Bone Histology

Which cell type is responsible for bone resorption and is derived from hematopoietic precursor cells of monocyte/macrophage lineage?

In bone histology, the lacunae visible in mature bone matrix are spaces that contain which cell type?

A 7-year-old boy from rural Maharashtra presents with progressive bowing of both legs over the past 18 months. On examination, he has anterior bowing of the tibiae bilaterally and frontal bossing. Serum calcium is 7.2 mg/dL (normal 8.5–10.5), phosphate is 2.8 mg/dL (normal 3.5–4.5), and alkaline phosphatase is markedly elevated at 420 U/L. X-ray of the tibia shows loss of sharp demarcation between the epiphysis and metaphysis, widened metaphyseal zones, and cupping of the growth plate. Which histological finding in the growth plate would most directly explain the radiological appearance?

A 68-year-old woman from Delhi presents with progressive back pain and height loss of 6 cm over 5 years. She has a history of early menopause at age 42 and limited sun exposure due to cultural practices. Serum calcium is 8.8 mg/dL, phosphate is 4.1 mg/dL, and alkaline phosphatase is 68 U/L (all normal). DEXA scan shows a T-score of –3.2 at the lumbar spine. A bone biopsy from the iliac crest is performed. Under light microscopy, the osteoid seams are of normal thickness but the mineralization lag time is markedly prolonged. What is the most likely histological diagnosis?