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LESSON - General Anatomy Primer (Part 3)
🕑 Added 2025-07-17 04:57:49 +0000 UTCPart 1 - Basics and Neck: https://www.patreon.com/posts/lesson-general-125387198
Part 2 - Torso: https://www.patreon.com/posts/134307861
Part 3 - Arms and Legs: You are Here
ARMS
1. Deltoids
The Deltoids are the big shoulder muscles. It consists of three heads (anterior, middle, and posterior), but all of them insert between the biceps and the brachialis.
More information about this can be found in the Front Torso section in Part 2!
2. Biceps
The star of the arm muscles, the part that everyone loves to see and show off. Its function is to bend the arm at the elbow.
One thing to note about the biceps is that it is not a circle, and it changes form depending on both the position and the rotation of the arm. Note that the Rotation matters a lot too!
Another thing to note: despite being the star, the biceps actually only makes up less than half of the mass of the upper arm. The rest is made up by the other big part…
3. Triceps
The less-famous, but larger half of the upper arm muscles. Its function is to extend/straighten the arm, counter to the biceps. It’s made up of the lateral head, the long head, and the medial head which is mostly hidden under the tendon.
It’s worth noting that when flexed, the tendon doesn’t bulge out while the lateral and long heads do.
In bara/muscle art, there’s a common mistake of putting too much size on the biceps and not enough (or worse, none at all) on the triceps. This mistake can make the arm look imbalanced, especially with hyper muscles. It’s important to hit a balance between the two to make the arm look appealing, even if it means reducing the biceps a little bit!
Another common mistake I often see is forgetting to take into account the arm’s rotation, usually resulting in showing too much biceps. Once again, this can make the arm look imbalanced or off.
4. Coracobrachialis
The elusive armpit muscle, usually visible during the biceps flex pose. It’s not a very actively functional muscle, but appearance-wise, it forms the keystone of the armpit area, connecting the intersection between all the other muscles.
More detailed info about this muscle and the armpit area will be covered in another lesson in the future!
5. Brachialis
The Brachialis is a muscle located under the biceps, and works together with the biceps to bend the arm at the elbow.
This muscle is pretty commonly forgotten or overtly minimized (usually for the sake of drawing the biceps or triceps bigger), and this can make the arm look off, so keep this in mind!
6. Brachioradialis
The Brachioradialis is a relatively passive, but significantly visible muscle at the elbow on the thumb side. You can identify the brachioradialis as the familiar L-ish shaped line next to the elbow, which is visible whether the elbow is bent or straightened.
Because the Brachioradialis’ tendon always inserts to the thumb side, it can be a useful tool for you to quickly establish the rotation of the forearm and hand relative to the rest of the arm. Here’s an example.
Because this muscle is located where a lot of other arm features intersect, drawing it in the correct shape and rotation is very crucial. Even a slight error in drawing the Brachioradialis can make the arm look off!
7. Forearm Group
The forearm group consists of many thin muscles that control the fingers and the hands. It’s not too important to remember each one, but I’ll provide a diagram just for reference.
Apart from the Brachioradialis, the individual forearm muscles rarely become big enough to show a lot of definition. In fact, even on the biggest, leanest bodybuilders, the muscle definition is often overshadowed by the veins that exist across the entire forearm area. These two videos can demonstrate what I mean: https://www.youtube.com/shorts/BX3VOwP7ixc and https://www.youtube.com/shorts/cRTkm7Ng9OM
Another important aspect of the forearms is that they have two bones, the ulna and radius, which can cross over one another. This crossing motion allows you to rotate your wrists.
Because the ulna shows up as the spike of your elbow and the little bump on your wrist at the pinky side, it can be a useful anchor when you're sketching the forearm. I usually use the ulna and the brachioradialis as my anchors, like this:
Make sure the ulna matches up with the pinky, and the brachioradialis matches up with the thumb!
8. Hands
Though technically not a part of the arm, I consider the hand to be the King of the arm. This is because the hand commands the position of every other muscle in the arm. See examples below.
As you can see, every other arm muscle moves in service of the hand. Even a slight difference in the rotation of the hand can cause the entire arm to change position.
And so when drawing the arms, it might be good to start by considering where the hands (or the wrists) are and how it’s rotated, and then use that to dictate how the rest of the arms should be drawn.
To be Continued
The Leg muscle groups will be added soon!
For now, you can refer to the 2022 Anatomy Primer to see those muscle groups: https://www.patreon.com/posts/lesson-general-67416944
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As always, if you have any questions, feel free to hit me up in the Art Labs channels in the AA Labs discord!
