Muscle and cartilage

• Joints

  • Give movement and stability
  • Lined by hyaline cartilage acting as elastic shock absorbers
• Solid Synarthroses

  • give structural integrity
  • allow minimal movement
  • no joint space
• Immovable, bo movement — synarthrosis
• little movement — synchondrosis
• Synovial joints

  • with joint space, allowing a wide range of motion
  • found between ends of bones with dense fibrous capsule, ligaments and muscle
• Synovial membranes

  • attached to the joint capsule between bone ends lined by Synoviocytes (types A & B)
• Synovial fluid

  • filtrate from plasma with hyaluronic acid
  • lubricates and supply nutrients to the cartilage
• Osteoarthritis

  • most common type of joint disease
• G: soft and granular articular surface

  • full thickness is shed off (produce “joint mice”)
• M - chondrocytic growth with osteophytes at the margin (mushroom-shaped osteophytes/ bony outgrowths)
• morning stiffness”, muscle spasms. usual joints affected : fingers, knee, cervical & lumbar joints — Osteoarthritis
• Rheumatoid arthritis

  • chronic systemic inflammatory disease, principally attacking joints
• Rheumatoid arthritis

  • heart, lungs, skin, muscles and blood vessels may be involved
• Rheumatoid arthritis

  Morphology:

  Joints:

  G: early changes – edema and hyperplasia of synovium later changes – pannus formation
• Rheumatoid arthritis

  Clinical Manifestations

  • musculoskeletal pain, later involving local joints
  • bilateral, symmetric joint involvement (digits, wrist, ankle, elbows)
  • warm, swollen and painful (progress in 4-5 years)
• also known as osteitis deformans — paget disease
• Paget Disease

  • caused by osteoclast dysfunction, resulting to focal increase in bone mass (disordered progressive state)
• Osteolytic stage – resorption of many cells w/ multinucleated nuclei
• Bone sclerosis –cortex and trabeculae are thick with soft porous bone inside (lack stability)
• Mixed Stage – bone surface lined by osteoclasts and osteoblasts in disorders of woven bone and lamellar bone (“mosaic” pattern)
• Myasthenia gravis

  • disease due to autoantibody against skeletal muscle acetylcholine receptor (AChR)
  • common in women younger than 40 y/o
• 65% with Thymic Hyperplasia; 15% Thymoma
• predispose to osteosarcoma -- Paget disease
• metaphyseal region of long bones (50% knee)
• most common primary malignant tumor of bone — osteosarcoma
• Osteoblasts

  • synthesize, transport and assemble the matrix and regulate its mineralization
• Hyaline

  • most common
  • ribs, nose, larynx, trachea - a precursor of bone
• weakest of the three types of cartilage - hyaline
• provides strength, and elasticity, and maintains the shape of certain structures — elastic cartilage
• strongest kind of cartilage - fibrocartilage
• CHONDROMA

  – benign tumors of hyaline cartilage that usually occur in bones of enchondral origin

  – most common of the intraosseous cartilage tumors
• Osteocytes

  • help to control calcium and phosphate levels in the microenvironment & detect mechanical forces and translate them into biologic activity
• Osteoclasts

  • specialized multinucleated macrophages derived from circulating monocytes that are responsible for bone resorption