Platelet aggregation is an important event in hemostasis. Which of the following statement is true for platelet aggregation in vascular injury?

Correct Answer: C

Rationale: The correct answer is C: Platelets change their shape during the process of platelet aggregation in vascular injury. Platelets undergo shape change from a discoid to a spiky form, leading to the exposure of their glycoprotein receptors, which then bind to fibrinogen and other platelets to form a platelet plug. This process is crucial for hemostasis and preventing excessive bleeding. Explanation for why other choices are incorrect: A: There will be initial vasodilation - Vasodilation is not a direct result of platelet aggregation but rather an initial response to vascular injury to increase blood flow to the area. B: Clotting factors play no role in its formation - Clotting factors are essential for the later stages of hemostasis, but platelet aggregation is primarily driven by platelet activation and shape change. D: Serotonin stimulates platelet aggregation - While serotonin is released from platelets upon activation, it does not directly stimulate platelet aggregation.

Correct Answer: C

Rationale: Virchow's node, also known as the left supraclavicular node, receives lymphatics primarily from the abdomen. The correct answer is C (prostate) because the prostate does not drain into Virchow's node. The stomach, breast, and testes all have lymphatic connections to Virchow's node. This is due to the anatomical location of these organs and their respective lymphatic drainage pathways. The stomach drains into the celiac lymph nodes, which then connect to Virchow's node. The breast drains into the axillary lymph nodes, which also communicate with Virchow's node. The testes drain into the para-aortic lymph nodes, which eventually lead to Virchow's node. Therefore, C is the correct answer based on the unique lymphatic drainage patterns of these organs.

Correct Answer: D

Rationale: In thrombasthenia, there is a deficiency or dysfunction of integrin αIIbβ3 (GPIIb/IIIa), leading to impaired platelet aggregation. Prolonged bleeding time (A) is seen due to defective platelet function. Platelet count (B) is typically normal as thrombasthenia does not affect platelet production. Platelet aggregation defect (C) is a characteristic feature of thrombasthenia. Prolonged clotting time (D) is not associated with thrombasthenia as it primarily affects platelet function, not the coagulation cascade. Hence, choice D is the correct answer.

Correct Answer: A

Rationale: Henoch Schonlein purpura is characterized by palpable purpura, abdominal pain, arthritis, and acute diffuse glomerulonephritis. Thrombocytopenia is not typically associated with Henoch Schonlein purpura, making choice A correct. Thrombocytopenia is more commonly seen in conditions like immune thrombocytopenic purpura. Choices B, C, and D are incorrect as palpable purpura, intussusception, and acute diffuse glomerulonephritis are commonly associated with Henoch Schonlein purpura.

Correct Answer: A

Rationale: The correct answer is A: hyperchlorhydria. Pernicious anemia is characterized by vitamin B12 deficiency due to impaired absorption, not excess stomach acid. Premature graying of hair is unrelated. Presence of anti-intrinsic factor antibody and risk of gastric polyps are associated with pernicious anemia, but not hyperchlorhydria. Therefore, choice A is the correct answer as it does not align with the typical symptoms and characteristics of pernicious anemia.