Innate immunity chapter Flashcards
The first line of defense is composed of?
External physical barriers to pathogens, skin & mucous membranes
The second line of defense
Internal and composed of protective cells, bloodborne chemicals, & the processes that inactivate or kill invaders
The first two lines of defenses (first line and second line) are called?
Innate immunity because they are present at birth prior to contact with infectious agents or their products. Innate immunity is rapid and works against a wide variety of pathogens, including parasitic worms, protozoa, fungi, bacteria, & viruses
The third line of defense is?
Adaptive immunity responds against unique species or strains of pathogens and alters the body’s defenses such that they act more effectively upon subsequent infection with the specific strain
The epidermis also contains phagocytic cells called?
Dendritic cells. They have slender, fingerlike processes that extend among the surrounding cells forming a network to intercept invaders. These cells both phagocytize pathogens nonspecifically and play a role in adaptive immunity
What is the role of blood vessels in the dermis layer?
They deliver defensive cells and chemicals
In addition to its physical structure, the skin has a number of chemical substances that nonspecifically defend against pathogens. Describe this
- Dermal cells secrete antimicrobial peptides
- Sweat glands secrete perspiration (contains salt), antimicrobial peptides, and lysozyme
- The salt draws water osmotically from invading cells, which inhibit their growth and kills them
What are antimicrobial peptides? (sometimes called defensins)
They are positively charged chains of 20-50 amino acids that act against microorganisms
Describe the role of lysozyme in sweat secreted by sweat glands
Its an enzyme that destroys the cell walls of bacteria by cleaving the bonds between the sugar subunits of the walls. Bacteria without cell walls are more susceptible to osmotic shock & digestion by other enzymes within phagocytes
Where are the mucous membranes
They line the lumens of the respiratory, urinary, digestive, and reproductive tracts. Like skin they act nonspecifically to limit infection both physically and chemically
Unlike surface epidermal cells, surface cells of the mucous membranes are?
Alive and play roles in the diffusion of nutrients and oxygen (in the digestive, respiratory and female reproductive systems) and in the elimination of wastes (in urinary, respiratory, and female reproductive systems)
How are organisms kept from invading through the thin mucous membranes?
In some cases they are not, which is why some mucous membranes, especially those of the respiratory and reproductive systems, are common portal of entry for pathogens
The epithelial cells of the mucous membranes are?
Tightly packed to prevent entry of pathogens, the cells are continually shed and then replaced via the cytokinesis of stem cells
Dendritic cells reside below the mucous epithelium to phagocytize invaders. These cells are also able to?
Extend pseudopodia between epithelial cells to “sample” the contents of the lumen, which helps prepare adaptive immune responses against particular pathogens that might breach the mucous barrier
What is microbial antagonism?
Our skin and mucous membranes are normally home to a variety of protozoa, fungi, bacteria, and viruses. These “normal microbiota” play a role in protecting the body by competing with potential pathogens in a variety of ways
