Essentials of Pathophysiology-Concepts of Altered Health States
Author: Carol Mattson Porth
This book was written with the intent of making the subject of pathophysiology an exciting exploration that relates normal body functioning to the physiologic changes that participate in disease production and occur as a result of disease, as well as the body’s remarkable ability to compensate for these changes. Indeed, it is these changes that represent the signs and symptoms of disease. Using a book such as this can be simplified by taking the time to find what is in the book and how to locate information when it is needed. The table of contents at the beginning of the book provides an overall view of the organization and content of the book. It also provides clues as to the relationships among areas of content. For example, the location of the chapter on neoplasia within the unit on cell function and growth indicates that neoplasms are products of altered cell growth. The index, which appears at the end of the book, can be viewed as a road map for locating content. It can be used to quickly locate related content in different chapters of the book or to answer questions that come up in other courses. ORGANIZATION The book is organized into units and chapters. The units identify broad areas of content, such as alterations in the circulatory system. The chapters focus on specific areas of content, such as heart failure and circulatory shock. The chapter outline that appears at the beginning of each chapter provides an outline of the content in the chapter. Icons identify specific content related to infants and children , pregnant women, , and older adults . Many of the units have a chapter that contains essential information about the structures being discussed in the unit. These chapters provide the foundation for understanding the pathophysiology content presented in the subsequent chapters. READING AND LEARNING AIDS In an ever-expanding world of information you will not be able to read, let alone remember, everything that is in this book, or in any book, for that matter. With this in mind, we have developed a number of special features that will help you focus on Boxes are used throughout the text to summarize and highlight key information. You will encounter two types of boxes: Key Concept Boxes and Summary Boxes. One of the ways to approach learning is to focus on the major ideas or concepts rather than trying to memorize a list of related and unrelated bits of information. As you have probably already discovered, it is impossible to memorize everything that is in a particular section or chapter of the book. First, your brain has a difficult time trying to figure out where to store all the different bits of information. Secondly, your brain doesn’t know how to retrieve the information when you need it. Thirdly, memorized lists of content can seldom be applied directly to an actual clinical situation. The Key Concept Boxes guide you in identifying the major ideas or concepts that form the foundation for truly understanding the major areas of content. When you understand and master the essential content for your current as well as future needs. It is essential for any professional to use and understand the vocabulary of his or her profession. Throughout the text, you will encounter terms in italics. This is a signal that a word and the ideas associated with it are important to learn. In addition, two aids are provided to help you expand your vocabulary and improve your comprehension of what you are reading: the glossary and the list of prefixes and suffixes. The glossary contains concise definitions of frequently encountered terms. If you are unsure of the meaning of a term you encounter in your reading, check the glossary in the back of the book before proceeding. The list of prefixes and suffixes is a tool to help you derive the meaning of words you may be unfamiliar with and increase your vocabulary. Many disciplines establish a vocabulary by affixing one or more sounds or letters to the beginning or end of a word or base to form a derivative word. Prefixes are added to the beginning of a word or base, and suffixes are added to the end. If you know the meanings of common prefixes and suffixes, you can usually derive the meaning of a word, even if you have never encountered it before. A list of prefixes and suffixes common to pathophysiology can be found on the inside covers. BOXES Tables and charts are designed to present complex information in a format that makes it more meaningful and easier to remember. Tables have two or more columns, and are often used for the purpose of comparing or contrasting information. Charts have one column and are used to summarize information. TABLES AND CHARTS ILLUSTRATIONS xiv To the Reader the concepts in the Key Concept boxes, you will have a framework for remembering and using all of the facts given in the text. KEY CONCEPTS COMPONENTS OF THE IMMUNE SYSTEM ■ The immune system consists of immune cells; the central immune structures (the bone marrow and thymus), where immune cells are produced and mature; and the peripheral immune structures (lymph nodes, spleen, and other accessory structures), where the immune cells interact with antigen. ■ The