Tuesday, October 29, 2013

A Banjo Player's Forearm: Let's Get Lost!

I was in a class at the Old Town School of Folk Music recently, and I saw this:

Well, I'm lying. What I actually saw was this:

Steve's forearm muscles are quite clear in the first photo, and in the photo above they've been diagrammed 
and labeled. The extensor group is shown in blue, and a small portion of the flexor group is shown in green. 
The ulna, which indicates a dividing line between the two groups, can also be seen. Muscles are as follows: ECRL (extensor carpi radialis longus); ECRB (extensor carpi radialis brevis); ED (extensor digitorum); EDM (extensor digiti minimi); ECU (extensor carpi ulnaris); Anc (anconeus); FCU (flexor carpi ulnalis-in the flexor group and, as such, shown in green); APL (abductor pollucis longus) and EPB (extensor pollucis brevis.) The tendon of extensor pollucis longus can be seen just to the right of the EPB muscle, but it was too small to label!)
This arm, readers, is that of one of my beloved music teachers, Steve Rosen, as he plays his banjo during the Old Time Ensemble at the Old Town School of Folk Music here in Chicago. As he played on this balmy summer evening, his forearm extensors danced. How could I help but dig out my phone to catch a quick photo?

Don't you love that feeling of complete absorption in an activity? Being so consumed, so lost in your work, that hours pass unnoticed? I often feel this way about this blog. And about playing music. If you don't know this feeling, I highly recommend you find a way to experience it. Love of your subject, intense concentration, and a sense of productivity is a combination difficult to match.

I think the reason anatomy blogging, art, and music all fall into category for me is that all three of them combine a puzzle-like quality with a wide degree of latitude for creative expression. Learning an instrument is an especially difficult puzzle, but it can still be solved in a number of ways. There is no single correct solution. There's room to experiment, embellish, and make any tune your own. It's no wonder it's so easy to become entranced in the process.

I'd have never learned any instruments in the first place if it wasn't for the talented and diverse faculty at the Old Town School. Of all the wonderful instructors in this fine institution, I've taken the most courses from Steve (above) and Paul Tyler, including fiddle, guitar, banjo, and a group course called the Old Time Ensemble.

This is a shot from last summer's class, at the end of which Paul and Steve celebrated with a little cherry cheesecake! The Wednesday evening section of this class has been team taught by these two for years, Entertaining and informative, it's a popular class that is taken repeatedly (sometimes for years) by many of Paul and Steve's devoted students and fans. Each of these gentlemen has an extensive background in Old Time string music, including time together in the Volo Bogtrotters, a... well... modern day Old Time string band. Watch them play a wonderful tune, Lost Indian, here.

Finally, there is more to Steve than his forearm or his banjo. He has many other physical features and interests. So let's diagram these as well:

Here is another diagram that more clearly shows the division of the two forearm compartments:

And a view of these muscles exposed:

You can read more about these muscles in the following posts:

I promised I'll get off forearms next time! Again, to learn more about Steve, go here. Better yet, treat yourself to a little of his banjo playing here.

Until next time!

Monday, October 21, 2013

More Advanced Anatomy Work: Roberto Almanza

I was sorting through student work from last Spring and I happened upon several anatomical pencil drawings by a former student, Roberto Almanza. They needed to be shared, so tonight's quick post is just for this purpose. 

The first piece shows the posterior torso. Notice the protruding spinous process of the C7 vertebra jutting out in the center of the trapezius muscle's tendinous floor. Also notice how Roberto renders the trapezius muscle's undulations as it wraps over the infraspinatous muscles on either side. I also like that he rendered the deltoid muscle's separate sections, and (this is my favorite part) he has included the posterior portion of the serratus anterior muscle as it shows through the latissimus dorsi muscles. Most artists forget this. We can also see teres minor, teres major, the lumbar sheath (and the bulge of the sacrospinalis muscle deep to it) and a small portion of the external oblique muscles. To read more about the posterior torso muscles, go to The Posterior Torso Muscles: Let's Go Back in Time and The Posterior Back Muscles, Part 2: Under the Radar. 

Next we have the anterior torso muscles. I like the way Roberto has shown the cut away and peeled back rectus sheath, allowing the rectus abdominis muscle, just deep to it, show clearly. Also seen here are the sternocleidomastoid muscles, the pectoralis major muscles, the serratus anterior muscles, the external obliques, and the right iliac crest. Read more about this part of the body at The Anterior Torso: Peel Away the Layers.

