Blood circulates within the cardiovascular system to provide a vehicle for the distribution of respiratory gases, nutrients, water, electrolytes, hormones, antibodies, drugs, metabolic waste, and heat throughout the body. Most of the major negative feedback control systems of the body defend normal blood composition (e.g., blood glucose concentration, blood volume, and arterial O2 partial pressure). Blood is composed of cellular elements (i.e., red blood cells, white blood cells, and platelets), which are suspended in blood plasma. A person who weighs 70 kg has approximately 5 L of blood, of which about 2 L is occupied by the formed cellular elements and 3 L is plasma.
This chapter will discuss mainly the physiologic regulation of the red blood cell mass and the mechanisms that prevent bleeding.
Plasma is the part of the extracellular fluid that is contained within the cardiovascular system. It is a dilute solution, which by weight is approximately 92% water, 7% protein, and 1% small dissolved solutes (e.g., ions, urea, glucose, amino acids, and lipids). The normal plasma concentrations of selected ions and small molecules are almost the same as those in the interstitial fluid because of the free exchange of water and small solutes across most blood capillaries (Table 3-1). In contrast, most capillaries are impermeable to plasma proteins. The resulting difference in protein concentration between the plasma and the interstitial fluids creates a colloid osmotic (oncotic) pressure gradient that opposes the filtration of plasma out of the capillaries (Chapter 4). Albumin is the most abundant type of plasma protein and, therefore, is the greatest contributor to the plasma oncotic pressure. The major types of plasma protein and their functions are listed in Table 3-2.
Table 3-1Normal Plasma Composition |Favorite Table|Download (.pdf) Table 3-1Normal Plasma Composition
|Substance ||Normal Value ||Normal Range |
|Sodium ||140 mM ||136–146 mM |
|Potassium ||4.5 mM ||3.5–5.5 mM |
|Chloride ||100 mM ||96–106 mM |
|Bicarbonate ||24 mM ||22–28 mM |
|Calcium* ||2.5 mM ||2.2–2.8 mM |
|pH (arterial) ||7.40 ||7.35–7.45 |
|Pco2 (arterial) ||40 mm Hg ||38–42 mm Hg |
|Po2 (arterial) ||90 mm Hg ||80–100 mm Hg |
|Glucose (fasting) ||80 mg/dL ||70–99 mg/dL |
|Urea (BUN) ||12 mg/dL ||9–18 mg/dL |
|Protein ||7 g/dL ||6–8 g/dL |
Table 3-2The Major Types of Plasma Proteins |Favorite Table|Download (.pdf) Table 3-2The Major Types of Plasma Proteins
|Plasma Protein ||Major Source ||Examples and Functions |
|Albumin ||Liver ||Main component of plasma oncotic pressure; binding of various substances |
|α-Globulins & α-Globulins ||Liver ||Examples (there are many) include hormone-binding proteins and the iron carrier protein transferrin |
|Coagulation proteins ||Liver ||Examples include plasminogen, prothrombin, antithrombin III, and fibrinogen |
|Immunoglobulins tissue ||Lymphoid ||Host defense reactions |
|Complement proteins ||Liver...|
Log In to View More
If you don't have a subscription, please view our individual subscription options below to find out how you can gain access to this content.
Want remote access to your institution's subscription?
Sign in to your MyAccess profile while you are actively authenticated on this site via your institution (you will be able to verify this by looking at the top right corner of the screen - if you see your institution's name, you are authenticated). Once logged in to your MyAccess profile, you will be able to access your institution's subscription for 90 days from any location. You must be logged in while authenticated at least once every 90 days to maintain this remote access.
If your institution subscribes to this resource, and you don't have a MyAccess profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus.
AccessPhysiotherapy Full Site: One-Year Subscription
Connect to the full suite of AccessPhysiotherapy content and resources including interactive NPTE review, more than 500 videos, Anatomy & Physiology Revealed, 20+ leading textbooks, and more.
Pay Per View: Timed Access to all of AccessPhysiotherapy
24 Hour Subscription $34.95
48 Hour Subscription $54.95
Pop-up div Successfully Displayed
This div only appears when the trigger link is hovered over.
Otherwise it is hidden from view.