Chapter 7.3 Innate Defenses Flashcards
Define Immunity
The ability to combat diseases and cancer, includes two innate lines of defense.These act indiscriminately against all pathogens.
What are the immunity’s two innate lines of defense?
- Barriers to entry. The body puts up barriers that aid in the prevention of pathogen entry.
- Phagocytic white blood cells, the neutrophils and macrophages. We will consider these two phagocytic white blood cells in the context of the inflammatory response, a special reaction of the body when first invaded. Protective proteins are also part of this line of defense.
What are the barriers of entry?
The body has built-in barriers, both physical and chemical, that serve as the first line of defense against an infection by pathogens.
Describe the barriers:Skin and Mucous Membranes
The skin is an effective physical barrier that prevents infection. Mucous membranes lining the respiratory, digestive, reproductive, and urinary tracts are also physical barriers to entry by pathogens.
Describe the barriers: Chemical Barriers
Include the secretions of sebaceous (oil) glands of the skin. These contain chemicals the weaken or kill certain bacteria on the skin. Perspiration, saliva, and tears contain an antibacterial enzyme called lysozyme. Saliva helps to wash microbes off the teeth and tongue, and tears wash the eyes. As urine is voided from the body, it flushes bacteria from the urinary tract.
How does the acid pH of the stomach act as a chemical barrier?
It inhibits growth or kills many types of bacteria. The acidity of the vagina and its thick walls discourages the presence of pathogens.
How is resident bacteria a chemical barrier?
A significant chemical barrier to infection is created by the normal flora, microbes the usually reside in the mouth, intestine, and other areas. By using available nutrients and releasing their own waste, these resident bacteria prevent potential pathogens from taking up residence.
Describe inflammatory response
The inflammatory response exemplifies the second line of defense against invasion by a pathogen. Inflammation employs mainly neutrophils and macrophages to surround and kill (engulf by phagocytosis) pathogens trying to get a foothold inside the body. Protective proteins are also involved. Inflammation is usually recognized by its 4 hallmark symptoms: 1. Redness 2. Heat 3. Swelling 4. Pain
Describe the four signs of the inflammatory response
They are due to capillary changes in the damaged area, and all serve to protect the body.
What do the chemical mediators do?
Chemical mediators, such as histamine, released by damaged tissue cells and mast cells, cause the capillaries to dilate and become more permeable. Excess blood flow due to enlarged capillaries cause the skin to redden and become warm. Increased temp. in an inflamed area tends to inhibit growth of some pathogens. Increased blood flow brings WBCs to the area. Increased permeability of capillaries allows fluids and proteins, including blood-clotting factors, to escape into the tissues. Clot formation in the injured area prevents blood loss. The excess fluid in the area presses on nerve endings, causing pain associated with swelling. Together, these events summon WBCs to the area.
Once the WBCs arrive at an injured area what happens?
They move out of the bloodstream into the surrounding tissue. The neutrophils are first and actively phagocytize debris, dead cells, and bacteria they encounter. The many neutrophils attracted to the area can usually localize any infection and keep it from spreading. If neutrophils die off in great quantity, they become a yellow-white substance called pus.
When an injury is not serious what is the inflammatory response?
It is short lived and the healing process will quickly return the affected area to a normal state. Nearby cells secrete chemical factors to ensure the growth (and repair) of blood vessels and new cells to fill in the damaged area.
What happens if the neutrophils are overwhelmed?
They call for reinforcements by secreting chemical mediators called cytokines, which attract more WBCs to the area, including monocytes.
Describe monocytes
They are longer-lived cells that become macrophages, even more powerful phagocytes than neutrophils. Macrophages can enlist the help of lymphocytes to carry out specific defense mechanisms.
What is inflammation in the body?
Inflammation is the body’s natural response to an irritation or injury and serves an important role. Once the healing process has begun, inflammation rapidly subsides. In some cases chronic inflammation may last for weeks, months, or even years if an irritation or infection cannot be overcome.
