Blood, Heart, and Circulation 445Jessica experienced heavy menstruation. This could
cause sufficient loss of iron to produce iron-deficiency
anemia, which would be revealed by a low red blood cell
count. Her mitral valve prolapse is a common condition
involving blood leaking past the mitral valve and produc-
ing a murmur, which is best heard by a stethoscope place
at the apex position of the heart. However, this usually
does not cause symptoms unless the leakage is great
enough to significantly reduce the output of the left ven-
tricle. Her atrial fibrillation was revealed by the lack of a P
wave in the ECG. This may not have obvious symptoms,
but it may cause fatigue if the cardiac output cannot
increase sufficiently when she is active. The major dan-
ger is the tendency to form blood clots in the heart. This
can cause an ischemic stroke, which damages neurons
because of the ischemia-induced lack of oxygen and
nutrients and excitotoxicity. The physician prescribed a
drug that inactivates factor X, thereby inhibiting the for-
mation of thrombin by both clotting pathways. Smoking
is a major risk factor for atherosclerosis, which promotes
coronary heart disease and the formation of a thrombus.
See the additional chapter 13 Clinical Investigations on
Mitral Valve Prolapse and AV Node Block in the Connect
site for this text.| CHECKPOINT Clinical Investigation SUMMARY
17a. Compare the composition of lymph and blood, and
describe the relationship between blood capillaries
and lymphatic capillaries.
17b. Explain how the lymphatic system and the
cardiovascular system are related. How do these
systems differ?- Describe the functions of lymph nodes and lymphoid
organs.
Summary
3. Platelets, or thrombocytes, are required for blood
clotting.
C. The production of red blood cells is stimulated by the
hormone erythropoietin, and the development of different
kinds of white blood cells is controlled by chemicals called
cytokines.
D. The major blood-typing groups are the ABO system and the
Rh system.
1. Blood type refers to the kind of antigens found on the
surface of red blood cells.
2. When different types of blood are mixed, antibodies
against the red blood cell antigens cause the red blood
cells to agglutinate.
E. When a blood vessel is damaged, platelets adhere to the
exposed subendothelial collagen proteins.
1. Platelets that stick to collagen undergo a release
reaction in which they secrete ADP, serotonin, and
thromboxane A 2.
2. Serotonin and thromboxane A 2 cause vasoconstriction.
ADP and thromboxane A 2 attract other platelets
and cause them to stick to the growing mass of
platelets that are stuck to the collagen in the
broken vessel.
F. In the formation of a blood clot, a soluble protein called
fibrinogen is converted into insoluble threads of fibrin.13.1 Functions and Components of the
Circulatory System 405
A. The blood transports oxygen and nutrients to all the cells of
the body and removes waste products from the tissues. It also
serves a regulatory function through its transport of hormones.
- Oxygen is carried by red blood cells, or erythrocytes.
- White blood cells, or leukocytes, serve to protect the
body from disease.
B. The circulatory system consists of the cardiovascular system
(heart and blood vessels) and the lymphatic system.
13.2 Composition of the Blood 406
A. Plasma is the fluid part of the blood, containing dissolved
ions and various organic molecules.
- Hormones are found in the plasma portion of the blood.
- The plasma proteins are albumins, globulins (alpha,
beta, and gamma), and fibrinogen.
B. The formed elements of the blood are erythrocytes,
leukocytes, and platelets. - Erythrocytes, or red blood cells, contain hemoglobin
and transport oxygen. - Leukocytes may be granular (also called
polymorpho-nuclear) or agranular. They function in
immunity.