The Immune SystemThe Body’s Lines of Defense

DiseaseDisease is defined as a condition that impairs or

interferes with the well being of an organism.

Some diseases are caused by the breakdown of normal body processes while others result from pathogenic agents.

Pathogenic organisms are disease-producing organisms, which can be viruses, bacteria, protists, or fungi.

Purpose of the Immune System

The immune system protects the body from infection and invasion by foreign substances.

It also recognizes and destroys altered cells.

http://www.youtube.com/watch?v=CeVtPDjJBPU

Three Lines of DefenseThe human body must constantly defend itself

against the many unwelcome intruders it encounters in the air, in food and in water.

It must also deal with abnormal body cells that sometimes turn into cancer.

Three lines of defense have evolved to help resist infection and possible death from fatal illnesses.

Three Lines of Defense (cont’d)

The first two lines of defense are considered nonspecific immune responses, meaning they do not distinguish one microbe from another.

The third line of defense is a specific immune response that reacts in specialized ways to various intruders.

OVERVIEW- RECAPWhat is the purpose of the immune system?

What is disease?

How many lines of defence does the body have?Why would this be important?

What does non-specific immune response mean? What does specific? Why would there be both?

The First Line of DefenseThe body’s first line of defense against foreign

invaders is largely physical…The skin and mucus membranes form a barrier against viral and bacterial invaders.

Like a medieval city that used walls and moats to defend against attack from outsiders.

The First Line of Defense (cont’d)

The skin also has chemical defenses in the form of acidic secretions, which keep it at a pH range of 3-5, which inhibits the growth of microbes.

Lysozyme is an antimicrobial enzyme secreted in human tears, saliva, mucus secretions and perspiration. It destroys the cell walls of bacteria, killing them.

Skin Video

The First Line of Defense (cont’d)

In the respiratory passage, invading microbes and debris become trapped in a layer of mucus or filtered by cilia.

In the stomach, there are acids and protein-digesting enzymes that destroy most of the invading microbes carried into the body with food.

FIRST LINE- RECAPWhat is the “first line” of defence?

How does the skin protect the body from attack?

How do the openings in the skin (mouth, eyes, nose, etc) make the body vulnerable? What methods have been developed to protect the body from attack?

The Second Line of Defense

A second line of defense can be mobilized if the invader takes up residence in the body.

This is a nonspecific defense mechanism that relies mainly on the process of phagocytosis (ingestion of invading microbes by certain types of white blood cells).

The Second Line of Defense (cont’d)

Leukocytes, or white blood cells, are cells that can engulf invading microbes or produce antibodies.

The shape and size of the nucleus, along with granules in the cytoplasm, can be used to identify different classes of leukocytes.

The Second Line of Defense (cont’d)

When a foreign particles penetrates the skin through an injury, special white blood cells, known as monocytes, migrate from the blood into the tissues, where they develop into macrophages.Macrophages = “Big eaters”

Microbes are engulfed by the macrophage and destroyed by enzymes within the macrophage.

The Second Line of Defense (cont’d)

Another phagocytic response involves white blood cells known as neutrophils.

Neutrophils are attracted to chemical signals given off by cells that are damaged by microbes.

Neutrophils engulf microbes and release lysosomal enzymes that digest both the microbe and the white blood cell.

The remaining fragments of protein, dead white blood cell and digested invader are called pus.

The Second Line of Defense (cont’d)

Tissue damage due to physical injury also initiates a localized inflammatory response. Inflammatory response = A nonspecific immune

response resulting in swelling, redness, heat and pain.

So, pus and inflammation are signs that the second line of defense has been at work.

Inflammatory responsehttps://www.youtube.com/watch?v=K3JS_eekIs8

The Second Line of Defense (cont’d)

A fever is another example of the body’s system-wide response to infection.

When infectious organisms spread throughout your body, neutrophils and macrophages digest the invaders and release chemicals into your bloodstream.

When the chemicals reach the part of your brain that controls temperature, it raises the temperature.

The higher temperature makes it harder for a bacteria to survive.

SECOND LINE- RECAPWhat is the “second line” of defence?

How do the leucocytes protect the body from attack?

How does inflammation protect the body?Why is it important to have cells from the

circulatory system arrive at the site of infection?

What is the impact of increased body temp?

What is an allergic reaction?

ReviewFirst Line of Defense

SkinMucusTearsSalivaStomach acid

Second Line of DefenseMacrophagesNeutrophils Inflammatory response

Third Line of DefenseThe body’s third line of defense is a specific

response to infection.

This is known as the immune response and will be covered tomorrow.

Immune response http://www.youtube.com/watch?v=WJEc2GDEfz8

Magic School Bus

http://www.youtube.com/watch?v=RFk02G6Q9GU

Bill Nye http://www.youtube.com/watch?v=GQFUziWNj2c

Intro video overview

http://www.youtube.com/watch?v=Non4MkYQpYA

Chloe and Nerb… contains info on the anatomy

https://www.youtube.com/watch?v=24IYt5Z3eC4