Most muscles cross at least one

Correct Answer: B

Rationale: Most skeletal muscles cross at least one joint to produce movement, as their primary function is to move bones around joints by contracting between their origin and insertion. For example, the biceps brachii crosses the elbow joint to flex the forearm. Tendons connect muscles to bones but aren't crossed by muscles. Bones are attachment points, not crossed entities. Ligaments connect bones to bones, not typically spanned by muscles in this context. Joints are the correct answer, as muscles' biomechanical role hinges on crossing them to facilitate motion, a fundamental principle in musculoskeletal anatomy evident in nearly every bodily action.

Correct Answer: D

Rationale: The masseter forcefully closes the jaw during chewing and is superficial, lying over the mandible's ramus, easily palpable. Temporalis, also a jaw closer, is deeper under the scalp. Lateral pterygoid protrudes and depresses the jaw, not closing it forcefully, and is deep. Medial pterygoid closes the jaw but is deep to the masseter. Masseter's superficial position and power make it the correct answer, as it's the primary, visible jaw-closing muscle, vital for mastication.

Correct Answer: B

Rationale: Smooth muscle operates without conscious control, managing essential involuntary functions. It lines the digestive tract, facilitating peristalsis to move food, and surrounds blood vessels, aiding in blood flow regulation not pumping, which is the heart's role, but still vital for circulation. Voluntary movements, like running, rely on skeletal muscle, not smooth muscle, which lacks the striations for such tasks. Claiming it controls all involuntary movements overstates its scope, as cardiac muscle handles heartbeats independently. 'None of the above' dismisses its clear role. Smooth muscle's involuntary nature and presence in visceral organs and vascular walls make it key for digestion and circulation support, distinguishing it from skeletal muscle's voluntary domain and cardiac muscle's specialized pumping, aligning with its physiological purpose across multiple systems.

Correct Answer: D

Rationale: Exercise strengthens muscles by stressing fibers, prompting growth and repair. Resistance training or cardio increases muscle mass, endurance, and power through repeated contraction and recovery. Diet and food provide nutrients protein, carbs but without exercise, they don't build strength directly, only support it. Sleeping aids recovery, allowing muscle repair, but doesn't actively strengthen. Exercise's mechanical stress triggers hypertrophy, enhancing fiber size and efficiency, unlike diet's passive fuel role or sleep's restorative one. Regular activity, like lifting or running, directly fortifies muscles, making it the primary driver, supported but not replaced by nutrition and rest, critical for physical capability.

Correct Answer: D

Rationale: Joints that are fibrous and immovable are classified as synarthroses, such as skull sutures, where dense connective tissue binds bones tightly, ensuring stability with no motion. Tendons connect muscles to bones, and tibia is a bone neither are joint types. Ligaments link bones, and femur is a bone, but this pairing doesn't define a joint category. Diarthrosis refers to freely movable synovial joints, like the knee, opposite to the question's intent. Synarthroses accurately describe fibrous, fixed joints, critical for structures requiring rigidity, like the cranium, distinguishing them from movable or cartilaginous joints in anatomical classification.