Functional Anatomy Practice Questions

Q: Muscles involved in centric relation

Temporalis & masseter. ***Temporalis & masseter*** - The **temporalis** and **masseter** muscles are primary elevators of the mandible and play a significant role in forcefully seating the condyles into their most **superior-anterior position** against the articular eminences, which defines **centric relation**. - These muscles contribute to the controlled **retraction** and **elevation** required to achieve a stable and reproducible condylar position in the glenoid fossa. *Medial and lateral pterygoids* - The **lateral pterygoid muscle** is primarily responsible for **protrusion** and **depression** of the mandible, as well as initiating lateral movements, which are movements away from centric relation. - The **medial pterygoid muscle** also aids in **protrusion** and **elevation**, but its primary action is to assist in **side-to-side movements** with the lateral pterygoid. *Temporalis and lateral pterygoid* - While the **temporalis** is critical for achieving centric relation by elevating and retracting the mandible, the **lateral pterygoid** muscle's primary actions of **protrusion** and depression work against establishing centered condylar position. - The combined action of these two muscles in this context would make it difficult to achieve or maintain the **retruded, superior-anterior position** of the condyles characteristic of centric relation. *None of the options* - This option is incorrect because the **temporalis** and **masseter** muscles are indeed directly involved in establishing and maintaining centric relation. - These muscles, through their **elevating** and **retracting** actions, seat the condyles in their most stable and reproducible position within the glenoid fossae.

Q: During a routine physical examination a 65-year-old male patient is tested for ease and flexibility of the movements of his lumbar region. Which of the following movements is most characteristic of the intervertebral joints in the lumbar region?

Lateral flexion. ***Lateral flexion*** - **Lateral flexion** (side bending) is the most characteristic movement of the lumbar spine among the given options. - This movement is primarily facilitated by the **frontal plane orientation of the facet joints** in the lumbar region. - The lumbar spine allows approximately **20-30 degrees of lateral flexion** to each side. - The structure of the intervertebral discs and facet joint orientation in the lumbar region particularly favor this movement. *Rotation* - **Rotation** is the LEAST characteristic movement of the lumbar spine. - The lumbar facet joints are oriented in the **sagittal plane**, which significantly **restricts rotational movement**. - The lumbar spine allows only about **5 degrees of rotation**, much less than the thoracic or cervical regions. - Most trunk rotation actually occurs at the thoracic spine, not the lumbar region. *Circumduction* - **Circumduction** is a combined, sequential movement (flexion → lateral flexion → extension → lateral flexion) typically seen in ball-and-socket joints. - While the spine can perform these individual movements, circumduction is not considered a characteristic or distinct movement of intervertebral joints. - This term is more applicable to joints like the shoulder and hip. *Extension* - **Extension** (backward bending) is certainly possible and important in the lumbar spine. - However, it is not the MOST characteristic movement—the lumbar spine allows approximately **20-25 degrees of extension**. [1] - Flexion (forward bending, 40-60 degrees) and lateral flexion are more prominent movements in the lumbar region during functional activities.

Q: What action is most affected by severing the tendon of the long head of the biceps brachii?

Forearm supination. ***Forearm supination*** - The **long head of the biceps brachii** is the **most powerful supinator** of the forearm, especially when the elbow is flexed. - The biceps has a **longer moment arm** for supination compared to the supinator muscle, making it biomechanically more effective. - Severing its tendon results in **significant weakness (20-30% loss)** in supination strength, particularly during resisted supination. - While the **supinator muscle** can still perform this action, it is considerably weaker and cannot fully compensate. *Elbow flexion* - Although the biceps contributes to elbow flexion, the **brachialis** is the primary elbow flexor (the "workhorse" of elbow flexion). - The **brachioradialis** also assists significantly. - Loss of the long head of biceps results in only **5-10% loss** of elbow flexion strength, as other muscles compensate effectively. *Shoulder abduction* - **Shoulder abduction** is primarily performed by the **deltoid** and **supraspinatus** muscles. - The biceps brachii is not a primary mover for shoulder abduction. *Wrist extension* - **Wrist extension** is controlled by muscles in the posterior compartment of the forearm, such as the **extensor carpi radialis longus** and **brevis**, and **extensor carpi ulnaris**. - The biceps brachii has no direct action on the wrist.

