The most frequently used portal of entry for pathogens is the
A) mucous membranes of the respiratory tract.
B) mucous membranes of the gastrointestinal tract.
C) skin.
D) parenteral route.
E) All of these portals are used equally.
A
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The vertebrate fish group that most likely gave rise to the tetrapods are the:
a. ray-finned fishes b. cartilaginous fishes c. hagfishes d. lampreys e. lobe-finned fishes
How do ray-finned fish keep from sinking?
a. they are constantly swimming b. their fins are constantly moving c. they have lungs that are always filled with air d. they have a swim bladder that is filled with gas e. they have a skeleton that is less dense than the surrounding water
Samara is an astronaut in deep space away from gravity. How could her urine move away from the kidneys and to the bladder in such a situation?
A) skeletal muscle movements B) peristalsis C) the Valsalva maneuver D) bladder suction pressure
An Rh-negative mother will need a special treatment if she gives birth to an Rh-positive baby. The treatment involves the destruction of any stray blood cells from the baby that pass into the mother's bloodstream. Why is this necessary?
A) Without this treatment, the mother's immune system will attack only her own blood cells. B) Without this treatment, antibodies will be formed in breast milk, which could harm the baby. C) The mother's immune system will attack the Rh-positive cells and produce antibodies that will attack a fetus in a subsequent pregnancy. D) The mother's immune system will attack her own blood cells and the cells in the fetus of a subsequent pregnancy.