Biology, Genetics & Bone Healing MCQs

The basic structural unit of compact (cortical) bone, consisting of concentric lamellae surrounding a central canal, is known as the:

Sclerostin, a glycoprotein produced by osteocytes, regulates bone mass primarily by inhibiting which of the following signaling pathways?

During the remodeling phase of tendon healing, the biomechanical strength of the tendon increases primarily due to the transition from:

An autologous iliac crest bone graft provides osteoconduction, osteoinduction, and osteogenesis. Which of the following materials possesses ONLY osteoconductive properties?

Which of the following bone morphogenetic proteins (BMPs) is an FDA-approved osteoinductive agent specifically indicated as an adjunct for the treatment of acute, open tibial shaft fractures stabilized with an intramedullary nail?

Primary bone healing (contact healing) achieved through rigid internal fixation with absolute stability is characterized primarily by which of the following microscopic processes?

During bone transport using the Ilizarov method (distraction osteogenesis), the new bone formed in the distraction gap is generated primarily through which of the following processes?

During bone resorption, osteoclasts utilize a specific enzyme to degrade the organic collagenous matrix of bone within the acidic environment of the sealing zone. Which of the following is the primary enzyme responsible for this process?

A patient who underwent external beam radiation therapy for a soft tissue sarcoma subsequently sustains a pathologic fracture of the irradiated femur. Which of the following best characterizes the cellular environment impairing fracture healing in this patient?

A 68-year-old woman is treated with a monoclonal antibody for severe osteoporosis. The drug binds to a specific receptor on osteoblast lineage cells to inhibit osteoclastogenesis. What is the molecular target of this medication?

A 4-year-old child presents with bowing of the lower extremities and widening of the physes. Laboratory studies reveal hypocalcemia, hypophosphatemia, and markedly elevated alkaline phosphatase. A defect in which of the following processes is most likely responsible?

Romosozumab is an anabolic agent used in the treatment of osteoporosis. It exerts its osteogenic effect by binding to and inhibiting which of the following?

A young patient presents with multiple fractures and generalized increased bone density on radiographs. Genetic testing reveals a mutation affecting the ruffled border of osteoclasts. A defect in which of the following enzymes is most likely involved?

Continuous, high-dose administration of Parathyroid Hormone (PTH) leads to net bone resorption. Which of the following best describes the cellular mechanism responsible for this effect?

While Type II collagen constitutes the vast majority of collagen in articular cartilage, a specific minor collagen type is uniquely responsible for anchoring the basal layer of cartilage to the underlying subchondral bone. Which type is it?

A severely malnourished patient presents with bleeding gums, petechiae, and joint pain. The underlying defect involves impaired hydroxylation of proline and lysine residues during collagen synthesis. This process requires which of the following as a cofactor?

Bone Morphogenetic Proteins (BMPs) are members of the TGF-beta superfamily that induce osteoblastic differentiation. Which intracellular signaling molecules are directly phosphorylated by BMP receptors upon ligand binding?

Primary (strain-free) bone healing occurs without callus formation. Which of the following is an absolute requirement for primary bone healing?

Which of the following molecules acts as a decoy receptor to inhibit osteoclastogenesis by binding to RANKL?

Intermittent administration of parathyroid hormone (PTH) primarily results in which of the following skeletal effects?