Chapter 23 The Circulatory, Respiratory, Digestive, and Excretory ...

Blood Type
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Blood type is a genetic characteristic associated with the presence or absence of certain molecules, called
antigens, on the surface of red blood cells. The most commonly known blood types are the ABO and
Rhesus blood types.
• ABO blood type is determined by two common antigens, often referred to simply as antigens A and
B. A person may have blood type A (only antigen A), B (only antigen B), AB (both antigens), or O
(no antigens).
• Rhesus blood type is determined by one common antigen. A person may either have the antigen
(Rh + ) or lack the antigen (Rh - ).
Blood type is important for medical reasons. A person who needs a blood transfusion must receive blood
that is the same type as his or her own. Otherwise, the transfused blood may cause a potentially lifethreatening
reaction in the patient’s bloodstream.
Lesson Summary
• The heart contracts rhythmically to pump blood to the lungs and the rest of the body. Specialized
cardiac muscle cells trigger the contractions.
• Arteries carry blood away from the heart, veins carry blood toward the heart, and capillaries connect
arteries and veins.
• The pulmonary circulation carries blood between the heart and lungs. The systemic circulation
carries blood between the heart and body.
• A disease that affects the heart or blood vessels is called a cardiovascular disease (CVD). The leading
cause of CVD is atherosclerosis, or the buildup of plaque inside arteries. Healthy lifestyle choices can
reduce the risk of developing CVD.
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