The skeletal muscles are the main functional units of the muscular system. There are more than 600 muscles in the human body. They vary greatly in shape in size, with the smallest one being the stapedius muscle in the inner ear, and the largest one being the quadriceps femoris muscle in the thigh.
The skeletal muscles of the human body are organized into four groups for every region of the body:
- Muscles of the head and neck, which include the muscles of the facial expression, muscles of mastication, muscles of the orbit, muscles of the tongue, muscles of the pharynx, muscles of the larynx, and muscles of the neck
- Muscles of the trunk, which include the muscles of the back, anterior and lateral abdominal muscles, and muscles of the pelvic floor
- Muscles of the upper limbs, which include muscles of the shoulder, muscles of the arm, muscles of the forearm and muscles of the hand
- Muscles of the lower limbs, which include hip and thigh muscles, leg muscles and foot muscles