First (1st) rib (anatomy)

The first rib is the most superior within the thoracic cavity. It is atypical in structure:

• head:
  • single articular facet for synovial joint with upper hemifacet on lateral body of T1
  • relatively small
  • reinforced by typical radiate ligament
• neck:
  • slopes superiorly and slightly posteriorly to join the shaft
  • relations:
    • anterior ramus of eighth cervical nerve on superior surface
    • anterior ramus of first thoracic nerve on inferior surface
    • posterior to anterior on thoracic surface: stellate ganglion or sympathetic chain, supreme intercostal vein, superior intercostal artery. These structures are in contact with the apposing cervical pleura.
• tubercle:
  • in anatomical position, most posterior point of rib
  • medial facet for synovial joint articulation with first thoracic vertebra transverse process
  • laterally provides attachment for;
    • lateral costotransverse ligament
    • costalis muscle
    • longissimus muscle
• angle: there is no angle as it has effectively fused with the tubercle
• shaft: see submenu
• general points:
  • the first rib is bent into a very tight curve to turn 180 degrees from vertebra to sternum
  • in the anatomical position, the rib is inclined 45 degrees to the horizontal