Anatomical Terms of Direction and Planes of Section


>>Hello and welcome to the
Penguin Prof [phonetic] channel. In today’s episode, I
want to introduce you to some directional terms
and planes of section that we’re going to be using
in the study of human anatomy. First of all, I need to describe
the anatomical position. The point of reference that
we’re going to be using and then I’m going to
give you a lot of examples of different terms that we
use to describe body regions and how we sort of
slice and dice images so we can better
understand where things are. Speaking of where things are. Anatomy is not very
different from traveling. So you want to kind
of approach anatomy like you approach
any kind of journey. As many of you know, Flops [phonetic] the
penguin loves to travel. And when you travel just
like when you study anatomy, you need three things. The first thing you need is
a current and correct map. The next thing that you’re going
to need is a point of reference. So that when you get directions
or when you look at the map, things actually make sense. You have to know where
you are, in other words. And then the third thing is you
need a common language, right? In order to be able
to read the map or understand people
if you ask for help. Anatomy is exactly the same. We’re going to need a
correct and a current map. This will come from
your textbook. Anatomy atlases,
tons of resources. You’re going to have to
have a point of reference. You have to know where you are. You have to be able
to use understanding of anatomical position. You have to know
where you are in order for the terms to make sense. And you need to speak
the language of anatomy. Right? We all have to
speak the same language. You know, you’re
going to find yourself in situations like this. You’re going to be looking at — this is actually a section
through the human body. And you may have absolutely
no idea what this is, where are you? You know. We’re going to
need these terms in order to describe what you’re looking at so you can understand
what you’re seeing. The language itself,
the language of anatomy is based
in Latin and Greek. Most of the terms are actually
descriptive even though they can be kind of long. And then of course, we also
have eponyms which are words that are named in
honor of people. Those you just kind
of have to memorize. I do have a couple
of other videos that you might want to look at. How to study anatomy
and medical terminology. And those will help you as you
dive into the study of anatomy but today’s video is about
position and directional terms. So first of all, our point of reference is what we call
the anatomical position. In anatomical position,
we have the patient or the subject standing erect. This can also be in the case
of a cadaver, for example, they’re not going to be standing
obviously but they will be lying on their back with their
belly side facing up and in this same position where the palms are facing
up or facing forward. The thumbs are facing
out to the side. That is the anatomical position. The eyes are facing forward and the feet are
parallel to each other. This is a really good time
to mention, by the way, right from left because
believe it or not, this can be very confusing. It is the subject’s right or
left or the patient’s right or left not the observer
that matters. So, for example, when we divide
the body into four quadrants. You’re looking at, for
example, the upper right and the upper left quadrant
of the subject not you. So I can’t tell you how many
times students will miss points because I will say on an exam,
you know, identify, for example, right or left if I’m asking
about chambers of the heart. And they miss the right or left. And they complain because how
come I didn’t get any credit? Well, you misidentified it. If you have a hard time with
right and left on yourself, this is just a little tip. If you face your
palms away from you, the left hand makes a
little L right there. So that’s kind of helpful, extra
little tip but like I said, you really need this because
if you’re looking at scans. These an intravenous pyelogram. We use it to look
at the renal system but you notice this
little identifier here. So the technician
has to place this when the patient
is getting the scan so that we can very easily see
which side is right or left. And you know, this
becomes really essential because people do make mistakes. And if you misidentify
right from left, you could leave your patient with one diseased kidney
instead of one healthy one. So that’s why we’re really
serious about learning right from left and it does take a
little while to get used to. Okay. So some directional terms
that we’re going to be using. Superior and inferior. We also use cranial and coddle
[phonetic] but I’m going to mention that in
just a second. Superior means towards the head or towards the upper
part of a structure. Inferior means low, right? So away from head or
towards a lower part. And you probably know
these terms anyway. If you feel superior, right,
you feel above everybody else. If you’re feeling inferior, maybe your self-esteem
is not so great. Right? So those are sort
of terms in common use. So I have some examples
for all of these terms. So the lungs are
superior to the liver. All right? So they are above the liver. On the other hand, the small
intestines are inferior to the stomach. Okay? So that’s how
we would use those. Anterior and posterior
can actually refer to the entire body. So for example, in anatomical
position, you see the front of the body or the
anterior part of the body. The other side being
the posterior but often we’re talking about,
from a side view, for example, things that are towards
the front of the body or towards the back of the body. We also use the terms dorsal
and ventral but I’m going to get back to those
in just a second. Just like the cranial
and coddle here. So anterior is towards the front and posterior is towards
the back or behind. So how we might use that as an
example, the ribs are anterior to — they’re in
front of the spine. The occipital bone,
the bone at the back of the head is posterior
to the frontal bone, right? The forehead at the
front of the head. The other terms that
I mentioned. The dorsal, ventral,
cranial, coddle. We use those a lot more often in
non-human animals specifically in quadrupeds because the terms
there make a lot more sense. You will see them in humans but with quadrupeds they’re a
lot more common than you see, you know, with other
animals you’re going to use these terms differently. Most of you probably know
the dorsal fin on a fish. Dorsal and ventral is
