Anatomy is the study of structure, and physiology is the study of function. These approaches are complementary and never entirely separable. When we study a structure, we want to know, What does it do? Physiology lends meaning to anatomy and, conversely, anatomy is what makes physiology possible. This unity of form and function is an important point to bear in mind as you study the body. Many examples of it will be apparent throughout the book—some of them pointed out for you, and others you will notice for yourself.
Anatomy—The Study of Form
The simplest way to study human anatomy is the observation of surface structure, for example in performing a physical examination or making a clinical diagnosis from surface appearance. But a deeper understanding of the body depends on dissection—the careful cutting and separation of tissues to reveal their relationships. Both
anatomy1 and dissection2 literally mean "cutting apart"; dissecting used to be called "anatomizing." The dissection of a dead human body, or cadaver,3 is an essential part of the training of many health science students (fig. 1.1). Many insights into human structure are obtained from comparative anatomy—the study of more than one species in order to learn generalizations and evolutionary trends. Students of anatomy often begin by dissecting other animals with which we share a common ancestry and many structural similarities.
Dissection, of course, is not the method of choice when studying a living person! Physical examinations involve not only looking at the body for signs of normalcy or disease but also touching and listening to it. Palpation4 is feeling structure with the fingertips, such as palpating a swollen lymph node or taking a pulse. Auscultation5 (AWS-cul-TAY-shun) is listening to the natural sounds made by the body, such as heart and lung sounds. In percussion, the examiner taps on the body and listens to the sound for signs of abnormalities such as pockets of fluid or air.
Structure that can be seen with the naked eye, whether by surface observation or dissection, is called gross anatomy. Ultimately, though, the functions of the body result from its individual cells. To see those, we usually take tissue specimens, thinly slice and stain them, and observe them under the microscope. This approach is
3cadere = to fall or die
4palp = touch, feel
5auscult = listen
Saladin: Anatomy & I 1. Major Themes of I Text I I © The McGraw-Hill
Physiology: The Unity of Anatomy and Physiology Companies, 2003 Form and Function, Third Edition called histology6 (microscopic anatomy). Histopathology is the microscopic examination of tissues for signs of disease. Ultrastructure refers to fine details, down to the molecular level, revealed by the electron microscope.
Physiology—The Study of Function
Physiology7 uses the methods of experimental science discussed later. It has many subdisciplines such as neurophysiology (physiology of the nervous system), endocrinology (physiology of hormones), and pathophys-iology (mechanisms of disease). Partly because of limitations on experimentation with humans, much of what we know about bodily function has been gained through comparative physiology, the study of how different species have solved problems of life such as water balance, respiration, and reproduction. Comparative physiology is also the basis for the development of new drugs and medical procedures. For example, a cardiac surgeon cannot practice on humans without first succeeding in animal surgery, and a vaccine cannot be used on human subjects until it has been demonstrated through animal research that it confers significant benefits without unacceptable risks.
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