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Normal Values of Erythrocytes, Leukocytes, and Platelets in Adult Human Blood*
Erythrocytes4.2–6.1 million/μL of blood
Platelets200,000–500,000/μL of blood
Leukocytes4000–11,000/μL of blood
Types of leukocytesPercentage of total leukocytesPrimary role
Polymorphonuclear granulocytes
Eosinophils1–4Allergic hypersensitivity reactions
Basophils0–0.75Allergic hypersensitivity reactions
Monocytes2–8Phagocytosis and antibody production
Lymphocytes15–40Antibody production and cell-mediated immunity

*Normal reference ranges vary somewhat with age, gender, and race. They may also vary from laboratory to laboratory. To confuse the issue further, various unit measurements are used to report blood data, and so caution must be used in examining data.

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Normal Constituents of Adult Human Plasma
ClassConstituentAmount/normal concentration range
Electrolytes (inorganic)
  • Sodium (Na+)
  • Potassium (K+)
  • Calcium (Ca2+)
  • Magnesium (Mg2+)
  • Iron (Fe3+)
  • Copper (Cu2+)
  • Hydrogen (H+)
  • 136–145 mEq/L
  • 3.5–5.0 mEq/L
  • 2.1–3.7 mEq/L
  • 1.2–1.8 mEq/L
  • 60–160 μg/dL
  • 70–155 μg/dL
  • 35–45 nmol/L (pH = 7.35–7.45)
  • Chloride (Cl)
  • Bicarbonate (HCO3)
  • Lactate
  • Sulfate (SO42−)
  • Phosphate (HPO42− mostly)
  • 95–105 mEq/L
  • 23–28 mEq/L
  • 0.67–1.8 mEq/L
  • 0.9–1.1 mEq/L
  • 3.0–4.5 mg/dL
  • Total (7% of plasma weight)
  • Albumin
  • Globulins
  • Fibrinogen
  • 6–8 g/dL
  • 3.4–5.0 g/dL
  • 2.2–4.0 g/dL
  • 0.3 g/dL
  • Glucose
  • Total amino acids
  • Cholesterol
  • Phospholipids
  • Triglycerides
  • 80–120 mg/dL
  • 40 mg/dL
  • 150–200 mg/dL
  • 150–220 mg/dL
  • 35–160 mg/dL
Waste products
  • Uric acid (from nucleic acids)
  • Blood urea nitrogen (from protein)
  • Creatinine (from creatine)
  • Bilirubin (from heme)
  • 2.6–7.2 mg/dL
  • 8–25 mg/dL
  • 0.2–0.9 mg/dL
  • 0.1–1.2 mg/dL

Key Cardiovascular Variables and Their Normal Determinants



Whenever damage occurs to a blood vessel, a variety of processes are evoked that are aimed at preventing or stopping blood from exiting the vascular space. The 3 primary processes are summarized in the following list:

  1. Platelet aggregation and plug formation: Occur as a result of the following steps:

      1. Vessel injury with endothelial damage and collagen exposure.

      1. Platelet adherence to collagen (mediated by the plasma protein, von Willebrand factor).

      1. Platelet shape change (from disks to spiny spheres) and degranulation with release of the following:

          1. Adenosine diphosphate, which causes platelet aggregation and “plugs” the hole.

          1. Thromboxane, which causes vasoconstriction and potentiates platelet adhesion and aggregation.

  2. Local vasoconstriction: Mediated largely by thromboxane but may also be induced by local release of other chemical signals that constrict local vessels and reduce blood flow.

  3. Blood clotting: The formation of a solid gel made up of the protein, fibrin, platelets, and trapped blood cells.

The critical step in blood clotting is the formation of thrombin from prothrombin, which then catalyzes the conversion of fibrinogen to fibrin. The final clot is stabilized by covalent cross-linkages between fibrin strands catalyzed by factor XIIIa (the formation of which is catalyzed by thrombin).


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