Nonspecific Defenses of the Host Vocabulary

Nonspecific Defenses

Defensive mechanisms that protect the host against all types of pathogens, regardless of their specific nature.

First Line of Defense

Physical and chemical barriers that prevent microbes from entering the body, including skin, mucous membranes, and their secretions.

Skin

A physical barrier formed by closely packed cells that provides protection against microbial entry.

Mucous Membrane

A tissue lining that secretes mucus, trapping microbes and preventing their movement.

Gastric Juice

A highly acidic secretion in the stomach containing hydrochloric acid, which destroys ingested microbes.

Lysozyme

An enzyme found in tears, saliva, and mucus that breaks down bacterial cell walls.

Second Line of Defense

Internal mechanisms that activate when pathogens bypass the first line of defense, including phagocytosis, inflammation, and antimicrobial substances.

Phagocytosis

The process by which white blood cells (phagocytes) engulf and digest foreign particles and microbes.

White Blood Cells (WBCs)

Blood cells involved in defense mechanisms; includes granulocytes, monocytes, and lymphocytes.

Granulocytes

A type of white blood cell containing granules. Subtypes include neutrophils, eosinophils, and basophils.

Neutrophils

Granulocytes that are highly phagocytic and active during the early stages of infection.

Eosinophils

Granulocytes involved in phagocytosis, with numbers increasing during protozoan and helminth infections.

Basophils

Granulocytes that release histamine, a chemical that promotes inflammation and vasodilation.

Monocytes

A type of white blood cell that transforms into macrophages in tissues and plays a role in the later stages of infection.

Macrophages

Phagocytic cells derived from monocytes that engulf pathogens and cellular debris during infections.

Lymphocytes

White blood cells primarily involved in specific immunity, including T cells and B cells.

Inflammation

A nonspecific response to tissue injury characterized by redness, swelling, pain, and heat.

Histamine

A chemical released by mast cells and basophils that promotes vasodilation and increases blood flow to injured areas.

Leukotrienes

Chemicals produced by mast cells and basophils that increase vascular permeability, allowing immune cells to reach the site of injury.

Complement System

A group of about 20 serum proteins that enhance the immune response by lysing bacteria, causing inflammation, and enhancing phagocytosis.

Classical Pathway (Complement System)

An activation pathway of the complement system initiated by antigen-antibody complexes.

Alternative Pathway (Complement System)

A complement activation pathway initiated by microbial polysaccharides, independent of antigen-antibody complexes.

C3A and C3B

Fragments of complement protein C3 that play key roles in inflammation (C3A) and phagocytosis enhancement (C3B).

Interferon

A protein produced by virus-infected cells that prevents the spread of the virus to nearby uninfected cells.