Skeletal

• Bones

  Active connective tissue that is constantly breaking down, regenerating, and repairing itself
• The average person gets a whole new skeleton every 7-10 years
• Functions of bones

  • Provide support and scaffolding
  • Enable movement
  • Store calcium, phosphate, and other minerals
  • Crucial for blood cell production
  • Regulate blood calcium levels
  • Produce the hormone osteocalcin
• Types of bones by location

  • Axial bones (skull, vertebral column, rib cage)
  • Appendicular bones (limbs, pelvis, shoulder blades)
• Types of bones by shape

  • Long bones
  • Short bones
  • Flat bones
  • Irregular bones
• Compact bone

  Dense, smooth-looking external layer of bone
• Spongy bone

  Porous, honeycomb-looking internal bone tissue made of trabeculae
• Red marrow

  Produces blood cells
• Yellow marrow

  Stores energy as fat
• Structure of long bones

  • Flared ends (epiphyses) with spongy bone and red marrow
  • Shaft (diaphysis) with hollow medullary cavity filled with yellow marrow
• Osteons

  Cylindrical, weight-bearing structural units of bone composed of concentric tubes (lamellae) of collagen fibers
• Lacunae

  Tiny spaces between lamellae that house osteocytes
• Osteoblasts

  Bone-building cells that construct the bone matrix
• Osteoclasts

  Bone-breaking cells that resorb old bone tissue
• Osteocytes


  Mature bone cells that monitor and maintain the bone matrix
• Bone remodeling

  1. Osteocytes detect stress/strain

  2. Osteoclasts resorb old bone tissue

  3. Osteoblasts rebuild new bone
• Exercise stimulates bone remodeling and increases bone strength
• Skeletal system

  System that includes bones and connective tissue like ligaments, tendons, and cartilage
• The human skeletal system has an important job of supporting the body, protecting organs, storing minerals, and enabling movement
• Axial skeleton


  Includes the bones in the skull, ears, throat, vertebral column, and ribcage
• Appendicular skeleton


  Includes the bones of the arms, shoulder girdle, legs, and pelvic girdle
• Types of bones by shape

  • Long bones
  • Short bones
  • Sesamoid bones
  • Flat bones
  • Irregular bones
• Compact bone tissue

  • Hard outer layer
  • Contains spongy bone tissue and bone marrow
• Osteoblasts

  Cells that make bone
• Osteocytes

  Cells that maintain bone structure
• Osteoclasts

  Cells that break down bone structure using lysosomes and acids
• Bone remodeling occurs where old bone is removed and new bone is rebuilt, with 5-10% of the skeleton remodeled each year
• Bones store minerals like calcium, which is important for processes like muscle contraction
• Chondroblasts

  Cells that make cartilage
• Chondrocytes

  Cells that maintain cartilage
• Bone fracture healing

  1. Fracture hematoma forms

  2. Internal and external callus forms

  3. Osteoclasts remove damaged bone

  4. Osteoblasts rebuild new bone
• Fractures can take 6-8 weeks to heal, depending on the type of fracture and other variables
• Severe bone fractures can lead to fat embolism syndrome, which requires emergency care
• Osteogenesis imperfecta

  Genetic disorder that affects collagen production, leading to brittle bones