Bone Structure and Function — MCQs
Which of the following is the primary mechanism of bone growth?
What is the primary organic component of bone?
Which of the following has the greatest concentration of osteogenic cells?
Healing of bone is affected by:
The inter radicular bone is:
Main blood supply to the head and neck of femur comes from
In osteoporosis, bone formation is increased by which drug?
The first primary ossification centre to appear of the carpal bones is
What are the X-ray findings associated with chronic otitis media?
What is the preferred treatment for congenital ptosis with poor levator muscle function?
Bone Structure and Function Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following is the primary mechanism of bone growth?
- A. Bone deposition (Correct Answer)
- B. Bone resorption
- C. Cortical drift
- D. None of the above
Explanation: ***Bone deposition*** - Bone deposition, or **ossification**, is the process by which **osteoblasts** synthesize and secrete new bone matrix, leading to an increase in bone mass and size [1]. - This process is fundamental to both **endochondral ossification** (growth in length) and **intramembranous ossification** (growth in width and formation of flat bones) [2]. - Bone deposition is the **primary mechanism** responsible for increasing bone mass during growth, making it the correct answer. *Bone resorption* - Bone resorption is the process by which **osteoclasts** break down old or damaged bone tissue [1]. - While essential for **bone remodeling** and calcium homeostasis, it primarily decreases bone mass rather than contributing to growth. *Cortical drift* - **Cortical drift** refers to the movement or relocation of bone surfaces due to a combination of apposition (deposition) and resorption on different surfaces. - It is a mechanism of **bone remodeling** and shaping but not the primary process responsible for overall bone growth [2]. *None of the above* - This is incorrect because **bone deposition is indeed the primary mechanism of bone growth**, as it directly leads to the formation of new bone tissue and increase in bone mass. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1182-1184. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Osteoarticular And Connective Tissue Disease, pp. 662-663.
Question 2: What is the primary organic component of bone?
- A. 10% collagen
- B. 10% noncollagenous protein
- C. 20% noncollagenous protein
- D. 90% collagen protein (Correct Answer)
Explanation: ***90% collagen protein*** - **Type I collagen** constitutes around 90% of the organic matrix of bone, providing its tensile strength and flexibility [1]. - This extensive collagen network forms the framework upon which **mineral crystals** (hydroxyapatite) are deposited [1]. *10% collagen* - This percentage is significantly lower than the actual proportion of collagen in the organic matrix of bone. - If collagen only represented 10%, bone would lack its characteristic **tensile strength** and elasticity [2]. *10% noncollagenous protein* - While noncollagenous proteins like **osteocalcin** and **osteonectin** are important for bone mineralization and cell signaling, they only constitute about 10% of the *organic matrix*, not the entire bone, and are not the *primary organic component* [1]. - The dominant organic component is collagen, which provides the structural scaffold [1]. *20% noncollagenous protein* - This percentage is inaccurate; **noncollagenous proteins** typically make up about 10% of the bone's organic matrix [1]. - A higher proportion of noncollagenous proteins would alter the bone's mechanical properties, potentially making it more brittle.
Question 3: Which of the following has the greatest concentration of osteogenic cells?
- A. Marrow- cancellous graft. (Correct Answer)
- B. Marrow- cortical graft.
- C. Costochondral graft.
- D. Cortical graft
Explanation: ***Marrow- cancellous graft*** - **Cancellous bone** contains a high concentration of **bone marrow**, which is rich in **osteogenic stem cells** and growth factors essential for bone formation. - These cells contribute significantly to **osteogenesis**, making cancellous grafts potent for bone healing and fusion. *Marrow- cortical graft* - While cortical grafts provide structural support, the **bone marrow** within them is less abundant and less readily accessible compared to cancellous grafts. - The primary contribution of a cortical graft with marrow is **mechanical strength**, with less emphasis on osteogenic cell concentration. *Costochondral graft* - A costochondral graft includes both **cartilage** and bone, making it useful for specific reconstructions, such as mandibular condyle regeneration. - However, its primary osteogenic potential comes from the osseous component, which typically has a lower concentration of osteogenic cells compared to a cancellous bone graft. *Cortical graft* - **Cortical bone** is dense and provides significant **structural support**, but it contains very few **osteogenic cells** and has limited intrinsic capacity for new bone formation. - Its main roles are providing **load-bearing strength** and acting as a scaffold, rather than contributing a high concentration of osteogenic cells.
