Final answer:
The intercostals T1 - T11 send signals to the intercostal muscles, which include three sets of muscles that assist in breathing by changing the dimensions of the rib cage. These muscles are innervated by intercostal nerves arising from T2 through T11 spinal nerves, aiding in inspiration and expiration.
Step-by-step explanation:
The intercostals T1 - T11 send signals to the intercostal muscles, which include the superficial external intercostal muscles, the internal intercostal muscles, and the innermost intercostal muscles. These muscles are significant components of the respiratory system, and their primary function is to assist in breathing by altering the dimensions of the rib cage. The spinal nerves of the thoracic region from T2 through T11 (since T1 typically contributes to the brachial plexus) give rise to the intercostal nerves that innervate these muscles. The superficial external intercostal muscles play a role in inspiration by raising the rib cage, which increases its volume. In contrast, the internal intercostal muscles are responsible for expiration, pulling the ribs together to constrict the rib cage. Together, these muscles alter the volume and pressure within the pleural cavities, facilitating airflow into and out of the lungs during the respiratory cycle.