Terminology
Student Learning Objectives:
•
Define and use common directional terminology
Terms to be identified:
Anatomical position
Superior
Inferior
Anterior
Posterior
Ventral
Dorsal
Midline
Medial
Lateral
Superficial
Deep
Introduction
Directional terminology is a standard set of words that are used in anatomy and the medical
field. Directional terminology is used to describe the relationship of a structure to the body as a
whole or to another body part. Many of the structures that you will learn about in this course
have parts of the name that use directional terms. In this exercise, we will look at the definitions
of some of these commonly used terms. Although there is no quiz on this material, you should
find it useful in learning the anatomy of most of the body organs and systems.
Anatomical Position
In order to properly use directional terminology, we must first place the body in anatomical
position. In anatomical position, the individual is standing erect, facing the viewer, with hands at
the sides, and palms and toes pointing forward. An individual in this position has all of the bones
in the body aligned side-by-side without crossing over one another and ensures that the body
parts are always in a standard location.
This is the position which you should think of when you are using directional terminology. In
most cases, the individual is not in anatomical position – when was the last time you were
standing with your hands at your sides and your palms forward! Most of the time, we are
standing in a leisurely position, or sitting, or laying down. When you are using directional
terminology, you must always think of the person in anatomical position, even if they are not.
Even though your body has changed position in space, your body parts have not moved from their
original position on your body.
Directional Terms
Most of the directional terms come in pairs – two words that have opposite meanings.
The first pair is superior and inferior. The term superior means “above”. The term
inferior means “below”. Here are a few examples:
ƒ
ƒ
ƒ
The pelvis is inferior to the chest.
The nose is superior to the mouth.
The mouth is inferior to the nose.
The next set is anterior and posterior. The term anterior means “front”. The term
posterior means “back”. Again, a few examples:
ƒ
ƒ
ƒ
The nose is an anterior structure of the body.
The spinal column is posterior to the breastbone.
The eyes are anterior to the ears.
The next pair is similar to anterior and posterior. Ventral and dorsal can be used
interchangeably with anterior and posterior when talking about structures that are not part
of the head. Ventral means “front” and can be used interchangeably with the term
anterior when referring to structures of the body that are not part of the head. Dorsal
means “back” and can be interchangeably with the term posterior when referring to
structures that are not part of the head.
Due to the human's upright, two-legged stance, the chin has rotated downward to improve
vision (and to keep you from drowning in the rain!). This alters the position of ventral
and dorsal on the head. As a result, dorsal in the head region refers to structures that are
towards the “top of the head”, while ventral in the head region refers to structures that are
towards the “area under the chin”. Generally in the human, the terms dorsal and ventral
are reserved for descriptions of brain structures only.
ƒ
ƒ
ƒ
The palms are on the ventral surface of the hand.
The vertebral column is dorsal to the breastbone.
The nose is on the ventral aspect of the face.
The next pair, medial and lateral refer to the closeness of a structure to the midline of the
body. The midline is an imaginary line drawn down the center of the body from head to
toe that divides the body into equivalent left and right halves. The term medial refers to
structures that are close to the midline. The term lateral refers to structures that are
further away from the midline, or towards the sides. A few examples of how these terms
might be used:
ƒ
ƒ
ƒ
The eyes are lateral to the nose.
The nose is a medial structure of the head.
The breasts are lateral structures of the body.
Students sometimes have difficulty using this pair of terms when structures of the arms
and legs are involved. Remember that these terms are always referencing the midline of
the body, not a midline on the limb. Also, remember anatomical position, because this
has a primary effect on the position of the hands.
ƒ
ƒ
The thumb is a lateral structure of the hand.
The ring finger is medial to the thumb.
The next pair of terms are generally used to describe structures on the limbs which are
unique in the fact that they are attached at one end and free at the other end. This pair of
terms refers to how close to the point of attachment a structure is. Proximal means that a
structure is close (or in close proximity) to the point of attachment. Distal means that a
structure is further (or at a distance) from the point of attachment. For the arm, reference
is to the shoulder. With the leg, reference is to the hip. Some examples of using these
terms two terms to describe structural relationships on the limbs:
ƒ
ƒ
ƒ
The hand is distal to the elbow.
The knee is proximal to the ankle.
The fingers are distal structures.
Proximal and distal are also sometimes used to describe parts of long tubular organs, such
as the small intestine and kidney tubules. Here, the attachment point is the beginning of
the tube. Proximal, then, would refer to structures close to the start of the tube and distal
would refer to structures near the end of the tube.
The final pair of terms refer to how close a structure is to the surface. Superficial refers
to a structure that is nearer the surface of the body or organ. Deep refers to a structure
that is further away from the surface of the body or organ. For example:
ƒ
ƒ
ƒ
The skin is superficial to the muscle.
The bones are deep to the muscles.
Connective tissues are usually found deep to epithelium.
You will see many of these words throughout the semester as we discuss various parts of
the body. You may want to periodically refer back to this handout when the words come
up again in future exercises.