Nokea
Dendritic cells migrating from tissues enter the lymph nodes through
- A. Thoracic duct
- B. HEV
- C. Afferent lymphatics
- D. Efferent lymphatics
Correct Answer: C
Rationale: The correct answer is C: Afferent lymphatics. Dendritic cells migrate from tissues to lymph nodes through afferent lymphatics, which are small vessels that carry lymph into the lymph nodes. Once inside the lymph nodes, dendritic cells interact with T cells to initiate immune responses. The thoracic duct (A) drains lymph from the entire body into the bloodstream, not directly into lymph nodes. High endothelial venules (HEV) (B) are specialized blood vessels in lymph nodes where lymphocytes enter from the bloodstream, not dendritic cells. Efferent lymphatics (D) carry lymph out of the lymph nodes, not into them.
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Which of the following nucleotide triplets best represents a codon?
- A. a triplet in the same reading frame as an upstream AUG.
- B. a triplet separated spatially from other triplets.
- C. a sequence in tRNA at the 3' end.
- D. a triplet that has no corresponding amino acid.
Correct Answer: A
Rationale: The correct answer is A because a codon is a triplet of nucleotides in mRNA that corresponds to a specific amino acid during protein synthesis. To be a codon, the triplet must be in the same reading frame as the start codon (AUG) to maintain the correct reading of the genetic code. Choice B is incorrect because codons are typically consecutive in mRNA. Choice C is incorrect as tRNA sequences are not codons. Choice D is incorrect because all codons correspond to specific amino acids.
Which types of hypersensitivity are mediated by antibodies?
- A. Type I, II, III, and IV
- B. Type I, II, III, and V
- C. Type I and IV only
- D. Type III and IV only
Correct Answer: B
Rationale: The correct answer is B: Type I, II, III, and V.
- Type I hypersensitivity involves IgE antibodies and immediate allergic reactions.
- Type II hypersensitivity involves IgG and IgM antibodies attacking self-antigens on cells.
- Type III hypersensitivity involves immune complex deposition.
- Type V hypersensitivity involves autoantibodies stimulating receptors.
Choices A, C, and D are incorrect because they do not include all types of hypersensitivity mediated by antibodies as specified in the question.
Carpal tunnel syndrome (CTS) is caused when the carpal tunnel compresses which location?
- A. Radial artery
- B. Brachial artery
- C. Median nerve
- D. Ulnar nerve
Correct Answer: C
Rationale: The correct answer is C: Median nerve. Carpal tunnel syndrome occurs when the median nerve is compressed within the carpal tunnel in the wrist. This compression leads to symptoms like numbness, tingling, and weakness in the hand and fingers. The other choices are incorrect because the radial artery (A) and the brachial artery (B) are blood vessels, not nerves. The ulnar nerve (D) runs along a different path in the arm and is not involved in carpal tunnel syndrome.
What is the medical term for the formation of abnormal red blood cells?
- A. Leukocytosis
- B. Thrombocytosis
- C. Hemolysis
- D. Anemia
Correct Answer: D
Rationale: The correct answer is D: Anemia. Anemia is the medical term for a condition where there is a decrease in the number of red blood cells or hemoglobin in the blood. The formation of abnormal red blood cells can lead to anemia, affecting the oxygen-carrying capacity of the blood. Leukocytosis (A) is an increase in white blood cells, thrombocytosis (B) is an increase in platelets, and hemolysis (C) is the breakdown of red blood cells, none of which specifically refer to the formation of abnormal red blood cells.
Secondary lymphoid tissues are where:
- A. Lymphocyte precursors become mature
- B. Inflammation occurs during re-infection with a given pathogen
- C. Lymphocytes become activated by antigen
- D. Gene rearrangement takes place
Correct Answer: C
Rationale: The correct answer is C because secondary lymphoid tissues, like lymph nodes and spleen, are where lymphocytes encounter antigens and become activated. This process leads to the proliferation and differentiation of lymphocytes, enabling them to mount an immune response against specific pathogens. Choices A, B, and D are incorrect because A pertains to primary lymphoid tissues, B describes a localized immune response, and D refers to the process of gene rearrangement that occurs in the primary lymphoid tissues during lymphocyte development.