Back to the exam of the human.
I suppose I never specified that it was humans that was the focus of this series, but consider it now specified. There may be some cross-over to the examination of other animals, and potentially to alien species. But I don’t want lawyers from some star system 100 light years away sending a subpoena because I mislead readers by not mentioning the fact that the crxyynsnnt was distal to the ancrunsty thingy. I also don’t want to be attacked by wombats.
By the way, I was kidding about the crxyynsnnt. It is nowhere near the ancrunsty thingy.
My last post was the first in a series on the upper extremity, otherwise known as the arm. One of the problems with the examination of the arms (and legs, for that matter) is identifying the relative location of things. Describing just where exactly bumps or pains are on the body would be much easier if we simply did this:
Life would certainly be much easier if we did that. Sadly, doctors adhere to the philosophy: “Why use a picture when you can use a thousand illegible Latin words?” This means that we need to use all sorts of terms that describe where things are. Here are some of those terms:
Medial and Lateral
Medial – Toward the middle, or toward the vertical midline of the body or organ. For example, saying “You have a zit on the medial aspect of your right eyebrow,” means that your festering follicle is on the side of your eyebrow furthest from your ear.
Lateral – Away from the middle, or away from the vertical midline of the body. So saying “You have another zit that is lateral to that huge one I just mentioned,” means that the first zit has a friend that prefers the climate nearer to the ear.
Medial and lateral can be confusing when used in reference to things on the arms and legs. The problem is that the part of your arm that is closest to the midline of your body depends on how you are holding them.
- If your palms are forward and your arms are at your side, your pinkies are closest to midline.
- If you keep your palms forward but raise your arms over your head, the thumbs are closest to midline.
- Then if you turn your palms around and hold your arms over your head, the pinkies are closest to midline.
- If you put your arms down and keep your palms facing backward, the thumbs are once again closest to midline.
- If you hold your arms out at a 90 degree angle, both the thumbs and pinkies are closest to midline.
If you do all of these in a public place, you will get a lot of inquisitive looks from people and you might get questioned by the police.
So the convention is to use medial and lateral as they occur with the hands down at the side and the palms facing forward. Why did they do it this way? I am sure it was rammed through congress as a hidden paragraph in some farming subsidy bill. I never had a say in this convention.
Another confusing thing about medial and lateral is that it can be used locally and globally. For instance, the medial part of a blood vessel is the middle of that vessel. So let’s say I have an unfortunate encounter with a wombat and am bitten on the big toe:
Those are not my toes, by the way. They kind of look like they’ve been stretched out. No wonder the wombat bit them.
So the question is, was the bite on the medial or lateral part of this unfortunately ugly toe? It depends on your frame of reference:
- If you use the toe as the frame of reference, the bite is lateral to the middle of the toe.
- If you use the foot as the frame of reference, the bite is on the lateral aspect, as it is away from the middle of the foot.
- If you use the body of this person (which hopefully looks better than the foot), then it is on the medial aspect, as the big toe is closer to midline.
- If you use the position of the wombat, then you really have trouble, as wombats are very mobile.
The convention used here (pushed through congress on a bill that makes English the official language of Idaho) is to use the body as the reference. This wombat bite is on the medial aspect of the foot.
Proximal and Distal
On things like the arms and legs that move around a lot, a useful description of location is the distance things are from where the body part attaches to the torso. The terms used here are proximal and distal.
Proximal - situated nearer to the center of the body or the point of attachment. This generally refers to arms and legs, as they are the main things that attach to the body.
Distal – Situated further from the point of attachment.
In this example, the Bulbasaur tattoo on Sly’s arm is proximal to the Pikachu tattoo.
Bow and Stern
There are several terms for the front and back of the body. The front of the body is referred to as the anterior or ventral side, while the back is referred to as the posterior or dorsal side. Just why they couldn’t pick one or the other is open to question. I suspect this thing got caught up in committee and then was filibustered in the senate. The difference in these terms come clear when we look to the animal kingdom. The fin that sticks out of the water when a lawyer shark swims is the dorsal fin. For animals that are longer in the horizontal direction, the terms anterior and posterior are confusing. Is the head of the venture capitalist shark anterior, or is the belly?
Animals that are the same in both vertical and horizontal axes (like wombats) are even more difficult.
Ahead and Afoot
Finally, we have that vertical access in humans (horizontal in sharks, and wombats). This is the most confusing of all. Something going toward the head is called one of three things:
While the tail-ward direction has two names:
I suspect the terms inferior and superior were shot down by those liberals (like horsey boy) who wondered if the self image of things away from the head would be harmed. But then there is the fact that we have only one other term for tailward and two for headward. This was probably the conservatives sticking it to them by keeping the lower parts at a disadvantage.
Oh when will you boys and girls stop fighting?
So that is the confusion of it all. There are more – like palmar, volar, and plantar – but I won’t bother you with that.
There has got to be a better way, folks. I mean, the anterior medial aspect of my cranium is hurting. It’s truly a pain in the inferior posterior medial torso.
Perhaps we should go to Washington DC with a bunch of bloggers, some specialist and some primary care (excluding patients, of course), and voice our opinions on this mess.
Nah. That’s a crazy idea!This material, written by me, is free to re-post and share under the Creative Commons agreement. In other words, use it all you want; just give me credit.