Hematology and Hematologic Emergencies

Comprehensive vocabulary flashcards covering the hematologic system, hematopoiesis, red and white blood cell disorders, hemostasis, coagulation pathways, blood typing, transfusion reactions, and clinical coagulopathies.

Hematology

The branch of medicine and biology dedicated to the study of blood, blood-forming tissues, and the organs involved in blood production.

Thrombocytopenia

An abnormal hematologic condition characterized by a deficient number of circulating platelets (thrombocytes), severely impairing primary hemostasis and clot formation.

Buffy Coat

The thin, intermediate whitish layer observed between plasma and packed erythrocytes in centrifuged blood, containing leukocytes (white blood cells) and thrombocytes (platelets).

Hematopoietic System

The integrated bodily system responsible for the generation and maturation of all blood components, encompassing blood cells, plasma, bone marrow, liver, spleen, kidneys, and thymus.

Hematopoiesis

The physiological process of forming, producing, and differentiating cellular blood elements from hematopoietic stem cells inside the body.

Pluripotent Stem Cells

Master stem cells residing in the bone marrow capable of extensive self-renewal and differentiating into any specialized cell of the three primary germ layers.

Ectoderm

The primary embryonic germ layer that develops into the nervous system (neural tissue) and the external epidermal layers of the skin.

Endoderm

The innermost embryonic germ layer that forms the epithelial lining of the gastrointestinal tract, respiratory system, endocrine glands, liver, and pancreas.

Mesoderm

The middle embryonic germ layer that gives rise to bone, cartilage, muscle, connective tissue, most of the cardiovascular system, and blood.

Myeloid Multipotent Cells

Bone marrow-derived progenitor cells that differentiate into megakaryocytes, erythrocytes, monocytes, neutrophils, eosinophils, and basophils.

Megakaryocyte

A large, polyploid bone marrow cell whose cytoplasmic fragmentation and disassembly yield circulating thrombocytes (platelets).

Thrombocytes

Platelets; small, anucleated cell fragments derived from megakaryocytes whose primary role is to aggregate and construct primary hemostatic plugs.

Lymphoid Cells

Multipotent stem cell derivatives that differentiate into lymphocytes, specifically T cells, B cells, and natural killer (NK) cells.

Natural Killer (NK) Cells

Cytotoxic lymphocytes of the innate immune system that destroy virus-infected and malignant cells, and can also function as antigen-presenting cells (APCs).

Antigen-Presenting Cells (APCs)

Immune cells (such as macrophages and dendritic cells) that internalize foreign pathogens, process them, and display antigenic peptide fragments on their surfaces to activate T cells.

B Cells

Bone marrow-matured lymphocytes that undergo clonal expansion upon antigenic stimulation, differentiating into antibody-producing plasma cells and long-lived memory cells.

Plasma Cells

Effector B lymphocytes dedicated to synthesizing and secreting massive quantities of antigen-specific immunoglobulins (antibodies).

Memory Cells

Differentiated, long-lived B lymphocytes that remain in lymphatic tissues to surveil for a specific antigen and mount a rapid, robust secondary antibody response upon re-exposure.

Cytotoxic T Cells ($\text{CD8}$)

Effector T lymphocytes bearing the $\text{CD8}$ surface coreceptor that recognize and destroy virus-infected, mutant, and foreign cells via pore-forming perforins.

Helper T Cells ($\text{CD4}$)

Immune-regulating T lymphocytes expressing $\text{CD4}$ that release cytokines to activate B cells, cytotoxic T cells, and other immune effectors.

Erythropoietin (EPO)

A glycoprotein hormone synthesized primarily by the kidneys ($90\%$) and liver ($10\%$) in response to hypoxia, stimulating red blood cell production in the bone marrow.

Red Bone Marrow

Hematopoietically active tissue situated predominantly within the cancellous and cortical bone of the metaphysis and epiphysis that actively produces erythrocytes.

Yellow Bone Marrow

Adipose-rich tissue residing primarily within the diaphysis of long bones that serves as a storage reserve and can convert back into red bone marrow during severe hypoxic or hematologic stress.

Blood Doping

The illicit administration or autologous reinfusion of packed erythrocytes (often following high-altitude hypoxic conditioning) to artificially augment arterial oxygen-carrying capacity and athletic endurance.

S1Q3T3 Pattern

An electrocardiographic finding characterized by a prominent S wave in Lead I, a Q wave in Lead III, and an inverted T wave in Lead III, highly specific for acute pulmonary embolism (PE).

