Chapter 14: Blood

A comprehensive vocabulary review of Chapter 14: Blood, covering blood composition, formed elements, hematopoiesis, red blood cell life cycle and anemias, leukocyte types and functions, plasma proteins and electrolytes, hemostasis, blood clotting cascades, and ABO/Rh transfusion compatibility.

Blood

The only type of connective tissue with a liquid extracellular matrix (plasma) that transports vital substances, distributes heat, and helps maintain interstitial fluid stability and homeostasis; has a normal pH of $7.3\text{--}7.5$, makes up about $8\%$ of body weight, and has a volume of $4\text{ to }5\,\text{liters}$ in females and $5\text{ to }6\,\text{liters}$ in males.

Formed elements

The cellular portion of blood that forms mostly in red bone marrow, comprising red blood cells ($95.1\%$ of formed elements), platelets ($4.8\%$), and white blood cells ($0.1\%$), accounting for about $45\%$ of total blood volume.

Plasma

The clear, straw-colored liquid matrix found at the top of a centrifuged blood sample, making up approximately $55\%$ of blood volume; composed of $92\%$ water, $7\%$ proteins, as well as electrolytes, wastes, nutrients, vitamins, hormones, and gases.

Hematocrit (HCT)

The percentage of red blood cells in a centrifuged blood sample, normally ranging between $35\text{ to }46\%$ in adult females and $40\text{ to }54\%$ in adult males.

Buffy coat

The thin layer found in the middle of a centrifuged blood tube between the plasma and red blood cells, composed of white blood cells and platelets and accounting for less than $1\%$ of total blood volume.

Universal Precautions

A set of specific safety measures (including PPE, fume hoods, sharps containers, and hand-washing) taken by healthcare workers assuming all patients may have been exposed to bloodborne pathogens like HIV, HBV, and HCV to prevent transmission.

Hematopoiesis

The process of blood cell formation that takes place in red bone marrow from hematopoietic stem cells (hemocytoblasts).

Hematopoietic stem cells (hemocytoblasts)

Stem cells located in red bone marrow that give rise to both lymphoid stem cells and myeloid stem cells, eventually producing all the formed elements of blood.

Erythrocyte

A biconcave disc-shaped red blood cell measuring $7.5\,\mu\text{m}$ in diameter and $2.0\,\mu\text{m}$ in thickness; lacks nuclei and mitochondria, produces ATP through glycolysis, and consists of about one-third hemoglobin to transport oxygen and carbon dioxide.

Oxyhemoglobin

A hemoglobin molecule combined with oxygen, giving blood a bright red color.

Deoxyhemoglobin

A hemoglobin molecule that has released its oxygen, giving blood a darker, bluish-red hue.

Erythropoiesis

The production of red blood cells in red bone marrow, regulated by a negative feedback mechanism and stimulated by the hormone erythropoietin.

Erythropoietin (EPO)

A hormone secreted by the kidneys and liver in response to low blood oxygen levels that stimulates red bone marrow to accelerate red blood cell production.

Intrinsic factor

A substance secreted by the stomach that is required for the absorption of vitamin $B_{12}$ in the small intestine, essential for red blood cell DNA synthesis.

Pernicious anemia

A type of anemia resulting from a deficiency of intrinsic factor from the stomach, which leads to inadequate absorption of vitamin $B_{12}$ and impaired DNA synthesis.

Aplastic anemia

A form of anemia caused by the destruction of red bone marrow by radiation, certain medications, cancer, viruses, or certain poisons, resulting in a decreased RBC count.

Hemolytic anemia

A condition characterized by a reduced RBC count caused by the premature destruction of red blood cells due to bacterial infections or blood transfusion incompatibilities.

Sickle cell anemia

A genetic condition caused by an abnormal gene that produces an abnormal hemoglobin structure, causing red blood cells to bend into rigid, sickle-like crescent shapes that can obstruct capillaries.

Thalassemia

An inherited anemia caused by a defective gene resulting in deficient hemoglobin synthesis and abnormally short-lived red blood cells.

Transferrin

A transport protein in blood plasma that carries iron released from decomposing hemoglobin to the red bone marrow for reuse.

Ferritin

An iron-protein complex in which excess iron from broken-down red blood cells is stored within the liver.

Biliverdin

A greenish pigment produced when the heme group of hemoglobin is broken down during red blood cell destruction by macrophages in the spleen and liver.

Bilirubin

An orange-yellow pigment converted from biliverdin that is excreted into bile by the liver or eliminated by the kidneys in urine as derivatives.

Diapedesis

The migration process in which white blood cells squeeze between the endothelial cells lining capillary walls to enter surrounding connective tissues and migrate to sites of injury or infection.

Positive chemotaxis

The directional attraction and movement of white blood cells toward an infection or injury site in response to chemicals released by damaged cells.

Neutrophil

A granulocyte characterized by fine cytoplasmic granules that stain light purple in acid-base stain and a nucleus with $2\text{ to }5$ lobes; makes up $50\text{ to }70\%$ of leukocytes, responds first to infections, and actively phagocytizes small particles.

Eosinophil

A granulocyte featuring coarse cytoplasmic granules that stain deep red in acid stain and a bilobed nucleus; makes up $1\text{ to }3\%$ ($1\text{ to }4\%$) of leukocytes, kills parasitic worms, and moderates allergic reactions.

Basophil

A granulocyte containing large, coarse granules that stain deep blue in basic stain and often obscure its lobed nucleus; accounts for less than $1\%$ of leukocytes and releases histamine to promote inflammation and heparin to inhibit blood clotting.

