What type of cartilage is found in the rib cage?

Correct Answer: C

Rationale: Hyaline cartilage, smooth and glassy, forms costal cartilage in the rib cage, connecting ribs to sternum, flexible yet supportive. Elastic is in ears, fibrocartilage in discs neither fit ribs. Hyaline's prevalence, per thorax, makes 'c' correct.

Correct Answer: D

Rationale: The lumbar region (lower back) is superior to the popliteal region (behind the knee), per anatomical regions lumbar above, popliteal lower on the leg. It's superior to gluteal , superior to umbilical , inferior to cervical . Superiority to popliteal, per body mapping, makes 'd' correct.

Correct Answer: A

Rationale: Thick myofilaments in sarcomeres are primarily myosin, a motor protein with a tail forming the filament backbone and heads projecting outward for actin binding. This structure, assembled from hundreds of myosin molecules, drives contraction via ATP-powered cross-bridge cycling. Thin filaments, conversely, comprise actin (a globular protein polymerized into strands), troponin (calcium-binding regulator), and tropomyosin (actin-covering modulator), not thick filaments. Combining myosin with troponin and tropomyosin lacks biochemical basis, as these regulate thin filaments. Actin alone forms thin filaments, not thick ones, and pairing myosin with actin misrepresents filament distinction. Myosin's unique tail-head configuration, detailed in structural biology, enables its role in force generation, distinct from thin filaments' regulatory proteins. Electron microscopy and X-ray diffraction reveal thick filaments as myosin aggregates, with heads engaging actin during contraction. This composition underpins muscle mechanics, ensuring thick filaments' contractile power, a fundamental concept in physiology distinguishing filament types.

Correct Answer: B

Rationale: A muscle's origin is its fixed attachment, typically the less movable bone, often more proximal (closer to the body's midline) in limb muscles. For example, the biceps brachii originates at the scapula (immovable relative to the arm) and inserts on the radius (movable). This anchors contraction, pulling the insertion toward the origin. 'Immovable' is relative bones shift slightly but the origin resists movement more, leveraging skeletal stability. Proximal positioning aligns with anatomical convention in limbs, though exceptions (e.g., abdominal muscles) exist. Aponeuroses, flat tendon sheets, may connect origins (e.g., rectus abdominis), but aren't universal. Movable origins contradict biomechanical principles: muscles shorten toward a stable point. Less proximal origins occur in rare cases, but the standard confirmed by dissection and kinesiology prioritizes the immovable, proximal end. This framework governs force direction, distinguishing origin from insertion in movement analysis.

Correct Answer: B

Rationale: The four-point crutch gait involves alternating crutch and leg movements (right crutch, left leg, left crutch, right leg), providing maximum stability due to three points of support on the ground at all times. This is ideal for patients needing balance and safety, such as those with weakness or partial weight-bearing restrictions. Non-weight bearing typically uses a swing-through gait, not four-point. Mimicking normal walking is closer to a two-point gait, which is less stable. Rapid pace aligns with swing gaits, not the deliberate four-point method. Stability is the key advantage here, making it suitable for patients recovering from lower limb injuries or neurological conditions, ensuring safe mobility over speed or normalcy.