Final answer:
The muscles that elevate the ribs during inspiration are the external intercostal muscles. They originate from the inferior border of the superior rib and insert onto the superior border of the inferior rib, helping to increase thoracic volume for inhalation. The internal intercostal muscles assist with expiration by drawing the ribs together.
Step-by-step explanation:
The muscles described in the question are the external intercostal muscles. These muscles are responsible for elevating the ribs during inspiration, or inhalation, and are an important component of the respiratory system. They have their origin on the inferior border of the superior rib and their insertion on the superior border of the inferior rib. Upon contraction, the external intercostal muscles pull the ribs upward and outward, increasing the volume of the thoracic cavity and allowing air to be drawn into the lungs.
The internal intercostal muscles, in contrast, are used for expiration and are located just beneath the external intercostal muscles. They help to draw the ribs together, which constricts the rib cage and aids in expelling air from the lungs. The diaphragm also plays a crucial role in respiration, contracting and moving downward to further increase thoracic volume and decrease pressure, enabling inspiration. It's important to note that while the diaphragm is the primary muscle of respiration, the intercostal muscles aid in altering the thoracic volume to facilitate breathing.