Paramedic 2.02 – Anatomy and Physiology: Planes and Sections of the Body

Paramedic 2.02 – Anatomy and Physiology: Planes and Sections of the Body


In this module, we will define various anatomical
planes and sections of the body. Once completed with this module, you should
be able to identify the planes and sections of the body and define directional and positional
terms used in anatomical landmarking. When defining anatomical structures in the
body, it can be helpful to utilize anatomical landmarks or to look at these structures from
specific points of view. To facilitate some of our future discussions on anatomy and physiology,
we need to first identify planes and section of the human body. These planes are essentially
cross-sections of the body that allow us to view anatomical structures from consistent,
standardized perspectives. At the onset, it is important to begin with
a standardized view of the human body so that references to anatomical structures and landmarks
are consistent. This is the purpose of what is known as anatomic position. In this position,
the person is standing, facing the provider, with the arms at the side, palms forward (toward
the provider), and the thumbs pointing away from the body. The frontal, or coronal, plane splits the
body in half along a vertical axis between the front and back. Imagine a thin sheet of
glass that slices the body from the head to the feet, from ear-to-ear, separating the
front of the body from the back. The front aspect of the body is referred to as the ventral
section and the back portion is the dorsal section. For the next plane, we will split the body
vertically again, but this time, rather than splitting the body between front and back,
the plane will divide the body between left and right. This sagittal, or lateral, plane
does not necessarily need to split the body evenly from left to right; it can be offset
to one side or the other. If this imaginary line or plane (referred to as the sagittal
axis) does indeed split the patient evenly into left and right halves, running down the
center of the nose and navel, the plane is referred to as mid-sagittal or the midline. Generally speaking, moving away from the mid-sagittal
axis is called lateral, although the two separate sides can be further defined by either left
or right. In doing so, however, it is important to use the patient’s, not the provider’s,
left and right. When referencing lateral structures from the
sagittal plane, it is important to note that the observer’s right is on the opposite
side from the subject’s right when the subject is in the anatomical position. (The same goes
for the left as well.) When referring to the patient’s anatomical structures in relationship
to the sagittal plane, be sure to always refer to the patient’s left or right side, not
your left or right as you are observing the patient. That way, regardless of whether the
patient is prone, supine, facing you, looking away, or whatever, the landmarks are always
constant as the patient’s left and right are constant, even if your perspective as
an observer or medical provider change in relationship to the patient’s positioning. If we split the body horizontally along the
waist, separating the top of the body from the bottom, this creates the transverse (or
axial) plane. The top section of the body given this transverse plane is referred to
as the cranial section. The bottom section is the caudal section. When using medical imagery, these different
planes or perspectives are used to take either cross-sections or longitudinal sections of
the body. A cross-section is one taken horizontally across the body, parallel to the transverse
plane. A longitudinal section is taken across the length (or longer portion) of the body,
parallel with either the frontal or sagittal plane. Returning back to anatomical position, we
should also look at some terms used to locate or describe body parts, organs, and features
in relation to other anatomical landmarks. As you move up and down the body, between
the feet and head, features located closer to the head are superior to those that are
located closer to the feet, and those closer to the feet are inferior to those that are
closer to the head. Moving between the front and back of the body,
features toward the front of the body are anterior to those toward the back, and those
toward the back are posterior to those toward the front. (While the terms ventral and dorsal
could also be used for anterior and posterior, respectively, those terms are used more frequently
when referring to the anatomy of other animals, not humans.) Once again referencing the midline (the mid-sagittal
plane), as you move away from the midline, features further away from the midline are
lateral to those that are closer. Inversely, features that are closer to the midline are
medial to those that are further away. When dealing with the extremities, features
further away from the body’s core are distal to those that are closer, while features closer
to the body’s core are proximal to those that are further away (those that are closer
to the hands or feet). Lastly, we also need to recognize movement
in and out of the body, from the surface of the skin into the core of the body and vice
versa. Anything closer to the exterior surface of the skin is superficial to features closer
to the core. Those closer to the core are considered deep to those closer to the exterior
of the skin. Where joints are involved in the extremities,
moving a distal point of an extremity toward the trunk of the body is called flexion. Inversely,
moving or extending that distal point of an extremity from a flexed position to a more
neutral or anatomical position away from the trunk of the body is called extension. The
anatomical position that we discussed earlier in the module has all the extremities in extension. If a joint flexes too far, it is said to have
suffered from hyperflexion. Inversely, hyperextension occurs when a joint extends beyond its maximum
level, which typically means bending backward. In reference to the body’s midline, moving
an extremity away from the midline is called abduction. (If it helps, while somewhat corny,
think of an alien abduction… If abducted by aliens, a person is taken away from the
earth. It is the same with abduction in this context, only the extremity is being moved
away from the midline.) Inversely, returning or moving an extremity
to the midline is adduction. (Think of it as “adding” the extremity to the midline.
Thus, it is called “‘add’-uction.”) There are also some additional positional
terms that we will quickly define here. To supinate is to turn the palm of the hands
up, and to pronate is to turn the palm of the hands down. When rotating a limb, internal rotation occurs
when the limb is rotated toward the midline, and external rotation is when the limb is
rotated away from the midline of the body. Body parts or conditions that appear or occur
on both sides of the body’s midline simultaneously are said to be bilateral. The eyes and lungs
are common examples of bilateral organs in the body. Body parts or conditions that appear or occur
on only one side of the body are unilateral. The spleen only exists on the left side of
the body; therefore, it is a unilateral organ. Abdominal pain on only one side of the body
is unilateral pain. If two things exist or occur on the same side
of the body, they are ipsilateral. If they are occurring on opposite sides of the body,
then they are contralateral. A person suffering from a stroke affecting the left side of the
brain, for instance, would commonly have left-sided facial drooping, meaning the facial drooping
is ipsilateral to the side of the brain injury, while extremity weakness would occur on the
right side of the body, contralateral to the side of the brain injury. That completes this module on planes and sections
of the body and you should now be able to identify the different planes and sections
of the body and define directional and positional terms used when describing anatomical features
of the body in relationship to other body regions or areas. This presentation was prepared by Waukesha
County Technical College in Pewaukee, Wisconsin and is distributed with an attribution, non-commercial,
share alike 4.0 international Creative Commons license. Copyright 2019, Waukesha County Technical
College. For information on WCTC’s numerous fire and EMS educational offerings, please
visit us online at WCTC.edu.

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