Overview
The first rib is the most superior of the twelve ribs and one of three atypical ribs (the others: eleventh and twelfth rib). It forms the border of the superior thoracic aperture. It slopes down anteriorly and has no discrete angle.
Structure
- Head – single facet for articulation with T1 vertebral body
- Neck – between head and shaft
- Shaft – flat, with broad superior and inferior surfaces, ends in costal cartilage
- Scalene tubercle – located on superior surface, separates anterior groove (for subclavian vein) from posterior groove (for subclavian artery)
- Transverse tubercle – projects from junction of neck and shaft, bears articular facet for T1 transverse process
Articulations
- Costovertebral joint – head and facet of T1 body
- Costotransverse joint – transverse tubercle and T1 transverse process
- Sternocostal joint – costal cartilage with manubrium of sternum
Ligamentous Attachments
- Radiate ligament – a branching ligament uniting the head of the rib with the bodies of the two vertebrae and the intervertebral disk between them
- Costotransverse ligament – short fibrous band that connects a rib with the transverse process of vertebra, between non-articular part of tubercle and T1 transverse process
- Costoclavicular ligament – binds the inferior medial clavicle (via the rhomboid fossa) to the first costal cartilage and the adjacent end of the first rib
- Sibson’s fascia
Muscular Attachments
- Scalenus anterior – scalene tubercle
- Scalenus medius – between transverse tubercle and groove for subclavian artery
- Intercostal muscles (external, internal, innermost)
- Subclavius – junction of anterior end of first rib and its costal cartilage, to inferior surface of middle third of clavicle
- Serratus anterior muscle (first digitation)
- Iliocostalis
Arterial Supply
- Internal thoracic artery – branch of the first part of subclavian artery
- First intercostal branch of supreme intercostal artery – branch of the costocervical trunk
Venous Drainage
- Supreme intercostal vein, a tributary of the brachiocephalic vein
Innervation
- First intercostal nerve (T1)
Relations
- Superior: anterior and middle scalene, inferior trunk of brachial plexus, subclavian vessels, subclavius, clavicle
- Inferior: 1st intercostal neurovascular bundle (anterior intercostal vein, artery and nerve), intercostal muscles
- Medial: apex of lung
- Lateral: scalenus posterior, axillary vessels, trunks of brachial plexus
- Anterior to neck: supreme intercostal artery and vein, sympathetic chain
Development
- Primary: shaft
- Secondary: head and tubercle
Anatomical Variants
- Osseous/fibrous articulation or fusion with cervical rib
- Bifid rib
- Rudimentary/hypoplastic first rib
- Pseudoarthrosis of first rib