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Bones, Part 1: The Axial Skeleton

Explore the components and functions of the bony thorax, including the sternum, ribs, and their attachment sites. Learn about common disorders and the aging process of the axial skeleton.

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Bones, Part 1: The Axial Skeleton

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  1. PART 7 Bones, Part 1:The Axial Skeleton

  2. Bony Thorax • Forms the framework of the chest • Components of the bony thorax • Thoracic vertebrae – posteriorly • Ribs – laterally • Sternum and costal cartilage – anteriorly • Protects thoracic organs • Supports shoulder girdle and upper limbs • Provides attachment sites for muscles

  3. The Bony Thorax Figure 7.19a

  4. The Bony Thorax Figure 7.19b

  5. Sternum • Formed from three sections • Manubrium – superior section • Articulates with medial end of clavicles • Body – bulk of sternum • Sides are notched at articulations for costal cartilage of ribs 2–7 • Xiphoid process – inferior end of sternum • Ossifies around age 40

  6. Sternum • Anatomical landmarks • Jugular notch • Central indentation at superior border of the manubrium • Sternal angle • A horizontal ridge where the manubrium joins the body

  7. Ribs • All ribs attach to vertebral column posteriorly • True ribs - superior seven pairs of ribs • Attach to sternum by costal cartilage • False ribs – inferior five pairs of ribs • Ribs 11–12 are known as floating ribs

  8. Ribs Figure 7.20a

  9. Ribs Figure 7.20b

  10. Disorders of the Axial Skeleton • Abnormal spinal curvatures • Scoliosis – an abnormal lateral curvature • Kyphosis – an exaggerated thoracic curvature • Lordosis – an accentuated lumbar curvature – “swayback” • Stenosis of the lumbar spine • A narrowing of the vertebral canal

  11. The Axial Skeleton Throughout Life • Membrane bones begin to ossify in second month of development • Bone tissue grows outward from ossification centers • Fontanels • Unossified remnants of membranes

  12. Fontanels Figure 7.21a

  13. Fontanels Figure 7.21b

  14. The Axial Skeleton Throughout Life • Many bones of the face and skull form by intramembranous ossification • Endochondral bones of the skull • Occipital bone • Sphenoid • Ethmoid bones • Parts of the temporal bone

  15. The Axial Skeleton Throughout Life • Curvatures of the vertebral column • Primary curvatures – thoracic and sacral curvatures • An infant's spine is C-shaped at birth • Secondary curvatures – cervical and lumbar curvatures • Develop when a baby begins to walk • Redistributes weight of the upper body over the lower limbs

  16. The Axial Skeleton Throughout Life • Aging of the axial skeleton • Water content of the intervertebral discs decreases • By age 55, loss of a few centimeters in height is common • Thorax becomes more rigid • Bones lose mass with age

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