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Skeletal System

Skeletal System. Chapter 5. The Skeletal System. Parts of the skeletal system Bones (skeleton) Joints Cartilages Ligaments Two subdivisions of the skeleton Axial skeleton Appendicular skeleton. Functions of Bones. Support the body Protect soft organs

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Skeletal System

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  1. Skeletal System Chapter 5

  2. The Skeletal System Parts of the skeletal system Bones (skeleton) Joints Cartilages Ligaments Two subdivisions of the skeleton Axial skeleton Appendicular skeleton

  3. Functions of Bones Support the body Protect soft organs Acts as a lever for attached skeletal muscles Store minerals and fats Blood cell formation (hematopoiesis)

  4. Bones of the Human Body The adult skeleton has 206 bones Two basic types of bone tissue Compact bone Spongy bone

  5. Articular cartilage Anatomy of a Long Bone • Diaphysis • Shaft • Composed of compact bone • Epiphysis • Ends of the bone • Composed mostly of spongy bone Proximal epiphysis Spongy bone Epiphyseal line Periosteum Compact bone Medullary cavity (lined by endosteum) Diaphysis Distal epiphysis (a) Figure 5.3a

  6. Anatomy of a Long Bone Periosteum Fibrous connective tissue membrane, covers outside of the diaphysis Perforating (Sharpey’s) fibers Hyaline cartilage lines joint surfaces Arteries Endosteum Yellow bone marrow Compact bone Periosteum Perforating (Sharpey’s) fibers Nutrient arteries (c) Figure 5.3c

  7. Articular cartilage Anatomy of a Long Bone Proximal epiphysis Spongy bone Epiphyseal line Periosteum Compact bone Medullary cavity (lined by endosteum) Diaphysis Distal epiphysis (a) • Epiphyseal plate (Young) • Flat plate of hyaline cartilage • Epiphyseal line (Adults) • Remnant of the epiphyseal plate Figure 5.3a

  8. Anatomy of a Long Bone Marrow (medullary) cavity Contains yellow marrow (mostly fat) in adults Infants: red marrow for blood cell formation In adults: red marrow is cavities of spongy bone

  9. Microscopic Anatomy of Compact Bone Osteon (Haversian system) Central canal and matrix rings Carries blood vessels and nerves Perforating (Volkmann’s) canal Carries blood vessels and nerves

  10. Osteon (Haversian system) Lamellae Blood vessel continues into medullary cavity containing marrow Spongy bone Perforating fibers Compact bone Periosteal blood vessel Central (Haversian) canal Periosteum Perforating (Volkmann’s) canal (a) Blood vessel Figure 5.4a

  11. Microscopic Anatomy of Bone Lacunae Cavities containing bone cells (osteocytes) Arranged in concentric rings called lamellae Lamellae Calcified cartilage surrounding lacunae

  12. Formation of 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

  13. Bone Growth (Ossification) Epiphyseal plates allow for lengthwise growth of long bones during childhood New cartilage is continuously formed Older cartilage becomes ossified Cartilage is broken down Enclosed cartilage is digested away, opening up a medullary cavity Bone replaces cartilage through the action of osteoblasts

  14. Bone Growth (Ossification) Bones are remodeled and lengthened until growth stops Bones are remodeled in response to two factors Blood calcium levels Pull of gravity and muscles on the skeleton Bones grow in width (called appositional growth)

  15. Articular cartilage Hyaline cartilage Spongy bone New center of bone growth New bone forming Epiphyseal plate cartilage Growth in bone width Medullary cavity Bone starting to replace cartilage Invading blood vessels Growth in bone length New bone forming Bone collar Hyaline cartilage model Epiphyseal plate cartilage In an embryo In a child In a fetus Figure 5.5

  16. Bone growth Bone remodeling Growing shaft is remodeled as: Bone grows in length because: Articular cartilage 1 Cartilage grows here. Epiphyseal plate 2 Cartilage is replaced by bone here. 1 Bone is resorbed here. 3 2 Cartilage grows here. Bone is added by appositional growth here. 4 Cartilage is replaced by bone here. 3 Bone is resorbed here. Figure 5.6

  17. Bone Remodeling • Osteocytes are mature bone cells • Osteoclasts digest organic matric in response to PTH • Increases blood calcium levels • Osteoblasts form organic matric in response to calcitonin • Decrease blood calcium levels • Mechanical and gravitational forces also affect remodeling 17

  18. Bone Remodeling • Balance between resorption and formation 18

  19. Bone Fractures Fracture—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

  20. Common Types of Fractures Comminuted—bone breaks into many fragments Compression—bone is crushed Depressed—broken bone portion is pressed inward Impacted—broken bone ends are forced into each other Spiral—ragged break occurs when excessive twisting forces are applied to a bone Greenstick—bone breaks incompletely

  21. Hematoma External callus Bony callus of spongy bone New blood vessels Internal callus (fibrous tissue and cartilage) Healed fracture Spongy bone trabecula 1 4 Hematoma forms. Fibrocartilage callus forms. Bony callus forms. Bone remodeling occurs. 2 3 Figure 5.7

  22. Inflammatory Conditions Associated with Joints Bursitis—inflammation of a bursa usually caused by a blow or friction Tendonitis—inflammation of tendon sheaths Arthritis—inflammatory or degenerative diseases of joints Over 100 different types Autoimmune disease

  23. Clinical Forms of Arthritis Osteoarthritis Most common chronic arthritis, related to normal aging processes Rheumatoid arthritis An autoimmune disease—the immune system attacks the joints Gouty arthritis Deposition of uric acid crystals from the blood

  24. Figure 5.33

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