I only required the students to label one of these drawings, and Roberto chose to label this one of the head and anterior neck. This one is mostly bone oriented, but we also see several anterior neck muscles, including sternocleidomastoid, sternohyoid and omohyoid. We also can see the thyroid and cricoid cartilages at the proximal end of the trachea, peeking out just between the sternohyoid muscles. Read more about the anterior neck in Anterior Neck: Theme and Variations and more about the head at The Head: Part 1 of Oh My Gosh, Who Knows?

Next we have the muscles of the dorsal forearm. 

And here's a close-up, in which we can more clearly see the muscles brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor carpi ulnaris, abductor pollucis longus and extensor pollucis longus. Read more about the forearms in The Dorsal Forearm, Part 1: Compartment Search, The Dorsal Forearm, Part 2: Which Side are You On, Anyway?, and The Dorsal Forearm, Part 3: The Final Chapter. 

And finally we have Roberto's leg rendering. This shows a lateral view of the left leg, including (among others) the peroneous longus and brevis muscles on the lateral lower leg, the gastrocnemius muscle on the posterior lower leg, the vastus lateralus, gluteus medius and maximus muscles, and the iliotibial band on the lateral thigh. To read more about the lateral leg, go to The Lateral Knee, A Change of Scenery, The

Many thanks to Roberto Almanza for these images. Please do yourself a favor and check out Roberto's illustration work here.

 I think I will get caught up on the elbow joint next. Until next time!

Saturday, August 17, 2013

The Anterior Torso: Peel Away The Layers

Hello everyone! I hope you've been enjoying the lazy days of summer. I certainly have— particularly the lazy part. I've been promising for months to continue posting student work from my Advanced Anatomy class, but other pursuits, such as drawing, painting, playing music, swimming, and sitting on the deck staring into space have gotten in the way. Well, today I rectify myself.

You saw Izzy Carranza's clay spine model in The Vertebral Column: Have Some Backbone, and the lovely watercolor work of Jeff Sant in A Beautiful Exaggeration: More Student Forearm Paintings. This time it's Justine Herrera's turn. Justine took my advanced class in the spring of 2012, so this is long overdue. Justine is a lovely, talented and hard working individual whom I've had the pleasure of knowing for several years. You can view more of her work here. For her final Advanced Anatomy assignment, Justine chose to create digital illustrations of the muscles of the anterior neck and torso.

I'm particularly glad to have Justine's permission to use her anterior torso piece here; after almost two and a half years of working on this blog, I have yet to cover that area. So... let's go!

Justine's illustration (below) shows the anterior torso muscles intact. This is not always the case. Often abdominal muscle illustrations show half of the muscles dissected out so more internal layers are exposed. Several layers of muscles and aponeuroses make up the anterior wall of the torso, and often it's in the interest of the viewer to see all of them, as well as their relationships to one another. For our purposes as artists, however, the superficial layers are what most affect the figure's surface appearance. As such, we will stick to those.

A side note, though (and pardon me as my inevitable, undeniable love for terminology once again creeps into my blog)— all the abdominal muscles in the area, including those hidden, have been assigned wonderfully descriptive names: The most superficial muscle on the abdomen (which can be seen here under the milky white, semitransparent rectus sheath) is called the rectus abdominis muscle. The word abdominis refers to the abdomen, and the word rectus means "erect" or "running up and down," which indicates the direction in which the fibers of this muscle run. Deep to this muscle runs another with a similar name. We can't see the tranversus abdominis muscle on the surface of the body, but its name also describes its fiber direction as well as its location on the abdomen; the word transversus means "side to side," the direction in which the fibers of this muscle run.

Let's take a look at Justine's digital illustration of the human anterior torso musculature. Please click on the image to see it at full size. You might even want to open this image in a separate window so you can keep it in front of you while reading the descriptions below.

Let's start by looking at the rectus abdominis muscle a little more closely. You'll notice in Justine's illustration that this muscle is broken up into eight little sections that are divided by thick tendinous lines. These divisions are what give the rectus abdominis muscle its "six-pack" appearance on the body's surface. Of course this six-pack is only visible if there is little adipose (fat) tissue obscuring it. In addition, it's actually an eight-pack! But typically only the six sections superior to the umbilicus (belly button) are seen on the surface, thus giving it more of a six-pack appearance.

There are two different (although very similar looking) types of structures dividing the rectus abdominis muscle into its sections. First we have the linea alba, the long vertical tendon running down the midline of the anterior torse, dividing the rectus abdominis muscle into two bilateral portions. The term linea alba is Latin for "white line." While the linea abla runs the entire length of the rectus abdominis muscle, the portion inferior to the umbilicus is almost never visible on the body's surface; if the linea alba does make a surface appearance, we usually see only the portion superior to the umbilicus. This is because there is typically more adipose tissue over the lower portion of the abdomen.

