ANATOMY

Detailed explanation-1: -Answer and Explanation: The correct answer is D. bouton. The transverse tubules, motor endplates, sarcolemma, and sarcoplasmic reticulum are part of the muscle fiber.

Detailed explanation-2: -A skeletal muscle fascicle consists of 20 to 60 fibers surrounded by a connective tissue sheath. A single muscle fiber is innervated by only one motor unit, but there may be two to three motor units within a fascicle. The muscle fibers of one motor unit may be distributed over 100 fascicles.

Detailed explanation-3: -Four distinct patterns of fascicles are seen within the whole of the muscle: parallel, convergent, pennate, and circular (Figure 2).

Detailed explanation-4: -Fascicle arrangements determine what type of movement a muscle can make. For instance, circular muscles act as sphincters, closing orifices. Muscles work in pairs to facilitate movement of the bones around the joints. Agonists are the prime movers while antagonists oppose or resist the movements of the agonists.