Blood Composition

Formed Elements

Erythrocytes• Transports oxygen to cells and tissues• Anucleate• ~7 µm• Few organelles• Hemoglobin– Iron rich protein–Binds with oxygen

Erythrocyte Characteristics• Small, flexible, bi-concave discs– Center is depressed to increase surface area– Cell must be flexible to fold to cross capillaries

• Amount of oxygen carried directly related to hemoglobin concentrations– ~250 million hgb molecules per cell!

Hemoglobin• Made up of 4 connected protein chains• Responsible for the red color of blood• Forms the heme molecule– Important• Carries oxygen, returns carbon dioxide• Helps maintain structure of cell

Leukocytes• Contain nuclei & organelles • Body’s “Army”– Defends/protects body– WBC’s move to fight infection• Can leave blood stream-diapedesis• Positive chemotaxis– Damaged cells give off chemicals to alert body– Activates WBC’s– Body will produce more of that type WBC

Leukocytes• Two major groups– Granulocytes• Cytoplasm contains visible granular inclusions• Lobed nuclei

– Agranulocytes• Cytoplasm does not have visible granules• Spherical nuclei

– Oval– Kidney shaped

Granulocytes• Neutrophils–Most numerous WBC–Multi-lobed nucleus–Fine granules–Phagocytic cell• FUNGI • BACTERIA

Granulocytes• Eosinophils– Bluish red nuclei– Nucleus is usually bi-lobed– Coarse, red granules– Increase due to• Allergies• Parasites

Granulocytes• Basophils– Rare WBC– Nucleus “u” or “s” shaped– Granules stain dark blue/purple– Helps mediate inflammatory response• Contains histamine

– Makes blood vessels leaky to allow WBC to get to inflammation site

• Contains heparin– Anti-coagulant

Agranulocytes• Lymphocytes– Small (slightly bigger than a RBC)– Dark staining nucleus– Second most numerous WBC– Tend to reside in lymph tissues– Important in antibody production– Increase in response to VIRUSES

Agranulocytes• Monocytes– Largest WBC– “U” or kidney shaped nucleus– Convert into macrophages in tissues– Seen in chronic infections

Platelets• Not a true cell– Fragments of megakaryocytes– Dark staining pieces– Critical to clotting process• Bind together to stop bleeding

Complete Blood Counts• Measures – The number of RBC’s– The number of WBC’s– The number of platelets– Hgb– Hematocrit

• Can include– Morphology of RBC’s– Size of RBC’s

Typical CBC results• RBC count (varies): – Male: 4.7 to 6.1 million cells/µL– Female: 4.2 to 5.4 million cells/µL

• WBC count: 4,500 to 10,000 cells/µL• Hematocrit (varies): – Male: 40.7 to 50.3 %– Female: 36.1 to 44.3 %

• Hemoglobin (varies): – Male: 13.8 to 17.2 gm/dL– Female: 12.1 to 15.1 gm/dL

Typical CBC results• Segmented neutrophils: (50–70%) • Lymphocytes: (15–45%) • Monocytes: (0–10%) • Eosinophils: (0–6%) • Basophils: (0–2%)