Blood

Functions of blood

• transports gases, nutrients and metabolic wastes
• delivers enzymes and hormones
• regulates pH and electrolyte composition of interstitial fluids
• restricts fluid losses by way of the clotting reaction
• defends the body against toxins and pathogens
• helps regulate body temperature

Composition of blood

Plasma - 55%

• water - 92% of plasma
• electrolytes, nutrients, organic wastes
• proteins

Formed elements (blood cells) - 45%

• Red blood cells, White blood cells, Platelets
• hematocrit - percentage of whole that is composed of red blood cells

Blood cells

Erythrocytes (Red blood cells)

cytoplasm contains hemoglobin

flattened, no nucleus, mitochondria or ribosomes

transport oxygen and carbon dioxide

Leukocytes (White blood cells)

Neutrophils (57%)

engulf pathogens and debris

Eosinophils (2.4%)

engulfs antibody bound pathogens

Basophils (0.6%)

release histamine

Monocytes (6.5%)

engulf pathogens and debris

enter tissues to become macrophages

Lymphocytes - small (28%)

B-lymphocytes form antibodies

T-lymphocytes attack viruses and invaded cells

Lymphocytes - large (3%)

NK-lymphocytes attack damaged or foreign cells

Platelets

clump together, activate coagulation

 

© David G. Ward, Ph.D.  Last modified by wardd 23 May, 2006