary role is restricting adduction and extension. - This ligament prevents excessive adduction and extension at the **hip joint**, contributing to joint stability. *Ischiofemoral ligaments* - The **ischiofemoral ligament** is located posteriorly and becomes taut during **internal rotation** and **extension**, limiting these motions. - Its primary role is to restrict extreme movements in **internal rotation** and **hyperextension** of the hip. *Iliofemoral ligaments* - The **iliofemoral ligament** is the strongest ligament of the hip joint and is positioned anteriorly, limiting **extension** and **external rotation**. - The inferior/medial band can limit **adduction**, while the superior band limits extension. - It forms an inverted 'Y' shape, known as the **Y-ligament of Bigelow**, providing significant hip stability. *Sacroiliac ligament* - The **sacroiliac ligaments** connect the sacrum to the ilium, stabilizing the **sacroiliac joint**, not the hip joint. - These ligaments are crucial for maintaining the integrity of the **pelvic girdle** and supporting weight bearing. **Clinical Note:** Hip **abduction** is primarily limited by the adductor muscle group tension, inferior joint capsule, and bony contact with the acetabulum, rather than by specific ligamentous structures.
Question 25: A healthy young athlete is sitting at the edge of the table with the knee at 90 degrees of flexion. He then fully extends the knee. What happens to the patella?
- A. Patella moves posteriorly away from the femur
- B. Patella moves distally in the trochlear groove
- C. Patella moves proximally in the trochlear groove (Correct Answer)
- D. Patella remains stationary
Explanation: ***Patella moves proximally in the trochlear groove*** - During **knee extension** from a flexed position, the quadriceps femoris muscle contracts, pulling the patella superiorly along the **trochlear groove** of the femur. - This proximal movement optimizes the **lever arm** of the quadriceps, enhancing efficiency of extension. *Patella moves distally in the trochlear groove* - The patella moves **distally (inferiorly)** during **knee flexion**, not extension, as it follows the femoral condyles and is pulled by gravity and the patellar ligament. - This distal movement brings the patella into a deeper part of the trochlear groove during flexion, which can lead to **increased patellofemoral contact pressure**. *Patella remains stationary* - The patella is a **sesamoid bone** embedded in the quadriceps tendon and patellar ligament, making it a dynamic structure that moves significantly with knee flexion and extension. - It acts as a **pulley** to change the direction of force in the quadriceps tendon, thus it cannot remain stationary during knee movement. *Patella moves posteriorly away from the femur* - The patella maintains close contact with the **femoral trochlear groove** throughout knee motion, gliding within it. - Moving posteriorly away from the femur would indicate **patellar subluxation or dislocation**, which is an abnormal event.
Question 26: Which of the following movements is least permitted in the lumbar region of the vertebral column?
- A. Flexion
- B. Extension
- C. Lateral flexion
- D. Rotation (Correct Answer)
Explanation: ***Rotation*** - The **lumbar spine permits the LEAST rotation** of all movements (~5° total rotation), making this the correct answer. - The PRIMARY limiting factor is the **sagittal (near-vertical) orientation of the lumbar facet joints**, which are oriented in the coronal plane and face medially/laterally. - This facet orientation creates a **mechanical block to rotational movement**, acting like interlocking barriers. - The thick **intervertebral discs** in the lumbar region also resist torsional forces, further limiting rotation. *Flexion* - The lumbar region permits **excellent flexion** (forward bending), with approximately 50-60° of range. - The **large, wedge-shaped intervertebral discs** allow substantial anterior compression and movement. - This is one of the primary movements of the lumbar spine. *Extension* - **Extension** (backward bending) is moderately permitted in the lumbar spine, with approximately 15-20° of range. - Eventually limited by contact between **spinous processes** and the posterior ligamentous structures. - Still considerably more movement than rotation. *Lateral flexion* - **Lateral flexion** (sideways bending) is well permitted, with approximately 20° of movement to each side. - The structure of the vertebral bodies and **compressible intervertebral discs** allows good range of motion in the coronal plane. - Significantly more mobile than rotation.
Question 27: What is the anatomical arrangement of fibers in the masseter muscle that contributes to its strength?
- A. Bipennate arrangement of fibers
- B. Parallel arrangement with oblique fibers (Correct Answer)
- C. Random arrangement of fibers
- D. Circumpennate arrangement of fibers
Explanation: The original text cannot be accurately cited with the provided references because they do not contain specific information regarding the masseter muscle's anatomical fiber arrangement. ***Parallel arrangement with oblique fibers*** - The **masseter muscle** has a complex arrangement with **parallel fibers running in oblique directions**, which is the key to its strength and power. - The **superficial part** has fibers running **obliquely downward and backward**, while the **deep part** has fibers running more **vertically**. - This arrangement allows the muscle to generate **powerful biting force** by combining multiple fiber orientations, maximizing cross-sectional area and force production. - The masseter is sometimes classified as **multipennate** due to this complex architecture, but the fundamental arrangement is **parallel fibers with oblique orientation**. *Bipennate arrangement of fibers* - A **bipennate arrangement** (like the rectus femoris) has fibers approaching a central tendon from two sides like a feather. - While the masseter is powerful, its fiber arrangement is better described as **oblique parallel** or **multipennate** rather than strictly bipennate. - The masseter's two heads (superficial and deep) have different fiber orientations, which is not characteristic of a simple bipennate muscle. *Random arrangement of fibers* - Skeletal muscles require an **organized fiber arrangement** for effective force transmission. - A **random arrangement** would result in inefficient force generation and poor coordination of muscle contraction. *Circumpennate arrangement of fibers* - **Circumpennate** (or multipennate) arrangement has fibers converging from multiple directions to central tendons, as seen in the **deltoid muscle**. - While some sources describe the masseter as multipennate due to its complex architecture, the more precise anatomical description emphasizes its **parallel fibers with oblique orientation** in distinct superficial and deep parts.
Question 28: Which muscle paralysis can cause winging of the scapula?
- A. Teres minor
- B. Deltoid
- C. Serratus anterior (Correct Answer)
- D. Supraspinatus
Explanation: ***Serratus anterior*** - Paralysis or weakness of the **serratus anterior muscle**, innervated by the **long thoracic nerve**, causes winging of the scapula. - This muscle is responsible for **protraction and upward rotation of the scapula**, keeping it flat against the chest wall; without its function, the medial border of the scapula protrudes posteriorly. *Teres minor* - The **teres minor** is part of the rotator cuff and is involved in **external rotation** and **adduction of the arm**. - Its paralysis would primarily affect shoulder movement and stability, but not directly lead to **scapular winging**. *Deltoid* - The **deltoid muscle** is the primary muscle for **abduction of the arm** beyond the first 15 degrees. - Paralysis of the deltoid would result in significant difficulty lifting the arm, but it does not cause the **scapula to wing**. *Supraspinatus* - The **supraspinatus muscle** initiates **abduction of the arm** (first 15 degrees) and helps stabilize the shoulder joint. - Its paralysis would impair arm elevation but does not directly result in **scapular winging**.
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