Which of the following bones lacks a styloid process?

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: 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.

Correct Answer: B

Rationale: The cranium has a vault (the upper, domed portion) and a base (the lower portion), with the base divided into anterior, middle, and posterior cranial fossae supporting the brain. 'Vault/base' correctly orders these anatomical regions.

Correct Answer: C

Rationale: The zygomatic bone, a paired irregular bone, articulates with the maxilla and forms the cheekbone, contributing to the orbit’s structure. The palatine forms the palate, and the lacrimal is a small orbital bone, neither being the cheekbone.