Explanation:

 Innate immune system: The strength of the innate, general defense is to be able to take action very quickly. It makes sure, for example that bacteria that have entered the skin through a small wound are detected and partly destroyed on the spot within a few hours. The innate defense consists of several elements:
a. The skin and all mucous membranes in the body openings, which form external barriers
b. Different defense cells from the white blood cell group (leukocytes)
c. Various substances in the blood and in body fluids
Protection from the outside: Skin and mucous membranes
All external and internal surfaces of the human body are a key element of the innate immune system. The closed surface of the skin and of all mucous membranes already forms a mechanical barrier for pathogens, which prevents them from entering. Additionally, chemical substances like acid, enzymes or mucus prevent the bacteria or viruses from gaining a foothold. Movements created, for example, by hair-like structures in the bronchi (cilia) or by bowel muscles stop germs from settling in the body. Tear fluid, sweat, or urine rinsing the urinary organs all has a similar effect.
Protection from the inside: Defense cells and proteins
If, despite all obstacles, pathogens make it past the skin or mucous membranes and enter the body, the innate system’s second line of defense comes into action. Inflammatory cells move to the site of infection, or defense cells that are already there are activated. Soluble protein substances of the complement system (see below) are activated, too, and help to defend the body. This leads to an inflammatory reaction where blood circulation is increased and the affected area becomes swollen and hot. Sometimes there is also a fever.
If bacteria or viruses manage to enter the body they can be eliminated directly on the spot by scavenger cells or phagocytes. Two types of defense cells are the most effective ones: macrophages, which are found in the tissue, and neutrophil granulocytes, which are in the blood and tissue. These cells enclose the pathogens and digest them in their interior. Scavenger cells can work best if the pathogen has already been marked by antibodies or proteins of the complement system. This makes the pathogen more “palatable” for the scavenger cells.
So at this point, antibodies of the adaptive immune system support the innate defense. Vice versa, the scavenger cells can help the adaptive immune system by taking up and digesting the marked pathogens very quickly.