[Trans] Hematolymphoid Physiology Flashcards

Vocabulary practice flashcards covering blood components, hemostasis, coagulation cascades, leukocytes, immunoglobulins, hematopoiesis, and blood typing based on the Hematolymphoid Physiology lecture notes.

Plasma

The liquid, extracellular component of blood making up approximately $55\%$ of total blood volume, composed of over $90\%$ water and serving as a transport medium for nutrients, hormones, and proteins.

Buffy Coat

A thin layer accounting for less than $1\%$ of total blood volume formed between plasma and erythrocytes upon centrifugation, containing leukocytes and platelets.

Serum

The clear fluid portion of blood that remains after blood has clotted, equivalent to plasma without clotting factors.

Hemostasis

The coordinated process of preventing blood loss following vessel injury, involving vascular constriction, platelet plug formation, blood coagulation, and natural anticoagulant mechanisms.

Primary Hemostasis

The initial stage of hemostasis comprising immediate vascular constriction and the formation of a temporary platelet plug at the site of vascular damage.

Secondary Hemostasis

The second stage of hemostasis in which blood coagulation forms a stable fibrin clot and fibrous tissue grows into the clot to close the vascular breach permanently.

Fibrinolysis

The process of dissolving an unnecessary or repaired blood clot, during which tissue plasminogen activator (t-PA) converts plasminogen into plasmin.

Plasmin

A proteolytic enzyme activated from plasminogen that digests fibrin fibers to dissolve blood clots following vessel repair.

Factor I (Fibrinogen)

An essential plasma protein involved in blood coagulation that is cleaved by thrombin to produce insoluble fibrin fibers.

Factor II (Prothrombin)

An inactive zymogen plasma protein that is converted into the active enzyme thrombin by prothrombin activator.

Factor III (Tissue Factor)

A factor released or exposed upon trauma to the vascular wall or surrounding tissues that serves as the main trigger for the extrinsic coagulation pathway.

Factor XII (Hageman Factor)

A plasma factor that is activated upon contact with exposed collagen or traumatized blood to initiate the intrinsic coagulation pathway.

Factor XIII (Fibrin-Stabilizing Factor)

A factor activated by thrombin in the presence of $Ca^{2+}$ that cross-links fibrin strands to stabilize the blood clot.

Thrombosthenin

A cytoplasmic contractile protein present in platelets alongside actin and myosin that enables platelet contraction and contributes to clot retraction.

Platelet Adhesion

The initial step of platelet plug formation in which platelets swell and adhere to exposed collagen and von Willebrand factor (vWF) via membrane glycoproteins.

Diapedesis

The movement of leukocytes squeezing through capillary walls or pores to leave the bloodstream and enter surrounding tissue spaces.

Chemotaxis

The directional migration of white blood cells along a concentration gradient of chemical signals toward a site of infection or tissue damage.

Dendritic Cells

Professional antigen-presenting cells (APCs) located in peripheral tissues and lymphoid organs that capture antigens and present them to T lymphocytes.

Histiocytes

Fixed, local tissue macrophages residing in the skin and subcutaneous tissues that can divide locally in response to infection or inflammation.

Epitope

The specific region or determinant on an antigen that is recognized and bound by an antibody or T-cell receptor.

Antigen

A molecule or substance capable of binding specifically to an antibody or a T-cell receptor.

Hapten

A small molecule with a molecular mass typically under $1{,}000$ daltons that is not immunogenic by itself and requires attachment to a larger carrier molecule to elicit an immune response.

Immunogen

A substance or molecule capable of independently inducing an immune response.

Alloantigen

An antigen present in some individuals of a species that can provoke an immune response in other individuals of the same species who lack it.

Xenoantigen

An antigen derived from a species different from that of the recipient.

Autoantigen

A normal self-protein or complex of proteins recognized by the immune system of the host.

Fab Region (Fragment Antigen-Binding)

The two variable arms of an antibody structure that contain variable domains of both heavy and light chains responsible for specific antigen recognition and binding.

Fc Region (Fragment Crystallizable)

The constant stem region of an antibody composed of heavy chain constant domains that mediates effector functions such as binding Fc receptors and activating complement.

IgG

The predominant monomeric immunoglobulin class in circulation that provides long-term humoral immunity and is capable of crossing the placental barrier.

IgA

An immunoglobulin class that exists as a monomer in blood and as a dimer in secretions such as breast milk and mucosal surface secretions.

IgM

A large pentameric immunoglobulin class that acts as the primary response antibody produced upon initial antigen exposure.

IgE

A monomeric immunoglobulin bound to mast cells and basophils that triggers histamine release and mediates Type 1 hypersensitivity and allergic responses.

IgD

A monomeric immunoglobulin expressed on the surface of naïve B cells where it functions as an antigen receptor for B-cell activation.

Helper T Cells ($CD4^+$)

A subset of T lymphocytes that regulate immune responses by secreting protein mediators called lymphokines, such as Interleukin-2.

Cytotoxic T Cells ($CD8^+$)

Effector T lymphocytes that directly attack and destroy virally-infected cells, tumor cells, or foreign tissue grafts by releasing perforins and granzymes.

Regulatory T Cells

CD4+ suppressor T lymphocytes that downregulate immune activity to prevent excessive tissue damage and maintain self-tolerance.

Mesoblastic Stage

The initial stage of embryonic hematopoiesis occurring at $2\text{--}3$ weeks AOG primarily within the yolk sac, producing primitive nucleated RBCs and embryonic hemoglobins.

Hepatic Stage

The second stage of fetal hematopoiesis occurring from $13\text{--}28$ weeks AOG where the liver serves as the primary site of blood cell production.

Medullary Stage

The third stage of hematopoiesis beginning around $36$ weeks AOG and continuing after birth, where the bone marrow becomes the dominant site for blood cell development.

Extramedullary Hematopoiesis

The resumption or occurrence of blood cell production outside the bone marrow, such as in the liver and spleen, typically triggered by underlying stress or disease.

Fetal Hemoglobin (HbF)

A hemoglobin tetramer composed of two alpha and two gamma chains ($\alpha_2 \gamma_2$) possessing higher oxygen affinity than adult hemoglobin.

Mean Corpuscular Volume (MCV)

A complete blood count index measuring the average physical size or volume of individual red blood cells, expressed in femtoliters.

Mean Corpuscular Hemoglobin (MCH)

A complete blood count index representing the average mass of hemoglobin contained inside a single red blood cell, expressed in picograms.

Mean Corpuscular Hemoglobin Concentration (MCHC)

A complete blood count index expressing the average concentration of hemoglobin within a given volume of packed red blood cells.

Red Cell Distribution Width (RDW)

A complete blood count measurement indicating the degree of variation in size and volume (anisocytosis) among circulating erythrocytes.

Universal Donor Blood Type

Type O negative ($O^-$) blood, characterized by red blood cells that lack A, B, and Rh surface antigens.

Universal Recipient Blood Type

Type AB positive ($AB^+$) blood, characterized by the absence of anti-A, anti-B, and anti-Rh antibodies in plasma.

Reverse Typing

A laboratory blood testing method that confirms blood group by testing patient serum against reagent red blood cells of known antigen types to identify circulating antibodies.