1. Chapter 37 The Human Defence System

2. 3.5.3 Responses in the Human -[D] The Defence System
Objectives – What you will need to know from this section
The Immune System
Describe the Defence System including skin/mucous membranes (of breathing, reproduction and digestive systems) and the Phagocytic white blood cells.
Describe the Specific Defence System, including antigen/antibody response
Define the term: Induced Immunity
Explain the terms: Vaccination & Immunisation
Describe the structure & reproduction of viruses & explain why they are classified as non living things.

4. Immunity is the ability of an organism to resist infection.
The human body is designed to protect itself from foreign cells, invaders or pathogens.
A pathogen is an organism that causes disease. Bacteria and Viruses are the best know pathogens.
YouTube - Introduction to how the immune system works
Fungi, protists and parasites can also cause disease

5. We have two lines of defence
General - acts against all pathogens
Specific / Immune System - acts against particular pathogens.

6. The general defence system
Barriers
Non-specific protective cells

7. Barriers - trap, harm or kill Pathogens
Skin (inc. sweat)
Breathing System (mucus, cilia)
Digestive System (acid in stomach)
Tear Glands contain the enzyme lysozyme in tears, keeps the surface of the eye free of bacterial infection.
microbes are identified by pattern recognition receptors, which recognize components that are conserved among broad groups of microorganisms,[26] or when damaged, injured or stressed cells send out alarm signals, many of which (but not all) are recognized by the same receptors as those that recognize pathogens.[27] Innate immune defenses are non-specific, meaning these systems respond to pathogens in a generic way.[14] This system does not confer long-lasting immunity against a pathogen. The innate immune system is the dominant system of host defense in most organisms.[11]

8. Learning Check 1 What is Immunity? What is a pathogen? E.g.s?
What are the two lines of defence?
What does the general defence system consist of?
Name some Barriers.

9. The skin
The body’s first line of defense, it acts as a barrier in preventing disease by protecting all the organs, blood vessels, and the lymph system.
Without the skin, bacteria and viruses could easily enter the blood system.

10. The Skin

11. 1. The Skin Epidermis – prevents entry of pathogens
Acid in sweat kills pathogens
Sebum /oils kills pathogens

12. 2. Mucus
The sticky, thick fluid produced by the mucous membranes that line all openings of the body – digestive, reproductive and respiratory tract.
When dust particles enter the body, they get trapped in the mucous membranes and are then digested.
A mucous membrane is a layer of epithelial tissue which lines an area of the body which comes into contact with air. Mucous membranes are moist because of the presence of glands which secrete a thick fluid known as mucus, and they are important for a number of bodily functions. Mucous membranes line the urogenital tract, digestive tract, and respiratory tract, with one of the more well known mucous membranes being the lining of the interior of the nose.

13. The mucous membranes / mucosae / mucosa are linings of the epithelium tissue that line the cavities and surfaces of structures throughout the body.

14. 3. Cilia
Some sections of mucous membrane e.g. respiratory tract also have small hairs / cilia which act as traps, and can push mucus to be swallowed.
Stomach acid then kills the pathogens.
A mucous membrane is a layer of epithelial tissue which lines an area of the body which comes into contact with air. Mucous membranes are moist because of the presence of glands which secrete a thick fluid known as mucus, and they are important for a number of bodily functions. Mucous membranes line the urogenital tract, digestive tract, and respiratory tract, with one of the more well known mucous membranes being the lining of the interior of the nose.

15. Nose hairs

16. Nose hairs Nose hair is the body’s natural air filtration system.
Nose hairs capture dust particles keeping them from accumulating in the lungs.
A sneeze is the body’s
way of ridding itself of
accumulated dust
particles.

17. Nose hair with pollen grain, mucus, dead skin

18. Learning Check 2
What is the body’s first line of defense? How does it play a role in preventing disease?
What is mucus? How does it play a role in preventing disease?
What are cilia? How do they play a role in preventing disease?
How do nose hairs play a role in preventing disease?

19. Our General Defence System
skin prevents entry

20. Phagocytes

21. 4. Phagocytes / White Blood Cells
They engulf / trap harmful materials / microbes / pathogens when they enter the body
They secrete chemicals to digest / destroy them causing high temps / fever - Inflammatory reaction, as immune system cells rushes to a location to deal with unwanted invaders.
Free phagocytes wander throughout tissues ‘searching’ for ‘foreign invaders’.
Fixed phagocytes reside in a particular area destroying pathogens that enter their space.

