In a long bone, which of the following parts are involved in an articulation?

Correct Answer: A

Rationale: The epiphysis (end) of a long bone articulates with other bones at joints. Metaphysis is growth region, diaphysis is shaft, symphysis is a joint type. Answer is A, per the document.

Correct Answer: B

Rationale: The average adult human has 206 bones, a standard anatomical count after fetal bones fuse (e.g., sacrum). 33 is the vertebral column, 639 is muscles, and variation is minimal post-development, making '206' correct.

Correct Answer: D

Rationale: The medullary cavity in long bones contains bone marrow (red for blood production, yellow for fat). Air isn’t present, blood is in vessels, cells are in matrix—not the cavity. 'Bone marrow' is correct.

Correct Answer: C

Rationale: Bone elongation during growth occurs at the epiphyseal plate (growth plate), where chondrocytes undergo mitosis, producing new cartilage that is later ossified into bone. Articular cartilage covers bone ends for joint movement, the periosteum supports bone growth in width, and diploe is spongy bone in flat bones—none of these are primary sites for elongation.

Correct Answer: B

Rationale: Hemopoiesis (blood cell production) occurs in red bone marrow, abundant in spongy bone of vertebrae, ribs, and pelvis in adults. The hyoid lacks marrow, maxilla has limited marrow, and scapula has some but less than vertebrae, which are a primary site.