Which of these is composed of very small vertebrae that have fused?

Correct Answer: A

Rationale: The coccyx (tailbone) consists of four small vertebrae that fuse in adulthood into a single structure. The sacrum, while also fused (five vertebrae), is larger and supports the pelvis, making 'coccyx' the better fit for 'very small.'

Correct Answer: B

Rationale: The radius is wider distally (near the wrist) and tapers proximally (toward the elbow), aiding wrist movement. Thus, it goes from wide to thin 'down' the arm toward the elbow.

Correct Answer: A

Rationale: Yes, an interosseous membrane connects the tibia and fibula along their lengths, similar to the forearm, providing stability and a surface for muscle attachment.

Correct Answer: C

Rationale: The shoulder joint (glenohumeral joint) is a ball-and-socket joint, where the humerus’s rounded head fits into the scapula’s glenoid cavity, allowing a wide range of motion (e.g., rotation, abduction). Hinge joints (e.g., elbow) allow one-plane movement, pivot joints (e.g., atlas-axis) rotate, and saddle joints (e.g., thumb) have a different articulation.

Correct Answer: B

Rationale: Long bones (e.g., femur, humerus) have a hollow shaft (diaphysis) and expanded ends (epiphyses), designed for weight-bearing and movement in the limbs. Flat bones (e.g., sternum) are thin, short bones (e.g., carpals) are cuboidal, and irregular bones (e.g., vertebrae) have complex shapes.