Chapter 7: Skeletal System

Chapter 7: Skeletal System

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 1. Support internal framework of body 2. Protection protects soft organs

3. Movement muscles attached by tendons 4. Storage minerals and fat 5. 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

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 (growth plates) Intramembranous Bones Certain flat bones of the skull develop from

layers of connective tissue Osteoblasts within membranous layers form bone tissue Primitive connective tissues give rise to the periosteum 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 Growth in length through continual thickening

of hyaline cartilage followed by ossification Epiphyseal plate consists of cells in different life stages Disk located between diaphysis and epiphysis Growth in diameter medullary cavity enlarged by osteoclasts destroying bone around cavity while new bone added around bone by osteoblasts Bone Growth (cont.)

Opposing forces of bone formation go on throughout life Formation exceeds resorption during growth years Balanced during young adult years Resorption greater after age 3540 causing weaker bones Response to stress includes increasing deposits of calcium and collagen fibers which increases bone strength

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 Bone Markings

Bone Markings 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 nonmovable 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 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

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