Plasma

The extracellular liquid matrix of blood, consisting of approximately $90\%$ water, $7\%$ proteins (chiefly albumin), electrolytes, dissolved sugars, and lipids.

Albumin

The most abundant plasma protein, synthesized by the liver, essential for generating intravascular colloid oncotic pressure to pull water into the circulatory system.

Hydrostatic Pressure

The physical force exerted by circulating blood against vascular walls, generated primarily by left ventricular contraction, driving water and small solutes outward through capillary fenestrations.

Oncotic Pressure

The osmotic pull exerted by non-permeable plasma proteins (principally albumin) that draws water from the interstitial space back into the capillary lumen via osmosis.

Potassium Distribution in Body Fluids

The physiological partitioning of total body potassium, where only $2\%$ resides in extracellular fluid and plasma, while $98\%$ is maintained inside cells to regulate repolarization.

Abdominal Aortic Aneurysm (AAA)

A pathological, focal dilation or bulging of the abdominal aorta that risks sudden, catastrophic rupture and lethal hemorrhage under elevated hydrostatic arterial pressures.

Erythrocytes

Anucleated, biconcave disc-shaped blood cells specialized for gas transport, maintaining a neutral electrical charge and containing hundreds of millions of hemoglobin molecules.

Hemoglobin

A quaternary iron-containing transport protein contained within erythrocytes that reversibly binds oxygen and carbon dioxide.

Heme Sites

The four iron-containing ($\text{Fe}$) prosthetic functional groups situated within a single hemoglobin molecule, each capable of reversibly binding one molecule of oxygen ($O_2$).

Hemoglobin Content per Erythrocyte

The quantity of approximately $250 \times 10^6$ ($2.5 \times 10^8$) individual hemoglobin molecules packed within a single mature red blood cell.

Oxygen-Carrying Capacity per Erythrocyte

The maximum volume of approximately $1 \times 10^9$ ($1\text{ billion}$) oxygen molecules that can be bound and transported by a single fully saturated erythrocyte.

Chloride Shift

The reciprocal exchange of chloride ions ($Cl^-$) and bicarbonate ions ($HCO_3^-$) across the erythrocyte membrane to maintain electrical neutrality as carbon dioxide enters or exits the cell.

Affinity

The thermodynamic attraction and chemical binding strength existing between a protein receptor (such as hemoglobin) and a specific ligand molecule.

Carbon Monoxide Affinity to Hemoglobin

The binding strength of hemoglobin for carbon monoxide ($CO$), which is $200$ to $800\text{ times}$ greater than its affinity for oxygen ($O_2$).

Normal Erythrocyte Lifespan

The standard survival duration of a healthy circulating red blood cell, which averages $120\text{ days}$ prior to reticuloendothelial destruction.

Epistaxis

The formal medical term for hemorrhage originating from the nostrils, nasal cavity, or nasopharynx (nosebleed).

Hematemesis

The vomiting of blood originating from the upper gastrointestinal tract, presenting as bright red liquid (active hemorrhage) or dark coffee-ground material (gastric acid-digested blood).

Hemoptysis

The expectoration or coughing up of blood or blood-tinged sputum originating from the respiratory tract, including the trachea, bronchi, or alveoli.

Melena

The passage of dark, black, foul-smelling, tarry stools resulting from the bacterial and enzymatic digestion of at least $150\,\text{ml}$ of blood originating from an upper gastrointestinal source.

Hematochezia

The passage of fresh, bright red blood directly from the rectum and anus, characteristic of lower gastrointestinal bleeding.

Diverticulitis

Inflammation and micro-perforation of abnormal outpouchings (diverticula) in the colonic wall, identified as the most common etiology of lower gastrointestinal hemorrhage.

Permissive Hypotension Therapy

A trauma resuscitation strategy utilizing conservative, titrated fluid boluses of $250$ to $500\,\text{ml}$ to restore a palpable radial pulse without dislodging newly formed, fragile hemostatic clots.

Tranexamic Acid (TXA)

An antifibrinolytic drug administered as $1\,\text{g}$ IV over $10\text{ minutes}$ that competitively blocks plasminogen activation, preventing plasmin from dissolving established fibrin clots.

Hemolysis

The mechanical, osmotic, or immunological breakdown and rupture of red blood cell membranes, releasing free hemoglobin into the surrounding plasma.

