Quick Facts
Location: Thoracic cage.
Bone Type: Flat bone.
Key Features: Head, neck, tubercle, body, angle, and costal groove.
Articulates With: Seventh and eighth thoracic vertebrae, eighth costal cartilage.
Arterial Supply: Posterior intercostal and musculophrenic arteries.
Related parts of the anatomy
Key Features & Anatomical Relations
The eighth rib is one of the three false ribs of the thoracic cage. It is considered a typical rib because it consists of a head with two articular facets, a neck, a tubercle, and a body. It does not have any extra bony features.
The eighth rib is classified as a flat bone and includes the following bony features:
- parts: head, neck, tubercle, body, and costal end;
- surfaces: internal and external surfaces, and superior and inferior borders;
- landmarks: angle, costal groove, crests on the head and neck, and articular facets on the head and tubercle.
More information regarding these and other bony features can be found in the Parts, Surfaces and Landmarks tabs for this bone.
The eighth rib is located:
- superior to the ninth rib;
- inferior to seventh rib;
- lateral to the eighth costal cartilage and seventh and eighth thoracic vertebrae.
It articulates with the:
- eighth costal cartilage at the eighth costochondral joint;
- seventh and eighth thoracic vertebrae at the eighth costovertebral joint.
Ossification
Ossification of the eighth rib occurs at ossification centers found in the:
- body, which appears in utero during the second month;
- head, which appears during puberty;
- tubercle, which appears during puberty.
The ossification centers for the head and tubercle fuse with the body of the eighth rib within the fourteenth to twentieth years (Cunningham, Scheuer and Black, 2016).
Variations
In some individuals:
- the eighth costal cartilage may articulate directly with the sternum, and not indirectly via the seventh costal cartilage, thereby making the eight rib a true rib;
- the eighth rib may be fused with adjacent ribs;
- the costal end of eighth rib may be bifid in appearance (Tubbs, Shoja and Loukas, 2016).
Surface Anatomy
The eighth rib is easily palpated and is located by palpating six ribs down from the second rib. Counting the seventh to tenth ribs is best done from the lateral aspect of the thoracic cage.
List of Clinical Correlates
- Fracture of eighth rib
- Flail chest
- Asphyxiating thoracic dysplasia/Jeune syndrome
References
Cunningham, C., Scheuer, L. and Black, S. (2016) Developmental Juvenile Osteology. Elsevier Science.
Tubbs, R. S., Shoja, M. M. and Loukas, M. (2016) Bergman's Comprehensive Encyclopedia of Human Anatomic Variation. Wiley.
Learn more about this topic from other Elsevier products
Rib Cage
PIRCM after age 3 is abnormal and can be reliably used as a sign of abnormal physiology (e.g., increased upper airway resistance).
