Which types of cells develop from yolk sacs (Mesoblastic phase)?

Correct Answer: D

Rationale: Correct Answer: D Rationale: 1. During the mesoblastic phase of erythropoiesis in the yolk sac, only erythroblasts develop. 2. Erythroblasts are precursors of red blood cells and are responsible for producing hemoglobin. 3. Other choices (A, B, C) mention specific types of hemoglobins or cells that are not directly related to the mesoblastic phase. 4. Hb F, Hg A2, Hg A are adult hemoglobin types, Gower 1 and Gower 2 are embryonic hemoglobins, and Portland Hgb is an abnormal hemoglobin. 5. Therefore, the correct answer is D because only erythroblasts develop from yolk sacs during the mesoblastic phase.

Correct Answer: B

Rationale: The correct answer is B: Improper disposal of phlebotomy equipment. This is the most frequent cause of needle punctures because if needles are not disposed of properly, they can pose a risk of accidental needle sticks to healthcare workers. Patient movement during venipuncture (A) can lead to complications but is not the most frequent cause of needle punctures. Inattention during needle removal (C) and failure to attach needle firmly to the tube holder (D) are also important factors to consider, but improper disposal of needles presents a higher risk of needle punctures.

Correct Answer: B

Rationale: The correct answer is B: P. ovale. P. ovale can cause relapses of malaria due to the presence of dormant liver stages (hypnozoites) that can reactivate weeks to years after the initial infection. P. falciparum, P. malariae, and P. knowlesi do not have hypnozoites and therefore do not cause relapses. P. falciparum is known for its severe manifestations, P. malariae has a long incubation period but does not cause relapses, and P. knowlesi mainly infects monkeys and rarely causes human malaria.

Correct Answer: D

Rationale: The correct answer is D: delayed hypersensitivity. Hemolytic disease of the newborn caused by Rh incompatibility is a type II hypersensitivity reaction. Rh incompatibility occurs when an Rh-negative mother carries an Rh-positive fetus, leading to the mother producing antibodies against the Rh antigen. This immune response is delayed and involves sensitized T cells. This results in the destruction of Rh-positive red blood cells in the newborn. Choice A (atopic or anaphylactic) refers to type I hypersensitivity, which involves immediate IgE-mediated reactions like allergies. Choice B (cytotoxic) is a close contender, as it also involves antibodies targeting specific antigens on cell surfaces, but it typically involves antibody-dependent cell-mediated cytotoxicity rather than delayed responses. Choice C (immune complex) relates to type III hypersensitivity, where immune complexes deposit in tissues and activate complement, causing inflammation. However, this mechanism is not the primary process in hemolytic disease of the newborn caused by

Correct Answer: D

Rationale: The correct answer is D (bovine serum albumin). Bovine serum albumin can act as a carrier protein, allowing hapten (penicillin) to bind and form a complex, triggering an immune response. This complex induces memory B cells, leading to a secondary response upon re-exposure to penicillin. Penicillin alone (choice A) is a hapten and cannot induce a secondary response without a carrier protein. Penicillin bound to egg albumin (choice B) is specific to egg albumin, not penicillin, and would not generate a response to penicillin. Egg albumin (choice C) is a protein unrelated to penicillin. Bovine serum albumin (choice D) is the correct carrier protein for penicillin in this context.