Chapter 1. An Introduction to the Human Body

1.1 How Structure Determines Function

Learning Objectives

By the end of this section, you will be able to:

  • Compare and contrast the study of anatomy and physiology
  • Discuss the fundamental structure-function relationship between anatomy and physiology

 

Human anatomy is the scientific study of the body’s structures. Some of these structures are very small and can only be observed and analyzed with the assistance of a microscope, while other, larger structures can readily be seen, manipulated, measured, and weighed. The word “anatomy” comes from the Greek root “ana” which means “to cut apart” and “tomia” which means “to cut.” Human anatomy was first studied by observing the exterior of the body, wounds of soldiers, and other injuries. Later, physicians were allowed to dissect bodies of the dead to augment their knowledge. When a body is dissected, its structures are cut apart in order to observe their physical attributes and their relationships to one another. Dissection is still used in medical schools, anatomy courses, and in pathology labs. In order to observe structures in living people, however, a number of imaging techniques have been developed. These techniques allow clinicians to visualize structures inside the living body such as a cancerous tumor or a fractured bone.

Like most scientific disciplines, anatomy has areas of specialization. Gross anatomy is the study of the larger structures of the body, those visible without the aid of magnification (image below, a). Gross and macro both mean “large,” thus, gross anatomy is also referred to as macroscopic anatomy. In contrast, micro means “small,” and microscopic anatomy is the study of structures that can be observed only with the use of a microscope or other magnification devices (image below, b). Microscopic anatomy includes cytology, the study of cells, and histology, the study of tissues. As the technology of microscopes has advanced, anatomists have been able to observe smaller and smaller structures of the body, from slices of large structures like the heart, to the three-dimensional structures of large molecules in the body.

01_01ab_gross_and_microscopic_anatomy

Figure 1.11

Gross and Microscopic Anatomy (images)

(a) Gross anatomy considers large structures such as the brain. (b) Microscopic anatomy can deal with the same structures, though at a different scale. This is a micrograph of nerve cells from the brain. LM × 1600. (credit a: “WriterHound”/Wikimedia Commons; credit b: Micrograph provided by the Regents of University of Michigan Medical School © 2012)

Anatomists take two general approaches to the study of the body’s structures: regional and systemic. Regional anatomy is the study of the interrelationships of all of the structures in a specific body region, such as the abdomen. Studying regional anatomy helps us appreciate the interrelationships of body structures, such as how muscles, nerves, blood vessels, and other structures work together to serve a particular body region. In contrast, systemic anatomy is the study of the structures that make up a discrete body system—that is, a group of structures that work together to perform a unique body function. For example, a systemic anatomical study of the muscular system would consider all of the skeletal muscles of the body.

Whereas anatomy is about structure, physiology is about function. Human physiology is the scientific study of the chemistry and physics of the structures of the body and the ways in which they work together to support the functions of life. Much of the study of physiology centers on the body’s tendency toward homeostasis. Homeostasis is the state of steady internal conditions maintained by living things. The study of physiology certainly includes observation, both with the naked eye and with microscopes, as well as manipulations and measurements. Current advances in physiology usually depend on carefully designed laboratory experiments that reveal the functions of the many structures and chemical compounds that make up the human body.

Like anatomists, physiologists typically specialize in a particular branch of physiology. For example, neurophysiology is the study of the brain, spinal cord, and nerves and how these work together to perform functions as complex and diverse as vision, movement, and thinking. Physiologists may work from the organ level (exploring, for example, what different parts of the brain does) to the molecular level (such as exploring how an electrochemical signal travels along nerves).

Form is closely related to function in all living things. For example, the thin flap of your eyelid can snap down to clear away dust particles and almost instantaneously slide back up to allow you to see again. At the microscopic level, the arrangement and function of the nerves and muscles that serve the eyelid allow for its quick action and retreat. At a smaller level of analysis, the function of these nerves and muscles likewise relies on the interactions of specific molecules and ions. Even the three-dimensional structure of certain molecules is essential to their function.

Your study of anatomy and physiology will make more sense if you continually relate the form of the structures you are studying to their function. In fact, it can be somewhat frustrating to attempt to study anatomy without an understanding of the physiology that a body structure supports. Imagine, for example, trying to appreciate the unique arrangement of the bones of the human hand if you had no conception of the function of the hand. Fortunately, your understanding of how the human hand manipulates tools—from pens to cell phones—helps you appreciate the unique alignment of the thumb in opposition to the four fingers, making your hand a structure that allows you to pinch and grasp objects and type text messages.

Chapter Review

Human anatomy is the scientific study of the body’s structures. In the past, anatomy has primarily been studied via observing injuries, and later by the dissection of anatomical structures of cadavers, but in the past century, computer-assisted imaging techniques have allowed clinicians to look inside the living body. Human physiology is the scientific study of the chemistry and physics of the structures of the body. Physiology explains how the structures of the body work together to maintain life. It is difficult to study structure (anatomy) without knowledge of function (physiology) and vice versa. The two disciplines are typically studied together because form and function are closely related in all living things.

 

Review Questions

 

Exercises

True or False? A scientist wants to study how the body uses foods and fluids during a marathon run is mostly likely an anatomist.

 

Critical Thinking Questions

Name at least three ways to use the information you learn about anatomy and physiology.

 

An understanding of physiology is essential for any career in the health professions. It can also help you make choices that promote your health, respond appropriately to signs of illness, make sense of health-related news, and help you in your roles as a parent, spouse, partner, friend, colleague, and caregiver.

 

In your opinion, would it be more important for an orthopedic surgeon who performs knee replacements to be an expert in anatomy or physiology? Why do you think this? How about an oncologist treating cancerous tumors in the lungs?

 

Glossary

anatomy
science that studies the form and composition of the body’s structures
gross anatomy
study of the larger structures of the body, typically with the unaided eye; also referred to as macroscopic anatomy
homeostasis
steady state of body systems that living organisms maintain
microscopic anatomy
study of very small structures of the body using magnification
physiology
science that studies the chemistry, biochemistry, and physics of the body’s functions
regional anatomy
study of the structures that contribute to specific body regions
systemic anatomy
study of the structures that contribute to specific body systems

 

Solutions

True or False Question:

  • False