Learning Objective: At the end of this lesson, the learner will be able to describe the anatomy, classification, articulations, and clinical relevance of the ribs.
The ribs are twelve pairs of curved bones forming the protective cage of the thorax. They articulate posteriorly with the vertebral column and anteriorly with costal cartilage, contributing both to the protection of thoracic organs and ventilation mechanics. During inspiration, the ribs elevate and expand the thoracic cavity, facilitating lung inflation.
Rib Structure
There are two types of ribs based on their morphology: typical and atypical. Typical Ribs (Ribs 3–9) Each typical rib consists of three parts:
- Head: Wedge-shaped, containing two facets—one articulating with its corresponding vertebra and the other with the vertebra above.
- Neck: A flattened segment connecting the head to the body; it bears the tubercle, which articulates with the transverse process of the vertebra.
- Body (shaft): Curved and flat, containing a costal groove on its internal surface that protects the intercostal nerve and vessels.
Atypical Ribs
| Rib | Distinguishing Features |
|---|---|
| 1st Rib | Shortest and broadest; single facet on head; superior surface with grooves for subclavian vessels. |
| 2nd Rib | Longer and thinner than the 1st; rough area for serratus anterior attachment. |
| 10th Rib | Single facet on the head for its vertebra. |
| 11th & 12th Ribs | No neck; single facet; floating ribs, as they lack anterior attachment. |
Articulations
Posterior Articulations: Each rib forms two joints with the thoracic vertebrae:
- Costovertebral joint: Between the rib head and the costal facets of two adjacent vertebrae.
- Costotransverse joint: Between the rib tubercle and the transverse process of its corresponding vertebra.
Anterior Articulations
- Ribs 1–7: Attach directly to the sternum via their own costal cartilage (true ribs).
- Ribs 8–10: Join the cartilage of the rib above (false ribs).
- Ribs 11–12: Have no anterior attachment (floating ribs).
Clinical Relevance
Rib Fractures
- Common in the middle ribs due to trauma.
- Risk of injury to lungs, spleen, and diaphragm from sharp fragments.
Flail Chest
- Occurs when multiple adjacent ribs are fractured in two places, causing a paradoxical movement—the segment moves inward during inspiration and outward during expiration.
- This impairs ventilation and oxygenation.
- Management involves stabilizing the chest wall to prevent paradoxical motion.
