Hematology 2 Hemostasis and Platelets Lecture Review

Vocabulary practice flashcards based on the Hematology 2 Lecture Guide for MT Licensure Exams.

Hemostasis

The maintenance of blood flow within the vascular system.

CTAD

An acronym for an anticoagulant containing citrate, theophylline, adenosine, and dipyridamole, used for coagulation tests and assays such as PF4 ($platelet factor-4$) and $\beta$-TG ($beta-thromboglobulin$).

Sodium Citrate Volume Adjustment Formula

The formula used for patients with high hematocrit (>55 \text{%}) is $C = (1.85 \times 10^{-3}) (100 - H) V$, where $C$ is the volume of sodium citrate in milliliters, $V$ is the total volume of blood-anticoagulant solution, and $H$ is the hematocrit in percent.

Petechiae

Small, pinpoint hemorrhages into the skin.

Purpura

Hemorrhages into the skin that are larger than petechiae.

Ecchymosis

Also known as a bruise; a type of hemorrhage into the skin.

Epistaxis

A medical term for a nosebleed.

Hemarthrosis

Hemorrhage into a joint.

Hemoptysis

The expectoration of blood from some part of the respiratory tract.

Hematemesis

The vomiting of blood.

Menorrhagia

Unusually heavy or prolonged menstrual periods.

Hematochezia

The passage of fresh blood per anus, usually in or with stools.

Melena

The passage of black, tarry stools.

Thrombosis

The pathological formation of blood clots in veins or arteries that obstruct blood flow.

Hypofibrinogenemia

Reduced levels of fibrinogen in the blood.

Dysfibrinogenemia

A condition where fibrinogen does not function normally or optimally.

Tunica Intima

Also known as tunica interna; the innermost coat of a blood vessel composed of simple squamous epithelium lining the lumen.

Tunica Media

The thickest coat of a blood vessel, composed of smooth muscle and elastic fibers.

Tunica Adventitia

Also known as tunica externa; composed of fibrous connective tissue containing autonomic nerve endings and the vasa vasorum.

Vasa Vasorum

Small networks of blood vessels that supply nutrients to the tissues of the vessel wall.

Sinusoids

Specialized types of capillaries found in locations such as the bone marrow, spleen, and liver.

Prostacyclin ($PGI_2$)

A substance produced by the eicosanoid pathway in endothelial cells that inhibits platelet activation and is also known as Prostaglandin $I_2$.

Thrombomodulin ($TM$)

A thrombin cofactor on endothelial cells that binds thrombin, reducing its clotting ability and activating Protein C and TAFI.

von Willebrand Factor ($VWF$)

A protein synthesized in endothelial cells and megakaryocytes that mediates platelet adhesion and stabilizes Factor VIII.

ADAMTS 13

Also known as VWF-cleaving protease; a plasma enzyme that regulates the size of circulating VWF by cleaving ultra-long VWF multimers into shorter segments.

Thrombocytes

Another name for platelets, which arise from bone marrow megakaryocytes and have a life span of $9.0$ days $\pm 1$ day.

Reticulated Platelets

Also known as stress platelets; newly released platelets that still contain RNA and are larger than usual platelets ($diameter > 6 \text{ }\nu\text{m}$).

Mean Platelet Volume ($MPV$)

The average volume of individual platelets in a specimen, with a reference range of $8 \text{ to } 12 \text{ fL}$.

Chromomere

The granular and central part of the platelet cytoplasm when viewed on a Wright-stained peripheral blood smear.

Hyalomere

The clear and peripheral part of the platelet cytoplasm when viewed on a Wright-stained peripheral blood smear.

Thrombopoietin ($TPO$)

Also known as c-Mpl ligand; the humoral factor produced primarily by the liver that stimulates megakaryocytopoiesis and platelet production.

Endomitosis

A process of nuclear division without cytoplasmic division, resulting in a polyploid nucleus.

MK-I stage

The megakaryoblast stage; the least differentiated megakaryocytic precursor which begins to develop $\alpha$-granules and the demarcation system.

Shedding (Thrombocytopoiesis)

The process by which one megakaryocyte may release $2,000 \text{ to } 4,000$ platelets.

Glycocalyx

The outer membrane surface of a platelet that contains glycoproteins and absorbs plasma proteins like albumin and fibrinogen.

