Final answer:
Smooth muscle, skeletal muscle, and heart relaxation during diastole are direct contributors to the movement of fluid through the lymphatic system, with skeletal muscles playing a significant role during body movements and breathing, and smooth muscle contractions in the vessel walls aiding in lymph movement.
Step-by-step explanation:
The direct contributors to the movement of fluid through the lymphatic system are B) Smooth muscle, C) Skeletal muscle, and E) Heart relaxing during diastole.
The lymphatic system does not rely on the heart as a pump, unlike the cardiovascular system. Instead, lymph is moved through the lymphatic vessels primarily by the contraction of skeletal muscles during body movements and breathing, as well as by the contraction of the smooth muscle in the walls of the lymphatic vessels. The movement of fluid during heart relaxation, or diastole, also contributes to the movement of blood through the veins, which can help facilitate lymph flow indirectly.
Lymphatic fluid enters the circulation at the junction of the jugular and subclavian veins, aided by one-way valves (semi-lunar valves) that prevent the backflow of lymph, ensuring it moves in the direction towards the heart.