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1 The Body
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What is anatomy?
Anatomy includes those structures that can be seen grossly (without the aid of
magnification) and microscopically (with the aid of magnification). Typically, when used by
itself, the term anatomy tends to mean gross or macroscopic anatomy-that is, the study of
structures that can be seen without using a microscopic. Microscopic anatomy, also called
histology, is the study of cells and tissues using a microscope.
Anatomy forms the basis for the practice of medicine. Anatomy leads the physician toward
an understanding of a patient's disease, whether he or she is carrying out a physical
examination or using the most advanced imaging techniques. Anatomy is also important for
dentists, chiropractors, physical therapists, and all others involved in any aspect of patient
treatment that begins with an analysis of clinical signs. The ability to interpret a clinical
observation correctly is therefore the endpoint of a sound anatomical understanding.
Observation and visualization are the primary techniques a student should use to learn
anatomy. Anatomy is much more than just memorization of lists of names. Although the
language of anatomy is important, the network of information needed to visualize the
position of physical structures in a patient goes far beyond simple memorization. Knowing
the names of the various branches of the external carotid artery is not the same as being
able to visualize the course of the lingual artery from its origin in the neck to its termination
in the tongue. Similarly, understanding the organization of the soft palate, how it is related
to the oral and nasal cavities, and how it moves during swallowing is very different from
being able to recite the names of its individual muscles and nerves. An understanding of
anatomy requires an understanding of the context in which the terminology can be
remembered.
How can gross anatomy be studied?
The term anatomy is derived from the Greek word temnein, meaning "to cut." Clearly,
therefore, the study of anatomy is linked, at its root, to dissection, although dissection of
cadavers by students is now augmented, or even in some cases replaced, by viewing
prosected (previously dissected) material and plastic models, or using computer teaching
modules and other learning aids.
Anatomy can be studied following either a regional or a systemic approach.
With a regional approach, each region of the body is studied separately and all
aspects of that region are studied at the same time. For example, if the thorax is to be
studied, all of its structures are examined. This includes the vasculature, the nerves,
the bones, the muscles, and all other structures and organs located in the region of
the body defined as the thorax. After studying this region, the other regions of the
body (i.e., the abdomen, pelvis, lower limb, upper limb, back, head, and neck) are
studied in a similar fashion.
In contrast, in a systemic approach, each system of the body is studied and followed
throughout the entire body. For example, a study of the cardiovascular system looks
at the heart and all of the blood vessels in the body. When this is completed, the
nervous system (brain, spinal cord, and all the nerves) might be examined in detail. This
approach continues for the whole body until every system, including the nervous,
skeletal, muscular, gastrointestinal, respiratory, lymphatic, and reproductive systems,
has been studied.
Each of these approaches has benefits and deficiencies. The regional approach works very
well if the anatomy course involves cadaver dissection, but falls short when it comes to
understanding the continuity of an entire system throughout the body. Similarly, the
systemic approach fosters an understanding of an entire system throughout the body, but
it is very difficult to coordinate this directly with a cadaver dissection or to acquire sufficient
detail.
Important anatomical terms
The anatomical position
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Figure 1.1 The anatomical position, planes, and terms of location and orientation.
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The anatomical position is the standard reference position of the body used to describe the
location of structures (Fig. 1.1). The body is in the anatomical position when standing
upright with feet together, hands by the side and face looking forward. The mouth is closed
and the facial expression is neutral. The rim of bone under the eyes is in the same
horizontal plane as the top of the opening to the ear, and the eyes are open and focused
on something in the distance. The palms of the hands face forward with the fingers straight
and together and with the pad of the thumb turned 90° to the pads of the fingers. The toes
point forward.
Anatomical planes
Three major groups of planes pass through the body in the anatomical position (Fig. 1.1).
Coronal planes are oriented vertically and divide the body into anterior and posterior
parts.
Sagittal planes also are oriented vertically, but are at right angles to the coronal
planes and divide the body into right and left parts. The plane that passes through the
center of the body dividing it into equal right and left halves is termed the median
sagittal plane.
Transverse, horizontal, or axial planes divide the body into superior and inferior
parts.
Terms to describe location
Anterior (ventral) and posterior (dorsal), medial and lateral, superior and inferior
Three major pairs of terms are used to describe the location of structures relative to the
body as a whole or to other structures (Fig. 1.1).
Anterior (or ventral) and posterior (or dorsal) describe the position of structures
relative to the "front" and "back" of the body. For example, the nose is an anterior
(ventral) structure whereas the vertebral column is a posterior (dorsal) structure. Also,
the nose is anterior to the ears and the vertebral column is posterior to the sternum.
Medial and lateral describe the position of structures relative to the median sagittal
plane and the sides of the body. For example, the thumb is lateral to the little finger.
The nose is in the median sagittal plane and is medial to the eyes, which are in turn
medial to the ears.
Superior and inferior describe structures in reference to the vertical axis of the body.
For example, the head is superior to the shoulders and the knee joint is inferior to the
hip joint.
Proximal and distal, cranial and caudal, and rostral
Other terms used to describe positions include proximal and distal, cranial and caudal, and
rostral.
Proximal and distal are used with reference to being closer to or farther from a
structure's origin, particularly in the limbs. For example, the hand is distal to the elbow
joint. The glenohumeral joint is proximal to the elbow joint. These terms are also used
to describe the relative positions of branches along the course of linear structures,
such as airways, vessels, and nerves. For example, distal branches occur farther away
toward the ends of the system, whereas proximal branches occur closer to and toward
the origin of the system.
Cranial (toward the head) and caudal (toward the tail) are sometimes used instead of
superior and inferior, respectively.
Rostral is used, particularly in the head, to describe the position of a structure with
reference to the nose. For example, the forebrain is rostral to the hindbrain.
Superficial and deep
Two other terms used to describe the position of structures in the body are superficial and
deep. These terms are used to describe the relative positions of two structures with
respect to the surface of the body. For example, the sternum is superficial to the heart, and
the stomach is deep to the abdominal wall.

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