✓ Correct answer: C. Von Willebrand factor.Upon damage to the lining of a blood vessel (endothelium) the body immediately takes steps to staunch the bleeding. Among the first things to occur is that platelets circulating in the blood bind directly to receptors in the collagen of the blood vessels. Von Willebrand factor, released by the endothelium and from the platelets, helps those platelets adhere to the collagen.<br/><br/>Choices A and D are incorrect, as PAF and glycoprotein IIb are steps in the pathway of primary hemostasis that do not directly strengthen the initial adhesion of platelets to collagen although they are necessary for eventual healing. Serine proteases (choice C) are part of a different pathway, secondary hemostasis, or the coagulation cascade that leads to fibrin formation and clotting.
Keep practising. Use the free ATI TEAS 7 PDF, watch the YouTube walkthrough, or unlock all 10 web questions with timed mock exams.
Free practice here. Timed mocks when you are ready.
Study the ATI TEAS 7 Exam Prep 2026 Test free question explanations, download the PDF, then unlock timed mock exams on the web when you want exam-day practice.
Theory