MLT GlobeBasic Pathology: Hemodynamic disorders – page 4
153 Basic Pathology MCQs on Hemodynamic disorders with answers and explanations.
Which substance limits clot extension by converting plasminogen to plasmin?
t-PA from endothelium activates plasmin, which degrades fibrin, restricting thrombi to the injury site. Factor XIII cross-links and stabilises fibrin.
A fragment of deep vein thrombus travelling to the lung passes through which structure before lodging in the pulmonary vasculature?
Venous emboli travel through the inferior vena cava, right atrium and right ventricle into the pulmonary arteries, where they lodge.
Which endothelial product inhibits platelet aggregation and causes vasodilation?
Prostacyclin and nitric oxide from intact endothelium inhibit platelet aggregation. Thromboxane A2 from platelets promotes aggregation and vasoconstriction.
Which ion is required for several steps of the coagulation cascade and is removed by citrate in blood collection tubes?
Calcium (factor IV) links vitamin K-dependent factors to phospholipid surfaces. Citrate and EDTA chelate calcium, preventing clotting in the tube.
Which blood component forms the primary haemostatic plug at a site of vascular injury?
Platelets adhere, activate and aggregate to form the primary plug, which is then stabilised by fibrin during secondary haemostasis.
A deep vein thrombus fragment crosses a patent foramen ovale and occludes a cerebral artery. This is termed:
Paradoxical embolism occurs when a venous embolus passes through an interatrial or interventricular defect into the systemic arterial circulation.
Which of the following acts as an anticoagulant rather than a participant in clot formation?
Heparin enhances antithrombin activity to inactivate thrombin and factor Xa. Fibrin, vWF and PAF all promote haemostasis.
An abnormal increase of fluid in the interstitial tissue spaces is called:
Oedema is excess interstitial fluid. Haemorrhage is extravasation of blood; hyperaemia is increased blood within dilated vessels.
Excess interstitial fluid is normally returned to the bloodstream through lymphatics that drain mainly into the:
Lymphatics collect interstitial fluid and return it to venous blood via the thoracic duct and right lymphatic duct. Lymphatic obstruction causes lymphoedema.
Unlike venous emboli, which lodge mainly in the lungs, systemic arterial emboli:
Arterial emboli may travel almost anywhere; the final site depends on their origin and the relative blood flow to downstream tissues.
Which change directly promotes oedema formation?
Oedema results from raised hydrostatic pressure, reduced plasma oncotic pressure, lymphatic obstruction, sodium retention or increased permeability.
The most important underlying cause of arterial thrombosis, through endothelial damage and disturbed flow, is:
Atherosclerotic plaques injure the endothelium and create turbulent flow, the main setting for arterial thrombosis. Immobility and varicosities favour venous thrombosis.
Oedema in which finger pressure leaves a persistent depression is called:
Pitting oedema reflects mobile interstitial fluid displaced by pressure, typical of cardiac or renal fluid overload. Myxoedema is non-pitting.
Which form of oedema is the most immediately life-threatening?
Brain swelling within the rigid skull raises intracranial pressure and can cause herniation and death.
Accumulation of fluid in the peritoneal cavity is called:
Ascites is peritoneal fluid collection; hydrothorax and hydropericardium affect the pleural and pericardial spaces, and anasarca is severe generalised oedema.
The most common form of thromboembolic disease, usually arising from deep vein thrombi of the legs, is:
Over 95% of pulmonary emboli arise from deep leg vein thrombi, making pulmonary thromboembolism the commonest thromboembolic disorder.
Congestion, in contrast to active hyperaemia, is best described as:
Hyperaemia is active arteriolar dilation (e.g. inflammation, exercise); congestion is passive accumulation of blood caused by impaired venous drainage.
Decompression sickness in divers who surface too quickly results from bubbles of which dissolved gas?
At high pressure more nitrogen dissolves in blood and tissues; rapid decompression releases it as bubbles. Oxygen and CO2 are metabolised and rarely form bubbles.
Arterial occlusion in a solid organ with end-arterial circulation, such as the kidney or spleen, typically produces a:
Solid organs with end arteries and dense tissue limit seepage of blood into the necrotic area, giving pale infarcts. Red infarcts occur in loose tissue or with dual supply.
A patient with bacterial endocarditis develops a splenic infarct that later turns into an abscess. This lesion is termed a:
Septic infarcts arise when infected valve vegetations embolise or microbes seed necrotic tissue, converting the infarct into an abscess. Bland infarcts lack infection.