True Ribs

True ribs are the first seven pairs of ribs (ribs 1–7) that attach directly to the sternum via their own costal cartilages. They form the upper part of the rib cage and play a critical role in protecting thoracic organs and supporting respiratory mechanics.

Location

True ribs are located in the superior portion of the thoracic cage. Each rib extends from its posterior articulation with a thoracic vertebra and curves anteriorly to connect directly to the sternum via an individual costal cartilage.

Definition

Ribs are classified as “true” if they attach directly to the sternum through their own costal cartilage. This distinguishes them from false and floating ribs, which have indirect or no sternal attachments.

Number and Classification

• True ribs: Ribs 1 through 7
• False ribs: Ribs 8 through 12 (attach indirectly or not at all)
• Floating ribs: Ribs 11 and 12 (no anterior attachment)

Anatomical Features

True ribs typically follow the structure of a “typical rib,” especially ribs 3–7. Each rib features:

• Head: Articulates with vertebral bodies (two demifacets)
• Neck: Connects the head and tubercle
• Tubercle: Articulates with the transverse process of the corresponding vertebra
• Angle: The bend of the rib where it curves forward
• Shaft: Long, curved body with a costal groove on the inferior margin
• Anterior end: Connects to costal cartilage that joins the sternum

Articulations

• Posterior: Each true rib articulates with the bodies and transverse processes of thoracic vertebrae (costovertebral and costotransverse joints)
• Anterior: Articulates directly with the sternum via its own costal cartilage (sternocostal joint)

Associated Muscles

• External intercostal muscles: Run between adjacent ribs and assist with inspiration
• Internal and innermost intercostals: Involved in expiration and stabilization of the rib cage
• Serratus anterior, pectoralis major and minor, scalenes: Attach to ribs for movement and support

Function

• Provide structural support to the upper thoracic wall
• Protect vital thoracic organs including the heart and lungs
• Enable expansion and contraction of the thoracic cavity during respiration
• Serve as attachment sites for muscles of respiration and upper limb movement

Blood Supply

• Arterial: Anterior intercostal arteries (from internal thoracic artery) and posterior intercostal arteries (from thoracic aorta)
• Venous: Intercostal veins draining into the azygos system and internal thoracic vein

Innervation

• Intercostal nerves (anterior rami of thoracic spinal nerves T1–T7)

Clinical Relevance

• Rib fractures: Commonly involve middle true ribs (especially 4–7); may result from blunt trauma or severe coughing
• CPR landmarking: The second true rib articulates at the sternal angle and is a reference point for rib counting
• Costochondritis: Inflammation of the costal cartilage causes pain along true ribs, especially in the upper chest
• Thoracic outlet syndrome: May involve compression of vessels or nerves near the first rib and clavicle