NOTES: The

Lymphatic/Immune

System

(Ch 12, part 2)

The body has nonspecific and specific defenses against infection.

Why don’t

YOU have

mold on your

skin???

• PATHOGEN: a disease-causing agent; causes infection

-pathogens include:

viruses fungi

bacteria protozoans

Examples of viruses:

• Papovavirus – papilloma (warts)

• Adenovirus – respiratory diseases

• Herpes virus – herpes

• Poxvirus – smallpox• Poxvirus – smallpox

• Parvovirus – roseola

• Picornavirus – polio

• Rhinovirus – common cold

Nonspecific Defenses:

• general defense

• provide protection against many different pathogensmany different pathogens

• involve physical and chemical barriers, fever, inflammation, phagocytosis

Specific Defenses:• very precise

• target certain pathogens

• also known as IMMUNITY

• involve specialized

lymphocytes (T cells and B lymphocytes (T cells and B

cells) that recognize and

respond to specific

pathogens

**nonspecific defenses are

quick to respond; specific

defenses are slower-to-

respond

NONSPECIFIC DEFENSES1) Species Resistance

• each species is resistant to certain

diseases that may affect other species

• examples: measles, mumps,

gonorrhea, and syphilis infect gonorrhea, and syphilis infect

humans but not other animal species

• one species may be resistant to a disease that affects another species because its tissues somehow fail to provide a suitable environment for the pathogen (temperature, chemical environment, etc.)

2) Mechanical Barriers = FIRST

LINE OF DEFENSE

● mechanical barriers / physical barriers include:

-skin (and associated hairs)

-mucous membranes-mucous membranes

-fluid (sweat and mucus)

● as long as they remain intact, they can keep out many pathogens

MUCUS

SKIN

SALIVA

**all other “nonspecific

defenses” are considered the

SECOND LINE OF DEFENSE

3) Chemical Barriers

• gastric juice: contains hydrochloric acid and enzymes (e.g. pepsin) that are lethal to pathogens

• tears: contain the enzyme • tears: contain the enzyme LYSOZYME

(which has antibacterial action)

• the salt in perspirationaccumulates on the skin and kills bacteria on the skin

3) Chemical Barriers (cont.)

• INTERFERONS: chemicals released by virus-infected cells; they stimulate other they stimulate other immune cells to:

-synthesize antiviral proteins that stimulate phagocytosis, block virus replication

4) Fever

• higher body temperature increases the rate of phagocytic cells

• also lowers iron levels in the blood (bacteria and fungi require iron, so this slows their growth)

5) Inflammation• a tissue response to injury or

infection

• produces: localized redness,

swelling, heat and pain

• chemicals released by • chemicals released by

damaged tissues attract WBCs

to the site

� the mass of WBCs,

bacterial cells, and damaged

tissue forms a thick fluid called

PUS

6) Phagocytosis – removes foreign

particles from the lymph and blood

• the most active phagocytes in blood are NEUTROPHILS and MONOCYTESMONOCYTES

• Monocytes give rise to MACROPHAGES

• MACROPHAGES are found in the

linings of blood vessels in the:

-bone marrow

-liver

-spleen

-lungs-lungs

-lymph nodes