Axial skeleton · Thorax
Rib (typical)
Ribs are the curved bones that form most of the thoracic cage. A typical rib (the third to ninth) has a head, neck, tubercle and body; the model shown is the right sixth rib. The first, second, tenth, eleventh and twelfth ribs are atypical.
- Latin (TA)
- Costa
- Type
- Flat bone: a long, curved, flattened bar of spongy bone with red marrow inside a thin shell of compact bone
- Side
- Paired — right and left
- Model size
- 19.6 cm longest
Showing a right bone. Rotate it to inspect every surface; switch sides to practise siding.
3D model: Z-Anatomy (CC BY-SA 4.0), derived from BodyParts3D © DBCLS (CC BY-SA 2.1 JP). Adapted by PharmaWallah. Credits & licence
Landmarks
10 of 11 marked on the modelTap a landmark to find it on the bone and read what it is.
The expanded posterior end of the rib.
Where: Posterior (vertebral) end, medial to the neck.
Why it matters: Articulates with the vertebral column at the joint of the head of the rib.
Related: Joint of head of rib (costovertebral joint).
Marked on the model at the point Z-Anatomy places this label.
Two small articular facets on the head, one above the other.
Where: Medial surface of the head, separated by the crest of the head.
Why it matters: The lower facet articulates with the body of its own vertebra; the upper facet articulates with the body of the vertebra above. For the sixth rib: T6 and T5.
Viva: With which vertebrae does the head of the sixth rib articulate?
Marked on the model at the point Z-Anatomy places this label.
The flattened, narrowed part between the head and the tubercle.
Where: Lateral to the head, in front of the transverse process of its own vertebra.
Why it matters: Attachment of the costotransverse ligament.
Related: Costotransverse ligament.
Marked on the model at the point Z-Anatomy places this label.
A knob on the outer surface at the junction of neck and body.
Where: Posterior part of the rib, lateral to the neck.
Why it matters: Has a medial articular part for the transverse process and a lateral rough non-articular part for the lateral costotransverse ligament.
Marked on the model at the point Z-Anatomy places this label.
A small smooth oval facet on the medial, lower part of the tubercle.
Where: Tubercle, medial part.
Why it matters: Articulates with the transverse costal facet of its own vertebra (T6 for the sixth rib) at the costotransverse joint.
Related: Costotransverse joint.
Marked on the model at the point Z-Anatomy places this label.
The point where the shaft turns sharply forwards, marked by a rough oblique line on the outer surface.
Where: Posterior part of the body, lateral to the tubercle.
Why it matters: Weakest part of the rib and a common site of fracture; the iliocostalis part of erector spinae attaches here.
Related: Iliocostalis.
Marked on the model at the point Z-Anatomy places this label.
The thin, flat, curved main part of the rib.
Where: From the tubercle to the anterior end.
Why it matters: Has an outer convex and inner concave surface and upper (rounded) and lower (sharp) borders; the intercostal muscles attach to its borders.
Marked on the model at the point Z-Anatomy places this label.
A groove on the inner surface along the lower border of the body.
Where: Inferior border, internal surface, most marked posteriorly and fading towards the front.
Why it matters: Protects the intercostal vein, artery and nerve (in that order from above down: VAN). A needle placed in an intercostal space is passed just above the upper border of the rib below to avoid them.
Related: Intercostal neurovascular bundle.
Viva: What lies in the costal groove, in order from above down?
Marked on the model at the point Z-Anatomy places this label.
The front end of the rib, with a cup-shaped depression.
Where: Anterior end of the body.
Why it matters: Receives the costal cartilage at the costochondral joint.
Related: Costochondral joint.
Classification & region
Flat bone: a long, curved, flattened bar of spongy bone with red marrow inside a thin shell of compact bone (classed as flat despite its length).
- Head
- The posterior (vertebral) end, with two articular facets separated by a crest.
- Neck
- The short narrowed part between the head and the tubercle.
- Tubercle
- A knob at the junction of neck and body, with an articular part (for the transverse process) and a non-articular part.
- Body (shaft)
- The thin, flat, curved main part, which bends forwards at the angle and has the costal groove on the inner surface of its lower border.
- Anterior (sternal) end
- A small cup-shaped depression into which the costal cartilage fits.
Hold it in the anatomical position
- The head and tubercle are at the back (posterior end); the cupped end for the costal cartilage is in front.
- The costal groove lies on the inner surface along the lower border: put it below and inside.
- The inner surface is concave and smooth; the outer surface is convex.
- The shaft slopes downwards and forwards from the tubercle, so the front end lies lower than the back end.
Right or left? Side determination
- Find the head (the end with two small facets) and place it posteriorly; the cup-shaped anterior end faces forwards.
- Find the costal groove and place it on the lower border, on the inner aspect.
- Now the concave inner surface faces the midline and the convex outer surface faces the side the rib belongs to.
- Check: the head points medially, towards the vertebral column. Viewed from behind (as if standing behind the person), the head of a right rib points to your left and the head of a left rib to your right.
Siding works only on a typical rib. The first, eleventh and twelfth ribs need their own rules (see atypical ribs below).
Check yourself: switch the 3D model to “Left bone” and apply the same steps.