The interrupting tendons further break the rectus abdominis muscles into sections. These tendons are similar to the linea alba except they run transversely through the muscle, and there are three bilateral sets of them. The interrupting tendons also may show on the surface of the body. Their relative locations are fairly consistent, and as such these lines can be drawn with accuracy using the following guidelines: 1) There are three sets; 2) The most inferior (lowest) set is at or very close to the level of the umbilicus; 3) the most superior (highest) set is at or just below the thoracic arch; 4) the middle set is centered between the upper and lower set, so the three sets are fairly equidistant from one another, and 5) the highest set tends to be the most arched, and the lowest set tends to be the least arched.

On either side of the rectus abdominis muscle we find the external oblique muscles. This muscle is also named for the direction of its fibers, which run at a 45 degree, or oblique, angle. This muscle is called the external oblique because of its relationship to another muscle with oblique fibers, the internal oblique. As the names tell us, the internal oblique muscle also has oblique fibers (although opposite to those of external oblique) and it is deep to the external oblique, meaning its location is more internal on the human body. While the internal oblique is not visible on the body's surface, its external oblique counterpart is. The external oblique muscles cover the sides of abdomen, and while its upper portion isn't all that remarkable in shape, its lower portion is more concretely identifiable. The lower portion of the external oblique muscle attached to the iliac crest (the bony ridge on the lateral hip). Just above this attachment, the external oblique tends to bulge out over the bone, casting a little shadow over the hip. This bulging portion of the external oblique muscle is commonly known as the flank pad. We'll cover this more thoroughly in a pelvis and hip post to come later.

The upper end of the external oblique muscle is fairly flat and nondescript, but we can, in this area, see it intertwining with the serratus anterior muscle. This muscle is named for its serrated (jagged) shape. There is also, as you can surmise from the name, a serratus posterior muscle, which is located on the posterior torso but is not typically visible on the body's surface. The serratus anterior muscle is quite visible on the surface, particular when it's being used to draw the two scapulae anteriorly. This is often the muscle body builders are showing off when they assume their stooped over aarrggh pose. (Think of Saturday Night Live's Hans and Franz.) If you follow the serratus anterior muscle posteriorly, you can see it disappearing under a posterior and lateral torso muscle, latissimus dorsi.

The last muscle we'll look at today is the pectoralis major, which is found on the anterior side of the thoracic cage. The word pectoralis come from pectus, which is Latin for "breast," and the word major tells us that their is also a pectoralis minor muscle, which is smaller than pectoralis major and deep to it, rendering it invisible on the body's surface.

One common mistake artists tend to make when drawing anterior chest muscles is lining up the lower border of the pectoralis major muscle with the thoracic arch. These two structures do not line up! The lower border of the pectoralis major muscle runs approximately 1.5" to 2" superior to the thoracic arch. There is sort of a flat "no man's land" in between the two, where the rectus sheath runs over the lower portion of the thoracic cage. This appears fairly flat and bony on the body's surface, as opposed the more full appearance of the pectoral muscles above.

Let's take a look at how some of these structures look on the surface of a mildly defined body. I've found that many surface anatomy references use extremely defined individuals as examples, and while this is not a bad thing, I think it is also useful to see how these structure look on more of an "average" individual— one not particularly defined or muscular, but with some obvious structures showing.

In the photo below, we can see the basic shapes of the abdominal muscles, plus the umbilicus and a bonus view of a few axillary (armpit) muscles.

One final point to cover: You may be wondering why are there so many layers of muscle and aponeuroses on the anterior wall of the abdomen, and why these muscles have fibers that run in all different directions (rectus, transversus, oblique.) These muscles layers (plus the aponeuroses among them) form a strong, protective wall on a portion of the trunk that needs it most. While the thoracic organs (primarily the heart and lungs) are protected by the thoracic cage, and posterior torso is protected by both the thoracic cage and the vertebral column, the abdomen has no bony protection at all! Odd, considering there are so many important abdominal organs there, including the stomach, the liver and gallbladder, the intestines and the spleen.) The thick, layered wall of abdominal muscles compensates for this lack of bony protection.

Next time we'll look at Justine's other final and equally beautiful illustration for Advanced Anatomy class, that of the anterior neck muscles. Thanks to Justine for letting me use her lovely work. Again, to see more of Justine's beautiful and diverse art, go here!

Until next time!

