Overview
This lecture covers the structure and function of the sternum, ribs, and their articulations with the thoracic vertebrae, completing the axial skeleton.
Sternum Structure
- The sternum consists of three parts: manubrium (top), body (middle), and xiphoid process (bottom).
- "Manubrium" means shield; "xiphoid" means dagger-shaped.
- The jugular notch is an indentation at the top of the manubrium for venous drainage.
Ribs and Costal Cartilage
- Ribs do not directly touch the sternum; they are connected by costal cartilage.
- True ribs (pairs 1–7) connect to the sternum via single pieces of cartilage.
- False ribs (pairs 8–12) may have cartilage that merges before reaching the sternum.
- Floating ribs (pairs 11–12) have no cartilage attachment to the sternum.
Rib Anatomy
- One end of a rib (sternal end) is flat and connects to costal cartilage; the other end attaches to vertebrae.
- Rib parts: head (attaches to vertebrae), neck, tubercle (articular facet), angle (sharp curve), and inferior margin.
- The costal groove on the inferior margin houses blood vessels and a nerve.
Rib–Vertebrae Articulations
- Only thoracic vertebrae interact with ribs.
- Each thoracic vertebra has a superior costal facet, inferior costal facet, and transverse costal facet for rib attachment.
- The rib head attaches to the inferior costal facet of one vertebra and the superior costal facet of another.
- The rib tubercle articulates with the transverse costal facet.
- Each rib articulates with two vertebrae, and each vertebra has three articulation points for ribs.
Key Terms & Definitions
- Sternum — flat bone in the chest’s center, made of manubrium, body, and xiphoid process.
- Manubrium — uppermost part of the sternum.
- Xiphoid Process — bottom, dagger-shaped part of the sternum.
- Jugular Notch — indentation atop the manubrium for jugular vein drainage.
- Costal Cartilage — cartilage connecting ribs to the sternum.
- True Ribs — ribs 1–7, direct cartilage connection to sternum.
- False Ribs — ribs 8–12, indirect or no cartilage connection.
- Floating Ribs — ribs 11–12, do not connect to sternum.
- Articular Facet — smooth joint surface where bones meet.
- Costal Groove — groove on rib’s underside for nerves and vessels.
- Thoracic Vertebrae — vertebrae in the rib area, with costal facets for rib articulation.
Action Items / Next Steps
- Review diagrams of the sternum, rib, and vertebral articulations.
- Prepare for discussion or study of the appendicular skeleton in upcoming lessons.