Hematological System: Structure, Function, and Alterations

Three primary functions of blood

Distribution, regulation, and protection.

Average blood volume in adults

4 to 5 liters in women; 5 to 6 liters in men.

Lifespan of a red blood cell (RBC)

Approximately 120 days.

Lifespan of platelets

Approximately 9 to 10 days.

Difference between plasma and serum

Plasma contains clotting factors; serum does not.

Hematocrit (HCT)

The percentage of total blood volume occupied by erythrocytes.

Normal hematocrit values

Male: 40.7% to 50.3%; Female: 36.1% to 44.3%.

Normal pH range of blood

7.35 to 7.45.

Most abundant plasma protein

Albumin, which contributes most to colloid osmotic pressure.

Transferrin

The plasma protein that transports iron through the circulation.

Ferritin

The primary intracellular storage protein for iron.

Anaerobic ATP generation in RBCs

Prevents erythrocytes from consuming the oxygen they transport.

Hemoglobin (Hb) structure

Four globin chains (two alpha, two beta), each bound to a heme group.

Heme composition

An iron atom (ferrous Fe²⁺) and a porphyrin ring.

Carbonic anhydrase

Enzyme in RBCs that converts carbon dioxide into bicarbonate ions.

Primary site of hematopoiesis in adults

Red bone marrow of the axial skeleton and girdles.

Erythropoietin (EPO)

Hormone released by the kidneys during hypoxia to stimulate RBC production.

Bilirubin conjugation

Occurs in the liver with glucuronic acid to make it water-soluble.

Diapedesis

The movement of white blood cells out of capillaries into tissue spaces.

Megakaryocytes

Giant bone marrow cells whose fragments form platelets.

Platelet inhibition factors

Nitric oxide (NO) and prostacyclin (PGI₂).

Three phases of hemostasis

Vascular spasms, platelet plug formation, and coagulation.

Vitamin K-dependent clotting factors

Factors II, VII, IX, and X.

Fibrinolysis

The breakdown of a clot by plasmin digesting fibrin strands.

Erythroblastosis fetalis cause

Rh incompatibility where maternal antibodies attack Rh-positive fetal red blood cells.

Fetal hemoglobin (HbF) oxygen affinity

Significantly higher than adult hemoglobin (HbA).

Lymphatic system function

Returns interstitial fluid and leaked plasma proteins to the blood.

Mean Corpuscular Volume (MCV)

Measures the average size of red blood cells.

Prothrombin Time (PT)

Measures the extrinsic pathway of coagulation.

Activated Partial Thromboplastin Time (aPTT)

Measures the intrinsic and common pathways of coagulation.

Normocytic-normochromic anemia causes

Acute blood loss, aplastic anemia, or chronic kidney disease.

Megaloblastic (macrocytic) anemia cause

Vitamin B12 or folic acid deficiency impairing DNA synthesis.

Pernicious anemia

Anemia caused by autoimmune destruction of parietal cells, depleting intrinsic factor.

Sickle cell anemia mutation

A single amino acid substitution in the beta-globin chain.

Sickle cell RBC lifespan

Reduced to 20 days or less.

Thalassemia major (Cooley's anemia)

Homozygous genetic defect causing severely reduced alpha or beta chain synthesis.

G6PD deficiency triggers

Infections, diabetic ketoacidosis, and oxidative drugs like aspirin or Bactrim.

Iron deficiency anemia presentation

Microcytic, hypochromic red blood cells with low serum ferritin.

Pancytopenia

Simultaneous decrease in red blood cells, white blood cells, and platelets.

Polycythemia vera

Neoplastic increase in RBCs, WBCs, and platelets, increasing blood viscosity.

Acute vs. chronic leukemia cells

Acute involves poorly differentiated blast cells; chronic involves well-differentiated cells.

Multiple myeloma hallmarks

Osteolytic bone lesions, elevated calcium, and Bence Jones proteins.

Reed-Sternberg cell

The giant, multinucleated B-cell hallmark of Hodgkin Lymphoma.

Virchow's Triad

Endothelial injury, abnormal blood flow, and hypercoagulability.

Thrombocytopenia threshold

A platelet count below 100,000/µl.

Thrombotic Thrombocytopenic Purpura (TTP) cause

ADAMTS13 enzyme deficiency leading to accumulated von Willebrand factor.

Hemophilia A deficiency

Inherited deficiency of clotting Factor VIII.

Hemophilia B deficiency

Inherited deficiency of clotting Factor IX.

Disseminated Intravascular Coagulation (DIC)

Widespread systemic clotting that consumes coagulation factors, causing severe bleeding.

Philadelphia chromosome association

Hallmark of CML, resulting from reciprocal translocation of chromosomes 9 and 22.

Three major aggregation sites of lymph nodes

Inguinal (groin), axillary (armpit), and cervical (neck) regions.

Band cells

Immature neutrophils measured to assess the rate of neutrophil production.

Immune thrombocytopenic purpura (ITP)

Autoimmune condition where the body produces antibodies against its own platelets.

Order of white blood cell abundance

Neutrophils, lymphocytes, monocytes, eosinophils, then basophils.

CD20 surface marker

Target on non-Hodgkin lymphoma cells for monoclonal antibody therapy.

Carbon monoxide lethal mechanism

Competes with oxygen for the ferrous ion in hemoglobin with higher affinity.

Sickle cell disease molecular mutation

Glutamic acid is replaced by valine at position 6 of the beta-globin chain.

Clinical significance of elevated neutrophils

Indicates an active bacterial infection.

Clinical significance of elevated eosinophils

Indicates a parasitic worm infection or allergic response.

Primary substances released by basophil granules

Histamine (a vasodilator) and heparin (an anticoagulant).

Precursor cells of tissue macrophages

Monocytes that have left the bloodstream.

Chloride shift mechanism in RBCs

Chloride ions enter the cell as bicarbonate ions exit.

Location where megakaryocytes release platelets

Bone marrow sinusoids, as blood flow shears off cell fragments.

Structural difference of fetal hemoglobin (HbF) compared to HbA

Contains two gamma chains instead of two beta chains.

Relationship between hematocrit and body fat

Inversely proportional; more adipose tissue leads to lower hematocrit.

Bilirubin transport in blood

Binds to albumin for transport to the liver.

Stimulators of leukopoiesis

Interleukins and colony-stimulating factors (CSFs).

Monocyte nuclear morphology

Kidney-shaped nucleus resembling a McDonald's arch.

Aspirin effect on platelets

Inhibits COX-1, reducing thromboxane A2 synthesis and platelet activation.

Trigger for extrinsic clotting pathway

Tissue factor (Factor 3) released by damaged perivascular tissue.

Natural anticoagulants in blood

Heparin, antithrombin 3, protein C, and protein S.

RhoGAM mechanism of action

Coats fetal RhD antigens, preventing maternal immune recognition and sensitization.

Percentage of population that is Rh-positive

Approximately 85%.