Q: What is the role of the anconeus muscle in elbow movement?

Assists in elbow extension. ***Assists in elbow extension*** - The **anconeus muscle** is a small muscle located on the posterior aspect of the **elbow joint**. - Its primary role is to assist the **triceps brachii** in **elbow extension** and to stabilize the elbow joint during pronation. - It acts as an **accessory extensor** and also tenses the capsule of the elbow joint to prevent it from being pinched during extension. *Wrist extension* - **Wrist extension** is primarily performed by muscles originating from the lateral epicondyle of the humerus, such as the **extensor carpi radialis longus and brevis** and **extensor carpi ulnaris** [1]. - The anconeus muscle is not involved in wrist movements. *Thumb abduction* - **Thumb abduction** is the movement of the thumb away from the palm, controlled by muscles like the **abductor pollicis longus** and **abductor pollicis brevis** [1]. - The anconeus muscle has no role in thumb movements. *Elbow flexion* - **Elbow flexion** is performed by anterior compartment muscles including the **biceps brachii**, **brachialis**, and **brachioradialis**. - The anconeus is located in the **posterior compartment** and produces the opposite action (extension), not flexion.

Q: Which muscle plays a key role in preventing lateral dislocation of the patella?

Vastus medialis. ***Vastus medialis*** - The **vastus medialis obliquus (VMO)** fibers pull the patella medially, counteracting the natural lateral pull exerted by the quadriceps femoris. - Its strength and proper activation are crucial in maintaining **patellar tracking** and preventing lateral subluxation or dislocation. *Rectus femoris* - The **rectus femoris** primarily acts as a hip flexor and knee extensor, with its pull being largely in the superior-inferior direction. - While it contributes to knee extension, its role in **medial stabilization** of the patella is minimal. *Vastus intermedius* - The **vastus intermedius** lies deep to the rectus femoris and primarily contributes to knee extension. - Its fibers run predominantly in the superior-inferior direction, offering little direct lateral-to-medial pull on the patella for stability. *Vastus lateralis* - The **vastus lateralis** pulls the patella in a superior and lateral direction, increasing the tendency for **lateral patellar dislocation**. - An imbalance where the vastus lateralis is significantly stronger or more active than the vastus medialis often contributes to patellar instability.

Q: Yoke muscle for the right superior rectus is:

Left Inferior Oblique. ***Left Inferior Oblique*** - Yoke muscles are pairs of synergistic muscles, one in each eye, that act together to produce conjugate eye movements in the same direction of gaze. - The **right superior rectus** and **left inferior oblique** are yoke muscles that work together during **upward and rightward gaze** (dextro-elevation) [1]. - Right SR elevates the **adducted** right eye, while left IO elevates the **abducted** left eye, producing coordinated upward-right movement [1]. - This follows **Hering's Law of Equal Innervation**, where yoke muscles receive equal and simultaneous innervation. *Left Superior rectus* - The left superior rectus is the **contralateral homologous muscle**, not a yoke muscle for the right superior rectus. - Both superior recti work together for **upward gaze in primary position**, but they are versional muscles, not yoke pairs. - Yoke muscles produce conjugate movements in oblique directions, not straight up. *Left Inferior rectus* - The left inferior rectus depresses the left eye and is an antagonist to elevation. - It would pair with the **right superior oblique** for downward-left gaze (levo-depression), not with the right superior rectus. *Left Lateral Rectus* - The left lateral rectus is responsible for **abduction** of the left eye (leftward gaze). - Its yoke muscle is the **right medial rectus** for leftward horizontal gaze (levoversion), not for upward-right gaze.

Q: Which of the following statements about articular cartilage is true?

