LESSON 3 - SKELETAL SYSTEM

• Skeletal system


  Composed of 206 bones that, along with cartilage, tendons, and ligaments, make up the framework or skeleton of the body
• Parts of the skeletal system

  • Axial skeleton
  • Appendicular skeleton
• Axial skeleton


  • Consists of 80 bones
  • Primary bones are the skull, spine, ribs and sternum (thorax)
• Appendicular skeleton


  • Consists of 126 bones
  • Primary bones are the shoulder or pectoral girdle, arms, hands, pelvic girdle, legs, and feet
• Anterior means front; posterior means back
• This is an anterior view of the skeleton
• Bones


  • Composed of about 50% water and 50% a solid, calcified, rigid substance known as osseous (AH see us) tissue
• Functions of bones


  • Provide shape, support, and the framework of the body
  • Protect internal organs
  • Serve as a storage place for minerals such as salts, calcium, and phosphorus
  • Play an important role in hematopoiesis (hee MAT ah poh EE siss) - the formation of blood cells that takes place in bone marrow
  • Provide a place to attach muscles
  • Make movement possible through articulation (manner in which the parts come together at a joint)
• Classifications of bones by shape

  • Long bones
  • Short bones
  • Flat bones
  • Irregular bones
• Long bones


  • Include the femur (thigh), tibia (larger shin), fibula (smaller shin bone), humerus (upper arm), radius (larger forearm), and ulna (smaller forearm)
• Short bones


  • Include the carpals of the wrist and tarsals of the ankle
• Flat bones


  • Include the skull, sternum (breastbone), and scapula (shoulder bone)
• Irregular bones


  • Include the vertebrae (spine), and pelvic
• Epiphysis


  Growing end
• Diaphysis


  Shaft
• Periosteum


  Outside covering
• Medullary


  Inner space containing bone marrow
• Endosteum


  Lining of medullary cavity
• Synarthrosis


  A joint that allows no movement, e.g. cranial suture
• Amphiarthrosis


  A joint that allows slight movement, e.g. vertebra
• Diarthrosis


  A joint that allows free movement in a variety of directions, e.g. knee, hip, elbow, wrist, and foot
• Types of body movements at diarthrotic joints

  • Flexion
  • Extension
  • Abduction
  • Adduction
  • Supination
  • Pronation
  • Circumduction
  • Protraction
  • Retraction
  • Dorsiflexion
  • Rotation
  • Inversion
  • Eversion
  • Trendelenburg
  • Lateral
  • Fowler's position
  • Recumbent
• Vertebral column


  Composed of separate bones called vertebrae, connected to form four spinal curves
• Spinal curves


  • Cervical curve
  • Thoracic curve
  • Lumbar curve
  • Sacral curve
• Pelvis


  The lower portion of the trunk of the body, formed by the hip bones, sacrum, and coccyx
• The male pelvis is shaped like a funnel and is heavier and stronger than the female. The female pelvis is oval to round, and wider than the male
• Bone growth and resorption


  Bone is continually remodeled, broken down by osteoclasts in a process called resorption, and formed again by osteoblasts. Bone formation and healing slow down as part of the aging process
• Osteoporosis


  An age-related loss of bone mass or density
• Principal types of bones

  • Long bones
  • Short bones
  • Flat bones
  • Irregular bones
• Long bones


  • Longer than they are wide
  • Consist of a long shaft with two bulky ends or extremities
  • Include bones of the thigh, leg, arm, and forearm
• Short bones


  • Roughly cube shaped with vertical and horizontal dimensions approximately equal
  • Consist primarily of spongy bone, covered by a thin layer of compact bone
  • Include the bones of the wrist and ankle
• Flat bones


  • Thin, flattened, and usually curved
  • Most of the bones of the cranium are flat bones
• Irregular bones


  • Bones that are not in any of the above three categories
  • Primarily spongy bone covered with a thin layer of compact bone
  • The vertebrae and some of the bones in the skull are irregular bones
• All bones have surface markings and characteristics that make a specific bone unique
• Surface markings and characteristics of bones

  • Holes
  • Depressions
  • Smooth facets
  • Lines
  • Projections
  • Other markings
• These usually represent passageways for vessels and nerves, points of articulation with other bones or points of attachment for tendons and ligaments
• Divisions of the skeleton

  • Axial skeleton
  • Appendicular skeleton
• Axial skeleton


  • 80 bones
  • Includes the bones of the head, vertebral column, ribs and breastbone or sternum
• Appendicular skeleton


  • 126 bones
  • Includes the free appendages and their attachments to the axial skeleton
• Bones of the axial skeleton

  • Skull (28 bones)
  • Vertebral column
  • Thoracic cage