What is the primary purpose of a Foley catheter?

Correct Answer: C

Rationale: A Foley catheter, a flexible tube inserted through the urethra into the bladder, primarily drains urine in patients unable to urinate naturally, such as post-surgery or with urinary retention. Its balloon tip secures it, allowing continuous drainage into a bag. It doesn't administer fluids or medications those use IVs or other catheters nor monitor pressure, which requires sensors. Draining urine, its core medical function, prevents complications like infection or kidney damage, distinguishing it in clinical practice.

Correct Answer: D

Rationale: Myosin heads stay bound to actin post-power stroke until another ATP binds, detaching myosin by altering its conformation, allowing the cycle to repeat or relax. More Ca²⁺ affects troponin, not detachment Ca²⁺ sustains contraction. Troponin doesn't bind actin directly for release. More acetylcholine restarts excitation, not detachment. ATP's binding to myosin triggers release, distinguishing it from Ca²⁺ or neurotransmitter roles, key to cross-bridge cycling.

Correct Answer: B

Rationale: Muscle cells hierarchically organize contractile units. Myofibrils, spanning the cell's length, are bundles of sarcomeres repeating units with thick (myosin) and thin (actin) myofilaments. Sarcomeres, about 2 micrometres long, link end-to-end within myofibrils, which extend tens to hundreds of micrometres. Myofilaments are shorter segments within sarcomeres, and troponin is a tiny protein on actin. Myofibrils' full-cell length distinguishes them as the longest, critical for coordinated contraction across the fibre, unlike shorter sarcomeres or molecular-scale components.

Correct Answer: C

Rationale: Ligaments, fibrous connective tissues, link bones across joints, stabilizing skeletal structure e.g., knee ligaments. Tendons and aponeuroses attach muscles to bones, facilitating movement, while sarcomeres are muscle contractile units. Ligaments' bone-to-bone connection distinguishes them from muscle-related structures, crucial for joint integrity and distinguishing skeletal support from contractile mechanisms in musculoskeletal anatomy.

Correct Answer: C

Rationale: Skeletal muscle cells feature neuromuscular junctions with acetylcholine, T-tubules for signal spread, and striations from sarcomere alignment, but aren't branched cardiac muscle is. Their long, cylindrical, multinucleate form suits voluntary movement, distinguishing them from branched, intercalated cardiac cells, key to their structural and functional identity in locomotion.