Afferent lymphatic vessels do not

Correct Answer: C

Rationale: Rationale: Afferent lymphatic vessels transport lymph containing antigens from tissues to lymph nodes (LN). Option C is correct because afferent lymphatics do not transport antigens directly from the blood to LN. Other choices are incorrect because afferent lymphatics enter LN at multiple sites (B), transport antigens from tissues to LN (A), and connect tissues to secondary lymphoid organs (D).

Correct Answer: D

Rationale: The correct answer is D because neurons are specialized cells that carry signals, making them the functional units of the nervous system. Neurons consist of a cell body, dendrites, and axons, fulfilling the criteria mentioned in options A, B, and C. Therefore, option D encompasses all the essential characteristics of neurons, making it the correct choice. Options A, B, and C individually do not fully capture the comprehensive nature of neurons, as they only cover specific aspects of what neurons are, whereas option D encompasses all the correct statements regarding neurons.

Correct Answer: C

Rationale: The correct answer is C: Anemia. Anemia is the medical term for an abnormal decrease in red blood cells. Red blood cells are responsible for carrying oxygen throughout the body, and a decrease in their numbers can lead to symptoms like fatigue, weakness, and paleness. Rationale: 1. Leukopenia (A) refers to a decrease in white blood cells, not red blood cells. 2. Thrombocytopenia (B) is a decrease in platelets, which are involved in blood clotting, not red blood cells. 3. Hemolysis (D) is the breakdown of red blood cells, not a decrease in their numbers. In summary, anemia is the correct answer as it specifically describes the condition of low red blood cell count, while the other choices are related to decreases in different components of blood.

Correct Answer: A

Rationale: The correct answer is A: He was the first to observe microorganisms. Van Leeuwenhoek's important contribution to microbiology was his discovery of microorganisms using his own handcrafted microscopes. This observation revolutionized the field by providing the first direct evidence of the existence of microorganisms. Choice B is incorrect because Leeuwenhoek's observations actually supported the idea of spontaneous generation. Choice C is incorrect because he did not link microorganisms to diseases. Choice D is incorrect because the process of fermentation was described by others before Leeuwenhoek.

Correct Answer: D

Rationale: The correct answer is D - All of the above. Lectin receptors recognize microbial carbohydrates, are expressed on phagocytes, and can be classified as pattern recognition receptors. Lectins are proteins that bind specifically to certain carbohydrates, allowing them to recognize and interact with pathogens. Phagocytes express lectin receptors to help identify and engulf pathogens. Additionally, lectin receptors are considered pattern recognition receptors because they recognize specific patterns or structures commonly found on pathogens. Therefore, all three statements are true, making option D the correct answer.