Thursday, June 6, 2013

A Beautiful Exaggeration: More Student Forearm Paintings

I promised I'd post more student work this month, so here we go. Last time we saw Izzy Carranza's lovely spine sculpture, so this time I thought we'd check out some beautiful watercolor paintings by my student Jeff Sant, also in the Spring 2013 Advanced Anatomy class.

You know I love arm anatomy, right? The disproportionate amount of arm posts on this blog sort of gives it away. So it was a lot of fun working with Jeff on this project, in which he drew a somewhat exaggerated arm outline and, in two separate paintings, placed bony and muscular anatomical structures in it. Let's first look at the muscle painting. Please do yourself a favor click on this lovely painting for a full size view.

Watercolor painting of hand, dorsal forearm, lateral arm, and
posterior shoulder musculature by Jeff Sant.

One of the cool things about this painting is its demonstration that even exaggerated anatomy can and should still take its cues from proportional anatomy. Yes, the hand might be larger than usual, yes some of the muscle shapes are unusually pronounced. But that's cool. We still want it to be based on what we've learned from more realistic anatomy examples. Exaggeration doesn't work unless it's based on reality. It's all about comparison.

Another thing I like about this image is the lovely colors and textures of different body tissues. The bones appear solid, calcified and a bit rough, the tendons appear fibrous and flexible, and the muscles appears meaty and striated. Too often paintings of anatomy look like paintings of plastic anatomy models. These tissues look alive.

So are you wondering what you're looking at in this painting? I thought you might be, so let's label it. Again, please click to enlarge.

Muscles are labeled in black. Bony landmarks are labeled in blue.

I haven't labeled everything in this image, but I tried to address anything you would or could see on the surface of the body. As usual surface appearance of structures depend on many variables, including body position, the amount of adipose tissue, and lighting in the room. But everything labeled here could be seen under the right circumstances. Muscles are labeled in black and bony landmarks are labeled in blue. Notice how many of the forearm extensors (including the extensor carpi ulnaris muscle, the extensor digiti minimi muscle, the extensor digitorum muscle, the extensor carpi radialis brevis muscle, and the anconeus muscle) all original on the lateral epicondyle of the humerus.

You can read more about these muscles in the following posts:

The Dorsal Forearm, Part 1: Compartment Search

The Dorsal Forearm, Part 2: Which Side Are You On, Anyway?

The Dorsal Forearm, Part 3: The Final Chapter

The Dorsal Forearm: One Last Encore

The Deltoid Area: Soft Shoulder and Varied Terrain

The Posterior Torso Muscles: Let's Go Back In Time

The Posterio Torso Muscles, Part 2: Under the Radar

Quick Forearm Study: My Pal Rich

Yeah, I told you I liked the forearm.

Soooo, let's go on to the bones of the arm. Yes, Jeff also did a lovely painting of just the bone anatomy. Here it is.

Watercolor painting of the skeletal structure of the hand, dorsal forearm, lateral arm,
and posterior shoulder by Jeff Sant.

Another very cool thing about these two paintings is that they line up accurately with one another. The same outline was used for each, and the bones of this one are arranged so they align perfectly with the muscles and bony landmarks of the other. In addition, while this painting allows us to see the complete structure of the bones, it also allows us to see why certain features of bones are more visible on the surface. For example, we can see the lateral epicondyle of the humerus because, although many forearm extensors originate there, none of them obscure it. And that epicondyle is just under the surface of the skin. The rest of the humerus, however (other than the medial epicondyle, which can't be seen from this view) is completely obscured by muscle tissue.

Now let's look at a labeled version of this painting to see which bone features are surface landmarks:

All bones are labeled. Those features that appear as surface landmarks are labeled in green.

I've labeled all the bones, but the features that are not obscured my muscle and as such appear as surface landmarks are labeled in green.

You can read more about the elbow joint in The Elbow Joint, Part 1: Anterior View, Supine Position.

One last thing I'd like to say is that my favorite part of teaching this class (other than all the lovely work that comes in at the end) is the process of working with students to figure out the great anatomy puzzles that we're presented with when they choose their final assignments. All of these pieces are so complex that they take many rounds of roughs and revisions before finalization. When getting together the work for this post, I found a nice little image that demonstrates part of this process-- a sketch from the beginning phases of Jeff's muscle painting. Often sketches are sent to me via email throughout the school week so I mark them up in Photoshop to try to help clarify things. This process, both in class and out of class, is one of my favorite parts of teaching. Here's the sketch with some color coded adjustments:

Well, I think that's enough for this time. Many thanks to Jeff for letting me use his work. Please check out more of Jeff's work here.

