Crash Course :Immune system part 1

Innate (Nonspecific) Defense System

The body's first line of defense; provides immediate, general protection against all foreign substances.

Surface Barriers

The skin and mucous membranes; the body's first physical and chemical line of defense.

Mucous Membranes

Epithelial tissues that line body cavities open to the exterior; secrete protective mucus.

Lysozyme

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

Defensins

Antimicrobial peptides produced by mucous membranes and skin that kill pathogens.

Phagocyte

A cell (e.g., neutrophil, macrophage) that engulfs and digests foreign particles and cell debris.

Neutrophil

The most abundant white blood cell; a phagocytic first responder to bacterial infection.

Macrophage

A large, long-lived phagocyte derived from a monocyte; engulfs pathogens and alerts the adaptive immune system.

Phagocytosis

The process by which a phagocyte engulfs and destroys a particle.

Natural Killer (NK) Cell

A lymphocyte that patrols the body and kills virus-infected cells and cancer cells by inducing apoptosis.

Inflammatory Response

A localized, nonspecific defensive tissue response to injury or infection.

Vasodilation

The widening of blood vessels; increases blood flow and causes redness/heat during inflammation

Histamine

A chemical released by mast cells and basophils that triggers vasodilation and increased permeability in inflammation.

Chemotaxis

The movement of cells (like phagocytes) in response to a chemical gradient (e.g., toward inflammatory chemicals).

Pus

A fluid mixture of dead neutrophils, tissue debris, and dead pathogens, often found at sites of infection.