Which molecule is primarily responsible for storing oxygen in muscle cells to support aerobic respiration during muscle contraction?

Correct Answer: C

Rationale: Myoglobin, a protein in muscle cells, binds and stores oxygen, releasing it for aerobic respiration during contraction when oxygen demand rises. ATP and creatine phosphate provide energy, while troponin regulates contraction, making 'Myoglobin' the correct answer.

Correct Answer: B

Rationale: The skeleton protects soft organs (e.g., skull protects brain), supports the body (via structure), and stores minerals (calcium, phosphorus) and fat (yellow marrow). Vitamin D production occurs in the skin upon sunlight exposure, not the skeleton, though bones use vitamin D to absorb calcium. Thus, 'produces vitamin D' is NOT a skeletal function.

Correct Answer: A

Rationale: The epiphyses of long bones are covered with articular (hyaline) cartilage at joints, reducing friction and protecting bone ends during movement. Red and yellow marrow are inside bones, and the endosteum lines the medullary cavity, making 'articular (hyaline) cartilage' correct.

Correct Answer: C

Rationale: Perforating canals (Volkmann’s canals) connect central canals (Haversian canals) in osteons, allowing blood vessels to travel between them. Canaliculi connect osteocytes, the medullary canal is the marrow cavity, and trabeculae are in spongy bone, making 'perforating canal' correct.

Correct Answer: B

Rationale: Endochondral ossification forms bones (e.g., long bones) from a hyaline cartilage model, which ossifies over time. Fibrocartilage is in joints, fibrous membranes are for intramembranous ossification, and adipose is fat, making 'hyaline cartilage' correct.