Which bone does not contain a paranasal sinus?

Correct Answer: C

Rationale: Paranasal sinuses are air-filled cavities in the frontal, ethmoid, sphenoid, and maxilla bones, reducing skull weight and resonating sound. The vomer, a thin midline bone in the nasal septum, lacks a sinus.

Correct Answer: A

Rationale: The sphenoid bone lacks a styloid process. The temporal bone has a styloid process (near the ear), and the ulna and radius have styloid processes at their distal ends in the wrist.

Correct Answer: B

Rationale: The periosteum is a dense connective tissue membrane covering the outer surface of bones, aiding in growth, repair, and attachment. The pericardium surrounds the heart, perichondrium covers cartilage, and endosteum lines the medullary cavity—only periosteum fits the description.

Correct Answer: B

Rationale: Vertebrae are classified as irregular bones due to their complex, unique shapes that don’t fit the long, short, or flat categories. Long bones (e.g., femur) are elongated, flat bones (e.g., sternum) are thin, and short bones (e.g., carpals) are cuboidal—vertebrae match none of these.

Correct Answer: B

Rationale: The ulna is a long bone in the forearm, characterized by a shaft (diaphysis) and ends (epiphyses), typical of long bones that support weight or enable movement. Ribs are flat, phalanges are short (despite length, they’re classified as short due to structure), and the mandible is irregular.