Our Body’s Defense System Immune System: Our Body’s Defense System

THE ROLE OF THE IMMUNE SYSTEM The Immune System is a collection of structures and processes within the body that prevent bacteria and pathogens from entering. If a bacteria or virus get into our body  Our immune system detects and eliminates it. When viruses and bacteria eliminate and damage anything that was able to reproduce it starts to cause problems.

Defenses of the body 1st Defense Skin –tough, outer layer, Protects body from pathogens, is oily/acidic Our skin secretes anti-bacterial substances which prevent us from waking up with mold on us! 2nd Defense Mucous Membranes Act as a barrier to pathogens/microbes trying to enter the body- Mucus traps microbes and sweeps them away Line all internal surfaces exposed to the outside (lungs,nose, etc)

D.O.T.B. continued… 3rd Defense Inflammatory Response Mast cells: Search for unknown proteins When found- Histamines released(make blood vessels more permeable, thus signaling inflammation) 4th Defense –WBC’S Inflammation brings in Leukocytes/WBC’s Move through circulatory system open gap in cell wall to reach pathogen (Diapedesis)

D.O.T.B. continued… Phagocytosis: Is when an immune cell known as a phagocyte ingests and kills invading organisms (phagocytes=neutrophils, eosinophils, dendritic cells, macrophages) The following WBC’s circulate in the blood stream awaiting chemical signals of invasion or inflammation Neutrophils-kill invading microbes, die shortly after Eosinophils-kill cells of invading parasites and bacteria Macrophages-kill invading pathogens,detects changes in normal cells (cancer), don’t die after englufing pathogens

D.O.T.B. continued….. Natural killer cells- destroys other human cell who present antigens to indicate their infection, “cell homicide” -binds to infected cell and secretes membrane dissolving enzymes Dendritic Cells- Engulf pathogens and carry information about them back to the spleen and lymph nodes. ( link innate------acquired immune system) Help us to better fight pathogens both in the present and the future.

LEUKYOCYTES/WBC’s If pathogens get past the skin and mucous membranes, as well as triggers an inflammatory response, the WBC’s then takes over the role of protecting the body. They do so by ingesting foreign chemicals and cellular debris, , by destroying infectious agents and cancer cells, or by producing antibodies. Leukocytes , Lymphocyte , Monocytes, Granulocytes, B-cells, Plasma cells WBC’S INCLUDE: T-cells, Helper T-cells, Killer T-cells, Suppressor T-cells, Natural killer cells, Neutrophils, Eosinophils, Basophils, Phagocytes, Macrophages

ANTIBODIES Highly specialized proteins produced by B-cells Swarm the invader and make it more difficult for them to function Act as “Tags” by marking the invaders to be destroyed and sending signals to phagocytes produced by plasma cells, Y shaped Each respond to specific antigen Antibody --> binds to toxin= antitoxin (When toxin is venom= antivenin) Binding- disables the chemical action of the toxin A large number of antibodies binds to an invader, this signals the complement system that the invader must be removed.

Complement system Complement system Series of proteins Each sensitive to specific antigen Proteins in complement system are floating freely in blood Proteins here are manufactured in liver Complement proteins - cause lysing (bursting) of cells and signal to phagocytes that a cell needs to be removed

LYMPH NODES Small, bean shaped structures (part of the lymphatic system) Contain filtering tissue and large number of cells Blood transfers food, water, and oxygen to lymph through capillary walls and lymph carries to the cells -absorbs proteins and wastes produced by cells and carries them away Lymph- clear fluid within the lymph nodes that carries those cells to different parts of the body. (bathes cells with water and nutrients) When the body is fighting infection lymph nodes enlarge and feel sore because the cells and bacteria in them are swelling

SPLEEN THYMUS Largest lymphatic organ in the body Contains white blood cells, which fight infection and disease Helps control the total volume of blood in the body Dipose’s of old or damaged blood vessels, old RBC’s recycled in spleen,platelets and WBC’S are stored ***Filters blood looking for foreign cells THYMUS Play a vital role in T cell maturation Located behind breast bone Vital to babies, adults can have theirs removed

BONE MARROW Yellow tissue in the center of the bones Assists the immune system by producing B-cell’s Produced new blood cells Rbc- fully formed in marrow then enter blood stream WBC - mature elsewhere

LYMPHOCYTES Attack specific pathogens the body already knows, help your body avoid infection Two different types: T-cells and B-cells T-CELLS Mature in the Thymus Gland Help destroy infected/cancerous cells Helper T cells- do not kill pathogens, but they activate and direct the cells that do B-CELLS Originate and mature in bone marrow B cells- make antibodies to attack bacteria and toxins

ANTIBODIES Highly specialized proteins produced by B-cells Swarm the invader and make it more difficult for them to function Act as “Tags” by marking the invaders to be destroyed and sending signals to phagocytes produced by WBC, Y shaped Each respond to specific antigen Antibody --> binds to toxin= antitoxin (When toxin is venom= antivenin) Binding- disables the chemical action of the toxin A large number of antibodies binds to an invader, this signals the complement system that the invader must be removed.

Complement system Complement system Series of proteins Each sensitive to specific antigen Proteins in complement system are floating freely in blood Proteins here are manufactured in liver Complement proteins - cause lysing (bursting) of cells and signal to phagocytes that a cell needs to be removed

Quick Quiz What is our immune systems first line of defense? What triggers the body’s inflammatory response? What is the role of the helper T cells? How would their absence affect the bodies ability to overcome pathogens? What is the role of the phagocytes in the immune system? What is phagocytosis? What cell produces Antibodies? Why are they sometimes reffered to as “tags”?

Helpful links: https://www.youtube.com/watch?v=CeVtPDjJBPU https://www.youtube.com/watch?v=z3M0vU3Dv8E