Briefly explain how the body's first line of defense against pathogens works

What will be an ideal response?


The first line of defense includes physical and chemical barriers. The skin, a major physical barrier, acts as an impermeable shield against invasion of the pathogens into the body. Skin forms a watertight barrier that is resistant to toxins and enzymes produced by most pathogens. Skin cells are continuously shed and replaced. Chemical protectors associated with the skin include oils and sweat that are slightly acidic, which prevents microbial growth and washes bacteria away. The mucous membranes that cover many surfaces in the body, including the respiratory, digestive, urinary, and reproductive systems, are also physical barriers. Other chemical barriers include acidic conditions of the stomach lining and vagina and lysozyme in tears and saliva.

Biology & Microbiology

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Human males are the ________ sex.

A) homozygous B) homogametic C) heterogametic D) heterozygous

Biology & Microbiology

What happens with blood flow at the arteriole end of a capillary?

a. Pressure forces some fluid out of the capillary into the interstitial fluid. b. Pressure forces some fluid into the capillary from the interstitial fluid. c. Osmotic pressure forces fluid out of the capillary into the interstitial fluid. d. There is no fluid movement in either direction. e. Osmotic pressure of the blood is lower than at the venule end.

Biology & Microbiology

E. coli is an intestinal bacterium that reproduces every 20 minutes. E. coli is representative of a(n) ____ species

a. r-selected b. k-selected c. type I d. logarithmic type-curve e. type IV

Biology & Microbiology

What is the organ in animals without teeth such as

earthworms and birds that accomplishes the same action as teeth? a. beak b. pharynx c. gizzard d. cloaca e. crop

Biology & Microbiology