Physiology of bones

• What components make up the musculoskeletal system?

  Muscles, skeleton, and connective tissue
• How many bones are in the human skeletal system?

  206 bones
• What is the role of collagen in the skeletal system?

  It provides a soft framework for bones
• What do hydroxyapatite crystals do in the skeletal system?

  They strengthen and harden the bone network
• What are the main functions of the skeletal system?

  • Movement: Allows for muscle attachment and enables movement
  • Support: Provides a hard framework for soft organs
  • Protection: Shields vital organs like the brain and spinal cord
  • Storage: Stores minerals and lipids
  • Hematopoiesis: Produces blood cells
• What are long bones and give examples?

  Long bones are found in arms and legs
• What are the classifications of bones?

  Long, short, flat, irregular, and sesamoid bones

  
• What are flat bones and give examples?

  Flat bones include the ribs, shoulder blades, hip bones, and cranial bones
• What is the organic matrix of bone made up of?

  The organic matrix is made up of collagen fibers
• What happens to the balance of organic and inorganic substances in bones as we age?

  Children have more organic substances, while the elderly have more inorganic substances
• What is the epiphysis of a long bone?

  The ends of the bone

  
• What is the diaphysis of a long bone?

  The shaft of the bone

  
• What is the function of articular cartilage?

  It cushions the ends of the bones and allows for smooth movement
• What is the periosteum?

  The hard outer covering of the bone
• What is the function of the endosteum?

  It lines the medullary cavity which contains the bone marrow
• What is the role of red bone marrow?

  It produces about 500 million blood cells a day
• What is the blood supply system for bones?

  Metaphyseal-epiphyseal, nutrient artery, and periosteal systems

  
• What is the difference between red and yellow bone marrow?

  Red marrow produces blood cells, while yellow marrow consists mainly of fat cells
• What is bone remodeling?

  • Deposition (formation) equals resorption (removal)
  • The human skeleton is completely regenerated every 10 years
  • Keeps skeleton effective for mechanical use
  • Helps maintain plasma Ca$^{2+}$ level
• What are osteoblasts?

  Cells that deposit new bone
• What do osteocytes do?

  They are osteoblasts trapped in the newly formed osteoid
• What is the function of osteoclasts?

  They dissolve and reabsorb bone

  
• How do osteoclasts break down bone?

  They secrete acids and release proteolytic enzymes

  
• What is new bone formation?

  • Blood vessels run through the Haversian canal
  • New bone is laid down in layers of concentric circles
  • Each new area of bone deposition is called an osteon

  
• What factors affect the balance between bone formation and resorption?

  Mechanical stress and hormonal regulation
• What is the role of parathyroid hormone (PTH) in bone metabolism?

  PTH raises plasma Ca$^{2+}$ levels by increasing osteoclast activity

  
• What does calcitonin do in bone metabolism?

  It decreases bone resorption by osteoclasts

  
• How is plasma Ca$^{2+}$ concentration controlled?


  PTH raises it, while calcitonin decreases it

  
• How does bone grow in length?

  Through the division and multiplication of chondrocytes in the epiphyseal plates

  
• What are the key points in bone growth and remodeling?

  • Growth in length occurs at epiphyseal plates
  • Osteoblasts form new bone
  • Osteoclasts resorb old bone
  • Balance between formation and resorption is crucial

  
• How does the musculoskeletal system enable movement?

  • Skeletal muscles are attached to bones across joints
  • Joints are held together by ligaments and cushioned by cartilage
  • Bones act as levers, joints as fulcrums, and muscles provide force
• What are the structural and functional classifications of joints?

  • Structural: fibrous, cartilaginous, synovial
  • Functional: synarthrosis (immobile), amphiarthrosis (slightly movable), diarthrosis (freely movable)
• What are the characteristics of fibrous joints?

  Joined by fibrous tissue, no joint cavity, and seldom movement
• What is the difference between synchondrosis and symphysis in cartilaginous joints?

  Synchondrosis is immovable, while symphysis is slightly movable
• What are the characteristics of synovial joints?

  Articulating bones are separated by a cavity containing synovial fluid

  
• What is the function of synovial fluid?

  It reduces friction, absorbs shocks, and supplies nutrients to cartilage
• What are the types of synovial joints?

  1. Pivot: Radius/ulna
  2. Hinge: Knee/elbow
  3. Saddle: Thumb
  4. Plane: Scapula/clavicle
  5. Condyloid: Wrist radius/scapoid
  6. Ball-and-socket: Hip/shoulder
• What is hyaline cartilage and where is it found?

  It is associated with the skeletal system and found as articular cartilage
• What is the main function of articular cartilage?

  To provide a low friction surface for the sliding of two bones
• How do chondrocytes obtain nutrition?

  They derive nutrition and oxygen from synovial fluid by diffusion