innate immunity

Immune system
A complex network of interacting cells, cell products, and cell forming tissues or organs that protects the body from pathogens and other foreign substances, destroys infected and malignant cells, and removes cellular debris: the system includes the thymus, spleen, lymph nodes and lymph tissue, stem cells, white blood cells, antibodies, and lymphokines (cytokines). The main function of the immune system is to prevent or limit infections by microorganisms such as bacteria, viruses, fungi, and parasites. The immune system consists of a vast array of components (tissues, cells and soluble factors).
There are two types of immune response: Innate (Natural) & Adaptive (Acquired)
Innate Immunity:
Innate means “inborn”, Innate immunity is resistance that exists prior to exposure to the microbe (antigen). It is nonspecific, Innate immunity does not improve after exposure to the organism, in contrast to acquired immunity, In addition innate immune processes have no memory, whereas acquired immunity is characterized by long-term memory. Innate immunity achieves two major functions: killing invading microbes and activating acquired (adaptive) immune processes.
A-The physical barriers
1-SKIN:
The first line of defense against microorganisms is the intact skin and mucous membranes. Skin provides a microbe- inhospitable dry environment Continuous sloughing of superficial epidermal layer which removes attached pathogens. Mucous membranes:
2-Mucous membrane
An intact epithelium is hard to pass. Mucous can trap pathogens at mucosal surfaces and preventing their attachment and entry.
Mucous traps pathogens ,sloughing of mucous membrane of GIT remove pathogens like in skin. Mucus contains a number of types of anti-microbial compounds, including lysozyme and secretory antibodies (IgA).
If microorganisms breach these lines and enter the body, then the innate arm of the immune system (second line of defense) is available to destroy the invaders. Because the components of the innate arm are preformed and fully active, they can function immediately upon entry of the microorganisms. The ability of the innate arm to kill microorganisms is not specific. For example, a neutrophil can ingest and destroy many different kinds of bacteria. Mucus contains a number of types of anti-microbial compounds, including lysozyme and secretory antibodies (IgA).
3-Cilia
The respiratory system is equipped with mechanical hurdles like the ciliary escalator that transports airborne particles out of the bronchial tree.