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.
Innate immunity provides the first line of defense against invading bacteria. The skin and mucous membranes provide physical and chemical barriers to infection. The normal bacterial flora antagonize colonization of body surfaces by nonindigenous bacteria.The internal tissues invariably contain bactericidal substances.he structural integrity of the body surfaces, i.e., the skin and mucous membranes, forms an effective barrier to initial lodgment or penetration by microorganisms. The skin is a very effective barrier to bacterium, so that no bacterium by itself is known to be able to penetrate unbroken skin.