Next time I'll be featuring more student work—that of the awesome Justine Herrera. You can see a shot of one of her pieces here. My bad phone shot absolutely doesn't do her work justice, but I will soon get higher quality images of it to share with you. See you then.

Wednesday, May 22, 2013

Up Close and Personal: Let H.A.F.A. Diagram YOUR Anatomy

This is quite possibly one of the stranger questions you've been asked, but have you ever wanted to have a photo of yourself— your neck, your back, your arm, your foot— diagrammed out anatomically like the photo below? If so drop me a line at kristin@gm-studio.com. Include any photos you have in mind and we'll discuss the options. Then I will diagram it to your specifications for $25 and up, depending on the area to be diagrammed and the detail level of the rendering. When the diagram is complete, I'll send you the finished digital file or FTP it to the service bureau of your choice for digital output. More information to come, so keep reading:

One of my first posts on this blog (and one of my favorites) was The Anterior Neck: Theme and Variations, in which the visible structures on the anterior neck and their variability were examined. As much as I wanted to write about the the beautiful and elaborate anatomy in this area, I could not find an appropriate image that showed everything I wanted to show. So I ended up taking a shot of my own neck and diagramming it out.

While it's an amateur photo taken with an inexpensive camera, I was able to choose position, lighting, and the structures that would show most. It serves its purpose. Since then I've typically relied on shooting my own photographs, both for this blog and for my book. Soon after this post was published, a friend saw it and subsequently sent me a photo of his beefy arm, asking if I'd diagram the muscles out for him.

Since then, I've been getting more and more requests to diagram muscles and bony landmarks on personal photos, not only from friends and relatives, but from readers of this blog. This is a lot of fun and it seems to be gathering momentum, so thought I may as well make it official and offer it to everyone.

Sooo... Have you ever wondered exactly which muscles and bones you're seeing on the surface of your own body? Well, let me diagram them for you. Just send me a clear, high resolution (at least 300ppi) image of the area in question (um, no private parts, please) and let me know how detailed you'd like the diagram. (See below for examples.) Prices go from $25 up, depending on the complexity of the area and the detail level requested.

The most detailed example would be the fully rendered anterior neck image shown above. Simpler diagrams would look more like the following, which just simple outlines, color coding, and labels:

This is the diagrammed dorsal forearm of my student Shannen.
Bones, muscles, and compartment divisions are color coded and labeled.

Another example of this level of detail can be seen here:

I can also take your color or grayscale photo and make it into a sepia image before laying in the diagram, as shown below:

The image above shows the sepia option, but not much a diagram. I'm happy to complete any level of rendering over an image that I've converted to sepia.

A final option is to show only a specific few muscles, and/or simply labeling visible muscles, as in the diagram below. This option, in which only a few structures are diagrammed, can also be rendered with greater detail, like that in the anterior neck diagram up above.

The above image is a much simpler forearm diagram. Only three of the extensors are drawn in, along with the dorsal hand tendons of one muscle. The lower image has only muscles labeled, with no diagramming at all. This wouldn't be as much fun for me, but I'd be happy to do it!

I've shown mostly arms here, but legs, feet, hands, abdomen, back, and head are all fine. I welcome a challenge! Just be sure the image you send is clear and high resolution, and that some level of surface landmark detail can be seen.

For a time frame and quote, send images to kristin@gm-studio.com.

And feel free to contact me at this address with any other questions!

Thursday, May 16, 2013

The Vertebral Column: Have Some Backbone

One of my favorite parts of the school year is the end of the Spring semester, when I get to collect the wonderful and varied assortment of final projects from my Advanced Anatomy students. These assignments are so much fun to collect because there is such a wide variety; the students are given the freedom to make just about anything they want, as long as their creation demonstrates some of the material they'd learned in class during the semester.

Many students this year chose projects that reflected their major— illustration students did anatomical illustrations, painting students did figure paintings with labeled surface landmarks, photography students shot photos of models demonstrating surface anatomy, and sculpture students like Izzy Carranza (below) made anatomical sculptures.

Izzy Carranza's spine sculpture from the Spring 2013 Advanced Anatomy class.

This lovely life size model of the human spine was crafted by Izzy in the sculpture lab during the last few weeks of school. Because it was too large and awkward to bring back and forth to class every day, Izzy would instead stop by at the beginning of class to check in, then bring me to the sculpture room to talk about his progress. So I got to see it develop in sort of time-lapse fashion. It began as a simple cylindrical slab of clay over a curved armature and slowly took shape into twenty four accurate—and even labeled—vertebrae.

