MEDICAL PHYSIOLOGY

Detailed explanation-1: -Answer and Explanation: Skeletal muscles are organized into layers of fibers. The outer layer are the muscle fascicles which are then divided into muscle fibers which are made up of hundreds of myofibrils which give the cell its striated appearance.

Detailed explanation-2: -Each muscle is made up of groups of muscle fibers called fascicles surrounded by a connective tissue layer called perimysium. Multiple units of individual muscle fibers within each fascicle are surrounded by endomysium, a connective tissue sheath.

Detailed explanation-3: -Within a muscle fiber, proteins are organized into organelles called myofibrils that run the length of the cell and contain sarcomeres connected in series. Because myofibrils are only approximately 1.2 m in diameter, hundreds to thousands (each with thousands of sarcomeres) can be found inside one muscle fiber.

Detailed explanation-4: -Skeletal muscle fiber Sarcolemma-membrane surrounding the muscle fiber. Transverse tubules-portion of the sarcoplasmic reticulum that stores and releases calcium during contraction and relaxation. Myoneural junction-where motor nerve endings terminate on the sarcolemma. Sarcoplasm-cytoplasm of muscle fibers.

Detailed explanation-5: -Muscle fibers are composed of thousands of myofibrils. The key difference between myofibril and muscle fiber is that myofibril is the basic rod-like unit of a muscle fiber while muscle fiber is the tubular cells of the muscle.