22. When Phagocytes / immune cells are activated they engulf, ingest & digest the invader using enzymes, destroying it.
“Eating” germ
Germ
Phagocyte
Others secrete chemicals that stimulate general defence and cause fever to destroy microbes at high temperatures.
When cells are infected they release a chemical – histamine = swelling and heat
Pus is produced - pus being the debris e.g dead bacteria and phagocytes.
The inflammatory process only last for as long as the infection exists

23. Phagocytsis

24. Phagocytosis

25. The Inflammatory Response
The inflammatory response (inflammation) occurs when tissues are injured by bacteria, trauma, toxins, heat, or any other cause.
There are 4 signs of inflammation:
Red & warm - increased blood flow to the affected area
Swelling - increased amount of blood & influx of phagocytic cells and proteins
Pain - expansion of tissues, causing pressure on nerve cells, and also due to the presence of pain mediators.

27. Monocyte engulfs an invader
Monocyte engulfs a bacterium

28. Animation phagocytosis
How the Body Works : When the Skin is Cut

29. Compliment proteins are proteins found in the blood that fight off infections and diseases.
They punch holes in the cell walls that surround the invading bacteria.
This causes certain fluids and molecules to flow into the bacterium and others to flow out.
The end result is that
the bacterial cell swells,
bursts, and dies.

30. Interferon is an antiviral protein produced by cells that have been invaded by a virus; inhibits / interferes with viral replication within host cells,
It has two important functions: 1- It signals neighboring cells and triggers their resistance mechanisms. 2- It activates other immune cells that kill invading pathogens.

31. Learning Check 3 What are Phagocytes?
How do they play a role in preventing disease?
What is the inflammatory response
What are 4 signs of inflammation?
What are Compliment proteins?
What is Interferon?

32. The specific defence system or Immune response

33. Microorganisms/germs
Such invaders include:
bacteria,
viruses,
fungi,
Parasites e.g. worms,
cancer cells, and even
transplanted organs and tissues

34. Nonself or Foreign
To defend the body against these invaders, the immune system must be able to distinguish between what belongs in the body (self) and what does not (nonself or foreign).
Any substances that are identified as nonself can stimulate an immune response in the body.

35. The specific defence system produces:
White blood cells / lymphocytes that produce chemicals called antibodies that kill infected cells by targeting specific pathogens.
antitoxins if the target is a poisonous chemical.
When a bacterial infection is established in the body, it is the function of the immune system to control or eradicate it. The initial reaction of the immune system to an infection differs, depending on the site which has been invaded, and on the nature of the invader. There can be many "triggers", that can kick the immune system into action.

36. Organs specific to the immune system:
Red Bone marrow – white blood cells made here
Spleen – white blood cells stored here
Thymus – white blood cells mature here
Lymph nodes - white blood cells stored & mature here.

38. Antigens
Microorganisms / germs produce chemicals called antigens on their surface.
Which stimulates the white blood cells to produce antibodies.
Such substances are called antigens.

39. Each type of antibody is highly specific to a single antigen.
Antibodies
Antibody: a specific protein produced by the lymphocytes on detection of an antigen.
Each type of antibody is highly specific to a single antigen.
They inactive antigens and allow them to be destroyed.

41. Learning Check 4 Name some Microorganisms/germs.
What does the specific defence system produces?
What Organs are specific to the immune system?
What are antigens?
What are antibodies?

42. IMMUNITY

44. Induced Immunity
Immunity due to antibody production after the antigens on the pathogen have been detected.
There are two types:
Active Induced Immunity
Passive Induced Immunity

45. 1. Active Induced Immunity
Natural: normal infection
Artificial: vaccination / immunisation
The patient produces the antibodies in response to antigen detection by phagocytes.
It is a long-term protection because of the long life of memory B cells.

