Biology, Genetics & Bone Healing MCQs

Platelet-rich plasma (PRP) relies on the degranulation of platelet alpha granules to release growth factors that promote tissue healing. Which of the following growth factors is NOT typically found in high concentrations within these alpha granules?

Sclerostin, an inhibitor of bone formation, exerts its effect by binding to LRP5/6 and directly inhibiting which of the following signaling pathways?

Demineralized bone matrix (DBM) primarily relies on which of the following components for its osteoinductive properties?

Absolute stability of a fracture construct (e.g., rigid plate fixation with compression) leads to primary bone healing. This process occurs via cutting cones and directly bypasses which typical phase of secondary fracture healing?

Intermittent administration of recombinant parathyroid hormone (teriparatide) is used clinically to treat osteoporosis. By what mechanism does intermittent PTH promote net bone formation?

Bone morphogenetic proteins (BMPs) play a crucial role in osteoinduction by promoting the differentiation of mesenchymal stem cells into osteoblasts. Which intracellular signaling pathway is primarily activated upon BMP binding to its cell-surface serine/threonine kinase receptor?

During the secondary bone healing of a tibial shaft fracture stabilized with a cast, a cartilaginous soft callus forms. Which transcription factor is most critical for the initial differentiation of mesenchymal stem cells into chondrocytes during this phase?

Denosumab is a monoclonal antibody utilized in the treatment of osteoporosis and giant cell tumor of bone. It exerts its effect by mimicking the function of an endogenous molecule. Which endogenous molecule does denosumab mimic, and what is its direct molecular target?

Parathyroid hormone (PTH) maintains serum calcium homeostasis through multiple systemic mechanisms. In the kidney, PTH specifically acts on which anatomical segment of the nephron to stimulate the synthesis of 1-alpha-hydroxylase, thereby increasing the production of active Vitamin D?

During fracture healing via endochondral ossification, the cartilaginous callus undergoes mineralization. Which specific collagen type is uniquely expressed by hypertrophic chondrocytes to facilitate matrix calcification in this phase?

A genetic defect resulting in the non-functional enzyme carbonic anhydrase II leads to an autosomal recessive form of osteopetrosis. What is the precise cellular mechanism by which this mutation impairs normal bone remodeling?

Microscopic examination of a cortical bone specimen reveals multiple secondary osteons (Haversian systems). The boundary separating each secondary osteon from the surrounding interstitial lamellae is marked by a cement line. Which of the following best describes this structure?

Osteoclasts dissolve the inorganic bone mineral matrix by secreting protons into the sealed clear zone, thereby lowering the local pH. Which intracellular enzyme is primarily responsible for generating these protons?

Which molecule, primarily produced by mature osteocytes, acts to inhibit osteoblast differentiation and bone formation by binding to LRP5/6 receptors and antagonizing the Wnt/beta-catenin signaling pathway?

Bone extracellular matrix consists of both an inorganic mineral phase and an organic phase. Which of the following is the most abundant non-collagenous protein in the bone extracellular matrix, often used clinically as a marker of osteoblastic activity?

A 45-year-old man undergoes open reduction and internal fixation of a diaphyseal radial fracture using a dynamic compression plate, achieving absolute stability. What is the primary cellular mechanism of bone healing expected in this scenario?

Denosumab is an antiresorptive medication utilized in the treatment of osteoporosis, giant cell tumor of bone, and bone metastases. It functions as a monoclonal antibody directly targeting and neutralizing which of the following molecules?

A patient presents with bleeding gums, perifollicular petechiae, and poor wound healing, indicating a deficiency of ascorbic acid (scurvy). Which specific intracellular step in collagen biosynthesis is directly impaired due to this deficiency?

Parathyroid hormone (PTH) is a major regulator of calcium homeostasis that stimulates osteoclastic bone resorption. However, mature osteoclasts lack PTH receptors. To induce resorption, PTH primarily binds to receptors located on which cell type?