Essentials Of Pathophysiology Concepts of Altered States 4th Edition By Porth
Essentials Of Pathophysiology Concepts of Altered States 4th Edition By Porth
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Chapter 12- Disorders of Hemostasis
Complete Chapter Questions With Answers
Sample Questions Are Posted Below
| 1. | A nursing student asks her instructor, “I don’t understand this coagulation system. When we donate blood, what keeps it from clotting in the bag?” The instructor responds: | |
| A) | “Calcium gluconate is added to the bag to keep it from clotting.” | |
| B) | “If the blood is used within 24 hours from retrieval, there will be no clot formation yet.” | |
| C) | “The blood bank adds heparin to every bag prior to actually collecting the blood from the donor.” | |
| D) | “Citrate is added to the blood bag, which prevents it from clotting.” | |
| Ans: | D | |
| Feedback: | ||
| The addition of citrate to blood stored for transfusion purposes prevents clotting by chelating ionic calcium. Calcium (factor IV) is required for coagulation to occur, and calcium is supplied by the body for the first two steps. Blood coagulation is regulated by several natural anticoagulants, such as antithrombin III and proteins C and S, which work by inactivating some of the clotting factors. Obviously, if blood not processed but used 24 hours later, it will have clotted. | ||
| 2. | While taking an exam on disorders of hemostasis, the students were asked to identify endothelial mediators that inhibit platelet aggregation and also vasodilate vessels. Which of the following would be considered a correct answer? Select all that apply. | |
| A) | Adenosine diphosphate | |
| B) | Prostaglandin I2 | |
| C) | Thromboxane A2 (TXA2) | |
| D) | Nitric oxide | |
| E) | Plasminogen | |
| Ans: | B, D | |
| Feedback: | ||
| If platelets are activated, they are inhibited from adhering to the surrounding uninjured endothelium by endothelial prostacyclin (prostaglandin I2 [PGI2]) and nitric oxide. Both of these mediators are potent vasodilators and inhibitors of platelet aggregation. Endothelial cells also elaborate an enzyme called adenosine diphosphatase that degrades ADP and further inhibits platelet aggregation. The plasma also contains a plasma protein called plasminogen that gets activated and converted to plasmin, an enzyme capable of digesting the fibrin strands of the clot. Release of the vasoconstrictor TXA2 is responsible for much of the vessel spasm. Dense granules mainly contain adenosine diphosphate (ADP), ATP, ionized calcium, serotonin, and histamine, which facilitate platelet adhesion and vasoconstriction at the site of vessel injury. | ||
| 3. | Following a lecture on hemostasis, a nursing student accidently cuts her hand while preparing supper for her family. She watches the laceration very closely. Sure enough, the first thing she notes is: | |
| A) | Small hair-like strands form a blood (fibrin) clot. | |
| B) | Limited bleeding initially as a response to the small vessel walls being sealed by a platelet plug. | |
| C) | Clot retraction by pushing serum out of the clot and joining the edges of the broken vessel. | |
| D) | Initially, it takes a few seconds for blood to appear as a result of vessel spasm. | |
| Ans: | D | |
| Feedback: | ||
| There are five stages in hemostasis, with the first step being transient vessel vasospasm. Vessel spasm is initiated by endothelial injury and caused by local and humoral mechanisms. It is a transient event, usually lasting less than 1 minute. For smaller vessels, release of the vasoconstrictor TXA2 is responsible for much of the vessel spasm. Formation of the platelet plug, development of an insoluble fibrin clot, and clot retraction happen after vessel spasm. | ||
| 4. | To form a platelet plug, platelets must adhere to the vessel inner layer. For this to occur, which protein molecule is required? | |
| A) | Von Willebrand factor | |
| B) | Plasminogen | |
| C) | Lipoprotein | |
| D) | Thromboxane A2 | |
| Ans: | A | |
| Feedback: | ||
| Platelet adhesion requires a protein molecule called von Willebrand factor (vWF). This factor is produced by both megakaryocytes and endothelial cells and circulates in the blood as a carrier protein for coagulation factor VIII. The plasma also contains a plasma protein called plasminogen, which gets activated and converted to plasmin, an enzyme capable of digesting the fibrin strands of the clot. The extrinsic pathway of coagulation, which is a much faster process, begins with trauma to the blood vessel or surrounding tissues and with the release of an adhesive lipoprotein called tissue factor (also known as thromboplastin or factor III) from the subendothelial cells. Thromboxane A2 (TXA2) is released during platelet aggregation, the step after adhesion. | ||
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