Spleen

A secondary lymphoid organ that filters blood, scavenges and destroys damaged or aged erythrocytes, and sequesters platelets.

Bohr Effect

The physiological decrease in hemoglobin's oxygen affinity triggered by elevated partial pressure of carbon dioxide, decreased pH (acidosis), elevated temperature, and increased 2,3-BPG, shifting the oxygen-hemoglobin curve rightward to offload $O_2$ into tissues.

2,3-Bisphosphoglycerate (2,3-BPG)

A glycolytic metabolic byproduct synthesized inside erythrocytes that binds to deoxygenated hemoglobin, reducing its affinity for oxygen and enhancing tissue oxygen delivery.

Haldane Effect

The physiological phenomenon occurring in pulmonary capillaries where high oxygenation promotes carbon dioxide dissociation from hemoglobin, shifting the curve leftward and increasing oxygen affinity.

Bicarbonate Buffer System

The fastest physiological chemical buffer system in the human body, transporting carbon dioxide through reversible hydration into carbonic acid and dissociation into bicarbonate and hydrogen ions ($CO_2 + H_2O \rightleftharpoons H_2CO_3 \rightleftharpoons H^+ + HCO_3^-$).

Renal Buffer System

The slowest physiological acid-base regulatory buffer system, altering hydrogen ion excretion and bicarbonate reabsorption over a span of hours to days.

Hematocrit

The volumetric percentage of whole blood composed of packed red blood cells following centrifugation in a calibrated tube.

Hematocrit Clinical Ranges

The standard resting volume of packed red blood cells, normally $45\%$ in adult males and $42\%$ in adult females; diagnostic criteria define anemia when falling below $40\%$ in men and $37\%$ in women, typically turning symptomatic below $30\%$.

Menorrhagia

Abnormally heavy or prolonged menstrual bleeding exceeding the typical female physiological blood loss of approximately $50\,\text{ml}$ per menstrual cycle.

Maternal Blood Volume Expansion

The physiological expansion of total circulating blood volume by $40\%$ to $45\%$ during pregnancy to adequately perfuse the growing uterus and placenta.

Aplastic Anemia

A severe form of anemia resulting from the suppression or destruction of hematopoietic stem cells within the bone marrow, caused by senescence, toxic exposures, radiation, or chemotherapy.

Iron Deficiency Anemia

A microcytic, hypochromic anemia caused by insufficient dietary intake or chronic blood loss, depleting the iron reserves required to synthesize functional hemoglobin.

Pernicious Anemia

A macrocytic anemia historically termed deadly, caused by the inability to absorb vitamin $B_{12}$, necessitating lifelong exogenous vitamin $B_{12}$ replacement infusions.

Renal Anemia

Anemia resulting from chronic kidney disease or renal failure, caused by damaged renal parenchyma failing to synthesize and secrete adequate erythropoietin (EPO).

Sickle Cell Disease

An inherited genetic hemoglobinopathy where abnormal hemoglobin crystallizes under deoxygenated conditions, twisting flexible biconcave erythrocytes into rigid, fragile, sickle-shaped crescents.

Vaso-Occlusive Crisis

A painful complication of sickle cell anemia caused by rigid sickled erythrocytes sludging, aggregating, and obstructing microcirculatory capillary beds, producing localized tissue hypoxia and ischemia.

Priapism

A sustained, agonizing, non-sexual erection of the penis caused by sickled erythrocytes occluding venous outflow from the corpora cavernosa.

Penile Decompression

An emergency therapeutic procedure performed during prolonged transport for ischemic priapism, inserting two large-bore ($14\text{-gauge}$) needles into the bilateral corpora cavernosa to aspirate stagnant blood.

Sickle Cell Lifespan

The markedly reduced survival duration of an abnormal sickled erythrocyte, surviving only $7$ to $14\text{ days}$ (compared to the normal $120\text{ days}$).

Hemorrhagic Anemia

An acute or chronic reduction in circulating erythrocyte mass caused directly by intravascular volume loss from internal or external bleeding.

Crystalloid Extravasation Rule

The physiological fluid redistribution principle dictating that approximately two-thirds ($66.7\%$) of an infused isotonic crystalloid IV bolus leaves the intravascular space and shifts into the interstitium within one hour.

Polycythemia

An abnormal hematologic state characterized by an elevated concentration of circulating red blood cells, defined clinically by a hematocrit exceeding $50\%$.

Polycythemia Vera

A primary myeloproliferative blood cancer characterized by autonomous, uncontrolled erythrocyte overproduction by the bone marrow.

