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The Skeletal System

The Skeletal System. Ch. 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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The Skeletal System

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  1. The Skeletal System Ch. 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 • Allow movement due to attached skeletal muscles • Store minerals and fats • Blood cell formation

  4. Bones of the Human Body • The adult skeleton has 206 bones • Two basic types of bone tissue • Compact bone • Homogeneous • Spongy bone • Small needle-like pieces of bone • Many open spaces Figure 5.2b

  5. Classification of Bones on the Basis of Shape Figure 5.1

  6. Classification of Bones • Long bones • Typically longer than they are wide • Have a shaft with heads at both ends • Contain mostly compact bone • Example: • Femur • Humerus

  7. Classification of Bones Figure 5.1a

  8. Classification of Bones • Short bones • Generally cube-shape • Contain mostly spongy bone • Example: • Carpals • Tarsals

  9. Classification of Bones Figure 5.1b

  10. Classification of Bones • Flat bones • Thin, flattened, and usually curved • Two thin layers of compact bone surround a layer of spongy bone • Example: • Skull • Ribs • Sternum

  11. Classification of Bones Figure 5.1c

  12. Classification of Bones • Irregular bones • Irregular shape • Do not fit into other bone classification categories • Example: • Vertebrae • Hip bones

  13. Classification of Bones Figure 5.1d

  14. Anatomy of a Long Bone • Diaphysis • Shaft • Composed of compact bone • Epiphysis • Ends of the bone • Composed mostly of spongy bone • Articular cartilage • Covers the external surface of the epiphyses • Made of hyaline cartilage • Decreases friction at joint surfaces

  15. Anatomy of a Long Bone • Medullary cavity • Cavity inside of the shaft • Contains yellow marrow (mostly fat) in adults • Contains red marrow (for blood cell formation) in infants • Epiphyseal plate • Flat plate of hyaline cartilage seen in young, growing bone • Epiphyseal line • Remnant of the epiphyseal plate • Seen in adult bones

  16. Anatomy of a Long Bone • Periosteum • Outside covering of the diaphysis • Fibrous connective tissue membrane • Sharpey’s fibers • Secure periosteum to underlying bone • Arteries • Supply bone cells with nutrients

  17. Microscopic Anatomy of Bone • Osteon (Haversian system) • A unit of bone containing central canal and matrix rings • Central (Haversian) canal • Opening in the center of an osteon • Carries blood vessels and nerves • Lacunae • Cavities containing bone cells (osteocytes) • Arranged in concentric rings • Canaliculi • Tiny canals • Radiate from the central canal to lacunae • Form a transport system connecting all bone cells to a nutrient supply

  18. Microscopic Anatomy of Bone Figure 5.3b–c

  19. 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

  20. Bone Growth (Ossification) • Epiphyseal plates allow for lengthwise growth of long bones during childhood • Bones are remodeled and lengthened until growth stops

  21. Articularcartilage Hyalinecartilage Spongybone New center ofbone growth New boneforming Epiphysealplatecartilage Growthin bonewidth Medullarycavity Bone startingto replacecartilage Bloodvessels Growthin bonelength New boneforming Bone collar Epiphysealplate cartilage Hyalinecartilagemodel In an embryo In a fetus In a child (a) Long Bone Formation and Growth Figure 5.4a

  22. Types of Bone Cells • Osteocytes—mature bone cells • Osteoblasts—bone-forming cells • Osteoclasts—bone-destroying cells

  23. 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 • Bone fractures are treated by reduction and immobilization

  24. Common Types of Fractures Table 5.2

  25. Repair of Bone Fractures • Hematoma (blood-filled swelling) is formed • Break is splinted by fibrocartilage to form a callus • Fibrocartilage callus is replaced by a bony callus • Bony callus is remodeled to form a permanent patch

  26. Hematoma Externalcallus Bonycallus ofspongybone Internalcallus(fibroustissue andcartilage) Newbloodvessels Healedfracture Spongybonetrabecula Bone remodeling Hematomaformation Fibrocartilagecallus formation Bony callusformation Stages in the Healing of a Bone Fracture Figure 5.5

  27. The Axial Skeleton • Forms the longitudinal axis of the body • Divided into three parts • Skull • Vertebral column • Bony thorax

  28. The Axial Skeleton Figure 5.6a

  29. The Axial Skeleton Figure 5.6b

  30. The Skull • Two sets of bones • Cranium • Facial bones • Bones are joined by sutures • Only the mandible is attached by a freely movable joint

  31. Human Skull, Lateral View Figure 5.7

  32. Human Skull, Anterior View Figure 5.11

  33. The Hyoid Bone • The only bone that does not articulate with another bone • Serves as a moveable base for the tongue • Aids in swallowing and speech

  34. The Hyoid Bone Figure 5.12

  35. The Fetal Skull • The fetal skull is large compared to the infant’s total body length • Fontanels—fibrous membranes connecting the cranial bones • Allow the brain to grow • Convert to bone within 24 months after birth

  36. The Fetal Skull Figure 5.13a

  37. The Fetal Skull Figure 5.13b

  38. The Vertebral Column • Each vertebrae is given a name according to its location • There are 24 single vertebral bones separated by intervertebral discs • Seven cervical vertebrae are in the neck • Twelve thoracic vertebrae are in the chest region • Five lumbar vertebrae are associated with the lower back

  39. The Vertebral Column • Nine vertebrae fuse to form two composite bones • Sacrum • Coccyx

  40. The Vertebral Column Figure 5.14

  41. The Vertebral Column • The spine has a normal curvature • Primary curvatures are the spinal curvatures of the thoracic and sacral regions • Present from birth • Secondary curvatures are the spinal curvatures of the cervical and lumbar regions • Develop after birth

  42. The Vertebral Column Figure 5.15

  43. The Vertebral Column Figure 5.16

  44. Sacrum and Coccyx • Sacrum • Formed by the fusion of five vertebrae • Coccyx • Formed from the fusion of three to five vertebrae • “Tailbone,” or remnant of a tail that other vertebrates have

  45. Sacrum and Coccyx Figure 5.19

  46. The Bony Thorax • Forms a cage to protect major organs • Consists of three parts • Sternum • Ribs • True ribs (pairs 1–7) • False ribs (pairs 8–12) • Floating ribs (pairs 11–12) • Thoracic vertebrae

  47. The Bony Thorax Figure 5.20a

  48. The Appendicular Skeleton • Composed of 126 bones • Limbs (appendages) • Pectoral girdle • Pelvic girdle

  49. The Appendicular Skeleton Figure 5.6a

  50. The Appendicular Skeleton Figure 5.6b

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