Overview

Pairs12 (7 true, 3 false, 2 floating)

Typical ribs3–9

Cervical rib prevalence≈0.5–1%

True ribs (1–7) reach the sternum directly through their own costal cartilages. False ribs (8–10) have cartilages that join the cartilage of the rib above, forming the costal margin. Floating ribs (11–12) have short cartilaginous tips ending in the posterior abdominal wall musculature.

A typical rib (3–9) has a head with two articular facets separated by a crest (for its own vertebra and the vertebra above, and the intervertebral disc); a neck; a tubercle with an articular facet for the transverse process of its own vertebra and a rough non-articular part (ligaments); and a long, thin, curved shaft (body) that turns forward at the angle (the weakest point and commonest fracture site, just anterior to the angle). On the inferior internal border runs the costal groove, sheltering the intercostal vein, artery and nerve (VAN, from above down).

Atypical ribs: 1st — shortest, broadest, most curved; flat surfaces facing up and down; single head facet (T1); scalene tubercle (scalenus anterior) separating the groove for the subclavian vein (anterior) from that for the subclavian artery and lower trunk of the brachial plexus (posterior). 2nd — thinner, longer, with a tuberosity for serratus anterior. 10th — single head facet. 11th and 12th — single facet, no neck or tubercle, no costotransverse joint; the 12th may be shorter than the 11th.

Location: Thoracic wall, from the thoracic vertebrae posteriorly to the sternum and costal margin anteriorly.

Parts & subdivisions

Head
Two demifacets and a crest (typical ribs).
Neck
Between head and tubercle; related to the sympathetic trunk anteriorly.
Tubercle
Articular facet for the transverse process; non-articular part for the lateral costotransverse ligament.
Angle
Point of greatest change in curvature; iliocostalis attachment; common fracture site.
Shaft and costal groove
Intercostal vein, artery and nerve run in the groove (VAN).
True ribs (1–7)
Attach directly to the sternum via costal cartilages.
False ribs (8–10)
Cartilages join the cartilage above (costal margin).
Floating ribs (11–12)
No anterior attachment.

Anatomy

Articulations: Joints of the heads of ribs and costotransverse joints posteriorly; costochondral joints anteriorly (cartilage to sternum or to the cartilage above).
Ossification: Endochondral; primary centre near the angle ≈week 6–9; secondary centres for the head and tubercle at puberty, fusing ≈20–25 years.

Function

Protect thoracic and upper abdominal viscera
Move during ventilation (pump- and bucket-handle movements)
Attachment of intercostal, serratus anterior, pectoral, abdominal and back muscles and the diaphragm
Contain red marrow

Clinical significance

Rib fractures

Middle ribs fracture most often, near the angle. Fracture of the 1st rib implies major trauma (subclavian vessels, brachial plexus); fractures of ribs 9–11 may lacerate the spleen (left) or liver (right). Children’s elastic ribs rarely break, so rib fractures in infants raise concern for non-accidental injury.

Intercostal procedures

Chest drains and thoracocentesis are inserted just above the upper border of the rib below (in the "safe triangle", 4th–5th intercostal space mid-axillary line) to avoid the neurovascular bundle in the costal groove.

Cervical rib

An extra rib from C7 may compress the subclavian artery or lower brachial plexus trunk (thoracic outlet syndrome).

Mnemonics

Intercostal neurovascular bundle

"VAN" from superior to inferior in the costal groove: Vein, Artery, Nerve.

Compiled from standard anatomy and physiology references — see the Skeletal System sources. For education only; not medical advice.