JAMES S. WHITE: Before we go much further,
we need to have some additional conversation about the nomenclature,
or how structures are named, with regard to the upper limb
and other body parts as they're related to something
called the anatomic position.
So if we look at the next slide, what you're seeing here
are two adults standing upright with their feet together,
and the palms of their hands facing forward.
In both of these individuals, what you're seeing
is what we describe as being the anatomic position.
And utilizing a series of planes or positions
where we actually look like we're cutting through the human body in three
mutually perpendicular planes, we arrive at a whole additional set
of terminology to describe where anatomic structures are
relative to one another, and relative to the plane that we are discussing.
For example, we can start this discussion by making an incision
or developing a plane that starts, for example, at the nose,
and passes directly through the back of the body wall-- this case the skull,
or the neck, or the trunk, or any other body part.
And when we create a plane that goes, in essence, from the front of the body
out the back wall of the body, that's considered to be the sagittal plane.
And based on the sagittal plane, we arrive
at a series of terms, two of them that describe
the relationships of anatomic structures relative to that plane.
For example, if a structure is closer to this so-called midsagittal plane that's
going right through the middle of the body from front to back,
that structure is considered to be medial.
And if a structure lies further away from
that mid-sagittal or sagittal plane, we describe that structure
as being lateral.
For example, in the anatomic position, there's the thumb,
and there's the pinky.
Obviously, two of our topics of discussion in the upper limb.
But we would say correctly in the anatomic position,
the thumb is lateral to the pinky, because it is further away
from this midsagittal plane.
We would also say in the same conversation
that the eye is medial to the ear, because it is situated closer
to that midsagittal plane.
Then oriented to exactly perpendicular to that
is another plane that basically goes, for example, beginning
at the level of one ear, and it goes out through the other ear.
So this second plane is called a frontal, or a coronal plane.
And it gives us, again, two additional anatomic terms
that describe the relationships of structures
relative to that coronal plane.
Any structure that lies closer to the front of the body
is considered to be anterior.
In contrast, any structure that lies closer to the back,
or the back of the body, is posterior.
For example, the umbilicus or the belly button
is a key anatomic landmarks on the anterior abdominal wall,
whereas basically the vertebral column that we can't see well here
is positioned in the midline in the posterior part of the body wall.
So again, we have a series of anatomic terms
that are describing the position of anatomic structures
relative to a coronal plane.
For example, the palm of the hand that we illustrated in lecture one,
faces forward.
Therefore, the palm other hand is anterior to the back
of the hand, which is called the dorsal aspect of the hand.
So again, we have two additional terms, which we will use quite readily,
to describe the relationship and position, for example,
of muscles and joints.
For example, this body part right here would
be the anterior aspect of the arm, and the part
of the body that's on the other side of that
would be the posterior aspect of the arm.
And we're going to organize muscles that are found in the arm in that exact way,
as an example.
Then, mutually perpendicular to the sagittal and the coronal
plane is a horizontal, or a transverse plane.
And obviously, the transverse plane basically
can occur at any level of the body.
We can have a transverse plane, as illustrated here through the forearm,
we could have a transverse plane through the arm, and so on.
But again, the presence of the transverse plane
creates two additional terms, describing structures relative to it.
Basically, structures that are toward the head,
or that lie above the transverse plane that's illustrated here,
are considered to be superior.
This doesn't mean that they are better.
They are just superior in terms of the anatomical position.
Whereas a structure that is situated below this transverse or horizontal
plane will be referred to as something that is inferior.
So looking at this anatomically, let's shift our attention to our friend
over here on the left, we would say using this terminology
that the elbow joint is superior to the hand.
But we would say also that the elbow joint is inferior to the shoulder,
based on the anatomic position relative to a hypothetical transverse plane.
Then, we will also be using two other terms that are specifically related
to, in this case, the upper limb.
Anatomists and health professionals also refer
to a series of structures that might be situated closer or further
away from a reference point, and the reference
point that we use for the upper limb might be at the area, for example,
of the shoulder.
So using the shoulder as a reference point,
we would describe structures that are either closer to the reference point,
meaning that they are proximal, compared with structures
that are further away from the reference point, which means they are distal.
So we will use the terms proximal and distal
with some frequency when we talk about structures relative to the shoulder.
So using that terminology, we would say that the arm is
proximal to the forearm, or the hand is distal to the forearm, using
this anatomic terminology.
So we're going to get used to using these terms
as we go forward when we're describing the anatomy of the upper limb.