immune cells consist of the lymphocytes (T and B lymphocytes), which are the primary cells of the immune system, and the accessory cells such as the macrophages, which aid in processing and presentation of antigens to the lymphocytes. ■ Cytokines are molecules that form a communication link between immune cells and other tissues and organs of the body. ■ Recognition of self from nonself by the immune cells depends on a system of MHC membrane molecules that differentiate viral-infected and abnormal cells from normal cells (MHC I) and identify immune cells from other types of cells (MHC II). The Summary Boxes at the end of each section provide a review of the main content that has been covered. Use the summaries to assure that you have covered and understand what you have read. In summary, heart failure occurs when the heart fails to pump sufficient blood to meet the metabolic needs of body tissues. The physiology of heart failure reflects an interplay between a decrease in cardiac output that accompanies impaired function of the failing heart and the compensatory mechanisms designed to preserve the cardiac reserve. Compensatory mechanisms that contribute to maintenance of the cardiac reserve include the Frank-Starling mechanism, sympathetic nervous system responses, the renin-angiotensinaldosterone mechanism, and myocardial hypertrophy. In the failing heart, early decreases in cardiac function may go unnoticed because these compensatory mechanisms maintain the cardiac output. This is called compensated heart failure. Unfortunately, the mechanisms were not intended for longterm use, and in severe and prolonged heart failure, the compensatory mechanisms no longer are effective and further impair cardiac function. Heart failure may be described as high-output or low-output failure, systolic or diastolic failure, and right-sided or leftsided failure. With high-output failure, the function of the heart may be supernormal but inadequate because of excessive metabolic needs, and low-output failure is caused by disorders that impair the pumping ability of the heart. With systolic dysfunction, there is impaired ejection of blood from the heart during systole; with diastolic dysfunction, there is impaired filling of the heart during diastole. Right-sided failure is characterized by congestion in the peripheral circulation, and left-sided failure by congestion in the pulmonary circulation. The manifestations of heart failure include edema, nocturia, fatigue and impaired exercise tolerance, cyanosis, signs of increased sympathetic nervous system activity, and impaired gastrointestinal function and malnutrition. In rightsided failure, there is dependent edema of the lower parts of the body, engorgement of the liver, and ascites. In left-sided failure, shortness of breath and chronic, nonproductive cough are common. Acute pulmonary edema is a life-threatening condition in which the accumulation of fluid in the interstitium of the lung and alveoli interferes with lung expansion and gas exchange. It is characterized by extreme breathlessness, crackles, frothy sputum, cyanosis, and signs of hypoxemia. In cardiogenic shock, there is failure to eject blood from the heart, hypotension, inadequate cardiac output, and impaired perfusion of peripheral tissues. Mechanical support devices, including the intra-aortic balloon pump (for acute failure) and the VAD, sustain life in persons with severe heart failure. Heart transplantation remains the treatment of choice for many persons with end-stage heart failure. TABLE 6-5 Manifestations of Hypokalemia and Hyperkalemia Laboratory Values Laboratory Values Serum potassium <3.5 mEq/L Serum potassium >5.0 mEq/L Thirst and Urine Increased thirst Inability to concentrate urine with polyuria and urine with low specific gravity Effects of Changes in Membrane Potentials in Neural and Muscle Function Gastrointestinal Anorexia, nausea, vomiting Abdominal distention Paralytic ileus (severe hypokalemia) Neuromuscular Muscle weakness, flabbiness, fatigue Muscle cramps and tenderness Paresthesias Paralysis (severe hypokalemia) Central Nervous System Confusion, depression Cardiovascular Postural hypotension Predisposition to digitalis toxicity Electrocardiogram changes Cardiac dysrhythmias Acid-Base Balance Metabolic alkalosis Hypokalemia Hyperkalemia Effects of Changes in Membrane Potentials on Neural and Muscle Function Gastrointestinal Nausea, vomiting Intestinal cramps Diarrhea Neuromuscular Weakness, dizziness Muscle cramps Paresthesias Paralysis (severe hyperkalemia) Cardiovascular Electrocardiogram changes Risk of cardiac arrest with severe hyperkalemia The full-color illustrations will help you to build your own mental image of the content that is being presented. Each drawing has been developed to fully support and build upon the ideas in the text. Some illustrations are used to help you picture the complex interactions of the multiple phenomena that are involved in the development of a particular disease; others can help you to visualize normal function or understand the mechanisms whereby the disease processes exert their effects. In addition, photographs of pathologic processes and lesions provide a realistic view of selected pathologic processes and lesions.