Question 4: Healing of bone is affected by:
- A. Hypoxia
- B. Micromovement
- C. Muscle interposition
- D. All of the options (Correct Answer)
Explanation: ***All of the options*** - **Hypoxia**, **micromovement**, and **muscle interposition** are all factors known to impede or negatively affect the normal healing process of a bone fracture. - The successful healing of a bone fracture relies on a series of biological events that can be disrupted by these adverse conditions, leading to delayed union or non-union. *Hypoxia* - **Hypoxia**, or insufficient oxygen supply, impairs the metabolic activity of cells essential for bone healing, such as osteoblasts and chondrocytes. - It interferes with **angiogenesis**, the formation of new blood vessels, which is critical for delivering nutrients and oxygen to the healing bone. *Micromovement* - Excessive **micromovement** at the fracture site prevents the formation of a stable callus and can stimulate the development of fibrous tissue or cartilage instead of bone. - While some motion is beneficial, uncontrolled or excessive micromotion can lead to a **non-union** or pseudarthrosis, as it constantly disrupts the delicate tissue bridges attempting to form. *Muscle interposition* - **Muscle interposition** refers to muscle tissue becoming trapped between the bone fragments, physically separating them and preventing direct bone-to-bone contact. - This physical barrier inhibits the formation of the **fracture hematoma** and subsequent callus, thus mechanically hindering the healing process.
Question 5: The inter radicular bone is:
- A. Osteophytic
- B. Cancellous (Correct Answer)
- C. Compact
- D. Exophytic
Explanation: ***Cancellous*** - The **interradicular bone** (between the roots of multirooted teeth) is primarily composed of **cancellous bone** (spongy bone). - This type of bone contains a network of **trabeculae** and marrow spaces, providing strength and lightweight structure while accommodating blood vessels and nerves. *Osteophytic* - **Osteophytic** refers to the presence of **osteophytes**, which are bone spurs or outgrowths, typically associated with degenerative joint disease, not the normal structure of interradicular bone. - This term describes an abnormal bony projection rather than the inherent tissue type. *Compact* - **Compact bone** (cortical bone) is dense and forms the outer layer of bones, including the **cortical plates** of the alveolar bone. - While it surrounds the cancellous bone in the jaws, the interradicular area itself is predominantly filled with cancellous bone. *Exophytic* - **Exophytic** describes a growth or lesion that protrudes outward from a surface, often used in pathology. - It does not refer to the normal structural composition of bone.
Question 6: Main blood supply to the head and neck of femur comes from
- A. Lateral circumflex femoral artery
- B. Medial circumflex femoral artery (Correct Answer)
- C. Artery of ligamentum teres
- D. Popliteal artery
Explanation: ***Medial circumflex femoral artery*** - The **medial circumflex femoral artery** is the primary arterial supply to the **head and neck of the femur**, particularly via its **retinacular branches**. - These branches ascend along the femoral neck within the joint capsule, supplying most of the femoral head. *Lateral circumflex femoral artery* - The **lateral circumflex femoral artery** primarily supplies the muscles of the **anterior compartment of the thigh**, including the quadriceps femoris. - While it contributes to anastomoses around the hip, its direct supply to the femoral head and neck is less significant than the medial circumflex. *Artery of ligamentum teres* - The **artery of the ligamentum teres** (foveal artery) supplies a small, variable portion of the **femoral head**, mainly in children. - Its contribution to the overall blood supply to the adult femoral head and neck is often negligible or absent. *Popliteal artery* - The **popliteal artery** is located in the **popliteal fossa** behind the knee joint and is the continuation of the femoral artery. - Its branches supply the structures around the knee and lower leg, not the femoral head and neck.
Question 7: In osteoporosis, bone formation is increased by which drug?
- A. Estrogen
- B. Bisphosphonates
- C. Teriparatide (Correct Answer)
- D. Calcitonin
Explanation: ***Teriparatide*** - Teriparatide is a recombinant form of **parathyroid hormone (PTH)** that, when administered intermittently, stimulates **osteoblast activity** leading to increased **bone formation**. - It is an **anabolic agent** used in osteoporosis to build new bone rather than just prevent bone loss. *Estrogen* - Estrogen is primarily used to prevent **bone loss** by **inhibiting osteoclast activity** and supporting bone mineralization. - It does not directly **increase bone formation** but rather maintains bone density. *Bisphosphonates* - Bisphosphonates inhibit **osteoclast-mediated bone resorption** by inducing apoptosis in osteoclasts. - They primarily **decrease bone breakdown** and do not directly stimulate new bone formation. *Calcitonin* - Calcitonin is a hormone that **inhibits osteoclast activity** and thus reduces bone resorption. - It is not a bone-forming agent but rather acts to **decrease bone breakdown** and is used for pain relief in vertebral fractures.
