Remodeling of bone is a function of

Correct Answer: A

Rationale: Bone remodeling involves osteoclasts (resorb bone) and osteoblasts (form bone), maintaining structure and calcium balance. Osteocytes maintain bone, chondrocytes form cartilage, and chondroblasts aren’t primary in bone remodeling.

Correct Answer: C

Rationale: In a fetus, erythropoiesis (erythrocyte formation) primarily occurs in the liver and spleen during early development, before red bone marrow takes over after birth. Sarcoplasm is muscle cell cytoplasm, and blood is where erythrocytes reside, not where they form, making the liver and spleen the correct fetal sites.

Correct Answer: B

Rationale: The adult human skeleton typically consists of 206 bones. This number accounts for the fusion of certain bones (e.g., sacrum, coccyx) that occurs after infancy, when the count is higher (around 270). 210 is close but slightly over, while 180 and 126 are significantly under the standard count.

Correct Answer: A

Rationale: The appendicular skeleton includes the pectoral girdles (4 bones), upper limbs (60 bones), pelvic girdle (2 bones), and lower limbs (60 bones), totaling 126 bones. The axial skeleton has 80 bones, making 100 and 110 incorrect estimates.

Correct Answer: A

Rationale: Most cranial bones (e.g., frontal, parietal, occipital) are flat, providing a broad, protective shield for the brain. Irregular bones (e.g., sphenoid, ethmoid) exist in the skull, but flat bones predominate in the cranium.