Biology 2

• Skeletal System


  Parts include: Bones (skeleton), Joints, Cartilages, Ligaments
• Two major divisions of the Skeletal System

  • Axial skeleton (skull, ribs and vertebra)
  • Appendicular skeleton (pelvis, extremities)
• Functions of Bones


  • Support of the body
  • Protection of soft organs
  • Movement due to attached skeletal muscles
  • Storage of minerals and fats
  • Blood cell formation
• The adult skeleton has 206 bones
• Compact bone


  Homogeneous
• Spongy bone


  Small needle-like pieces of bone with many open spaces
• Classification of Bones on the Basis of Shape

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


  • Typically longer than wide
  • Have a shaft with heads at both ends
  • Contain mostly compact bone
• Examples of Long Bones

  • Femur
  • Humerus
• Short bones


  • Generally cube-shape
  • Contain mostly spongy bone
• Examples of Short Bones

  • Carpals
  • Tarsals
• Flat bones


  • Thin and flattened, usually curved
  • Thin layers of compact bone around a layer of spongy bone
• Examples of Flat Bones


  • Skull
  • Ribs
  • Sternum
• Irregular bones


  • Irregular in shape
  • Do not fit into other bone classification categories
• Examples of Irregular Bones

  • Vertebrae
  • Hip
• Diaphysis


  Shaft of a long bone, composed of compact bone
• Epiphysis


  Ends of a long bone, composed mostly of spongy bone
• Articular cartilage


  Covers the external surface of the epiphyses, made of hyaline cartilage, decreases friction at joint surfaces
• Medullary cavity


  Cavity of the shaft, contains yellow marrow (mostly fat) in adults, contains red marrow (for blood cell formation) in infants
• In embryos, the skeleton is primarily hyaline cartilage
• During development, much of this cartilage is replaced by bone
• Cartilage remains in isolated areas like the bridge of the nose, parts of ribs, and joints
• Epiphyseal plate growth


  1. New cartilage is continuously formed

  2. Older cartilage becomes ossified

  3. Cartilage is broken down

  4. Bone replaces cartilage
• Bones are remodeled and lengthened until growth stops
• Bones change shape somewhat and grow in width
• Bone fracture


  A break in a bone
• Types of bone fractures

  • Closed (simple) fracture - break that does not penetrate the skin
  • Open (compound) fracture - broken bone penetrates through the skin
• Bone fracture treatment


  1. Reduction - realignment of the bone

  2. Immobilization
• Common Types of Fractures

  • Transverse
  • Oblique
  • Spiral
  • Comminuted
  • Impacted
• Axial Skeleton


  Forms the longitudinal part of the body
• Parts of the Axial Skeleton

  • Skull
  • Vertebral column
  • Bony thorax
• Skull


  Two sets of bones: Cranium and Facial bones, joined by sutures, only the mandible is attached by a freely movable joint
• The hyoid bone is the only bone that does not articulate with another bone
• Vertebral column


  Vertebrae separated by intervertebral discs, has a normal curvature, each vertebrae is given a name according to its location
• Bony thorax


  Forms a cage to protect major organs, made up of the sternum, ribs, and thoracic vertebrae
• Pectoral (Shoulder) Girdle


  Composed of the clavicle and scapula, allows the upper limb to have exceptionally free movement
• Bones of the Upper Limb

  • Humerus (arm)
  • Ulna, Radius (forearm)
  • Carpals (wrist), Metacarpals (palm), Phalanges (fingers)
• Pelvic Girdle


  Composed of the hip bones, which are fused pairs of ilium, ischium, and pubic bones, protects several organs and supports the weight of the upper body
• Bones of the Lower Limb

  • Femur (thigh)
  • Tibia, Fibula (leg)
  • Tarsus (ankle), Metatarsals (sole), Phalanges (toes)
• Arches of the Foot

  Bones of the foot are arranged to form two longitudinal arches and one transverse arch