Integrin $\alpha_{IIb}\beta_3$

Also known as GP IIb/IIIa; the key fibrinogen receptor necessary for platelet aggregation.

Integrin $\alpha_2\beta_1$

Also known as GP Ia/IIa; a membrane receptor that binds to collagen.

Tenase Complex

A coagulation complex consisting of Factor $9a$, platelet factor-3 ($PF-3$), Calcium, and Factor $8a$.

Prothrombinase Complex

A coagulation complex consisting of Factor $10a$, platelet factor-3 ($PF-3$), Calcium, and Factor $5a$.

Surface-Connected Canalicular System ($SCCS$)

An invagination of the platelet plasma membrane that serves as a route for endocytosis and the secretion of $\alpha$-granule and lysosome contents.

Dense Tubular System ($DTS$)

A condensed remnant of the rough endoplasmic reticulum in platelets that sequesters calcium and bears enzymes for the eicosanoid synthesis pathway.

Aspirin

Also known as acetylsalicylic acid; it blocks the synthesis of Thromboxane $A_2$ ($TXA_2$) by permanently acylating cyclooxygenase.

Brecher and Cronkite Method

The reference method for platelet counting using a phase-contrast microscope and 1 \text{%} ammonium oxalate as a diluent.

Platelet Lumiaggregometry

A test that measures both platelet aggregation and ATP release from dense granules using a firefly-derived luciferin-luciferase reagent.

Hereditary Hemorrhagic Telangiectasia

Also known as Rendu-Osler-Weber Syndrome; the most common inherited vascular bleeding disorder.

Ehlers-Danlos Syndrome

Also known as Cutis Hyperelastica; a disorder characterized by hyperextensible skin, hypermobile joints, and fragile tissues.

Henoch-Schonlein Purpura

Also known as Allergic Purpura; a condition most common in children involving immunologic damage to endothelial cells, gastrointestinal hemorrhage, and joint swelling.

Scurvy

A condition caused by Vitamin C deficiency, leading to defects in the synthesis of collagen and hyaluronic acid.

Bernard-Soulier Syndrome ($BSS$)

A platelet adhesion disorder caused by a deficiency of the GP Ib/IX/V complex.

Glanzmann’s Thrombasthenia

A platelet aggregation disorder caused by a deficiency of the GP IIb/IIIa complex.

Gray Platelet Syndrome

An alpha-granule deficiency characterized by large, gray platelets and lifelong mild bleeding tendencies.

Contact Group

A group of clotting factors comprising Factors $XII$, $XI$, Prekallikrein ($PK$), and High-molecular-weight Kininogen ($HMWK$) which are Vitamin K-independent.

INR (International Normalized Ratio)

A standardized way of reporting PT results using the formula $INR = (\frac{Patient\text{ }PT}{Mean\text{ }Normal\text{ }PT})^{ISI}$ to correct for variations in thromboplastin sensitivity.

Warfarin

An oral anticoagulant and Vitamin K antagonist (brand name Coumadin) that interferes with the synthesis of Factors $II$, $VII$, $IX$, and $X$.

Protamine Sulfate

A protein used for neutralizing unfractionated heparin (UFH).

Activated Coagulation Time ($ACT$)

A point-of-care clot-based screening test useful for monitoring high dosages of unfractionated heparin.

Stypven Time

Also known as Russel’s Viper Venom Time; it is used to detect deficiencies in fibrinogen, prothrombin, and Factors $V$ and $X$, but does not detect Factor $VII$ deficiency.

Reptilase Time

A test using venom from the Bothrops atrox snake that is capable of converting fibrinogen to fibrin and is unaffected by heparin.

Thrombosthenin

A contractile protein important for clot retraction.

Euglobulin Lysis Time

A test for fibrinolysis where proteins that precipitate under acid conditions (euglobulins) are clotted with thrombin and observed for the time needed for complete lysis.

D-dimer Test

A test where the presence of D-dimer indicates that a stable, cross-linked fibrin clot has been lysed by plasmin.

Alpha-2-antiplasmin

The primary inhibitor of free plasmin in the circulation, synthesized in the liver.

TAFI

Thrombin-Activatable Fibrinolysis Inhibitor; an enzyme activated by the thrombin-thrombomodulin complex that functions as an antifibrinolytic.