Thoeacic Cage

SECTION 3: THORACIC CAGE

Overview of Thoracic Cage

• The thoracic cage consists of:
  • The sternum.
  • 12 pairs of ribs.
  • Thoracic vertebrae.

Rib Classifications

• True Ribs (Rib pairs 1-7):
  • Attach directly to the sternum via their own costal cartilage.
• False Ribs (Rib pairs 8-12):
  • Do not attach directly to the sternum.
  • Include Floating Ribs (Rib pairs 11-12) that do not attach to the sternum at all.

STERNUM

Structure of the Sternum

• The sternum is an elongated bony structure that serves as an anchor for the anterior thoracic cage.
• It consists of three main parts:
  1. Manubrium:
  • The wider, superior section of the sternum.
  • Contains the Jugular Notch:
    • A shallow, U-shaped border at the top of the manubrium.
    • Visible at the anterior base of the neck, located between the medial ends of the clavicles.
  • Contains two Clavicular Notches:
    • Shallow depressions found on either side of the manubrium.
    • Site of the sternoclavicular joint where the sternum connects to the clavicle.
    • The first ribs also attach here.
  1. Body:
  • The elongated central portion of the sternum.
  • Joins the manubrium at the Sternal Angle:
    • This joint is not flat and forms a slight bend.
  1. Xiphoid Process:
  • The inferior tip of the sternum.

Anatomical Features of the Sternum

• Clavicular notch (on manubrium) - point of articulation with clavicle.
• Sternal angle - the junction between the manubrium and body.
• Xiphoid process - small triangular structure at the inferior end of the sternum.

RIBS

Parts of a Typical Rib

• Head of the Rib:
  • The posterior end that articulates with the costal facet on the thoracic vertebra.
• Neck of the Rib:
  • The narrowed section lateral to the head.
• Tubercle of the Rib:
  • A small bump on the posterior surface that articulates with the facet on the transverse process of the vertebra.
• Body (Shaft) of the Rib:
  • The remainder of the rib after the neck.

Rib Classifications

• Ribs are:
  • Curved, flat bones that make up part of the thorax.
  • Articulate posteriorly with the T1-T12 thoracic vertebrae.
  • Anteriorly, most ribs attach to the sternum either directly or indirectly via costal cartilage (hyaline cartilage).

Numbering and Classification

• There are 12 pairs of ribs:
  • Rib Pairs 1-7 (True Ribs):
  • Directly attached to the sternum through costal cartilage.
  • Rib Pairs 8-12 (False Ribs):
  • Costal cartilages do not attach directly to the sternum.
  • Last two pairs (11-12) are Floating Ribs:
    • These ribs do not attach to the sternum at all.