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 answer is because of the blood-brain barrier. This layer of cells keeps your brain safe from pathogens and other toxins. It is composed of brain cells and blood vessel cells. It plays a crucial role in protecting the most important organ in your body: the brain. The blood-brain barrier is like the moat outside a castle, preventing harmful invaders from entering.