So... how about a spine post?

The human spine is a 4-arched column of 24 vertebrae, plus two more bones, the sacrum and the coccyx. The arches of the spine curve anteriorly and posteriorly, so the curves can only be seen from a lateral view. The two posterior curves of the spine form the backs of two separate bony cavities. The two anterior curves balance out the posterior curves for an overall vertical orientation. The curves of the spine also serve to give it sort of a spring-like quality--the ability to contract and expand when pressure is placed on and released from it. These curves, along with the spine's great number of small bones, contribute to its flexibility, both anteriorly and posteriorly.

The image below shows these curves and the body cavities that two of them form.

The human vertebral column curves anteriorly and posteriorly, so the curves can only be seen from a lateral view. The two posterior curves form the back of two body cavities— the thoracic cavity and the pelvic cavity.  There are seven cervical vertebrae, 12 thoracic vertebrae,  five lumbar vertebrae, and a sacrum and coccyx.

The above image also shows the different areas of the spine and the different types of vertebrae. From the top down, the first section of the spine is the cervical spine, in which we have seven cervical vertebrae. Cervical means of the neck, and these are, of course, the vertebrae in the neck. The cervical vertebrae are numbered from the top down, so the most superior is referred to a the first cervical vertebra, or C1. Then the next is C2, all the way down to C7.

The next section is the thoracic spine, which is given its name because of its relationship to the thorax-- the rib cage and the structures inside it. There are twelve thoracic vertebrae vertebrae in this section, and they are referred to as T1, T2, all the way down to T12.

The next section is the lumbar spine, which forms the small anterior curve on the lower back. There are five lumbar vertebrae in this section, and they are referred to as L1, L2, all the way down to L5. On a side note, some people have a sixth lumbar vertebra, but this is not very common.

The last section of the spine is made up of two bones, the sacrum and the coccyx. These are both solid bones in the ossified skeleton, but they begin in the cartilaginous infant skeleton as more vertebrae! The sacrum, although a solid bone, starts out as five sacral vertebrae in the infant skeleton, and the coccyx, or tailbone, starts out as four coccygeal vertebrae at that time. When you hear people say that infants have more bones than adults, this is what they're talking about.

One more element that makes the spine so flexible is the presence of intervertebral discs— disks of cartilage that lie among the vertebrae. (Inter- means between.) These discs not only allow a greater range of motion among the vertebrae, but they also add cushioning and act as shock absorbers. There are discs among all vertebrae except between C1 and C2. There is no disc here because this articulation is a bit different than those along the rest of the spine. The articulation between C1 and C2 is the point at which our side-to-side head movements occur (as in shaking your head "no") and that movement requires that there is no disc. There is, however, a disc between the last vertebra (L5) and the sacrum. We can see the discs rendered in blue in the close up lumbar spine image below.

This image shows a close up anterior view of the spine with cartilaginous intervertebral discs (in blue) among the vertebrae. Notice there is also a disc between L5 and the sacrum.

As figure artists, we uses the spine's general shape and curvature as a starting point when rendering teh back. The anterior/posterior curves are apparent in just about any body position. But there is one other aspect of the spine the concerns us. One the posterior side of each vertebra, we can find a long spike, or a spinous process. This is the one feature of the vertebrae that we can see and feel on the surface of the body. They are easy to spot running down the posterior midline of the torso.

While every vertebra has a spinous process, not every one can be seen on the body's surface. The spinous processes of the first six vertebra (C1 through C6) are relatively short, and they obscured by soft tissue on the posterior neck— the nuchal ligament, to be specific. But the next spinous process, that of C7, is quite suddenly longer than those above it. As such, it is given the name vertebra prominens, which just means prominent vertebra. The image below shows this.

The spinous process of C7 is quite suddenly much longer than those superior to it. As such, it's the first we can see on the human body's surface. We can often see the next few below it as well, but never  those above it, as they are obscured by the nuchal ligament.

C7 is easy to spot because it's almost always the first spinous process we can see when going from the top down on the posterior torso. It's easy to orient youself on the human spine if you can find C7 first.  The spinous process below that would be that of T1, then T2, etc. We may not be able to see every spinous process along the spine, but we will almost always see (or at least feel) that C7 and we'll never see anything up above that. Whether or not the spinous processes of the thoracic or lumbar vertebrae show depends on several variables— the amount of soft tissue, the position of the body, the lighting, etc.

