We live in a virtual sea of bacteria; we have evolved ways of protecting ourselves.

BARRIERS: Our Goal? Keep the Beasties Out!

1. SKIN: protected by•many layers of dead dry cells that are leathery.

•pores are protected by sweat•sweat washes out pores •contains lytic enzymes which burst whatever beasties that try and get in.

•hair shafts protected by oils and lytic enzymes

2. EYES: Protected by •tears contain lytic enzymes and wash the eyeballs.

3. EARS: Protected by •Wax: semi-liquid paste that traps beasties and contains lytic enzymes

•Cilia: microscopic hairs that ‘wave’ rhythmically and transport the wax out of the ear.

•Hairs: help to trap the beasties.

•Eardrum: physical barrier keeps beasties out of middle and inner ear.

4. NOSE & RESPIRATORY SYSTEM: Protected by•Mucus: sticky and has lytic enzymes.•Cilia: transports “dirty” mucous from the lungs back to the throat where it is swallowed.•White Blood Cells: live in the air sacks (alveoli) of our lungs; they eat dirt, debris, and beasties = scavengers. 5. MOUTH: Protected by•Saliva: contains lytic enzymes•Native Bacteria: normal bacteria that live in your mouth will attack and destroy the new bacteria (competitive)

6. STOMACH: Protected by•Hydrochloric Acid (HCl): strong (3M) kills a lot of bacteria & spores(?)

7. INTESTINES: Protected by•Small Intestine: digests beasties for food•Large Intestine: is protected by native bacteria (E. coli) that fights off foreigners.  8. REPRODUCTIVE SYSTEM: Protected by•Male system – not usually any problems.•Female system:•Barrier is at the cervix – mucous plug. •Also native bacteria, acidic environment, and WBC’s.

If the bacteria gets past our physical barriers, then…

IMMUNE SYSTEM: BEASTIES IN BLOOD STREAM

1. WHITE BLOOD CELLS (WBC’s) are phagocytic; they engulf and digest beasties.

•They leave the blood go to the site of infection.

•Problem: WBC’s reproduce every 3 hours and when they engulf a beasties they both die. Bacteria reproduce every 20 minutes (under optimum conditions).

•Solution: Fever (increased metabolic rate)•This will slow the bacterial reproduction rate down (every 3 hours) so our WBC can keep up!

Produced in our bone marrowOur stem cells can produce several

different kinds of bacteria-fighting immune cells.

Leukocytes (neutrophils, eosinophils, and macrophages) engulf foreign invaders.

Complement, or complementary proteins help phagocytotic cells engulf foreign cells

After phagocytosis, the cell releases a packet of enzymes that destroy the bacteria

Unfortunately the white blood cell dies too.

Lymphocytes produce antibodies.One kind, T cells, find antigens on

bacteria, or receives messages from leukocytes, and then signal an attack.

T cells pass information along to B cells

B cells produce antibodiesAntibodies can stay on the surface of

B cells, or they can be released and travel through the body to attack bacteria.

Are “Y” shaped proteins that targe foreign invaders

Antibodies have specific genes that allow them to “match” certain bacteria and viruses

Antibodies attach and hang on to the foreign invader, and wait for a macrophage to come along and eat the whole thing.

After an infection is gone, most of your white blood cells that were used, die.

Memory T cells remain though They hold an imprint of the antigen,

and can mobilize B cells super fast if they need to again

Invading pathogens are destroyed before they are even able to multiply.

This is why we rarely get the same infection twice