Skeletal System Notes

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  • 1.The Skeletal System: Structure, Function, and Diseases of the bones and joints

2. The Skeletal System

  • Parts of the skeletal system
    • Bones (skeleton)
    • Joints
    • Cartilages
    • Ligaments (bone to bone)(tendon=bone to muscle)
  • Divided into two divisions
    • Axial skeleton
    • Appendicular skeleton limbs and girdle

3. 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

4. Bones of the Human Body

  • The skeleton has 206 bones
  • Two basic types of bone tissue
    • Compact bone
      • Homogeneous
    • Spongy bone
      • Small needle-likepieces of bone
      • Many open spaces

5. Microscopic Anatomy of Bone 6.

  • Bones are classified by theirshape :
  • long
  • short
  • flat
  • irregular

7. Classification of Bones on the Basis of Shape 8. Classification of Bones

  • Long bones
    • Typically longer than wide
    • Have a shaft with heads at both ends
    • Contain mostly compact bone
      • Examples: Femur, humerus

9. Gross Anatomy of a Long Bone

  • Diaphysis
    • Shaft
    • Composed of compact bone
  • Epiphysis
    • Ends of the bone
    • Composed mostly of spongy bone

10. Structures of a Long Bone

  • Periosteum
    • Outside covering of the diaphysis
    • Fibrous connective tissue membrane
  • Sharpeys fibers
    • Secure periosteum to underlying bone
  • Arteries
    • Supply bone cells with nutrients

11. 12. Classification of Bones

  • Short bones
    • Generally cube-shape
    • Contain mostly spongy bone
      • Examples: Carpals, tarsals

13. Classification of Bones

  • Flat bones
    • Thin and flattened
    • Usually curved
    • Thin layers of compact bone around a layer of spongy bone
      • Examples: Skull, ribs, sternum

14. Classification of Bones

  • Irregular bones
    • Irregular shape
    • Do not fit into other bone classification categories
      • Example: Vertebrae and hip


  • Surface features of bones
  • Sites of attachments for muscles, tendons, and ligaments
  • Passages for nerves and blood vessels
  • Categories of bone markings
    • Projections and processes grow out from the bone surface
    • Depressions or cavities indentations

16. Types of Bone Cells

  • Osteocytes
    • Mature bone cells
  • Osteoblasts
    • Bone-forming cells
  • Osteoclasts
    • Bone-destroying cells
    • Break down bone matrix for remodeling and release of calcium
  • Bone remodeling is a process by both osteoblasts and osteoclasts

17. Changes in the Human Skeleton

  • In embryos, the skeleton is primarily hyaline cartilage
  • During development, much of this cartilage is replaced by bone
  • Cartilage remains in isolated areas
    • Bridge of the nose
    • Parts of ribs
    • Joints

18. Bone Growth

  • Epiphyseal plates allow for growth of long bone during childhood
    • New cartilage is continuously formed
    • Older cartilage becomes ossified
      • Cartilage is broken down
      • Bone replaces cartilage

19. 20. Bone Fractures

  • 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 fractures are treatedby reduction and immobilization
    • Realignment of the bone

21. Common Types of Fractures 22. Stages in the Healing of a Bone Fracture 23. Axial skeleton supports and protects organs of head, neck and trunk Axial skeleton: skull (cranium and facial bones) hyoid bone (anchors tongue and muscles associated with swallowing) vertebral column (vertebrae and disks) bony thorax (ribs and sternum)Appendicular skeleton includes bones of limbs andbones that anchor them to the axial skeleton Appendicular skeleton: pectoral girdle (clavicles and scapulae) upper limbs (arms) pelvic girdle (sacrum, coccyx) lower limbs (legs) Articulation-where joints meet, connect, and are formed. 24. 22 bones in skull 6 in middle ears 1 hyoid bone 26 in vertebral column 25 in thoracic cage 4 in pectoral girdle 60 in upper limbs 60 in lower limbs 2 in pelvic girdle 206 bones in all 25. 26. The Axial Skeleton

  • Forms the longitudinal part of the body
  • Divided into three parts
    • Skull
    • Vertebral column
    • Bony thorax

27. The Axial Skeleton 28. The skull 8 sutured bones in cranium Facial bones: 13 sutured bones, 1 mandible Cranium encases brain attachments for muscles sinuses 29. 30. Bones of the Skull 31. Allows for growth 32. Human Skull, Superior View 33. Human Skull, Inferior View Figure 5.9 34. Paranasal Sinuses

  • Hollow portions of bones surrounding the nasal cavity

35. The Hyoid Bone

  • The only bone that does not articulate with another bone
  • Serves as a moveable base for the tongue

36. The Vertebral Column

  • Vertebrae separated by intervertebral discs
  • The spine has a normal curvature
  • Each vertebrae is given a name according to its location

37. Vertebral column7 cervial vertebrae 12 thoracic 5 lumbar 1 sacrum (5 fused1 coccyx (4 fused) Vertebrae vary in size and morphology 38. 39. Structure of a Typical Vertebrae 40. Thoracic cage ribs thoracic vertebrae sternum costal cartilages True ribs are directly attached to the sternum (first seven pairs) Three false ribs are joined to the 7 thrib Two pairs of floating ribs 41. 42. Joints

  • Fibrous - Fibrous joints connect bones without allowing any movement. The bones of your skull and pelvis are held together by fibrous joints.
  • Cartilaginous - Cartilaginous joints are joints in which the bones are attached by cartilage. These joints allow for only a little movement, such as in the spine orribs.
  • Synovial - Synovial joints allow for much more movement than cartilaginous joints. Cavities between bones in synovial joints are filled with synovial fluid. This fluid helps lubricate and protect the bones. Bursa sacks contain the synovial fluid.within fixed limits


  • A joint, or articulation, is the place where two bones come together.
  • There are three types of joints classified by the amount of movement they allow:
    • Immovable
    • slightly movable
    • freely movable

44. Types of Joints

  • Hinge-A hinge joint allows extension and retraction of an appendage. (Elbow, Knee)


  • Ball and Socket-A ball and socket joint allows for radial movement in almost any direction. They are found in the hips and shoulders. (Hip, Shoulder)


  • Gliding-In a gliding or plane joint bones slide past each other. Mid-carpal and mid-tarsal joints are gliding joints. (Hands, Feet)


  • Saddle-This type of joint occurs when the touching surfaces of two bones have both concave and convex regions with the shapes of the two bones complementing one other and allowing a wide range of movement. (Thumb)

48. Structures Associated with the Synovial Joint

  • Bursae flattened fibrous sacs
    • Lined with synovial membranes