A student brought this lovely photo by Eugene Suo-Me to class one day after we'd finished the spine unit. It beautifully demonstrates the appearance of the spinous processes on the body's surface. Please check out more of Eugene's beautiful photography here.

This beautiful photograph by Eugene Suo-Me shows several spinous processes. Those of C1 through C6 are obscured by the nuchal ligament. But after that, C7 shows up quite suddenly and prominently, hence its name vertebrae prominens. After that, we can usually see the spinous processes of the first few thoracic vertebrae, if not more.

Finally, here is an example of a body position in which we can see lumbar vertebrae. In this pastel nude study by Degas, the figure is bending forward, which makes the soft tissue on the lower posterior torso stretch out over the bony spine. As such the spinous processes in this area (the lumbar region) are more pronounced. I think we can see the spinous process of C7 in this image as well.

The spinous processes of some of the lumbar vertebrae, as well as that of C7 can be seen in Degas' pastel nude.

Well that's it for today. I do have quite a few more wonderful advanced anatomy projects to show here, so one of those will most likely be next. Until next time.

Friday, March 1, 2013

The Cephalic Vein: You're Sooo Superficial

I haven't written much about veins on this blog, and I don't know why. Veins are awesome. Veins are your friends. Their pals arteries aren't too shabby either. And in figure drawing, it's not a bad thing to know how to draw them in the right places. While some vein placement is quite variable from person to person, there are certain veins that we can always count on to peek out at us in the same places. These include the external jugular vein on the neck (which I briefly mentioned in The Anterior Neck: Theme and Variations,) the great saphenous vein on the inner leg, and the basilic, median cubital, and cephalic veins on the arm.

Veins are different from arteries in that they typically carry deoxygenated blood (as opposed to oxygenated blood, which is typically carried by arteries.) There is an exception to this in the case of the pulmonary arteries and veins, which I'd love to explain now but would rather save for a future, general blood vessel post. Who can resist a good general blood vessel post?

For now I just want to show you a nice example I found of a prominent cephalic vein showing on the radial side of the wrist. This is one of two places we may typically see the cephalic vein. (The other is on the upper arm, running over the lateral side of the biceps brachii muscle, just before the vein enters the deltoid furrow, the crease between the deltoid and pectoralis major muscles. I will save that view for another compelling blood vessel post.)

Let's just take a look at this view today:

The cephalic vein, because its superficial location over the radial side of the wrist and its easy access, is often used as a site for I.V. placement. Its course may be fairly straight, or more jagged like the one seen here. It will continue upward on the ventral side of the forearm, run over the lateral side of the biceps brachii muscle, and enter the deltoid furrow, where is often disappears from surface view. If it doesn't disappear there, it will disappear when it runs deep to the clavicle and merges with the subclavian vein.

As a bonus, there are four tendons clearly visible here as well. Let's take a look.

On the radial side of the wrist, just at the base of the thumb, we can see the tendons of extensor pollucis longus and extensor pollucis brevis muscles. The muscles, as their names tell us, extend the thumb, and one is longer than the other. (Just slightly so: The tendon of extensor pollucus longus extends all the way to the first distal phalanx of the thumb, and the tendon of extensor pollucus brevis extends only to the first proximal phalanx, so both can be extended independently of one another. You can read more about these thumb tendons in The Dorsal Hand: The Dorsal Foot's Better Looking Sibling.

On the ventral side of the wrist, we can see the tendons of two ventral compartment muscles, palmaris longus and flexor carpi radialis. Don't be alarmed if you can't find your own palmaris longus tendon; it's missing in 12 to 15 percent of the human population. You can read more about these tendons in The Ventral Forearm: What are those Tendons? 

That's it for now. Thanks for stopping by. More to come soon. Perhaps anterior torso? More superficial veins? Ooh, how about more terminology? It's so hard to decide. We'll see.

Friday, January 25, 2013

More Random Landmark Sightings in the Art of Old Friends

One of my favorite things to do as a medical artist is observe other artists' figure work and search for anatomical landmarks. I especially enjoy doing this on stylized figures that are exaggerated in one way or another. I've done this before with a friend's drawing in a post called Sternocleidomastoid: Don't Forget the Cleido! This post featured the art of my friend Shawn Campbell, a wonderful artist and one of two great art friends I was fortunate enough to meet in middle school (back when it was still called junior high school.) His work is not only beautifully rendered, but anatomy is always sound. And as I mentioned in that post, knowledge of the human skeletal and muscle structure is not only useful when drawing realistically but also when drawing a human (or humanoid) with stylized or exaggerated features.

