The shape of a cell is maintained by which of the following?

Correct Answer: A

Rationale: The correct answer is A: Microtubules. Microtubules are structural components of a cell that help maintain its shape by providing support and stability. They form a network of filaments that serve as tracks for organelle movement and help in cell division. Spindle fibers (choice B) are involved in cell division, ribosomes (choice C) are responsible for protein synthesis, and centrioles (choice D) play a role in organizing microtubules during cell division. However, only microtubules are directly responsible for maintaining the shape of a cell through their structural support function.

Correct Answer: D

Rationale: The correct answer is D: 16. A Multipotential Stem Cell can differentiate into various blood cell types, including erythrocytes. Through the process of erythropoiesis, each Multipotential Stem Cell can produce up to 16 erythrocytes. This is achieved through several stages of cell division and maturation. Choice A (8) is incorrect because the number of erythrocytes produced is greater. Choice B (1) is incorrect as a Multipotential Stem Cell can differentiate into multiple cells. Choice C (12) is also incorrect as the maximum number of erythrocytes produced is 16.

Correct Answer: B

Rationale: The correct answer is B: Koilonychia. Koilonychia is a clinical sign associated with iron deficiency anemia characterized by spoon-shaped nails. This occurs due to the decreased production of hemoglobin, leading to changes in the nail bed. Fever (choice A) is not a typical sign of iron deficiency anemia. Rash (choice C) is not a common manifestation of this condition. Weight gain (choice D) is also not a typical sign, as iron deficiency anemia is more commonly associated with weight loss or failure to thrive. Therefore, choice B is the most appropriate sign to look for in a patient with iron deficiency anemia.

Correct Answer: C

Rationale: The correct answer is C: Disseminated intravascular coagulation (DIC). In septic shock, the body's response can lead to widespread activation of clotting factors, causing both clotting and bleeding. Low platelets and elevated PT/APTT are common in DIC due to consumption of clotting factors and platelets. Thrombotic thrombocytopenic purpura (A) presents with microangiopathic hemolytic anemia, not typical in this case. Hemophilia (B) is a genetic disorder resulting in specific clotting factor deficiencies, not consistent with the patient's presentation. Von Willebrand disease (D) is a deficiency in vWF, leading to mucosal bleeding, not the systemic coagulopathy seen in DIC.

Correct Answer: B

Rationale: The correct answer is B because class II MHC proteins on donor cells are recognized by helper T cells, leading to the activation of cytotoxic T cells which then kill the donor cells. This process is crucial in graft rejection as it triggers an immune response against the foreign cells. Choice A is incorrect because class II MHC proteins are not receptors for interleukin-2. Choice C is incorrect as class II MHC proteins do not induce the production of blocking antibodies. Choice D is incorrect because class II MHC proteins do not induce IgE production, which is involved in allergic reactions, not graft rejection.