1. Unit 3 Compensating Mechanisms Defenses Against Disease
Pathophysiology-Unit 2-Compensating Mechanisms
Unit 3 Compensating Mechanisms Defenses Against Disease
Pathophysiology - Borders

2. A sneeze propels thousands of microscopic droplets out of the nose and mouth at a rate of 200 miles per hour!
There may be as many as 100,000 bacteria released during a single sneeze; viruses are also spread in this manner.
Figure: 32-CO Title: Defenses Against Disease Caption: A sneeze propels thousands of microscopic droplets out of the nose and mouth at a rate of 200 miles per hour! There may be as many as 100,000 bacteria released during a single sneeze; viruses are also spread in this manner.
SVideo-Slow Motion Sneezing

3. Basic mechanisms of defense

4. Parasites
Organisms that live and reproduce on or within other life forms, doing harm in the process
Microbes : viruses, bacteria, fungi, and protists
Since 1980s,
several viruses have emerged as threats to people,
HIV, Ebola virus, hantavirus and West Nile virus and SARS
Cold virus strains and constantly mutating strains of influenza virus
Bacteria:
Deadly strains of the common intestinal bacterium E. coli and respiratory bacterium Streptococcus pyrogens (flesh-eating bacteria)

5. Three forms of protection against disease
NONSPECIFIC EXTERNAL BARRIERS
Skin
Mucous membranes
if barriers are penetrated the body responds with
Three forms of protection against disease
NONSPECIFIC INTERNAL DEFENSES
Phagocytic and natural killer cells
Inflammation
Fever
Figure: 32-1 main
Title:
Levels of defense against infection
if nonspecific defenses are insufficient, the body responds with
Both nonspecific defenses operate regardless of the exact nature of the invader, repelling, killing, or neutralizing the threat
SPECIFIC IMMUNE RESPONSE
Cell-mediated immunity
Humoral immunity

6. Nonspecific External Barriers
Prevent most disease-causing microbes from entering the body
Primarily anatomical structures and secretions
Skin, hair, cilia, tears, saliva, and mucus
Skin and mucous membranes of the respiratory system, digestive system, urogenital tracts

7. Skin and its Secretions
Outermost layer of skin- dry, dead cells
Microbes landing on the skin do not obtain the water and nutrients they need to survive
Skin cells are constantly sloughed off and replaced
Bacteria and fungi that can gain a foothold on the skin will usually be shed
Secretions from sweat glands, sebaceous glands, and wax-secreting glands contain natural antibiotics

8. Mucous Membranes
Eye, line the digestive, respiratory and urogenital tracts
The mucus and tears secreted contain antibacterial enzymes– lysozymes
Destroy bacterial cell walls
Mucus physically traps microbes (nose and mouth)
Cilia on the membranes lining the respiratory tract sweep up the mucus, microbes until it is coughed or sneezed out of the body, or swallowed

9. Mucous Membranes
In stomach, extreme acidity and protein-digesting enzymes kill the invaders.
In intestine – inhabited by bacteria that are harmless
Secrete substances that destroy invading foreign bacteria or fungi
In the urinary tract, slight acidity of urine
In vagina, acidic secretions and mucus

11. Nonspecific Internal Defenses
Three main categories
leukocytes
Phagocytic cells- engulf and directly destroy microbes
Natural killing cells– destroy cells of the body that have been infected by viruses
Inflammatory response
Simultaneously recruits phagoctic cells and natural killer cells and walls off the injured area, isolating the infected tissue from the rest of the body
Fever
Slows down microbial reproduction and enhances the body’s own fighting abilities

12. Phagocytic White Blood Cells
Macrophages and neutrophils
Patrol the body’s tissues through the circulatory system
Ingest dead and dying cells, cellular debris, and microbes by phagocytosis (Figure 32-3)
Act as housekeepers to scavenging dead and dying cells
Act as antigen-presenting cells

13. Figure: 32-3
Title:
The attack of the macrophages
Caption:
(a) A phagocyte reaches for a rod-shaped bacteria. (b) This macrophage has stuffed itself with bacteria, which are visible through a hole in its plasma membrane.

14. Natural Killer Cells Strike at the body’s own cells
cancerous or virus infected cells
Recognizing these cells by any abnormal molecules on their surface
Secrete enzymes that attack the infected or cancerous cell
Secrete proteins that open up holes in its membrane

15. Inflammation
Causes mucous membranes to become leaky and injured tissues to become warm, red, and swollen
It attracts phagocytic cells to the area, promotes blood clotting, causes pain that stimulates protective behaviors
mechanism
Histamine is released from mast cells
Relaxes the smooth muscle and causing increased blood flow and make capillary walls "leaky“ –drive watery fluid filtered from the blood through capillary walls into the region around the wound

16. Inflammation Mechanism
Chemicals released by wounded cells and mast cells and microbes attract macrophages and neutrophils to the area
Cytokines released by macrophages supplement histamine in making the capillaries leaky, attract more WBCs to the area and facilitate the cells’ movement through the capillary walls
Blood clots isolate the injury site
Pain, alert the injured person to protect the area from further damage

17. 1 Tissue damage carries bacteria into wound.
2 Wounded cells release chemicals that stimulate mast cells.
Figure: 32-4
Title:
The inflammatory response
Caption:
Question Why can white blood cells, but not red blood cells, leave a capillary?
3 Mast cells release histamine.
4 Histamine increases capillary blood flow and permeability.
5 Phagocytes leave capillaries and ingest bacteria and dead cells.