Leukocytes

White blood cells; nucleated cellular elements synthesized in the bone marrow that protect the body against pathogens, eliminate malignant cells, and clear cellular debris.

Leukopenia

An abnormally low circulating white blood cell count that impairs immune defenses and leaves the host vulnerable to fatal infections.

Leukocytosis

An elevation in circulating leukocyte levels above reference values, representing a physiological immune response to bacterial infection or a hematologic malignancy.

Phagocytosis

The cellular process by which specialized phagocytes (macrophages and neutrophils) engulf, ingest, and destroy foreign microbes and cellular debris.

Diapedesis

The active physiological process by which leukocytes squeeze through the endothelial junctions of fenestrated capillary walls to enter infected or damaged extravascular tissues.

Chemotaxis

The directional biochemical signaling process that guides the migration of leukocytes along a chemical concentration gradient toward sites of tissue injury or infection.

Monocytes

Large agranular leukocytes produced in the bone marrow that circulate briefly in peripheral blood before extravasating into tissues to become tissue macrophages.

Macrophages

Large, tissue-resident phagocytic cells derived from monocytes that engulf debris, eliminate pathogens, and present antigens to T lymphocytes.

Granulocytes

A primary class of white blood cells containing secretory cytoplasmic granules filled with inflammatory mediators and enzymes, comprising neutrophils, eosinophils, and basophils.

Neutrophils

The most abundant circulating leukocyte in humans; highly mobile phagocytes that serve as the primary frontline cellular defense against acute bacterial infections.

Eosinophils

Specialized granulocytes containing hydrolytic enzymes whose primary physiological function is the destruction of parasitic helminths and pinworms.

Basophils

Circulating granulocytes whose cytoplasmic granules contain histamine and heparin, playing a major role in mediating systemic allergic reactions and inflammation.

Mast Cells

Granule-rich immune cells residing in connective tissues and mucosal linings that bind IgE antibodies and discharge mediators upon activation.

Degranulation

The rapid exocytic rupture and emptying of intracellular granules from mast cells and basophils, releasing high concentrations of histamine and heparin.

Heparin

An endogenous glycosaminoglycan anticoagulant stored within mast cells and basophils that prevents local thrombosis and increases vascular permeability during leukocyte diapedesis.

Histamine

A vasoactive chemical amine released during degranulation that triggers prominent arteriolar vasodilation, increases capillary fenestration, and induces bronchoconstriction.

Thymosin

A regulatory hormone synthesized and secreted by the thymus gland that stimulates T cell maturation and immune competence.

Thymus

The primary lymphoid organ located in the superior mediastinum where naive lymphoid progenitor cells undergo selection and mature into immunocompetent T lymphocytes.

Perforins

Cytolytic pore-forming proteins secreted by cytotoxic T cells and NK cells that insert into target cell membranes, permitting water influx that causes cell lysis.

Immunoglobulin G (IgG)

The most abundant antibody isotype in human circulation, conferring long-term humoral immunity against bacteria and viruses and crossing the placenta.

Immunoglobulin E (IgE)

The specialized antibody isotype that attaches to high-affinity receptors on mast cells and basophils, mediating acute type I hypersensitivity and anaphylactic reactions.

Autoimmune Disease

A pathological state arising when host immune tolerance breaks down, prompting antibodies and T cells to target and destroy the body's own healthy tissues.

Graves' Disease

An autoimmune disorder disproportionately affecting females in which autoantibodies overstimulate the thyroid gland, resulting in hyperthyroidism, goiter, tachycardia, and severe hyperthermia.

Thyroid Storm

A life-threatening endocrine hypermetabolic crisis complicating hyperthyroidism, presenting with severe sinus tachycardia, high blood pressure, and extreme core hyperpyrexia.

Type 1 Diabetes Mellitus

An autoimmune disease characterized by the T cell-mediated destruction of insulin-producing pancreatic beta cells.

Islets of Langerhans

Microscopic endocrine cell clusters comprising approximately $2\%$ of total pancreatic tissue that synthesize and secrete hormones, including insulin from beta cells.

Pancreatic Exocrine Function

The digestive physiological role executed by approximately $98\%$ of the pancreas, producing alkaline enzyme-rich pancreatic juices secreted directly into the duodenum.

HIV Infection Mechanism

The viral infection and targeted destruction of helper T cells ($\text{CD4}$), which impairs the coordination of cell-mediated and humoral immunity.