The other lifelong art friend I was fortunate enough to meet at Lincoln Junior High was Chris Boyd, also known as Crazy3DMan. He and his wife Michelle have also been lifelong art friends with whom I've shared friendship, ideas, meals, conversations, rants and of course, art. Today Chris is a freelance artist who specializes in character design, illustration and concept art, which he creates with both 2D and 3D media. Chris also co-founder of Squirtgun Studios, a Chicago studio that specializes in concept, design, illustration, motion graphics, photography and copywriting. 

Like Shawn, Chris's figure work, no matter how stylized or exaggerated, is always anatomically sound. I was looking at some of his characters recently, and this one caught my eye. The first image shows it alone, and the second has labels I added to show all the wonderful, accurate anatomical landmarks Chris included.

Chris's original soldier illustration.

Chris's soldier sketch with subtle but accurate anatomical landmarks labeled.

Although the smallest pencil marks can signify these surface landmarks, it's still so important that their shape and location are drawn accurately. And they are here. Let's look at some of them more closely.

The image below zeroes in on the thyroid cartilage, the medial epicondyle of the humerus, the head of the ulna, the extensor digitorum tendons, the olecranon process of the ulna, and the lateral epicondyle of the humerus.

The thyroid cartilage is pretty exaggerated on this dude. Which is totally fine, since it's typically larger in an adult male. This is because the thyroid cartilage houses the larynx which manipulates the volume and pitch of our voice. A deeper voice warrants a larger larynx and a larger thyroid cartilage in which to house it. You can read more about this in an anterior neck post called The Anterior Neck: Theme and Variations. 

On the back of the soldier's right hand, we can see the tendons of the extensor digitorum muscle. The muscle itself runs along the dorsal side of the forearm, but its tendons, which insert onto the dorsal side of digits II through V, split apart and become visible on the dorsal surface of the hand. We can see three of these tendons in Chris's drawing. You can read more about the extensor digitorum muscle in my post The Dorsal Forearm Part 2: Which Side Are You On, Anyway? and more about its tendons in particular in The Dorsal Forearm: One Last Encore.

On the dorsal surface of the soldier's left arm we can see evidence of the extensor carpi ulnaris muscle and its tendon. The muscle body is more proximal on the arm and reads as a small bulge with a shadow below it. That shadow is a small furrow that divides the forearm extensors from the forearm flexors. More distal on the forearm, we can see the long tendon of this muscle, just before it runs over the head of the ulna. You can also use the above links to find out more about this muscle and its relationship to the head of the ulna. And to read more about the crease between the two forearm muscle groups, check out The Dorsal Forearm Part 1: Compartment Search. 

The last landmarks we can see in this close up are the lateral epicondyle of the humerus (just barely) and the olecranon process of the ulna. The olecranon process is simply the portion of the elbow we lean on. The lateral epicondyle is just lateral to the olecranon process and is often barely visible when the elbow joint is extended and the arm is straight. But when the elbow joint is flexed and the arm is bent, the olecranon process dips down lower and the lateral epicondyle sticks out a bit. Most artists forget to show both bumps when the arm is flexed, but not Chris. In this situation, the elbow will have two slight bumps-- one more proximal, which is the lateral epicondyle, and one more distal, which is the olecranon process. You can read more about these two structures at The Elbow Joint, Part 1: Anterior View, Supine Position.

Below we have a close up featuring the last two landmarks spotted in Chris's image.

With one very subtle line, Chris has shown the location of the medial epicondyle of the humerus (as opposed to the lateral, discussed above. Unlike the lateral epicondyle, the medial epicondyle can usually be seen no matter what position the arm takes. This epicondyle appears as a small bump on the inner elbow. Just proximal to this bump, we can see a long muscle attaching to it. This is most likely where we'd see the medial head of the triceps muscle, but I didn't label that here. The triceps is one muscle this blog has not adequately addressed just yet.

The last two landmarks shown in Chris's sketch are on the soldier's right ventral wrist. There are two very small marks indicating tendons that can often be seen there. You may want to scroll up to the unlabeled sketch at the top of the page to see these more clearly at first. The second of the two marks is very subtle and difficult to see at low resolution. These two tendons are those of the flexor carpi radialis muscle and the palmaris longus muscle. While the latter is missing in some individuals, it is most commonly present. And when it is, it's often easily visible. The flexor carpi radialis tendon is always there, but it may not appear as superficial. You can read why at my very first post, The Ventral Forearm: What are those Tendons?

I'll be back soon. The next post will probably revisit the elbow joint. I started that series awhile ago and completely forgot about it. Also, requests are always welcome. Until next time!