Tuesday, February 2, 2010 Obj: I will compare and contrast body defenses (day 1) BR: Explain what lymph is and where it comes from.

Body Defenses The body is constantly in contact with bacteria, fungi, and viruses The body has two defense systems for foreign materials – Nonspecific defense system – Specific defense system

Body Defenses Nonspecific defense system – Mechanisms protect against a variety of invaders – Responds immediately to protect body from foreign materials Specific defense system – Specific defense is required for each type of invader – Also known as the immune system

Nonspecific Body Defenses Body surface coverings – Intact skin – Mucous membranes Specialized human cells Chemicals produced by the body

How does the skin act as a nonspecific defense? – Physical barrier to foreign materials – pH of the skin is acidic to inhibit bacterial growth What is the function of the skin (integumentary)?

Defensive Cells Phagocytes (neutrophils and macrophages) – Engulfs foreign material into a vacuole – Enzymes from lysosomes digest the material Figure 12.7a

Inflammatory Response Triggered when body tissues are injured Produces four cardinal signs – Redness – Heat – Swelling – Pain Results in a chain of events leading to protection and healing

Functions of the Inflammatory Response Prevents spread of damaging agents Disposes of cell debris and pathogens (something that causes disease or illness) Sets the stage for repair

Steps in the Inflammatory Response Figure 12.8

Fever – What it is Abnormally high body temperature Hypothalmus heat regulation can be reset by pyrogens (secreted by white blood cells) High temperatures inhibit the release of iron and zinc from liver and spleen needed by bacteria

Fever – How it works The hypothalamus in the brain (this controls your body temperature) increases your body temperature above normal (so you are not in homeostasis) This increase in temperature causes an unbearable environment for pathogens (things that can cause disease or illness) so they cannot survive. Fever also increases the speed of tissue repair