Thursday, March 22, 2007

Hard Fact


In my para-previous post, I referred to an injury to my medial digital nerve. Because our bodies are movable, it's necessary to have standard terminology in reference to positions; when your hand is palm up, medial and lateral are the opposite of when it's palm down. Thus, the "Anatomic Position," the reference posture by which, among other things, medial and lateral are determined. This guy is in it.

And here's something amusing. In addition to medial/lateral we refer to "dorsal" and "ventral." In the anatomic position, ventral is the front, and dorsal is the back. We're seeing this guy's ventral surfaces. So what? Well, there are these things called the dorsal veins of the penis. And whaddya know? In the specimen standing there at the top of this post, we're looking at the surface on which those veins run. But it's ventral! So there's only one explanation: in the anatomic position, the penis is erect! Those anatomists! Wonder what goes on in their labs...

[Short post. Long series coming up.]

14 comments:

Richard said...

That's hilarious!

I never thought of that.

Erica said...

I too have wondered what makes the dorsal vein dorsal - but even my twisted mind failed to make the leap to a blue joke that goes as far back as anatomical position... Thanks for the grins.

The Peanut Gallery said...

That is one of the few things I remember from gross anatomy - that the anatomical position of the penis is erect. That was a real giggle inducer for us first year.

Anonymous said...

petaller? what does that mean?

Sid Schwab said...

I used the diagram because it demonstrates the "anatomic position." The labels, well, it's the best I could find. I ignored them, and you should, too.

beajerry said...

As many women age, their superior breast surfaces become ventral?

Greg P said...

Everything comes down to precision in language. I think "medial digital nerve" is not so clear. We can talk about the medial and lateral aspects of the upper extremities, with the anatomic position being, as in your diagram, arms extended at the sides, palms forward.
Sometimes the term "mesial" is used to refer to something toward the center of a structure, in this case the mesial part of the arm would be toward the central axis of the arm.
My own preference is to use the terms "radial aspect" or "ulnar aspect" to relate things to the forearm bones as reference points.

Wyatt said...

Heh, those anatomists. Isn't the anatomical position supine, though, in which case gravity no longer exerts its influence and the little guy flips up revealing its underbelly?

Sid Schwab said...

Pretty sure the anatomic position is just like the guy in my picture.... Standing, er, erect.

Anonymous said...

what about the dorsalis pedis artery? It's on the superior (top) face of foot, so shouldn't it be called superioris pedis?

I thought that all the terms came from the first dissections, where the subject would be supine (why else were the hands positioned that way?), but funny theory.

James Ryan said...

hellooooo...my name is ryan, i'm a 4th year medical student at manchester uni, england. I'm currently doing a project on andreas vesalius and the dignity of anatomical teaching and the dissection process and would like to know whether anyone here knows exactly where the anatomical position originates from? My theories are the virtruvian man and Christ showing hsi wounds...its been suggested that its the way the body lies on the table but naturally the body wouldn't have its thumbs pointing outwards with its palms open...any ideas? email james.hamill@student.manchester.ac.uk THANKS!

James Ryan said...

hellooooo...my name is ryan, i'm a 4th year medical student at manchester uni, england. I'm currently doing a project on andreas vesalius and the dignity of anatomical teaching and the dissection process and would like to know whether anyone here knows exactly where the anatomical position originates from? My theories are the virtruvian man and Christ showing hsi wounds...its been suggested that its the way the body lies on the table but naturally the body wouldn't have its thumbs pointing outwards with its palms open...any ideas? email james.hamill@student.manchester.ac.uk THANKS!

Anonymous said...

why is the anterior surface of the foot even called dorsal surface then? sure we can make the penis conform to the ventral and dorsal terms by imagining it in the erect position, so that the ventral surface becomes anterior and the dorsal surface which is continuous with the anterior surface of the abdomen becomes posterior. but i could not possibly think of a way of reorienting the foot into a position such that its dorsal surface would be consistent with such anatomic orientation. error here lies in the assumption that the terms 'ventral' and 'dorsal' are always synonymous to the terms 'anterior' and 'posterior'.

the penis and the foot are parts of the human anatomy that are more horizontally oriented than the rest of the body in the standard anatomic position. in that light, anatomists saw it fit to name their surfaces according to how the body surfaces of lower animals that creep are named, hence the ventral and dorsal terms. in organisms that creep, the dorsal surface is the surface that faces upward or faces the ceiling or the sky, and the belly or the surface that faces the ground is called the ventral surface. this is the most consistent reason of why the surfaces of the penis and the foot are named as such. but of course, we name the ventral surface of the foot as plantar surface because it is more descriptive. an exception to this rule are the hands in the standard anatomic position, because 'dorsal' in this instance is synonymous to 'posterior'. however we can think of the hands as the upper extremity homologue of the foot. since the plantar area is homologous to the palmar area, it would be reasonable to call the opposite surface of the hand as 'dorsum' also.

with that being said, i don't think it really matters if the penis is erect or flaccid in the standard anatomic position, since whether erect or not, the dorsal and the ventral surfaces will still be the same. however, i have yet to encounter an official anatomic illustration portraying the penis as erect in the standard anatomic position. so i guess i disagree with you. the standard anatomic position of the penis is flaccid and hanging just like what would be expected in a naked man standing erect with the upper extremities on the sides, slightly abducted, with palms facing forward and the lower extremities slightly apart, with the foot on the ground pointing forward.

Sidney Schwab said...

You might be right, although I'm not sure I agree that dorsal and ventral are the same whether erect or flaccid.