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.
The first part of the immune system that meets invaders such as bacteria is. a group of proteins called the complement system. These proteins flow freely in the blood and can quickly reach the site of an invasion where they can react directly with antigens-molecules that the body recognizes as foreign substances.nnate immunity also includes the external barriers of the body, like the skin and mucous. membranes (like those that line the nose, throat, and gastrointestinal tract), which are the. first line of defense in preventing diseases from entering the body.