Which arrangement best describes a bipennate muscle?

Correct Answer: A

Rationale: A bipennate muscle, like rectus femoris, has fibers angling into a central tendon from both sides, resembling a feather's two-sided barbs, boosting force output. All-direction angling fits convergent patterns (e.g., pectoralis major), not bipennate. One-sided angling describes unipennate (e.g., tibialis posterior). Opposite angles misrepresent bipennate fibers align similarly on both sides. This dual-sided structure maximizes fiber packing and strength, distinguishing it from multidirectional, single-sided, or misangled patterns, critical for powerful joint actions.

Correct Answer: C

Rationale: The kidney's layered anatomy includes the cortex as the outer region, the renal pelvis as the innermost collecting area, and the renal medulla as the intermediate zone. The medulla, situated between the cortex and pelvis, contains renal pyramids triangular structures that channel urine toward the pelvis via collecting ducts. Unlike the cortex, which filters blood, the medulla concentrates urine, regulating water and electrolyte balance through its loop of Henle and collecting tubules. The nephron is a functional unit crossing multiple layers, not a layer itself, while the renal pelvis is a central cavity. The medulla's middle position and its role in urine concentration distinguish it, reflecting the kidney's progressive processing from filtration to excretion.

Correct Answer: D

Rationale: Seaweeds concentrate iodine far above ocean levels, requiring energy to move it against its concentration gradient from low outside to high inside. Active transport, using ATP-powered pumps, achieves this, unlike diffusion or passive transport, which move substances down gradients without energy. Osmosis involves water, not solutes like iodine. Active transport's energy dependency enables seaweeds to accumulate iodine for metabolic needs, such as thyroid hormone precursors, showcasing a key adaptation in marine organisms for nutrient uptake.

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: B

Rationale: Muscle structure descends from large to small: myofibrils (organelles within fibers) contain sarcomeres (contractile units), which comprise thin (actin) and thick (myosin) filaments. Muscle belly, the whole muscle, is larger, so starting there misorders scale. Sarcomeres, between Z-lines, house filaments, not vice versa filaments build sarcomeres, sarcomeres build myofibrils. Starting with filaments then sarcomere reverses this hierarchy, and myofibril as largest ignores its cellular role. The correct sequence reflects anatomical organization, distinguishing myofibril as a bundle of sarcomeres, each with filaments, key to understanding contraction's structural basis.