By respiratory system we usually mean the passages that transport incoming air to the lungs and to the microscopic air sacs called alveoli where gases are exchanged. The term respiration refers to the whole chain of processes from the inhalation of air to the use of oxygen in the cells. Index. Reference.
Phagocytes are the white blood cells that protect the body by eating (phagocytosing) dirt, bacteria and dead or dying cells. They are important for fighting infections. They are also important for becoming immune. Phagocytes are important in all animals and are very complex in vertebrates.
Phagocytes include white blood cells of the immune system, such as monocytes, macrophages, neutrophils, and mast cells. Dendritic cells (i.e. antigen-presenting cells) are also capable of phagocytosis. In fact, they are called professional phagocytes because they are effective at it. 1.