Articulations
- With the bodies of its own vertebra and the vertebra above, and the disc between (t6 and t5 for the sixth rib) at the Joint of the head of rib (costovertebral joint), synovial plane joint — Articular facets of the head..
- With the transverse process of its own vertebra (t6 for the sixth rib) at the Costotransverse joint, synovial plane joint — Articular facet of the tubercle..
- With the costal cartilage at the Costochondral joint, primary cartilaginous joint — Cup-shaped depression of the anterior end..
Muscle and ligament attachments
| Structure | Type | Where on the bone |
|---|---|---|
| External, internal and innermost intercostal muscles | other | Upper and lower borders of the body (connecting adjacent ribs). |
| Serratus anterior | origin | Outer surface of the upper ribs, including the sixth. |
| External oblique | origin | Outer surface of the lower ribs, including the sixth. |
| Iliocostalis (erector spinae) | insertion | Angle of the rib. |
| Levatores costarum | insertion | Outer surface between the tubercle and the angle. |
| Radiate ligament of the head of rib | ligament | Front of the head. |
| Intra-articular ligament | ligament | Crest of the head. |
| Costotransverse ligament | ligament | Back of the neck. |
| Superior costotransverse ligament | ligament | Crest of the neck. |
| Lateral costotransverse ligament | ligament | Non-articular part of the tubercle. |
Functions
- Forms most of the thoracic cage, protecting the heart, lungs and upper abdominal organs.
- Moves during breathing to change the size of the thoracic cavity.
- Gives attachment to the muscles of respiration, the trunk and the upper limb.
- Contains red bone marrow.
Clinical & practical relevance
- Rib fractures are common after chest injury; the angle is the weakest part. A broken rib end can injure the lung (pneumothorax) or, low down, the liver or spleen.
- Because the neurovascular bundle runs in the costal groove, needles and chest drains are passed just above the upper border of a rib.
- A cervical rib (an extra rib from the seventh cervical vertebra) can compress the lower trunk of the brachial plexus or the subclavian artery.
Identification tips
- Groove goes down and in. Head goes back. Then the outer convexity tells you the side.
- Lower facet of the head = own vertebra; upper facet = vertebra above.
- VAN from above down in the costal groove.
- Atypical ribs: 1, 2, 10, 11, 12. Single-facet heads: 1, 10, 11, 12.
Common student mistakes
- Putting the costal groove on the upper border: it is on the lower border, inner surface.
- Siding a rib with the head in front: the head is posterior.
- Thinking a rib joins the sternum directly: it joins a costal cartilage, which joins the sternum (true ribs) or the cartilage above (false ribs).
- Using typical-rib siding rules on the first rib.
Common exam questions
Which ribs are typical and which atypical?Show answer
Third to ninth are typical; first, second, tenth, eleventh and twelfth are atypical.
Name the parts of a typical rib.Show answer
Head (two facets and a crest), neck, tubercle, angle and body (with the costal groove), and the anterior end for the costal cartilage.
How do you side a typical rib?Show answer
Head behind, costal groove below and inside; the concave surface faces the midline and the convex outer surface faces the rib's own side.
What are true, false and floating ribs?Show answer
True ribs (1–7) join the sternum by their own cartilages; false ribs (8–12) do not: the 8th to 10th join the cartilage above, and the 11th and 12th are floating ribs that end free in the abdominal wall.
Describe the features of the first rib.Show answer
Broadest and most curved, and usually the shortest; flat surfaces face up and down; a single facet on the head; a scalene tubercle on its inner border; grooves for the subclavian vein and artery on its upper surface; no costal groove.
What lies in the costal groove?Show answer
The intercostal vein, artery and nerve, from above down.
What joints does a typical rib form?Show answer
The joint of the head with two vertebral bodies, the costotransverse joint with its own transverse process, and the costochondral joint with its cartilage.
Revision summary
- Typical ribs: 3rd to 9th. The model is the right sixth rib.
- Head: two facets (own vertebra and the one above) separated by a crest.
- Tubercle: articular part for its own transverse process, non-articular part for a ligament.
- Angle: where the shaft turns forward; weakest point.
- Costal groove: lower border, inner surface; vein, artery, nerve.
- Atypical: 1st (broad, flat, scalene tubercle), 2nd (tuberosity for serratus anterior), 10th–12th (single facet on head; 11th and 12th short, no tubercle).
Test yourself on the rib (typical)
Spotting questions on bones, sides and landmarks — untimed, with explanations.
Joints of the rib (typical)
References
- Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. 5th ed. Philadelphia: Elsevier; 2023.
- Moore KL, Dalley AF, Agur AMR. Moore's Clinically Oriented Anatomy. 9th ed. Philadelphia: Wolters Kluwer; 2023.
- Federative International Programme for Anatomical Terminology (FIPAT). Terminologia Anatomica. 2nd ed. FIPAT.library.dal.ca; 2019. fipat.library.dal.ca/TA2
- Kervyn G, Zielinski M, Vinent L, et al. Z-Anatomy: the libre 3D atlas of anatomy. Models derived from BodyParts3D, The Database Center for Life Science (CC BY-SA 2.1 JP). CC BY-SA 4.0. www.z-anatomy.com/
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