Plasma Components

The blood is mostly water and red blood cells. The packed cell volume or volume of RBCs is

about 45 percent. This is also referred to as the hematocrit, which is about 41 percent in

females and about 47 percent in males. The percentage of plasma is about 59 percent in

females and 53 percent in males. Blood is either dusky red or bright red, depending on the

amount of oxygen that is in the sample. Its viscosity is about 5 times that of water, making it

have some resistance to flow.

The temperature of blood is about 100.4 degrees, slightly higher than a normal internal body

temperature. This is because of the friction created by viscous blood in the vessels. The normal

pH of blood is 7.35-7.45 in a healthy individual. There are buffers that regulate the pH. About 8

percent of a person’s body weight is blood, accounted for by a volume of blood being 4-6 liters

(higher in males).

PLASMA COMPONENTS

Most of the components of plasma are plasma proteins. There are some proteins that are

unique to plasma and some that are found in other tissues. The proteins you should know

include:

• Albumin—this protein has the highest concentration in the plasma. Albumin is a binding

protein that transports steroids, fatty acids, and other non-hydrophilic substances. It is

the main protein contributing to the osmotic pressure inside blood vessels, keeping

water within the vessels. Accounting for about 54 percent of protein in the plasma, a normal level is about 3.5-5.0 g/dL in the blood plasma.

• Globulin proteins—this is the second most common type of protein in the plasma.

Alpha and beta-globulins can transport lipid-soluble vitamins, fatty acids and other

lipids, and iron in the bloodstream. Gamma globulins are important for the immune

system. They contribute to the osmotic pressure to a lesser degree than albumin.

Globulins account for 38 percent of the total plasma protein volume.

• Fibrinogen—this is made by the liver and contributes to blood clotting. It accounts for

just seven percent of the total plasma protein volume in the blood.