A heart attack is

Correct Answer: D

Rationale: The correct answer is D because a heart attack, also known as a myocardial infarction, involves damage to the cardiac muscle due to a blocked coronary artery. Choice A is correct as it directly relates to the definition of a heart attack. Choice B is also correct as a blocked coronary artery is the main cause of decreased blood flow to the heart muscle leading to a heart attack. Choice C is incorrect as it refers to a stroke, which is the death of brain tissue due to blocked arteries in the head, not a heart attack. Therefore, A & B (choices A and B) are the correct options, making D the correct answer.

Correct Answer: C

Rationale: The correct answer is C: Aplastic anemia. Aplastic anemia is a condition where the bone marrow doesn't produce enough blood cells, including red blood cells. Iron deficiency anemia (A) is caused by a lack of iron in the body, not a deficiency in red blood cell production. Sickle cell anemia (B) is a genetic disorder affecting the shape of red blood cells, not the production. Pernicious anemia (D) is caused by a lack of vitamin B12, which leads to a deficiency in red blood cell production, but it is not the medical term specifically used for this condition.

Correct Answer: B

Rationale: Step-by-step rationale: 1. Lysozyme is an enzyme that destroys bacterial cell walls. 2. This action acts as a preformed chemical barrier against pathogens. 3. Mucus (choice A) is a physical barrier, not a preformed chemical one. 4. Tight junctions (choice C) and cilia (choice D) are structural components, not chemical barriers. Summary: - Choice B, Lysozyme, is correct as it actively targets and destroys pathogens. - Choices A, C, and D are incorrect as they do not directly function as preformed chemical barriers.

Correct Answer: C

Rationale: The correct answer is C: Mast cells: acute phase response. Mast cells are actually involved in allergic responses, not the acute phase response of the immune system. The acute phase response is primarily mediated by cytokines and acute-phase proteins. Interferons protect against viral infections, ROS help kill pathogens inside cells, and selectins aid in leukocyte extravasation during inflammation.

Correct Answer: D

Rationale: The correct answer is D, "All of the above." Immunoglobulins are antibodies produced by the immune system to recognize and bind to foreign molecules called antigens. These antigens can be proteins (choice A), carbohydrates (choice B), or lipids (choice C). Therefore, immunoglobulins can bind to all classes of biological molecules. Choices A, B, and C are incorrect as they each represent individual classes of molecules that can be targeted by immunoglobulins, but the correct answer encompasses all of them.