Question 8: The first primary ossification centre to appear of the carpal bones is
- A. Capitate (Correct Answer)
- B. Pisiform
- C. Triquetral
- D. Scaphoid
Explanation: The first primary ossification centre to appear of the carpal bones is ***Capitate*** - The **capitate** is the first carpal bone to show an ossification center, typically appearing around **1-3 months of age**. [1] - This early ossification is an important marker in assessing **bone age** in children. *Scaphoid* - The **scaphoid** ossifies later than the capitate, usually between **4 and 6 years of age**. - Its ossification center is often **bi-lobed** and can be confused with a fracture on X-ray if not recognized. *Triquetral* - The **triquetral** ossification center generally appears between **2 and 4 years of age**. - This makes it a mid-range ossifier among the carpal bones, not the first. *Pisiform* - The **pisiform** is typically the last carpal bone to ossify, with its center appearing between **8 and 12 years of age**. - Its delayed ossification makes it a useful indicator for assessing **skeletal maturity** in older children and adolescents.
Question 9: What are the X-ray findings associated with chronic otitis media?
- A. Honeycombing of mastoid
- B. Sclerosis with cavity in mastoid (Correct Answer)
- C. Clear-cut distinct bony partition between cells
- D. Increased pneumatization of mastoid cells
Explanation: ***Sclerosis with cavity in mastoid*** - Chronic otitis media leads to **long-standing inflammation** and **destruction** of the mastoid air cells, resulting in dense, **sclerotic bone** with cavity formation due to bone erosion. - This is the **characteristic X-ray finding** in chronic otitis media, indicating osseous remodeling and bone destruction from persistent infection. - The sclerosis represents reactive bone formation, while cavities form from **coalescence** of destroyed air cells. *Honeycombing of mastoid* - Honeycombing describes a **normal, well-pneumatized mastoid** with numerous small, distinct air cells visible on X-ray. - This appearance indicates a healthy mastoid bone with good aeration and is **inconsistent** with chronic inflammation. - Chronic otitis media causes bone remodeling and sclerosis, **not** preserved pneumatization. *Clear-cut distinct bony partition between cells* - This describes **normal mastoid anatomy** where air cells are well-defined and separated by thin, intact bony septa. - In chronic otitis media, these septa are typically **eroded or thickened** by inflammation, leading to loss of distinctness. - The inflammatory process causes destruction and sclerosis, **not** preservation of normal architecture. *Increased pneumatization of mastoid cells* - Increased pneumatization indicates **excessive air cell development**, which is opposite to the changes seen in chronic infection. - Chronic otitis media causes **destruction and sclerosis** of air cells, not increased pneumatization. - This would be seen in normal developmental variants, not chronic inflammatory disease.
Question 10: What is the preferred treatment for congenital ptosis with poor levator muscle function?
- A. Muscle suspension technique (Correct Answer)
- B. Muscle advancement procedure
- C. Conservative management
- D. Direct muscle repair
Explanation: ***Muscle suspension technique*** - For congenital ptosis with **poor levator function** (typically <4 mm excursion), suspending the eyelid from the **frontalis muscle** is the preferred surgical approach. - This technique utilizes the forehead muscle to elevate the eyelid, compensating for the weak levator muscle. *Muscle advancement procedure* - This technique, generally **levator advancement** or **resection**, is indicated for ptosis with **good to fair levator function** (typically >5 mm excursion). - It involves strengthening the existing levator muscle, which would be ineffective in cases of poor function. *Conservative management* - **Conservative management** is generally reserved for **mild ptosis** or when surgical intervention is not immediately necessary, often involving observation. - It is **not appropriate** for congenital ptosis with poor levator function that often leads to **amblyopia** if left untreated. *Direct muscle repair* - Direct muscle repair is not a standard term for ptosis surgery; surgical procedures like **levator resection** or **aponeurotic repair** modify the levator muscle. - In cases of **poor levator function**, directly repairing or strengthening a severely compromised muscle is **unlikely to yield effective eyelid elevation**.
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free