Which cells aid in the body's defense processes by secreting histamine and heparin?
Eosinophils
Basophils
Neutrophils
Platelets
Monocytes
The Correct Answer is B
A. Eosinophils: These granulocytes primarily function in the destruction of multicellular parasites and the modulation of inflammatory responses. While their granules contain various cytotoxic enzymes and cytokines, they are not the primary source of systemic histamine or heparin. Their role is more closely associated with IgE-mediated parasiticidal activity.
B. Basophils: These are the least abundant leukocytes and contain prominent cytoplasmic granules rich in histamine and heparin. Histamine acts as a potent vasodilator to increase blood flow to infected areas, while heparin functions as an anticoagulant to prevent localized clotting. These secretions facilitate the recruitment of other immune cells to the site of injury.
C. Neutrophils: These cells are the primary phagocytic responders to acute bacterial infections and utilize oxidative bursts to neutralize pathogens. Their primary granules contain myeloperoxidase and defensins rather than histamine or heparin. They focus on the direct destruction of microorganisms rather than the chemical modulation of vascular permeability.
D. Platelets: Also known as thrombocytes, these are cellular fragments essential for hemostasis and thrombus formation. While they release serotonin and clotting factors from their alpha and delta granules, they do not secrete heparin. In fact, platelets are involved in the coagulation cascade that heparin is designed to inhibit.
E. Monocytes: These agranulocytes serve as precursors to macrophages and lack the specific chemical-filled granules found in basophils. Their primary defensive contribution is through phagocytosis and the secretion of pro-inflammatory cytokines like tumor necrosis factor. They do not utilize histamine or heparin as their primary signaling or defense molecules.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
A. natural active: This form of immunity is acquired through natural exposure to a pathogen during an environmental infection. The body develops its own antibodies and memory cells following the clinical or subclinical course of the disease. It does not involve medical intervention like the administration of a vaccine.
B. artificial active: Vaccination involves the deliberate clinical introduction of attenuated or inactivated antigens into the body. This medical intervention stimulates the recipient’s immune system to produce its own antibodies and long-lived memory cells without causing the disease. It provides long-lasting protection through an induced immune response.
C. natural passive: This immunity occurs through the natural transfer of preformed antibodies from one individual to another, such as from mother to fetus via the placenta. It provides immediate but temporary protection because the recipient’s own immune system is not activated. No memory cells are produced during this process.
D. artificial passive: This involves the clinical injection of exogenous antibodies or antivenoms to provide immediate protection against a specific toxin or pathogen. The immunity is temporary as the injected proteins are eventually degraded and no memory cells are created. It is used for post-exposure prophylaxis rather than long-term prevention.
E. innate: Innate immunity refers to the non-specific, first-line defense mechanisms that are present from birth. It includes physical barriers like the skin and generic cellular responses like phagocytosis. Unlike vaccination, it does not involve the recognition of specific antigens or the development of immunological memory.
Correct Answer is A
Explanation
A. 20; 32: The primary dentition consists of 20 teeth, including incisors, canines, and molars, which erupt during infancy. The permanent secondary dentition replaces these with 32 teeth, adding premolars and third molars. This represents the standard anatomical formula for human odontogenesis and maturation.
B. 16; 20: These figures underestimate the count for both deciduous and permanent stages of dental development. A child typically possesses more than 16 teeth once the primary set is complete. An adult with only 20 teeth would be considered partially edentulous, missing significant posterior dentition.
C. 28; 20: This choice incorrectly suggests that infants have more teeth than adults. Human dental development involves an increase in total tooth count as the jaw expands to accommodate larger structures. 28 teeth represent a permanent set excluding the wisdom teeth, not the deciduous set.
D. 32; 20: This inversion implies that the deciduous set is larger than the adult permanent set. Deciduous teeth are smaller and fewer in number to fit the pediatric alveolar bone. The adult mandible and maxilla are anatomically designed to support a more extensive 32-tooth array.
E. 32; 32: While some adults have 32 teeth, no infant develops 32 deciduous teeth in a healthy physiological state. The primary dentition lacks the premolars and third molars found in the permanent set. Using the same number for both stages ignores the transition of dental eruption.
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