Natural killer (NK) cells
can kill cancer cells before the immune system is activated
are a type of phagocyte
are also called cytotoxic T cells
are cells of the adaptive immune system
The Correct Answer is A
A. Can kill cancer cells before the immune system is activated: NK cells are part of the innate immune system and can recognize and destroy virus-infected or cancerous cells without prior sensitization. They provide a rapid, non-specific defense before adaptive immunity is engaged.
B. Are a type of phagocyte: NK cells do not engulf pathogens like phagocytes; instead, they induce apoptosis in target cells by releasing cytotoxic granules. Their mechanism of action is different from phagocytosis.
C. Are also called cytotoxic T cells: Cytotoxic T cells are part of the adaptive immune system and require antigen presentation for activation. NK cells are distinct and act independently of antigen-specific activation.
D. Are cells of the adaptive immune system: NK cells are components of innate immunity, providing immediate defense against abnormal cells. They do not rely on prior exposure to specific antigens, unlike adaptive immune cells.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
A. Lymph transport is faster than that occurring in veins:Lymph moves much more slowly than blood in veins. Its movement relies on low-pressure mechanisms rather than a central pump like the heart, so this statement is incorrect.
B. Under normal conditions, lymph vessels are very high-pressure conduits:Lymphatic vessels operate under low pressure. They have thin walls and rely on external forces, valves, and vessel contractions to move lymph, not high internal pressure.
C. Lymph transport depends on the movement of adjacent tissues, such as skeletal muscles:Lymph flow is aided by skeletal muscle contractions, respiratory movements, and rhythmic contractions of smooth muscle in the vessel walls. These mechanisms compress lymphatic vessels, helping push lymph toward the thoracic duct and ultimately the bloodstream.
D. Lymph transport is only necessary when illness causes tissue swelling:Lymph circulation is continuous under normal conditions to maintain fluid balance and immune surveillance. Swelling during illness increases demand, but transport is always required.
Correct Answer is A
Explanation
A. Blood vessel diameter:Vessel diameter has the greatest influence on blood flow resistance because resistance is inversely proportional to the fourth power of the radius. Small changes in diameter, especially in arterioles, can dramatically increase or decrease resistance, making it the most significant factor.
B. Blood vessel type:While different types of vessels (arteries, arterioles, capillaries, veins) have structural differences, the type itself does not directly determine resistance as much as the diameter within those vessels.
C. Blood viscosity:Blood viscosity affects resistance, with thicker blood increasing friction. However, normal physiological variations in viscosity are relatively minor compared with the impact of changes in vessel diameter.
D. Total blood vessel length:Longer vessels contribute to higher resistance, but vessel length is generally constant in adults. Therefore, its effect on resistance is less significant than diameter, which can change dynamically through vasoconstriction or vasodilation.
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