Which bone in the axial skeleton plays a crucial role in the articulation of the upper limb with the axial skeleton and is often referred to as the 'collarbone'?

Correct Answer: D

Rationale: The clavicle, or collarbone, is part of the axial skeleton in some classifications due to its role in the thoracic cage, but it’s often considered part of the pectoral girdle in the appendicular skeleton. Here, it’s listed as axial, connecting the sternum to the scapula, aiding upper limb articulation. Thus, 'Clavicle' is correct.

Correct Answer: B

Rationale: The 'all-or-none' principle states that a muscle fiber contracts fully or not at all when stimulated above a threshold. It doesn’t contract partially; the strength varies with the number of fibers recruited, not individual fiber response, making 'The idea that muscles can either contract fully or not at all' correct.

Correct Answer: B

Rationale: The human spine, or vertebral column, consists of 26 individual bones in children (33 before some fuse in adulthood), collectively called vertebrae. These include 7 cervical, 12 thoracic, 5 lumbar, 5 sacral (fused into the sacrum), and 4 coccygeal (fused into the coccyx). Ribs protect the chest, skull bones form the head, and pelvic bones support the lower body, making 'vertebrae' the correct answer.

Correct Answer: C

Rationale: At joints, cartilage—specifically articular cartilage—covers bone ends, acting as a cushion to absorb shock and reduce friction during movement (e.g., knee cartilage). Ligaments stabilize joints by connecting bones, tendons attach muscles to bones, and muscles move bones, but cartilage directly protects and cushions, making it the correct answer.

Correct Answer: B

Rationale: The diaphysis is the long, cylindrical shaft of a long bone, primarily compact bone, providing strength. The epiphysis is the end, the endosteum lines the interior, and the periosteum (misspelled here as 'periosteium') is the outer membrane, making 'diaphysis' the correct answer.