Rami

Each spinal nerve is only about 1-2 centimeters long before it divides into two branches called rami. The branch that serves the back or dorsal surface of the body is called the dorsal ramus. The branch that serves the front or ventral surface of the body is called the ventral ramus.

The 31 pairs of dorsal rami remain individual branches that serve the skin and musculature of the back of the body.

The 31 pairs of ventral rami are larger and serve the ventral surface of the body and the limbs. The ventral rami in the thoracic region remain as individual branches known as the intercostal nerves. These nerves serve the muscles of the thoracic cage, abdomen, and anterolateral trunk.

The ventral rami outside of the thoracic region form four individual complexes, each known as a nerve plexus.

Figure 1: Formation of the rami