Organs of the circulatory system are the heart, blood, and blood vessels (arteries and veins). The circulatory system interacts with other systems, such as the lungs (respiratory system), liver (digestive system), and kidneys (digestive system).
Skin, hair, nails, sweat and oil glands. Function: Serves as a barrier against infection and injury; helps to regulate body temperature; provides protection against ultraviolet radiation from the sun.
Phlegm is the mucus that is produced in the respiratory system. Phlegm acts as a natural defense mechanism to protect you against any bacterial and viral infections of the respiratory system. It contains various chemicals which fight virus and bacteria.