Hyoid Bone and Vertebral Column

• Hyoid bone


  Closely related to the mandible and temporal bones, the only bone of the body that does not articulate (form a joint) with any other bone, suspended in the midneck region about 2 cm (1 inch) above the larynx (voicebox), anchored by ligaments to the styloid processes of the temporal bones, horseshoe-shaped, with a body and two pairs of horns, serves as a movable base for the tongue and as an attachment point for neck muscles that raise and lower the larynx when we swallow and speak
• Vertebral column (spine)


  Axial support of the body, extends from the skull to the pelvis, transmits the weight of the body to the lower limbs, formed from 26 irregular bones connected and reinforced by ligaments, flexible and curved structure, runs through the central cavity the delicate spinal cord
• Vertebral column development


  Before birth consists of 33 separate bones called vertebrae, 9 of these eventually fuse to form the sacrum and coccyx, 24 single bones - 7 cervical, 12 thoracic, 5 lumbar
• Intervertebral discs


  Pads of flexible fibrocartilage that cushion the vertebrae and absorb shock while allowing the spine flexibility, high water content (about 90 percent) and are spongy and compressible in young people, water content decreases and discs become harder and less compressible as a person ages
• Spinal curvatures


  • Primary curvatures (thoracic and sacral) present at birth, secondary curvatures (cervical and lumbar) develop after birth, allow us to center our body weight on our lower limbs with minimum effort
• Common features of vertebrae

  • Body (disclike, weight-bearing part facing anteriorly)
  • Vertebral arch (arch formed from the joining of all posterior extensions)
  • Vertebral foramen (canal for spinal cord)
  • Transverse processes (two lateral projections)
  • Spinous process (single posterior projection)
  • Superior and inferior articular processes (allow joints with adjacent vertebrae)
• Cervical vertebrae


  • 7 vertebrae (C1 to C7), first 2 (atlas and axis) have unique functions, 'typical' cervical vertebrae are C3 to C7 - smallest and lightest, spinous processes often short and divided, transverse processes contain foramina for vertebral arteries
• Thoracic vertebrae


  • 12 vertebrae (T1 to T12), larger than cervical, articulate with ribs, body heart-shaped with costal facets, transverse processes articulate with rib tubercles, spinous processes long and hook sharply downward
• Lumbar vertebrae


  • 5 vertebrae (L1 to L5), massive and blocklike, short hatchet-shaped spinous processes, sturdiest vertebrae due to stress in lumbar region
• Sacrum


  Formed by fusion of 5 vertebrae, articulates superiorly with L5 and inferiorly with coccyx, each winglike ala articulates laterally with hip bone forming sacroiliac joint, posterior midline surface has median sacral crest and posterior sacral foramina, vertebral canal continues as sacral canal terminating in sacral hiatus
• Thoracic cage


  Formed by sternum, ribs, and thoracic vertebrae, protective cage of slender bones and cartilages around organs of thoracic cavity
• Sternum


  • Flat bone formed by fusion of 3 bones - manubrium, body, and xiphoid process, attached directly to first 7 pairs of ribs, has 3 important landmarks - jugular notch, sternal angle, xiphisternal joint
• Ribs


  12 pairs, all articulate with vertebral column posteriorly and curve downward and toward anterior body surface, true ribs (first 7 pairs) attach directly to sternum, false ribs (next 5 pairs) attach indirectly or not at all, last 2 pairs are floating ribs, intercostal spaces between ribs filled with intercostal muscles that aid in breathing