Final answer:
The serratus anterior originates on the ribs and inserts onto the scapula. Its main action is protracting and stabilizing the scapula.
Step-by-step explanation:
The serratus anterior is a large and flat muscle that originates on the ribs and inserts onto the scapula.
It is responsible for protracting and stabilizing the scapula, allowing for movements such as reaching forward or pushing against something.