18. Fever combats large-scale infections
Onset of fever is controlled by the hypothalamus, (body’s thermostat)
Macrophagesendogenous pyrogens (fire-maker)raises the thermostat’s set point in hypothalamus↑fat metabolism↑, constriction of surface blood vessels, and heat-producing behaviors (shivering)
Other cytokines  [Fe]blood ↓  growth of bacteria↓

19. Fever Enhances the body’s normal defenses
Increases the activity of phagocytic WBCs that attack microbes
Immune cells multiply more rapidly
Produce more antibodies
harms invading microbes
102Fo, force bacteria to reproduce more slowly ad to require more iron for reproduction

20. Fever Interferon Cytokine
Synthesized and released by some type of cells infected by viruses
Travel to other cells and increases their resistance to viral attack

21. Immune response
Immune cells selectively destroy the particular toxin or microbe
remember the invader
Allowing a faster response it if reappears in the future
Immune system
Lymphocytes --Produce the immune response, the chemical antibodies
Chemical antibodies
Organs in which the lymphocytes are produced and reside are collectively termed

22. Key cellular player
Table: 32-T1 Title: The Body's Cellular Armory

23. B cells and T cells
Arise from lymphocyte precusor cells in the bone marrow
Some are released into the bloodstream and travel to the thymus to complete their differentiation into T (thymus) cells
B (bone) cells differentiate in the bone marrow

24. Immune responses produce by B cells and T cells
Three steps:
Recognize the invader
Lauch an attack
Retain a memory of the invader to ward off future infections

25. Foreign Invaders exhibit Characteristic Antigens
Large, complex molecules serve as antigen
Proteins,
Polysaccharides,
glycoproteins
Invading microbe
Toxin
Location of antigens
Located on the surfaces of invading microbes or cancer cells
Viral or bacterial antigens are also exposed on the plasma membranes of macrophages that engulf them
May be dissolved in the blood or extracellular fluid
Snake venom

26. Antibodies and T-Cell Receptors Recognize and Bind to Foreign Antigens
Key to the immune cells to recognize antigens
Antibodies – produced by B cells
Remain attached to the surfaces of the B cells that produce them
Become dissolved in the blood stream
T-cell receptors – produced by T cells

27. Antibody structure light chain heavy chain variable regions
antigen
antigen
light chain
heavy chain
Particular shape
Electrical charge
Specific
Figure: 32-5
Title:
Antibody structure
Caption:
Antibodies are proteins composed of two pairs of peptide chains (light chains and heavy chains) arranged like the letter Y. Constant regions on both chains form the stem of the Y; variable regions on the two chains form a specific binding site at the end of each arm of the Y. Different antibodies have different variable regions, forming unique binding sites. Question Why do antibody molecules have both constant and variable regions?
variable regions
constant regions

28. Cells of the immune system launch an attack
Two types of attack
Humoral immunity
B cells
Circulating antibodies they secrete into the bloodstream
Attack invaders before they can enter body cells
Cell-mediated immunity
Cytotoxic T cells
Attack invaders that have made their way into body cells
Helper T cells

29. Helper T cells Stimulate both humoral and cell-mediated immunity
Have T-cell receptors for microbial antigens
Presented on the plasma membranes of macrophages that have engulfed the invaders
Or on the surfaces of infected cells
Binding of the receptor with antigens
Release cytokines that stimulate cell division and differentiation in both the B cells and cytotoxic T cells

30. Cell-mediated immunity
T cells
Helper T cells,
Cytotoxic T cells
Memory T cells
Helper T cells bind antigens on the surfaces of infected or cancerous cells produce cytokines stimulate T-cell division and differentiation cytotoxic T cells
Cytotoxic T cells release proteins that disrupt the infected cell’s plasma membrane

31. CELL-MEDIATED IMMUNITY memory cytotoxic T cell
HUMORAL IMMUNITY
HELPER T CELLS
CELL-MEDIATED IMMUNITY
virus
viral antigen
macrophage
infected cell
antibody
B cell
helper T cell
cytotoxic T cell
Figure: 32-11
Title:
A summary of humoral and cell-mediated immune responses
memory helper T cell
memory cytotoxic T cell
plasma cell
memory B cell
cytotoxic T cell
infected cell
Targets: invaders outside cells (viruses, bacteria, fungi, protists, toxins)
Simulates both humoral and cell-mediated immunity by releasing cytokines
Targets: defective body cells (infected cells, cancer cells), transplants