Quick Facts
Location: Thoracic cage.
Bone Type: Flat bone.
Key Features: Head, neck, tubercle, body, angle, and costal groove.
Articulates With: Eighth and ninth thoracic vertebrae, ninth costal cartilage.
Arterial Supply: Posterior intercostal and musculophrenic arteries.
Related parts of the anatomy
Key Features & Anatomical Relations
The ninth 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 ninth 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 ninth rib is located:
- superior to the tenth rib;
- inferior to eighth rib;
- lateral to the ninth costal cartilage and eighth and ninth thoracic vertebrae.
It articulates with the:
- ninth costal cartilage at the ninth costochondral joint;
- eighth and ninth thoracic vertebrae at the ninth costovertebral joint.
Ossification
Ossification of the ninth 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 ninth rib within the fourteenth to twentieth years (Cunningham, Scheuer and Black, 2016).
Variations
In some individuals:
- the ninth rib may be fused with adjacent ribs;
- the costal end of the ninth rib may be bifid in appearance (Tubbs, Shoja and Loukas, 2016).
Surface Anatomy
The ninth rib is easily palpated and is located by palpating seven 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 ninth 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
The rib cage forms the bony margins of the chest wall and is composed of the ribs, costal cartilages, sternum and thoracic vertebrae.
