Which is moved the least during muscle contraction?

Correct Answer: A

Rationale: The origin, the muscle's fixed attachment point (e.g., scapula for biceps brachii), moves the least during contraction, anchoring the muscle as it pulls the insertion (movable end, e.g., radius) toward it. The insertion shifts significantly to produce movement. Ligaments , connective tissues stabilizing joints, don't move but stretch slightly under tension. Joints pivot or flex, moving more than the origin. The origin's relative stability, often proximal and attached to larger bones, ensures effective leverage, making 'a' the correct answer in muscle dynamics.

Correct Answer: D

Rationale: The sartorius, a long, strap-like muscle from iliac spine to tibia, flexes the hip and knee while rotating the thigh laterally, enabling leg crossing (e.g., tailor's pose). Gluteus maximus extends the hip, piriformis rotates it externally, and gracilis adducts the thigh none fully replicate crossing's combined flexion/rotation. Sartorius's unique diagonal action across hip and knee, dubbed the 'tailor's muscle,' makes 'd' the correct choice.

Correct Answer: D

Rationale: The hyoid bone, in the anterior neck, is unique as it doesn't articulate with any other bone, suspended by ligaments and muscles (e.g., suprahyoid, infrahyoid) to support the tongue and larynx. The mandible articulates with the temporal bone at the TMJ. Nasal bones articulate with each other and the frontal/maxilla. The cricoid cartilage , not a bone, connects to the thyroid cartilage. The hyoid's free-floating status, critical for swallowing and speech, makes 'd' the correct answer.

Correct Answer: B

Rationale: Extension is straightening the knee, increasing the angle between the femur and tibia, as when standing, driven by quadriceps contraction. Flexion bends the knee, decreasing the angle. Adduction moves the leg toward the midline, abduction away neither straighten it. Extension's role in aligning the leg, a basic joint motion, makes 'b' the correct term in kinesiology.

Correct Answer: B

Rationale: Voluntary muscles, or skeletal muscles, are under conscious control, enabling deliberate movements like walking or lifting. The hind limb, encompassing muscles like the quadriceps and hamstrings, exemplifies this attached to bones via tendons, they contract via somatic nervous system signals, allowing precise actions. The heart contains cardiac muscle, involuntary and self-regulating via pacemaker cells, beating without conscious input. The liver, a glandular organ, lacks muscle tissue; it metabolizes nutrients but doesn't move voluntarily. The lungs rely on the diaphragm and intercostal muscles for breathing, but these are partly involuntary, driven by autonomic reflexes, and the lung tissue itself isn't muscle. Skeletal muscles, striated and multinucleated, differ from cardiac (striated, single-nucleus) and smooth (non-striated, involuntary) types in structure and control. Anatomy texts highlight the hind limb's role in locomotion, with muscles like the gastrocnemius enabling voluntary flexion, contrasting with organs where autonomic control dominates, making it the clear site of voluntary muscle presence.