46. 2. Passive Induced Immunity
Occurs when foreign antibodies are given to body.
Provides short-term immunity
Natural: a child getting antibodies from the placenta or mother’s milk
Artificial: getting an injection of foreign antibodies against a particular pathogen e.g. anti-tetanus

47. pass across the placenta to the foetus and remain for several months –
Mother’s milk - Colostrum (the first breast milk) contains lots of antibodies which pass into the baby.
A mother’s antibodies
pass across the placenta
to the foetus and remain
for several months –
providing short-lived
protection
Mother’s
antibodies

48. Secondary response •rapid response to recognised challenge •exceeds primary response

49. Live but weakened pathogen (cannot reproduce).
Types of Vaccines
Contain:
Dead pathogen
Live but weakened pathogen (cannot reproduce).
Parts of the pathogen that carry the antigen.
Immunize For Good - How Vaccines Work
1:58MINS

50. Vaccination
A vaccine induces active immunity against a specific pathogen by stimulating the formation of antibodies & memory cells.
A vaccine is a dead microbe that is injected into the body and triggers antibodies but does not cause the disease.
If the real germ ever attacks you, the antibodies are present to remove it before it can cause the disease and do damage.
Suitable vaccines may cause some discomfort but give faster and greater antibody production against infection such that no symptoms occur when subsequently infected.

51. Examples of Vaccines MMR: defense against measles, mumps and rubella.
3 in 1: defense against diphtheria, whooping cough and tetanus
Vaccination
Why aren’t they always effective?
Natural infections persist within the body for a long time so the immune system has time to develop an effective response, vaccinations from dead microbes do not do this.
Less effective vaccines need booster injections to stimulate secondary response and to reinforce the immune response.

52. Immunisation The protection against disease by: vaccination or
the injection of antibodies into a person to produce a passive and or an active response.
hildimm/Immschedule/

54. Learning Check 5 What is Induced Immunity? Name the 2 types.
What is Active Induced Immunity? Name the 2 types.
What is Passive Induced Immunity? Name the 2 types.
What are Vaccines? How do they work?
What is Immunisation?

55. HIGHER LEVEL

56. THE
IMMUNE RESPONSE

57. Lymphocytes
Lymphocytes are 2 types of white blood cell which are produced in the Lymph nodes.
B-cells / B-lymphocytes- mature in the bone marrow.
T-cells / T-lymphocytes - mature in the thymus gland.
Lymph nodes are a part of the lymph system, a network of vessels, which transport white blood cells, or phagocytes, throughout the body to combat disease.

58. B-cells / B lymphocytes
Produce antibodies
When a B-cell encounters an antigen / a foreign protein, e.g. on the surface of a bacterium
It stimulates the production of lots of B- cells / antibodies,
These attach to the antigen marking them for destruction.
B cells have antibodies attached to their surface,

60. Primary immune response
Some B cells change into memory cells, which remember that specific antigen, and others change into plasma cells.
Helper T cells help B cells in this process.
Plasma cells produce antibodies that are specific to the antigen that stimulated their production.
The antibodies are embedded in the plasma membrane of the cell and are called antibody receptors.
When the receptors in the membrane recognise an antigen on the surface of a pathogen the B-cell divides rapidly into plasma and memory cells.

61. The activated B cells produce lots of antibodies, < 1000/sec.

62. Secondary immune response:
Thereafter, whenever B cells encounter the antigen again, memory B cells very rapidly recognize the antigen, multiply, change into plasma cells, and produce antibodies.
This response is quick and very effective.

63. These antibodies travel to the blood, lymph, lining of gut and lungs to bind to pathogens and toxins that are circulating in tissues or body fluids, and mark them for destruction by monocytes.
The plasma cells produce antibody molecules.

64. T-cells / T-lymphocytes
There are 4 Types of of T- cells / T-lymphocytes

65. killer T-cells produce perforin, which destroys infected cells
helper T-cells recognise antigens & stimulate B-cells to produce antibodies
killer T-cells produce perforin, which destroys infected cells
suppressor T-cells stop the activity of B & T cells & turn off the immune response
memory T-cells memorise antigens, survive a long time to trigger immunity to the same antigen in later years.
memory T-cells memorise the antigen

66. Monocyte
Monocyte

68. Learning Check 6 What Lymphocytes? Name the 2 types.
What are B-cells / B lymphocytes? How do they work?
What is the Primary immune response?
What is the Secondary immune response?
Name the 4 Types of T- cells / T- lymphocytes.
What is the function of each?