1-4: Hematologic System and Blood Composition

Flashcards covering blood composition, hematopoiesis, red and white blood cell functions, hemostasis, and clinical assessments.

Hemostasis

The balance between clot formation and fibrinolysis (clot breakdown).

Plasma

The liquid component of blood that accounts for $55\%$ of whole blood volume and transports proteins, nutrients, clotting factors, and wastes.

Formed elements

The cellular components of blood making up $45\%$ of its volume, consisting of erythrocytes (RBCs), leukocytes (WBCs), and platelets.

Normal Platelet Count

$$150,000-450,000/\mu L$$

Normal Leukocyte Count

$4,000-11,000$ or $4-11 \times 10^3/\mu L$

Normal Erythrocyte Count

$$4-6 \times 10^6/\mu L$$

Neutrophils

Granulocytes that act as first responders for infection using phagocytosis; they make up $50-70\%$ of the leukocyte differential.

Lymphocytes

Cells responsible for the immune response, producing antibodies to kill foreign bodies and fighting viruses and cancer ($20-40\%$ of WBCs).

Hematopoiesis

The process of blood cell production occurring in the bone marrow of flat bones such as the pelvis and sternum.

Myeloid stem cells

Stem cells that differentiate into most blood cells.

Lymphoid stem cells

Stem cells that differentiate specifically into lymphocytes.

Reticulocytes

Immature form of erythrocytes; high levels indicate increased red blood cell production due to blood loss or destruction.

Erythropoiesis

The production of red blood cells, stimulated by hypoxia and controlled by erythropoietin.

Erythropoietin (EPO)

A hormone produced by the kidneys that regulates red blood cell production in the bone marrow when blood oxygen levels are low.

RBC Production Requirements

Nutrients including Iron, Vitamin $B_{12}$, Vitamin $B_6$, and Folic acid.

Granulocytes

A category of leukocytes that includes neutrophils, eosinophils, and basophils.

Thrombocytes

Another name for platelets, which function in clotting by adhering to vessel walls and forming a platelet plug.

Albumin

A protein produced in the liver that maintains oncotic pressure to keep fluid in vessels; low levels can cause edema.

Fibrinogen

A clotting factor produced by the liver that remains inactive until an injury occurs.

Primary Hemostasis

The immediate response to injury involving vasoconstriction ($20-30\text{ min}$) and platelet adherence, activation, and aggregation.

Secondary Hemostasis

The activation of clotting factors where prothrombin is converted to thrombin and fibrinogen is converted to fibrin to form a mesh.

Fibrinolysis

The process of breaking down clots after healing where plasminogen is converted to plasmin to break down the fibrin clot.

Spleen

An organ that filters old RBCs, recycles iron, stores blood and platelets, and has immune functions; it can be removed without major harm.

Liver

The organ responsible for producing most clotting factors; dysfunction here increases bleeding risk.

Pediatric Hematologic Considerations

At birth, there is an increase in RBCs and WBCs but decreased platelets; Vitamin K is administered for clotting factor production.

Geriatric Hematologic Considerations

Aging leads to decreased bone marrow and stem cells, reduced hemoglobin, and a diminished ability to handle blood loss or infection.

St. John's Wort

An herb known to decrease the effectiveness of the medication Coumadin.

Abnormal Lymph Nodes

Nodes that are hard, fixed, enlarged, or tender; non-tender nodes may indicate malignancy, while tender nodes usually indicate inflammation.