Monocyte

The largest type of white blood cell, an agranulocyte with a kidney-shaped, oval, or lobed nucleus that makes up $3\text{ to }9\%$ of leukocytes; leaves the bloodstream to become a tissue macrophage that phagocytizes large particles, dead cells, and debris.

Lymphocyte

The smallest white blood cell, an agranulocyte containing a large spherical nucleus surrounded by a thin rim of cytoplasm; makes up $25\text{ to }33\%$ of circulating leukocytes and includes T cells (directly attack pathogens) and B cells (produce antibodies).

Leukocytosis

An abnormally high white blood cell count exceeding $10{,}500/\mu\text{L}$, commonly indicating acute bacterial infections, vigorous exercise, or severe loss of body fluids.

Leukopenia

An abnormally low white blood cell count falling below $3{,}500/\mu\text{L}$, associated with conditions such as typhoid fever, influenza, measles, mumps, chicken pox, AIDS, polio, and anemia.

Differential WBC count

A diagnostic procedure that lists the percentages of each type of white blood cell in a sample to help identify specific infections or disorders.

Platelet (thrombocyte)

A small, enucleated cytoplasmic fragment measuring less than half the size of a red blood cell, produced by megakaryocytes in response to thrombopoietin; normal count is $150{,}000\text{ to }400{,}000/\mu\text{L}$, and it functions in hemostasis by sticking to broken vessel surfaces and releasing serotonin.

Albumins

The most abundant plasma proteins ($60\%$ of total), synthesized by the liver, that play a key role in maintaining the colloid osmotic pressure of blood.

Alpha and beta globulins

Plasma proteins synthesized by the liver that make up a subcategory of globulins and function in transporting lipids and fat-soluble vitamins.

Gamma globulins

A class of plasma globulins produced by lymphatic tissues (plasma cells) that constitute circulating antibodies providing immunity.

Fibrinogen

A large soluble plasma protein ($4\%$ of total plasma proteins) synthesized in the liver that is converted to insoluble fibrin threads during blood coagulation.

Nonprotein Nitrogenous Substances (NPNs)

Molecules that contain nitrogen but are not proteins, including urea ($\sim 50\%$ of NPNs), uric acid, amino acids, creatine, and creatinine.

Blood urea nitrogen (BUN)

A laboratory test measuring urea concentration in the blood, where an elevated level indicates impaired renal function and failure of the kidneys to excrete urea properly.

Hemostasis

The physiological process that halts bleeding from a broken vessel, consisting of vascular spasm, platelet plug formation, and blood coagulation.

Vascular spasm

The rapid, reflexive contraction of vascular smooth muscle stimulated by direct wall injury or pain receptors, prolonged by serotonin released from platelets to restrict blood loss.

Platelet plug

A physical barrier formed when platelets adhere to exposed collagen and rough surfaces of an injured blood vessel, and subsequently adhere to each other to help prevent blood escape.

Extrinsic clotting mechanism

A rapid blood coagulation pathway triggered when blood contacts damaged blood vessel walls or tissues outside vessels, initiated by the release of tissue thromboplastin (factor III).

Intrinsic clotting mechanism

A blood coagulation pathway that can initiate without tissue damage when blood contacts a foreign surface or collagen within a broken vessel, initiated by Hageman factor XII.

Prothrombin activator

An enzymatic complex generated by clotting factor cascades that, in the presence of calcium ions ($\text{Ca}^{+2}$), converts prothrombin (factor II) into active thrombin.

Thrombin

An active enzyme converted from prothrombin that cleaves soluble fibrinogen molecules into fragments, which then join to form insoluble strands of fibrin.

Fibrin

An insoluble, thread-like mesh of protein polymers converted from fibrinogen by thrombin that traps blood cells and platelets to form a stable blood clot.

Serum

The pale yellowish fluid that is squeezed out of a retracting blood clot, consisting of plasma minus fibrinogen and most clotting factors.

Plasmin

A fibrin-digesting enzyme that dissolves the insoluble fibrin threads of a blood clot after tissue repair is underway.

Thrombus

An abnormal, stationary blood clot formed inside an unbroken or damaged blood vessel.

Embolus

A thrombus or fragment of an abnormal blood clot that breaks loose and travels through the bloodstream.

Atherosclerosis

The accumulation of fatty deposits (plaque) along arterial linings, which narrows the lumen and creates a rough surface that can stimulate abnormal thrombus formation.

Prostacyclin (PGI2)

A prostaglandin synthesized and released by healthy vascular endothelial cells that prevents platelets from adhering to intact blood vessel walls.

Antithrombin

A circulating anticoagulant protein that binds directly to thrombin, inactivating it and preventing the clotting cascade from spreading beyond the injury site.

Agglutination

The clumping of red blood cells that occurs when specific plasma antibodies encounter and cross-link corresponding surface antigens on incompatible donor red blood cells.

Universal donor

An individual with blood type O (specifically O-), whose red blood cells lack both antigen A and antigen B, preventing agglutination when transfused into recipients with anti-A or anti-B antibodies.

Universal recipient

An individual with blood type AB (specifically AB+), whose plasma lacks both anti-A and anti-B antibodies, allowing them to receive red blood cells of any ABO blood type.

Erythroblastosis fetalis

A life-threatening hemolytic disease of the newborn occurring when an Rh-negative mother, previously sensitized to Rh antigen D during an earlier pregnancy or transfusion, produces anti-Rh antibodies that cross the placenta to attack the red blood cells of an Rh-positive fetus.