Plasma is a straw-colored liquid consisting of water and dissolved solutes. The major solute of the plasma in terms of its concentration is Na+. In addition to Na+, plasma contains many other ions, as well as organic molecules such as metabolites, hormones,

Test Yourself Before You Continue

1. State the components of the circulatory system that function in oxygen transport, in the transport of nutrients from the digestive system, and in protection.

2. Describe the functions of arteries, veins, and capillaries.

3. Define the terms interstitial fluid and lymph. How do these fluids relate to blood plasma?

Centrifuged Blood Sample

Blood _ plasma

Formed _ elements

Blood Smear


Blood Smear

Blood Plasma And Buffy Coat Chart

■ Figure 13.1 The constituents of blood. Blood cells become packed at the bottom of the test tube when whole blood is centrifuged, leaving the fluid plasma at the top of the tube. Red blood cells are the most abundant of the blood cells—white blood cells and platelets form only a thin, light-colored "buffy coat" at the interface between the packed red blood cells and the plasma.

368 Chapter Thirteen

Table 13.1 Representative Normal

Plasma Values


Normal Range

Blood volume

80-85 ml/kg body weight

Blood osmolality

280-296 mOsm

Blood pH



Creatine phosphokinase (CPK)

Female: 10-79 U/L

Male: 17-148 U/L

Lactic dehydrogenase (LDH)

45-90 U/L

Phosphatase (acid)

Female: 0.01-0.56 Sigma U/ml

Male: 0.13-0.63 Sigma U/ml

Hematology Values


Female: 37%-48%

Male: 45%-52%


Female: 12-16 g/100 ml

Male: 13-18 g/100 ml

Red blood cell count

4.2-5.9 million/mm3

White blood cell count




Male: 300-1,100 ng/100 ml

Female: 25-90 ng/100 ml

Adrenocorticotropic hormone (ACTH)

15-70 pg/ml

Growth hormone

Children: over 10 ng/ml

Adult male: below 5 ng/ml


6-26 |U/ml (fasting)



24-30 mmol/l


2.1-2.6 mmol/l


100-106 mmol/l


3.5-5.0 mmol/l


135-145 mmol/l

Organic Molecules (Other)


120-220 mg/100 ml


70-110 mg/100 ml (fasting)

Lactic acid

0.6-1.8 mmol/l

Protein (total)

6.0-8.4 g/100 ml


40-150 mg/100 ml

Urea nitrogen

8-25 mg/100 ml

Uric acid

3-7 mg/100 ml

Source: Excerpted from material appearing in The New England Journal of Medicine, "Case Records of the Massachusetts General Hospital," 302:37-38 and 314:39-49. 1980, 1986.

Source: Excerpted from material appearing in The New England Journal of Medicine, "Case Records of the Massachusetts General Hospital," 302:37-38 and 314:39-49. 1980, 1986.

enzymes, antibodies, and other proteins. The concentrations of some of these plasma constituents are shown in table 13.1.

Plasma Proteins

Plasma proteins constitute 7% to 9% of the plasma. The three types of proteins are albumins, globulins, and fibrinogen. Albumins account for most (60% to 80%) of the plasma proteins and are the smallest in size. They are produced by the liver and provide the osmotic pressure needed to draw water from the surrounding tissue fluid into the capillaries. This action is needed to maintain blood volume and pressure. Globulins are grouped into three subtypes: alpha globulins, beta globulins, and gamma globulins. The alpha and beta globulins are produced by the liver and function in transporting lipids and fat-soluble vitamins. Gamma globulins are antibodies produced by lymphocytes (one of the formed elements found in blood and lymphoid tissues) and function in immunity. Fibrinogen, which accounts for only about 4% of the total plasma proteins, is an important clotting factor produced by the liver. During the process of clot formation (described later in this chapter), fibrinogen is converted into insoluble threads of fibrin. Thus, the fluid from clotted blood, called serum, does not contain fibrinogen, but it is otherwise identical to plasma.

Plasma Volume

A number of regulatory mechanisms in the body maintain homeostasis of the plasma volume. If the body should lose water, the remaining plasma becomes excessively concentrated—its osmolality (chapter 6) increases. This is detected by osmorecep-tors in the hypothalamus, resulting in a sensation of thirst and the release of antidiuretic hormone (ADH) from the posterior pituitary (chapter 11). This hormone promotes water retention by the kidneys, which—together with increased intake of fluids— helps to compensate for the dehydration and lowered blood volume. This regulatory mechanism, together with others that influence plasma volume, are very important in maintaining blood pressure as described in chapter 14.

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Essentials of Human Physiology

Essentials of Human Physiology

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