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Anatomy · Anatomical structures

Costal Groove

Sulcus costae

Costal groove (sulcus costae) is a depression located along the inferior margin of the internal surface of the rib body. In the topographic anatomy of the lateral chest wall, the groove participates in the formation of an osteomuscular space associated with the intercostal neurovascular bundle. The presence of the groove depends on the specific rib: it is absent on the 1st and 2nd ribs; it may be visible on the 11th rib; as a rule, it is absent on the 12th rib.

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LocationAlong the inferior margin of the internal surface of the rib body.
Bundle topographyThe intercostal vein, artery, and nerve are arranged from superior to inferior.
FeatureAbsent on the 1st and 2nd ribs; may be visible on the 11th; as a rule, absent on the 12th.
3 min readFor medical studentsUpdated 09/24/2026
Material prepared by WhiteCoat Pro editorial team based on platform study guidesReviewed by medical editor: Aulov A. A., general practitioner · 09/24/2026

Where is the costal groove located?

The costal groove serves as an anatomical landmark on the body of the rib (corpus costae). A rib consists of the head (caput costae), which faces the spine, the neck (collum costae), and its longest part, the body. The body features the costal angle (angulus costae), and the costal groove runs along the lower margin of the internal surface.

  • Location — the groove runs along the inferior margin of the internal surface of the rib body.
  • Termination — the groove ends with the crest of the rib (crista costae).
  • Features of the 1st and 2nd ribs — on the 1st rib (costa prima), which is small in size and lies almost in the horizontal plane, there is no groove on the inferior surface; the inferior surface is smooth. On the 2nd rib (costa secunda), the costal groove is also absent.
  • Features of the floating ribs (XI–XII) — these ribs (costae fluctuantes) have a simpler structure: they lack a costal tubercle, the costal angle is not pronounced, and the head lacks a crest. The costal groove may only be visible on the 11th rib; as a rule, it is absent on the 12th rib.

What is associated with the costal groove?

The costal groove (sulcus costae) participates in the formation of the osteomuscular space of the lateral chest wall. This space is formed by the groove itself, along with the external and internal intercostal muscles.

Medial to the sulcus costae on the internal surface of the chest wall lie the innermost intercostal muscles (mm. intercostales intimi); together with the vessels and nerve, they form the neurovascular bundle.

Topography of the intercostal neurovascular bundle from superior to inferior:

  • Vein.
  • Artery.
  • Nerve.

Topographic features: the intercostal nerve often extends beyond the margin of the costal groove into the interfascial/intermuscular tissue. Anterior to the midaxillary line, the vessels and nerves are not covered by the ribs.

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Clinical significance in trauma

The anatomical features of the intercostal vessels explain bleeding in chest wall wounds:

  • Difficult hemostasis — the fascial sheath of the vessels is fused with the periosteum. Therefore, the vessel walls do not collapse when injured.
  • Bleeding from both ends — there are anastomoses between the anterior and posterior intercostal arteries, forming an arterial ring.
How to memorize

The order of structures in the intercostal neurovascular bundle from top to bottom: VAN — Vein, Artery, Nerve.

Class and exam questions

Is the costal groove present on all ribs?

No. The costal groove is absent on the 1st and 2nd ribs. It may be visible on the 11th rib; as a rule, it is absent on the 12th rib.

Why is bleeding from an intercostal artery difficult to stop?

The fascial sheath of the vessels is fused with the periosteum, so the vessel walls do not collapse when injured. In addition, anastomoses between the anterior and posterior intercostal arteries form an arterial ring, causing bleeding from both ends.

How is the intercostal nerve positioned relative to the groove?

In the neurovascular bundle, the nerve is located below the vein and artery. It often extends beyond the edge of the costal groove into the intermuscular tissue, and anterior to the mid-axillary line, the vessels and nerves are not covered by the ribs.

How does the absence of a groove help identify the 1st rib?

The 1st rib lies almost in a horizontal plane and has distinct superior and inferior surfaces. There is no costal groove on its inferior surface; it is smooth.

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What else to study on this topic

  • Body of rib (Corpus costae)
  • Innermost intercostal muscles (Mm. intercostales intimi)
  • First rib (Costa prima)
  • Floating ribs (Costae fluctuantes)

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