1. Defense against infectious disease
Topic 6.3

2. Exposure may not lead to disease
Pathogen: any living organism or virus that is capable of causing disease
viruses, bacteria, protozoa, fungi, and various worms
Exposure may not lead to disease

3. Preventing Invasion of Pathogens
Barrier to infection
Epidermis (top)
Constantly being replaced as dermal cells die and move upwards  good barrier against most pathogens
Dermis (underneath) – alive
Sweat glands, capillaries, sensory receptors, dermal cells
Intact skin  we are protected

4. Mucus Other entry method: breathing (nasal or mouth)
Cells of mucous membranes produce/secrete lining of sticky mucus
Cilia lined tissue
Move trapped pathogens up and out mucous-lined tissues
Traps incoming pathogens
Secretes lysozyme
Chemically damage many pathogens

5. Area with mucous membrane
What it is and does
Trachea
Tube which carries air to and from the lungs
Nasal passages
Tubes which allow air to enter the nose and then the trachea
Urethra
Tube which carries urine from bladder to the outside
Vagina
Reproductive tract leading from uterus to the outside

6. Blood Clotting Bruising
Braking small blood vessels (capillaries, arterioles, venules) allowing blood to escape the closed circulatory system
Allows entry point for pathogens
Clots
Seals damaged blood vessels
Prevents excessive blood loss and entering pathogens

7. Blood Clotting Damaged blood vessel Prothrombin (clotting protein)
Chemicals (clotting factors)
which convert
Chemicals released
Platelets adhere to damaged area
Thrombin (enzyme)
one large cell breaks into many fragments
Soluble Fibrinogen (clotting protein)
Insoluble Fibrin (forms mesh)
Short life span

8. Discuss causes of blood clotting in coronary arteries.
What would be a consequence of this?

9. Production of more antibodies in less time

10. Immune System Respose Leucocytes – white blood cells
Fight off pathogens that pass our primary barriers
Macrophage:
Large WBC
Able to change cellular shape to surround invading cell – process called phagocytosis
Ability to move in/out of blood vessels to fight infections

11. Macrophage
Recognizes ‘self’ (normal cells) from ‘not-self’ (invading cells)
Based on protein molecules of surface of all cells/viruses
‘Self’ cells not ingested, ‘not-self’ cells are ingested via phagocytosis
Contain lots lysosomes to chemically digest foreign body
Non-specific response – identity of pathogen not known

12. Antigens:
All cellular invaders (viruses included) have protein receptors (antigens) embedded on membranes – identifies cells as ‘not-self’
Can have several antigens on surface, triggers production of several different antibodies
Antibodies:
Protein molecules produced in response to specific type of pathogen

13. Antibodies:
Is a protein that is Y shaped
At end of forks of the Y is a binding site
Where antibody attaches itself to antigen
B Lymphocytes (Plasma Cell)
Antibody producing leucocytes
One B lymphocyte, one antibody

14. Immune Response A specific antigen type is identified
A specific plasma cell is identified that can produce an antibody which will bind to the antigen
Plasma cellclone themselves (mitosis) to rapidly increase the number of identical B cells
Begin antibody production
Released antibodies circulate in bloodstream, find their antigen match
Various mechanisms, antibodies helps eliminate pathogen
Some plasma cells remain in bloodstream for second infection (memory cells).

15. Viruses
Find a cell type that matches their own proteins in a complementary way
Allows them to enter host cell for replication
Causes damage to those particular cells, and not others
Example: Cold Virus (Rhinovirus)
Proteins match mucous membrane cells, causes inflammation of those cells only

16. Targets Helper T Cells
Functions as communicator cell in bloodstream
Which cells need to undergo the cloning process and begin antibody production
Latency period
Infection occurs, but cells remain alive
Infection
Helper T Cells start to die, antibody production does not occur
results in set of symptoms collectively call acquired immunodeficiency syndrome (AIDS)

17. Transmission
Person to person through bodily fluids
Sex
Sharing of needles
Blood transfusions
Pregnancy, labor, delivery, breastfeeding

18. Antibiotics are chemicals – take advantage of biochemical differences between pro- and eu-karyotic cells
Inhibits production of new cell wall
Block DNA replication
Why not Viruses?
Selectively block protein synthesis
Viruses make use of our own cells metabolism  do not have their own
Any chemical that could inhibit their processes would affect our cells as well

19. Antibiotics are very specific
Due to large bacterial numbers  variation occurs in population
Antibiotic resistant bacterial strains