- Anti-sphering agents in blood prevent RBC from changing shape
- Average for Human: male = 5 million RBC/mm3 blood; female = 4.5 million RBC/mm3 blood
- Life-span of human RBC is about 3 months
- Capable of distortion in shape due to elasticity, allows travel through capillaries
w/ diameter smaller than RBC
- Spontaneously form into stacked columns when removed from circulation = rouleaux
- Hemoglobin is respiratory pigment responsible for O2 and CO2 transport (at different sites). Average hemoglobin content = 0.14 g/ml blood (female), 0.16 g/ml blood (male)

- WBCs common in saliva, digestive tract, and excretory tract
Two Categories of Leukocytes: based on presence or absence of granules in cytoplasm

1. Granular Leukocytes = Granulocytes
a) neutrophils
b) eosinophils
c) basophils
2. Agranular Leukocytes = Agranulocytes
a) lymphocytes
b) monocytes

1) Neutrophils - about 65% of all WBCs; 9-12 micrometers; polymorphonuclear leukocyte =
nucleus with 2-5 lobes interconnected with fine strands (the lower # of lobes indicate
younger cells)

- abundant fine specific granules in cytoplasm that are neither strongly acidic or basic staining
- specific and azurophilic granules provide lavender-staining cytoplasm

- azurophilic granules = lysosomes; specific granules = anti-bacterial actions
- usually circulate in bloodstream for short period (9-10 hrs) then enter body tissues
where they are actively motile and act to phagocytose and digest invading bacteria,
part of acute inflammatory response


2) Eosinophils - about 3% of all WBCs; 10-14 micrometers; nucleus usually bilobed

- cytoplasm filled with large acidophilic granules, stain red with eosin; these granules
represent primary lysosomes
Acidophilia = association of basic substances w/in cell w/ acid dyes
Basophilia = association of acidic substances w/in cell w/ basic dyes

- Eosinophils have immunological role = phagocytosis of antigen-antibody complexes
formed during immune response
- present in high numbers in some allergic reactions, role in regulating local
inflammatory response
- phagocytose and kill larval stages of parasitic worms

3) Basophils - 1% of all WBCs; 8-10 micrometers; nucleus usually with 2 lobes,
sometimes more, often takes on "S" shape; cytoplasm filled with large blue-staining
(basophilic) granules which contain heparin and histamine, cell membrane may be
irregular due to conformity with granules

- not actively ameboid and show relatively little phagocytic activity
- when basophil stimulated by an antigen or by tissue injury, responds by
degranulation - causes histamine release. Histamine release initiates inflammatory
reaction causing vasodilation and increasing permeability of blood vessels.

1) Lymphocytes - about 25% of all WBCs in humans, 50% in birds, 70% in rodents

- Three sizes may be present in blood:
Small = dark dense heterochromatin nucleus, very little cytoplasm
Intermediate = slightly larger due to more cytoplasm
Large = larger with more cytoplasm, lighter vesicular euchromatin in nucleus,
rarely found in blood - instead in lymph nodes
- cytoplasm slightly basophilic and lacks granules in most cases
- Two types of lymphocytes:

1) B-lymphocytes = differentiate in bone marrow
2) T-lymphocytes = differentiate in thymus

Both show great immunological activity: B - produce antibodies, T - autorecognition,
hypersensitivity, stimulation of B-lymphocytes

2) Monocytes - about 6% of all WBCs; largest leukocyte 12-15 micrometers; nucleus shape
varies from kidney-shaped to horseshoe-shaped, but always indented; lighter staining
than lymphocytes

- cytoplasm without granules and stains pale blue-gray
- monocytes are phagocytic; when monocytes leave bloodstream they rapidly
transform to macrophages that are very actively phagocytic ingesting bacteria, dead
cells, tissue debris; also stimulate antibody production by lymphocytes.