The Body’s Second Line of Defence

1. The Body’s Second Line of Defence

2. If a pathogen penetrates the barriers, the “First Line of Defence”, a group of non-specific defence mechanisms is initiated.

3. Syllabus requirements – “identify defence adaptations including : • inflammation response • phagocytosis • lymph system • cell death to seal off pathogen”

4. Inflammation Response “inflammation” means to set on fire involves delivery of blood and fluid to a site or injury or infection results in localised temperature increase, redness, swelling & pain at the injury / infection site

5. Acute inflammation of a sebaceous gland under the eye

6. inflammation may be acute (short term). Host overcomes infection, gets rid of dead cells, and repairs damage. • e.g. cuts, abrasions, burns. • inflammation may be chronic (long term). Ongoing “battle” may occur between pathogen and host resulting in long term symptoms • e.g. tuberculosis

7. Healing burn Healing wound

8. Mycobacterium tuberculosis infection of the lung

9. inflammation is caused by series of chemicals released as a result of damage to cells. • Seratonin, produced by mast cells, causes dilation and increased permeability of blood vessels in the affected area • Histamine attracts more phagocytes to the infection site

10. Increased blood vessel permeability delivers more blood to the affected area causing swelling, an increase in temperature, and a local increase in phagocyte numbers • Clotting of blood that accumulates in the swollen area limits pathogen movement to other parts of the body

12. Phagocytosis • Phagocytes are white blood cells (leukocytes) that engulf and destroy micro-organisms and foreign materials that enter the body in a process called phagocytosis Blood smear showing rbc’s and various types of leukocytes

13. http://www.colorado.edu/epob/epob1220lynch/image/figure11a.jpghttp://www.colorado.edu/epob/epob1220lynch/image/figure11a.jpg

14. there are a number of different types of phagocytes with differing function • neutrophils, the most common white blood cell type, are short lived (1-2 days) phagocytes which arrive quickly at injury sites and inactivate smaller pathogens.

15. Macrophages (“big eaters”) develop from monocytes, the largest type of white blood cell when the monocyte leaves the bloodstream. Macrophage engulfing bacteria

16. http://ntri.tamuk.edu/immunology/phagocytosis.gif

17. The Lymphatic System • consists of lymph, lymph nodes, lymph vessels, thymus, spleen, tonsils, adenoids, and lymphoid tissue in the digestive system • many phagocytes are found in lymph nodes – they remove foreign particles as lymph is squeezed through lymph vessels by muscular movement • lymph tissue is also involved in the production of lymphocytes in the specific immune response

19. Cell Death to Seal off Pathogen • a pathogen/s may be sealed off in a cyst or in a granuloma • a granuloma forms in chronic infections, e.g. leprosy and tuberculosis • a granuloma contains a central core of dead tissue surrounded by layers of macrophages, lymphocytes and fibroblasts (tough outer wall) • cysts and granulomas isolate pathogens and prevent their spread

20. Granuloma on vocal chord Granuloma on finger Tuberculosis granuloma in lung tissue