Bleeding Time, Platelet Function, and Clot Retraction Vocabulary

35 vocabulary flashcards summarizing key terms related to bleeding time tests, platelet and vascular disorders, medication effects, and clot retraction concepts.

Bleeding Time

Laboratory test measuring how long it takes a standardized skin puncture to stop bleeding; reflects platelet plug formation and vascular integrity.

Platelet Count

Number of platelets per microliter of blood; low values can prolong bleeding time and impair clot formation.

Thrombocytopenia

Condition of decreased platelet count resulting in prolonged bleeding time and increased bleeding risk.

Platelet Function

Ability of platelets to adhere, aggregate, and secrete contents; defects prolong bleeding time even with normal counts.

Glanzmann Thrombasthenia

Congenital disorder caused by absent or defective GPIIb/IIIa receptor, leading to impaired platelet aggregation and prolonged bleeding.

NSAIDs

Non-steroidal anti-inflammatory drugs that reversibly inhibit platelet COX-1, reducing aggregation and extending bleeding time.

Vascular Disorders

Diseases affecting blood-vessel walls (e.g., Ehlers-Danlos) that hamper vasoconstriction and lengthen bleeding time.

Ehlers-Danlos Syndrome

Connective-tissue disorder with fragile vessels and impaired constriction, producing prolonged bleeding times.

Collagen Disorders

Abnormalities in collagen that disrupt platelet adhesion and aggregation, extending bleeding time.

Von Willebrand Disease

Inherited deficiency or defect of vWF causing faulty platelet adhesion and prolonged bleeding time.

Bernard-Soulier Syndrome

Congenital defect of the GPIb-IX-V complex; characterized by giant platelets, thrombocytopenia, and prolonged bleeding.

Antiplatelet Drugs

Medications such as aspirin and clopidogrel that impair platelet function and prolong bleeding time.

Anticoagulants

Agents like warfarin and heparin that target clotting factors; monitored by PT/APTT but may indirectly affect bleeding time.

Hypertension

Elevated blood pressure that can alter vessel function and influence bleeding time results.

Temperature (Effect on Hemostasis)

Low ambient temperatures slow platelet aggregation and vasoconstriction, artificially prolonging bleeding time.

Primary Hemostasis

Initial phase of stopping bleeding involving platelet plug formation; assessed in part by bleeding time.

Qualitative Platelet Disorders

Group of dysfunctions where platelet number is normal but adhesion, aggregation, or secretion is defective.

GPIIb/IIIa Receptor

Platelet surface integrin essential for aggregation; mutated or absent in Glanzmann thrombasthenia.

Platelet Aggregation

Process by which platelets bind together via fibrinogen bridges; critical for forming the platelet plug.

GPIb-IX-V Complex

Platelet receptor for vWF; its defect in Bernard-Soulier syndrome impairs adhesion.

Giant Platelets

Abnormally large platelets seen in Bernard-Soulier syndrome, often accompanied by thrombocytopenia.

Storage Pool Disorders

Group of congenital defects with absent or deficient platelet granules, leading to secretion failure and bleeding.

Platelet Granules

Alpha and dense storage vesicles containing ADP, serotonin, and proteins needed for aggregation and hemostasis.

Aspirin-Induced Platelet Dysfunction

Acquired impairment caused by irreversible COX-1 inhibition, leading to prolonged bleeding despite normal counts.

Uremic Platelet Dysfunction

Platelet adhesion/aggregation defect due to toxins in chronic kidney disease, causing bleeding tendency.

Cyclooxygenase-1 (COX-1)

Platelet enzyme that converts arachidonic acid to prostaglandin H2 and ultimately TXA2; irreversibly acetylated by aspirin.

Thromboxane A2 (TXA2)

Potent platelet aggregator and vasoconstrictor produced from COX-1 pathway; decreased by aspirin and NSAIDs.

Irreversible Platelet Inhibition

Permanent loss of platelet COX-1 activity (e.g., from aspirin) lasting for the platelet’s 7–10-day lifespan.

Bleeding Time Test Precautions

Standardized puncture depth, controlled temperature, medication review, and proper timing required to avoid erroneous results.

Clot Retraction (CRT)

Process where a formed clot shrinks through platelet actin-myosin contraction, stabilizing the wound.

Platelet Contractile Proteins

Actin and myosin within platelets that interact to pull fibrin strands together during clot retraction.

Fibrin Cross-Linking

Factor XIII–mediated stabilization of fibrin strands; essential for strong clots and effective retraction.

Factor XIII Deficiency

Coagulation defect causing weak fibrin cross-linking, poor clot retraction, and bleeding tendency.

Hypofibrinogenemia

Low fibrinogen level that yields impaired clot formation and reduced retraction.

Dysfibrinogenemia

Qualitative fibrinogen defect producing structurally abnormal fibrin and poor clot retraction.