1. CHAPTER 7: SKELETAL SYSTEM
Bone Physiology and Joints

3. Human Skeleton
Adult skeleton is composed of 206 bones (babies have 300).
Two divisions:
Axial Skeleton – bones that form the longitudinal axis of the body
Appendicular skeleton – bones of the limbs and girdles
Skeletal system includes bones, joints, cartilages, and ligaments

4. Functions of Bones Support – internal framework of body
Protection – protects soft organs
Movement – muscles attached by tendons
Storage – minerals and fat
Blood cell formation – marrow cavities

5. Classification of Bones
Two basic types of bone tissue:
Compact Bone: dense, looks smooth, homogenous
Spongy Bone: composed of small needlelike pieces of bones and lots of open space

6. Types of Bones Long bone – ex. Include humerus, femur
Short bone – examples include tarsals and carpals
Flat bone – include frontal, ribs, and scapula
Irregular bone – include vertebrae, mandible, ear bones

7. Long Bone Structure
Diaphysis is hollow, shaft like portion composed of compact bone
The diaphysis is covered and protected by a fibrous connective tissue membrane – the periosteum.

8. Long Bone Structure
Epiphyses are at ends of long bone and made up of a spongy or cancellous bone
Articular cartilage is thin hyaline cartilage that covers surface of epiphyses to decrease friction at joints

9. Long Bone Structure The cavity of the shaft is storage for adipose
Called yellow marrow or medullary cavity.
Red marrow is found in infants in this area and in flat bones of adults (makes blood cells).
Projections and depressions mark bones

10. Bone Markings

11. Bone Markings

12. Microscopic Structure of Bone
Mainly calcified matrix of calcium salts with collagenous fibers
Matrix of compact bone is made of thousands of structures called haversian systems (osteons)

13. The Haversian System (Osteon)
Lamellae – concentric, cylinder-shaped rings of calcified matrix
Lacunae – microscopic spaces containing bone cells -osteocytes
Canaliculi – tiny canals radiating from lacunae, connecting them with haversian canal
Haversian canal – extends lengthwise through center of each system; contains blood and lymph vessels

14. Bone Formation - Ossification
Skeleton pre-formed in hyaline cartilage models
Endochondral ossification is a process that replaces hyaline cartilage with true bones
Most change into bone but not complete until age 25
Osteoblasts within membranous layers form bone tissue

15. Resorption Resorption is the process of breaking down bone
Osteoclasts – bone destroying cells, release Ca2+ into blood.
When calcium levels are too high, calcium is deposited in bone matrix as calcium salts

16. Joseph Merrick Lived 1862 – 1890 in England
Known as the “Elephant Man” due to his deformities
Thought to be either Proteus Syndrome or Neurofibromatosis
Caused great enlargement of bone and surrounding tissue
Died due to a dislocation of the neck (strain from head weight)

17. Merrick Skeleton

18. Bone Growth and Resorption
Epiphyseal plate – site of growth in length, by thickening of hyaline cartilage followed by ossification
Disk located between diaphysis and epiphysis
Growth in diameter – medullary cavity enlarged by osteoclasts destroying bone added around bone by osteoblasts

19. Bone Growth (con’t.)
Opposing forces of bone formation go on throughout life
Youth: Formation > resorption
Young adult: balance
Age : Resorption greater causing weaker bones

20. Bone Fractures and Repair
Fracture is any break of a bone
Simple – skin remains unbroken
Compound – skin is broken
Effective healing requires alignment and immobilization
Reduction – proper set or alignment of fracture
Osteomyelitis – bone infection

21. Steps in Bone Repair
Blood escapes from ruptured blood vessels – forms hematoma
Spongy bone and fibrocartilage form in damaged areas
A bony callus replaces fibrocartilage
Osteoclasts remove excess

22. Bone Diseases
Osteoarthritis (OA) – chronic degenerative condition that affects articular cartilage. Aging
Cartilage softens and exposed bones thicken, restricting movement
Rheumatoid Arthritis (RA) – autoimmune disease affecting synovial joints. Cause unknown.
Thicken into pannus which erodes articular cartilage
Osteoporosis – bone-thinning disease
50% of women, 20% of men

23. Vertebral Disorders
Either congenital or developmental from disease, poor posture or unequal muscle pull on the spine

24. Joints of the Skeletal System
Articulations are joints between two bones.
They hold bones together but also permit movement between them.
Can be classified by degree of movement or by type of tissue holding them together

25. Classification based on Movement
Synarthrosis – non-movable joints
Amphiarthroses – slightly movable joints
Diarthoses – freely movable joints

26. Classification based on Tissue
Fibrous joints – united by fibrous tissue.
Syndesmosis – long fibers of conn. Tissue
Includes joints between distal ends of radius and ulna; tibia and fibula
Cartilaginous joints – united by cartilage.
Example: pubic symphysis of pelvis
Synovial joints – joints united by synovial membrane

27. Synarthrotic Joints Gomphosis – roots of teeth to maxilla and mandible
Sutures – between flat bones
Gomphosis – roots of teeth to maxilla and mandible

28. Amphiarthrotic Joints – slight movement
Synchondrosis – growth plate
Symphysis – pad of cartilage

29. Diarthrotic – The Synovial Joint
Articular cartilage covers the ends of long bones
A joint capsule, strengthened by ligaments holds bones together
Synovial membrane lines inside of joint capsule

30. Menisci and Bursae Menisci – divides some joints into compartments
Bursae – between skin and bony projections; cushion and aid in movement of tendons

31. Types of Synovial Joints
Ball-and-socket – shoulder and hip
Allow greatest variety of movement

32. Condyloid Includes joint between metacarpals and phalanges
Allow a wide variety of movement

33. Gliding Articular surfaces are nearly flat
Movements are sliding back and forth
Include tarsals and carpals

34. Hinge
Include elbow and knee
Permits movement in only one plane

35. Pivot Found at proximal ends of radius and ulna
Permits rotational movement

36. Saddle Found between metacarpal and carpal of thumb
Allows variety of movements

37. Types of Movements Flexion – decrease angle
Extension – return from flexed position
Abduction – move away from midline
Adduction – move toward midline
Rotation – pivoting bone on central axis
Circumduction – moving distal end of bone in a circle causing entire bone to circle
Supination – turning palm out
Pronation – turning palm in

38. More Movements Inversion – turning sole inward
Eversion – turning sole outward
Protraction – moving body part forward
Retraction – reverse of protraction
Elevation – moving part upward
Depression – moving part downward