BIO 203 Lecture Notes - Lecture 16: Mucous Membrane, Thermostat, Anatta

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The body’s defense system
The body generally defends you against anything that it does not recognize as
being part of or belonging inside you
Common targets of the defense system include
Disease-causing bacteria, viruses, prions, protozoans, fungi,
parasitic worms
Cancer cells
Once normal body cells whose genetic changes cause unregulated
cell division
Three lines of defense
Physical and chemical surface barriers
Keep foreign organisms or molecules out
Internal cellular and chemical defenses
Attack any foreign organisms or molecule that has gotten past the surface
Immune response
Destroy specific targets and remember them
Physical barriers
Nearly impenetrable
Resistant to most toxins and enzymes of invading organisms
Mucous membranes
Line the respiratory and digestive tracts
Sticky mucus traps microbes
Chemical barriers
Sweat and oil glands of the skin
Produce chemicals that slow or prevent the growth of bacteria
The lining of the stomach
Produces hydrochloric acid and protein-digesting enzymes that destroy
Slows bacterial growth with acidity
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Washes microbes from the urethra
Saliva and tears
Contain lysozyme, an enzyme that kills bacteria
Second line of defense
Defensive cells
Defensive proteins
Defensive cells and natural killer cells
Phagocytes (WBCs) that engulf pathogens
Neutrophils: arrive first
Macrophages: develop from monocytes that leave the circulatory system
Eosinophils: attack pathogens that are too large for phagocytosis, such as
parasitic worms
Natural killer (NK) cells
Also a type of WBC
Search out abnormal cells, including cancer cells, and kill them
Interferons: slow viral reproduction
Small proteins secreted by a cell infected by a virus
Attract macrophages and natural killer cells that destroy infected cells
Stimulate neighboring cells to make proteins that prevent the viruses from
Complement system: assists other defensive mechanisms
Group of proteins that enhances both nonspecific and specific defense
Destroy pathogens, enhance phagocytosis, stimulate inflammation
Destroys invaders and helps repair and restore damaged tissue
Four signs
Mas cells release histamine which causes blood vessels to dilate
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