Skeletal

• Skeleton


  • Framework of the body
  • Without it the body would be without form
  • Wouldn't even be possible to walk upright
  • Protects vital organs like the brain, heart, and lungs
• Sections of the skeletal system


  • Axial skeleton
  • Appendicular skeleton
• Axial skeleton


  • Forms the main trunk of the body
  • Consists of the skull, spinal column, ribs, and sternum
• Sternum


  The breast bone
• Skull


  Composed of 8 different bones
• Spinal column


  • Also known as the vertebral column
  • 26 vertebrae
  • Intervertebral disc between each
  • Protects the spinal cord
• Intervertebral disc


  Acts as a shock absorber between each vertebra
• Ribs


  • 24 ribs or 12 pairs
  • 7 pairs of true ribs
  • 5 pairs of false ribs, last 2 pairs are floating ribs
  • Protect vital organs like the heart, blood vessels, and lungs
  • Responsible for blood production (hematopoiesis)
• Appendicular skeleton


  • Forms the extremities of the body
  • Includes the shoulder girdle, arm bones, pelvic girdle, and leg bones
• Shoulder girdle


  • Comprised of 4 bones: 2 clavicles and 2 scapulas
  • Bones to which the arm bones attach
• Arm


  • Composed of 3 bones: humerus (upper arm), radius and ulna (lower arm)
  • Wrist bones (8 carpals)
  • Hand bones (5 metacarpals, 14 phalanges)
• Pelvic girdle


  • Structure to which the leg bones are attached
  • Made up of 2 hip bones (ilium, ischium, symphysis pubis)
• Leg


  • Femur (thigh bone)
  • Patella (kneecap)
  • Tibia and fibula (lower leg)
  • Ankle bones (7 tarsals)
  • Foot bones (5 metatarsals, 14 phalanges)
  • Calcaneus (heel)
• Long bones


  • Hard, dense bones that provide strength, structure, and mobility
  • Example: femur
• Anatomy of a long bone


  • Shaft (diaphysis)
  • Two ends (proximal epiphysis, distal epiphysis)
  • Medullary canal filled with yellow marrow
  • Endosteum membrane lining the medullary canal
  • Periosteum tough membrane covering the outside of the bone
• Ligaments and cartilage


  Important supportive structures for joints
• Skeletal system


  Includes bones and connective tissue like ligaments, tendons, and cartilage
• Functions of the skeletal system


  • Supporting the body
  • Protecting organs
  • Storing important minerals
  • Producing blood cells
  • Enabling movement (with muscles)
• An adult human generally has 206 bones
• 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 bone shapes


  • 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
• Chondroblasts


  Cells that make cartilage
• Chondrocytes


  Cells that maintain cartilage
• Bone growth


  1. Cartilage serves as a template

  2. Osteoblasts help bones grow in length and diameter
• Bone fracture healing


  1. Fracture hematoma forms

  2. Internal and external calluses form

  3. Osteoclasts remove damaged bone

  4. Osteoblasts remodel new bone
• Joints of the skeleton


  Define the motion of the body and its limitations
• Joints that are fibrous and cartilaginous hardly move, and some, like the connection of the two pubic bones, don't move at all
• Types of synovial joints


  • Hinge
  • Pivot
  • Ball & Socket
  • Ellipsoid
  • Saddle
  • Plane
• Hinge joint


  • Allows movement only on one axis
  • Structure prevents rotation this way or that way
  • Allows flexion and extension
• Pivot joint


  • Allows rotation along the long axis
  • A cylindrical bone fits into a ring of bone and ligament
• Hinge joint at the elbow

  Prevents the ulna from twisting
• Combination of the pivot at the top and at the bottom


  Creates the twisting motion for pronation and supination
• Ball & Socket joint


  • Allows movement in all axes - flexion, extension, abduction, adduction, rotation, and circumduction
  • The hip has a deep socket, which gives it stability, but limits some range of motion
  • The shoulder joint has a shallower socket, which gives it greater range of motion, but takes away some stability
• Ellipsoid joint


  • Prevents rotation
  • Allows flexion/extension, abduction/adduction, circumduction
  • The ball, or oval head also slides inside the socket
• Saddle joint


  • Both bones have a concave and convex surface
  • The concave plane of one fits on the convex plane of the other
  • Allows flexion, extension, abduction, adduction, circumduction, and very slight rotation