Has no nerve supply. ***Has no nerve supply*** - Articular cartilage is **aneural**, meaning it lacks nerve endings, which is why damage to it doesn't immediately cause pain until underlying bone or surrounding tissues are affected [1]. - Its aneural nature contributes to its low metabolic activity and limited capacity for repair. *Very vascular structure* - Articular cartilage is **avascular**, meaning it lacks a direct blood supply [1]. - It receives nutrients primarily through diffusion from the synovial fluid [1]. *Surrounded by thick perichondrium* - Articular cartilage is typically **not covered by a perichondrium**, unlike most other types of cartilage. - The absence of perichondrium prevents potential ossification of the articular surface. *Fibrocartilage* - Articular cartilage is primarily composed of **hyaline cartilage**, not fibrocartilage [1]. - **Hyaline cartilage** provides a smooth, low-friction surface for joint movement and acts as a shock absorber [1].

Q: Which is the primary muscle causing supination of the forearm?

Supinator. ***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.

Q: Which muscle plays a role in winking?

Orbicularis oculi. ***Orbicularis oculi*** - This muscle is responsible for **closing the eyelid** and is essential for actions like blinking, squinting, and winking. - Its fibers encircle the eye and facilitate the **controlled closure** required for winking. *Levator labii superioris* - This muscle primarily functions to **elevate the upper lip**, playing a role in facial expressions such as sneering or smiling. - It has no direct involvement in the movement of the eyelids or the act of winking. *Corrugator supercilii* - This muscle is located in the eyebrow region and is responsible for **drawing the eyebrows medially and inferiorly**, creating vertical wrinkles between the eyebrows. - It is associated with expressions of frowning or concern, not eyelid closure. *Levator palpebrae* - This muscle is responsible for **opening the upper eyelid**, thus counteracting the action of the orbicularis oculi. - While essential for eye movement, it is not involved in the closing action required for winking.

Question 1

Muscles involved in centric relation

Accepted Answer

Temporalis & masseter

Answer

Medial and lateral pterygoids

Answer

Temporalis and lateral pterygoid

Answer

None of the options

Question 2

During a routine physical examination a 65-year-old male patient is tested for ease and flexibility of the movements of his lumbar region. Which of the following movements is most characteristic of the intervertebral joints in the lumbar region?

Accepted Answer

Lateral flexion

Answer

Rotation

Answer

Circumduction

Answer

Extension

Question 3

What action is most affected by severing the tendon of the long head of the biceps brachii?

Accepted Answer

Forearm supination

Answer

Shoulder abduction

Answer

Elbow flexion

Answer

Wrist extension

Question 4

What is the role of the anconeus muscle in elbow movement?

Accepted Answer

Assists in elbow extension

Answer

Wrist extension

Answer

Thumb abduction

Answer

Elbow flexion

Question 5

Which muscle plays a key role in preventing lateral dislocation of the patella?

Accepted Answer

Vastus medialis

Answer

Rectus femoris

Answer

Vastus intermedius

Answer

Vastus lateralis

Question 6

Yoke muscle for the right superior rectus is:

Accepted Answer

Left Inferior Oblique

Answer

Left Lateral Rectus

Answer

Left Superior rectus

Answer

Left Inferior rectus

Question 7

Which of the following statements about articular cartilage is true?

Accepted Answer

Has no nerve supply

Answer

Very vascular structure

Answer

Surrounded by thick perichondrium

Answer

Fibrocartilage

Question 8

Which is the primary muscle causing supination of the forearm?

Accepted Answer

Supinator

Answer

Brachioradialis

Answer

Anconeus

Answer

Biceps brachii

Question 9

Which muscle plays a role in winking?

Accepted Answer

Orbicularis oculi

Answer

Levator labii superioris

Answer

Levator palpebrae

Answer

Corrugator supercilii

Question 10

Which statement accurately describes a characteristic of synovial joints?

Accepted Answer

Hyaline cartilage covers the articular surfaces of synovial joints.

Answer

The metacarpo-phalangeal joint is a condyloid joint.

Answer

Cartilage can sometimes divide the joint into two cavities.

Answer

Stability is inversely proportional to mobility in synovial joints.

Functional Anatomy — MCQs

Functional Anatomy — MCQs

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