Intercostalrummet

Intercostalrummet, or the intercostal space, is the anatomical space between two adjacent ribs within the thoracic wall. There are eleven such spaces on each side, numbered according to the rib above them (the space between the first and second ribs is the first intercostal space, and so on, down to the space between the eleventh and twelfth ribs).

Boundaries and contents: Each intercostal space is bounded above by the rib of the same number and below by the next rib. Anteriorly, spaces are related to the sternum and costal cartilages; posteriorly, they relate to the vertebral column. Within each space run the intercostal muscles (external, internal, and innermost), and the intercostal neurovascular bundle, which travels along the inferior edge of the rib above and consists of the posterior intercostal artery and vein and the intercostal nerve. Lymphatic vessels and connective tissue are also present. The intercostal nerves are the anterior rami of the thoracic spinal nerves and provide motor innervation to the intercostal muscles and sensory innervation to the chest wall and overlying skin.

Clinical relevance: The intercostal spaces are important landmarks for procedures such as thoracentesis and chest tube insertion. To avoid injury to the neurovascular bundle that lies along the inferior border of each rib, needles or tubes are typically directed just above the superior border of the lower rib within the chosen intercostal space. Variations in vascular supply come from the posterior intercostal arteries and their anterior counterparts, which can have clinical implications in trauma or surgical contexts. The intercostal spaces also play a key role in respiratory mechanics, as the intercostal muscles contribute to the expansion and compression of the thoracic cage during breathing.