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View Full Version : Anatomy practice -- the rib cage


jfrancis
June 12th, 2004, 03:00 PM
The rib cage, along with the skull and the pelvis, is one of the important, fairly unchanging bony structures of the figure.

I have a bit of a hard time completely grasping the shape of its volume. Here's a bit of what I know about it.

The form is a lot like an egg with the top and bottom cut off.

The bones "sag" off of the spine so that the front every rib is lower than the back.

The first set of ribs is the same as the neck hole.

The spine seems fairly deep inside the rib cage because the ribs arch off the spine like valentine hearts, not simple hoops.

The ribcage is widest around the eighth ribs.

Here is a simplified approximation of the relationship between the spinal column and the rib cage as I understand it. It's not perfect, and the stripes are meant to convey surface information, not to be literal tracings of each bone. But I think it's a useful tool in grasping the rib cage.

http://www.digitalartform.com/assets/gfxArtist/WIP/ribCollage1.jpg

If you can capture the spine and rib cage, and then hang the shoulder girdles (the scapulae in back and clavicles in front) off of it properly, you've gone a long way toward defining the form of the upper body.

winjer
June 12th, 2004, 11:24 PM
An important bit you left out is the sternum. Its a great landmark that can tell you where to run neck muscles, pectorals and clavicles to. All the ribs start from the spinal vertabrae and run around to the sternum. The general shape you have is pretty good.

jfrancis
June 13th, 2004, 12:37 AM
Good point. The way the sternum defines the pit of the neck, the little angle change where the second set of ribs hits and the manubrium becomes the gladiolus -- all important.

the main thing I was finding I was having trouble with was just conceptualizing the gross shape of the rib cage -- especially in off axis views.

I know the details pretty well. I just feel "cold" about what I know -- like I don't quite "feel" it. If I had a skeleton, I'd draw it a bit from off axis angles. The books tend to focus on schematic views.

I think just going through this process has caused me to have to understand the forms better.