Structure and Functions (Magill’s Medical Guide, Sixth Edition)
The cardiovascular system is made up of the heart, arteries, veins, and lungs. The heart serves as a pump to deliver blood to the arteries for distribution throughout the body. The veins bring the blood back to the heart, and the lungs oxygenate the blood before returning it to the arterial system.
Contraction of the heart muscle forces blood out of the heart. This period of contraction is known as systole. The heart muscle relaxes after each contraction, which allows blood flow into the heart. This period of relaxation is known as diastole. A typical blood pressure taken at the upper arm provides a pressure reading during two phases of the cardiac cycle. The first number is known as the systolic pressure and represents the pressure of the heart during peak contraction. The second number is known as the diastolic pressure and represents the pressure while the heart is at rest. A typical pressure reading for a young adult would be 120/80. When blood pressure is abnormally elevated, it is commonly referred to as high blood pressure, or hypertension.
The heart is separated into two halves by a wall of muscle known as the septum. The two halves are known as the left and right heart. The left side of the heart is responsible for high-pressure arterial distribution and is larger and stronger than the right side. The right side of the heart is responsible for accepting low-pressure venous return and redirecting it to...
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Disorders and Diseases (Magill’s Medical Guide, Sixth Edition)
Numerous variables may affect the flow of blood. The autonomic nervous system is connected to muscle within the wall of the artery by way of neurological pathways known as sympathetic branches. Various drugs and/or conditions can trigger responses in the sympathetic branches and produce constriction of the smooth muscle in the arterial wall (vasoconstriction) or relaxation of the arterial wall (vasodilation). Alcohol consumption and a hot bath are examples of conditions that produce vasodilation. Exposure to cold and cigarette smoking are examples of conditions that produce vasoconstriction. Various drugs used in the medical environment are capable of producing similar effects. The diameter of the lumen of an artery influences the pressure and the flow of blood through it.
Another condition that alters the arterial diameter is atherosclerosis, a disease primarily of the large arteries, which allows the formation of fat (lipid) deposits to build on the inner layer of the artery. Lipid deposits are more commonly known as atherosclerotic plaque. Plaque accumulation reduces the diameter of the arterial lumen, causing various degrees of flow restriction. Plaque is similar to rust accumulation within a pipe which restricts the flow of water. A restriction of flow is referred to as a stenosis. The majority of stenotic lesions occur at the places where arteries divide into branches, also known as bifurcations. In advanced...
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Perspective and Prospects (Magill’s Medical Guide, Sixth Edition)
Historically, the vasculature of the human body was evaluated by placing one’s fingers on the skin, palpating for the presence or absence of a pulse, and making note of the patient’s symptoms. Prior to the 1960’s, treatment of the circulatory system was very limited or nonexistent, resulting in a high death rate and large numbers of amputations, strokes, and heart attacks. The development of arteriography (the angiogram), a procedure in which dye is injected into the vessels while X rays are obtained, revealed more about the vasculature and the nature of disease involving it. In conjunction with arteriography came corrective bypass surgery.
This period of development was followed by vast improvements in diagnostics, treatment, and knowledge of preventive maintenance. Today, synthetic bypass grafts are commonplace and are used to reroute flow around an obstruction. In many cases, procedures such as atherectomy and angioplasty, in which plaque or a thrombus is removed through a catheter inserted into the vessel, are often performed as outpatient procedures.
Diagnostic imaging of the cardiovascular system and the study of hemodynamics with the use of ultrasound have been useful for patient screening, the monitoring of disease progression, and the postoperative evaluation of surgical/interventional procedures. Ultrasound is a particularly valuable diagnostic tool because, compared to X rays or...
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For Further Information: (Magill’s Medical Guide, Sixth Edition)
Bick, Roger L., ed. Disorders of Thrombosis and Hemostasis: Clinical and Laboratory Practice. 3d ed. Philadelphia: Lippincott Williams & Wilkins, 2002. An excellent introduction to the diagnosis and management of clotting and bleeding disorders.
Guyton, Arthur C., and John E. Hall. Human Physiology and Mechanisms of Disease. 6th ed. Philadelphia: W. B. Saunders, 1997. A well-written text for medical students interested in learning the physiological effects of disease. Parts 3 and 4 pertain to the heart and circulation.
Marieb, Elaine N., and Katja Hoehn. Human Anatomy and Physiology. 9th ed. San Francisco: Pearson/Benjamin Cummings, 2010. Nonscientists at the advanced high school level or above will be able to understand this fine textbook. It includes a complete glossary, index, pronunciation guide, and other helpful features.
Saltin, Bengt, et al., eds. Exercise and Circulation in Health and Disease. Champaign, Ill.: Human Kinetics, 2000. This book is a compilation of integrated topics in cardiovascular regulatory physiology from more than forty authors.
Strandness, D. Eugene, Jr. Duplex Scanning in Vascular Disorders. 4th ed. London: Lippincott Williams & Wilkins, 2009. This book is written for medical vascular specialists and is somewhat technical in nature; however, it is well written. The beginning of each chapter defines the importance...
(The entire section is 213 words.)