DEXA Anatomy & Physiology of Bone Structure — Questions and Answers
Question 1: Which bone cells are responsible for bone formation?
- Osteoclasts
- Osteoblasts (Correct answer)
- Chondrocytes
- Fibroblasts
Correct answer: Osteoblasts
Osteoblasts are specialized cells responsible for synthesizing and depositing new bone matrix, a process known as bone formation or ossification. They play a crucial role in bone growth, repair, and remodeling by laying down collagen and other proteins that become mineralized. This activity is essential for maintaining bone strength and integrity.
Question 2: What is the main mineral found in bone?
- Calcium chloride
- Potassium sulfate
- Calcium phosphate (Correct answer)
- Sodium bicarbonate
Correct answer: Calcium phosphate
The primary mineral component of bone is calcium phosphate, specifically in the form of hydroxyapatite crystals. These crystals provide bone with its rigidity and strength, making it capable of supporting the body and protecting organs. Calcium phosphate is vital for bone health and is the target mineral measured in DEXA scans.
Question 3: Where is spongy bone found?
- Shaft of long bones
- At the ends of long bones (Correct answer)
- Outer surface of flat bones
- Within cartilage
Correct answer: At the ends of long bones
Spongy bone, also known as cancellous or trabecular bone, is characterized by its porous, lattice-like structure. It is primarily found at the ends of long bones (epiphyses) and within the interior of flat and irregular bones. This structure provides strength without excessive weight and houses red bone marrow.
Question 4: Which hormone regulates calcium levels in bone?
- Insulin
- Thyroxine
- Parathyroid hormone (Correct answer)
- Cortisol
Correct answer: Parathyroid hormone
Parathyroid hormone (PTH) is a crucial regulator of calcium levels in the blood and bone. When blood calcium levels are low, PTH is released, stimulating osteoclasts to resorb bone and release calcium into the bloodstream. It also promotes calcium reabsorption in the kidneys and vitamin D activation, which aids calcium absorption from the gut.
Question 5: What is the function of osteoclasts?
- Bone formation
- Calcium absorption
- Bone resorption (Correct answer)
- Cartilage production
Correct answer: Bone resorption
Osteoclasts are large, multinucleated cells responsible for bone resorption, the process of breaking down bone tissue. They secrete acids and enzymes that dissolve the mineral matrix and organic components of bone. This process is essential for bone remodeling, repair, and the release of calcium into the bloodstream.
Question 6: Which bone type protects internal organs?
- Long bones
- Flat bones (Correct answer)
- Short bones
- Irregular bones
Correct answer: Flat bones
Flat bones, such as the skull, sternum, scapulae, and ribs, are characterized by their broad, flat surfaces. Their primary function is to provide extensive protection for internal organs and offer large areas for muscle attachment. For example, the skull protects the brain, and the ribs protect the heart and lungs.
Question 7: Which bone marrow is active in hematopoiesis?
- Yellow marrow
- Spongy tissue
- Red marrow (Correct answer)
- Cartilage
Correct answer: Red marrow
Red bone marrow is the primary site of hematopoiesis, the process of producing all types of blood cells, including red blood cells, white blood cells, and platelets. It is found in spongy bone, particularly in the ends of long bones, flat bones, and irregular bones. Yellow marrow, in contrast, primarily stores fat.
Question 8: What structure covers the bone surface?
- Endosteum
- Synovium
- Periosteum (Correct answer)
- Ligament
Correct answer: Periosteum
The periosteum is a tough, fibrous membrane that covers the outer surface of most bones. It contains blood vessels, nerves, and lymphatic vessels that nourish the bone, and it serves as an attachment point for tendons and ligaments. The periosteum also plays a vital role in bone growth, repair, and remodeling.
Question 9: What type of joint connects the femur and pelvis?
- Hinge joint
- Pivot joint
- Ball-and-socket joint (Correct answer)
- Gliding joint
Correct answer: Ball-and-socket joint
The joint connecting the femur (thigh bone) and the pelvis (specifically the acetabulum) is a ball-and-socket joint, known as the hip joint. This type of synovial joint allows for a wide range of motion in multiple planes, including flexion, extension, abduction, adduction, rotation, and circumduction. Its structure provides both mobility and stability.
DEXA Anatomy & Physiology of Bone Structure
Which bone cells are responsible for bone formation?