CHAPTER 7: SKELETAL SYSTEM Bone Physiology and Joints

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

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

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

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

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.

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

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

Bone Markings

Bone Markings

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)

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

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

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

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)

Merrick Skeleton

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

Bone Growth (con’t.) Opposing forces of bone formation go on throughout life Youth: Formation > resorption Young adult: balance Age 35-40+: Resorption greater causing weaker bones

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Hinge Include elbow and knee Permits movement in only one plane

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

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

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

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