color coded in penguins. I always find that, I
don’t know, really handy. Anyway. Lateral and medial. You notice a lot of these
words occur in pairs. So if you draw a line
midway down the body or what we call the
midline, when you move away from the midline, we
call that lateral. So you’re moving
out to the side. When you move toward the
midline, we call that medial. You’re moving toward
the midline. Examples of how we use this, the
lungs are lateral to the heart. The trachea is medial to
— actually both clavicles. So the trachea, your
windpipe, is medial to — it’s actually right
on that midline. It is medial to the
clavicles or your collar bone. Intermediate means between. So for example, the clavicle,
or the collar bone is between. It is intermediate between the
acromion process of the scapula. That’s kind of the bony
part that sticks out. And the sternum or the
breastbone, the upper part of the breastbone
called the manubrium. So the clavicle lies
between those two structures. So you’ll see that
term quite a bit. Proximal and distal. Again, you’re probably familiar
with the roots of these words. Proximal means close to
and distal means far from. And we’re always
talking about the trunk of the body unless
otherwise indicated. So for example, the scapula
is proximal to the humerus. So the scapula or the shoulder
blade is closer to the trunk of the body than the humerus. The wrist or the bones of the
wrist which we call the carpals, they are distal to the elbow. That means that these
bones, the wrist bones, are farther from the trunk of
the body in anatomical position, of course, than is the elbow. So we use proximal and
distal quite a bit. Superficial or external
deep or internal. So you can pick and choose
which terms that you like. You’re going to see both of
them in very, very common use. Superficial or external means
toward the body’s surface. Deep or internal,
obviously, means deep or away from the body surface. We use these a lot when you’re
talking about layers of things. So, for example, here’s
a layer through the skin. The epidermis is
superficial to the dermis. Meaning it is external to. It is closer to the outside. The hypodermis where you see
that layer of subcutaneous fat. That’s called the hypodermis,
hypo actually means below. That is deep to the dermis. And then terms like
hypodermic needles, right? Makes sense. Those are needles that are
injected into the hypodermis. Contralateral and
ipsilateral refer to the sidedness of things. Contra means against. So contralateral meaning
on opposite sides. Ipsi comes from a Latin
root that means the same. So for example, your right and
left arms or wings depending if you’re a penguin or not are
contralateral but your right arm or wing and your right
foot, those are ipsilateral. Those are on the same side. And you might think, well you
know this is pretty obvious. Why would you need
a term for that? This is going to be really
helpful when we start talking about different skeletal
muscles. Many of them that occur in
pairs they can either contract together and they cause one type
of action or they can contract, you know, only one
side or the other. So these terms actually will be
very useful but we don’t need to normally refer to
the arms and legs. It’s pretty obvious, I think. Okay. And a couple of notes
here on planes of section and how we slice
and dice things up. So here’s a little
pop quiz for you. What are these? What are those? Well it’s kind of
a trick question because they’re actually two
images of the same thing. Why do they look so
different though? Right. This is a question that my students have
all the time especially when we jump into histology. They look so different. The reason is they’re
cut in different planes. So we have different
planes of section. You see the cross
section on one side and the longitudinal
section on the other. We’re going to explain
those in just a second but let me give you an
example of what I mean by it’s the same thing. Here’s another little pop quiz. What are these? Okay. Hopefully this
is not much of a quiz and you recognize this. But it’s exactly
the same answer. It’s a cucumber but
it’s a cucumber in two different sections. Okay. Now you get it, right? So one different
style of slicing, we call a cross section,
and what you’re left with is a cucumber that’s round. The other side, when
you cut it lengthwise, you have a longitudinal section and you have a long
skinny piece of cucumber. Now, because you have
experienced lots of cucumbers in your life, it doesn’t
matter how I cut it, you know what it is but in
histology and in anatomy, you just haven’t seen
enough of this stuff so you don’t yet recognize it. So these are the
different planes of section. We have the coronal
or frontal section. The coronal or frontal
plane can actually divide into the anterior
and posterior side. We have a sagittal or
longitudinal plane. That’s a lengthwise slice. If you cut right
down the midline, we call that a midsagittal
slice or midsagittal plane. And then we have the
transverse or the cross section. And that’s going to be
how you cut a cucumber into little circles. Just to give you three
really quick examples. Right through the brain,
we’re going to look at the three different planes of
sections that I just mentioned so that you can see
that, of course, you’re looking at a human brain. These are all MRI scans
of the same thing. The same structure but notice
they look dramatically different and that’s because when you
change the way that you look at something, you’re going to see dramatically different
structures and you’re going to use different types of
imaging to see different things. But it is a really challenging
part of anatomy especially when you get into cross
sectional anatomy. It’s difficult to know
sometimes where you are. Some tips that I have on this. You really just need to look at as many different
references as possible. Look from as many
angles at the same thing. So you start to see
the patterns. The other thing is you
want to read the captions. The captions of every image
will tell you what is the plane of section. How was that image made? You need to know that in order
to what you’re looking at. So because I’m going to get
a lot of questions on this, that image I showed
you in the beginning. Now you can see the
anterior and the posterior. What I had labeled
there, that is the aorta. That’s the biggest
artery of the body where blood leaves the heart
for systemic circulation. As always, I hope
that this was helpful. Thank you so much for visiting
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