Blood Composition and Types of Blood Elements

• Blood color ranges from bright red, when oxygen rich, to a dull brick red when oxygen poor.
• The volume of blood is about 5-6 Liters in males, and about 4-5 Liters in females.
• Blood is connective tissue, characterized by cells within a matrix.
• Plasma is the nonliving fluid in the matrix, while cells and cell fragments are the formed elements.
• Plasma dissolves more than 100 substances, mainly water (over 90%), along with nutrients like gases, hormones, wastes, metabolites, proteins, and electrolytes.
• Plasma composition varies as cells remove or add substances.

Types of Blood Elements

• Erythrocytes (red blood cells/RBCs) are the most numerous blood cells which are sacs of hemoglobin that transport most of the blood's oxygen and carbon dioxide
• Leukocytes (white blood cells/WBCs) are part of the body's nonspecific defenses and immune system.
• Platelets function in hemostasis (blood clotting).
• Formed elements account for about 45% of whole blood; plasma accounts for the other 55%.

Subtypes of Leukocytes (White Blood Cells)

• Granulocytes phagocytize pathogens or debris; neutrophil type.
• Eosinophils kill parasitic worms and slightly phagocytic- play a complex role in allergy and asthma.
• Basophils release histamine and other mediators of inflammation and also contain the anticoagulant heparin.
• Agranulocytes mount an immune response by direct cell attack or lymphocyte via antibody production.
• Monocytes locate in tissues and develop into macrophages that phagocytize pathogens or debris.

Platelets

• Platelets seal small tears in blood vessels and are very important in blood clotting.

Blood color varies with oxygen levels. The blood volume differs between males and females. Blood, a connective tissue, consists of plasma and formed elements like erythrocytes, leukocytes and platelets. Plasma is mainly water and contains nutrients, gases, hormones, and electrolytes.