Intercostal space

The intercostal space is the space between two ribs. Since there are 12 ribs on each side, there are 11 intercostal spaces, each numbered for the rib superior to it.

Each intercostal space contains several key structures, including muscles, nerves, and blood vessels.

1. Muscles: The intercostal muscles are divided into three layers:

• External intercostal muscles: These muscles run obliquely from the lower border of one rib to the upper border of the rib below, and they are primarily involved in inspiration.

• Internal intercostal muscles: These muscles lie deep to the external intercostals and run perpendicular to them. They are primarily involved in forced expiration.

• Innermost intercostal muscles: These are the deepest layer and are separated from the internal intercostals by the intercostal nerves and vessels.

2. Nerves: The intercostal nerves are the anterior rami of the thoracic spinal nerves (T1-T11). They run along the costal groove on the inferior aspect of each rib and provide motor innervation to the intercostal muscles and sensory innervation to the overlying skin and parietal pleura.

3. Blood Vessels: The intercostal arteries and veins run alongside the intercostal nerves within the costal groove. The intercostal arteries are branches of the thoracic aorta (posterior intercostal arteries) and the internal thoracic artery (anterior intercostal arteries). The veins drain into the azygos and hemiazygos systems