Bony Thorax—Sternum and Ribs Summary

Bony Thorax Overview

• Serves as an expandable chamber for respiration (inspiration/expiration).
• Comprises sternum, thoracic vertebrae, and 12 pairs of ribs.
• Protects respiratory organs and mediastinal structures (heart, vessels).

Sternum Anatomy

• Thin, narrow, flat bone with three divisions.
• Length: ~7 inches (18 cm).
• Divisions:
  • Manubrium (2 inches, 5 cm)
  • Body (4 inches, 10 cm)
  • Xiphoid process (ossifies around age 40).
• Palpable landmarks:
  • Jugular notch (T2-T3)
  • Sternal angle (T4-T5)
  • Xiphoid process (T9-T10).

Rib Structure

• Ribs are numbered by corresponding thoracic vertebra.
• True ribs (1-7): connect directly to sternum.
• False ribs (8-12):
  • Ribs 8-10 connect via costocartilage from rib 7.
  • Ribs 11-12: floating ribs (no anterior connection).

Rib Anatomy

• Each rib has two ends:
  • Posterior (vertebral) end with head, neck, tubercle.
  • Anterior (sternal) end.
• Shaft has an angle where curvature occurs (angle of rib).
• Costal groove protects blood vessels and nerves.