LESSON - General Anatomy Primer (Part 1)

This is a general primer of muscle anatomy for artists. It will explain the basic concepts about muscle, introduce you to each muscle that you should know about as an artist, and give you some useful tips about how to draw them.

NOTE: this is NOT a substitute for anatomical studies. Ideally, your primary source of anatomical knowledge should come from hands-on experience through drawing them using real-life or photo references. This primer is only meant to be a guide and reference document for you to look back to whenever you’re having trouble understanding muscles in your artistic endeavours.

If you’re looking for a lesson on how to draw fat, check here: https://www.patreon.com/posts/lesson-anatomy-71774827

Part 1 - Basics and Neck: You are Here
Part 2 - Torso: https://www.patreon.com/posts/134307861
Part 3 - Arms and Legs: https://www.patreon.com/posts/lesson-general-3-134309486

BASICS

When artists talk about “muscles”, we generally mean skeletal muscle, as opposed to other types of muscle (smooth muscle and cardiac muscle). Skeletal muscle is the stuff that moves the human body.

Origin and Insertion
Every muscle is made up of fibers that go in one uniform direction. Each end of the muscle is anchored on a bone or on another muscle/tendon; the end that is usually closer to the center of the body is called the “Origin”, while the other, which is usually attached to the body part being moved by the muscle, is called the “Insertion”. 

In most cases, a muscle’s insertion is a single point or a small area, but its origin may be a point, several points, or even a very broad area along a bone. 

For example, the Biceps has its insertion on the Radius, which is one of the forearm bones (the thumb side), and, being a two-headed muscle, it has two origin points located close to each other on the Scapula (shoulder blade). 

In contrast, the Pecs’ insertion is on the Humerus (upper arm bone), and its origin fans out and goes along the Clavicle (collar bone) and the Sternum (breast bone).

Where a muscle is anchored influences how much it deforms/changes shape. For example, muscles attached to the arms, like the pecs, deltoids, and lats, deforms a lot since the arm is a very active body part. 

Specific notes about how each muscle deforms will be discussed in their respective sections. 

Note: There are actual medical/scientific terms for the specific parts of the bone on which the muscles are attached, such as the “Coracoid process” of the scapula where one of the heads of the biceps is attached, but I will stick to simpler terms when I can.

Superficial vs Deep muscles
Muscles that are visible on the surface of the human body are called Superficial muscles, while those that are deeper and not immediately visible are called Deep muscles. 

Superficial muscles include pretty much all of the muscles that an artist may be familiar with, from the biceps, triceps, pecs, lats, quads, etc. This primer will touch on most of these muscles. 

In contrast, deep muscles are not super essential for artists to know about, since they're typically not visible (barring exceptional cases). This classification includes the pectoralis minor, transverse abdominals, rhomboids, etc.

Note, you may find the Deep muscles drawn on anatomy diagrams on google and such, but remember to check if the diagram has cut away the superficial muscles in order to show the deep muscles. See example below:

The rhomboids, which are normally covered up by the traps, are visible on one side since the outermost muscle layers were not drawn.

Muscle Action and Interaction
A muscle can only do one thing: Pull. It does so by contracting, i.e. compressing itself into a shorter, but bulkier state. When a muscle pulls, it can only do so according to the direction of its strands.

In many cases, there’s a pair of muscles/muscle groups pulling on opposite sides. This allows for Flexion (bending) and Extension (straightening) by alternating which muscles contract and which muscles relax. This is one common kind of Muscle Interaction. 

Other notable muscle interactions include:

• Abduction: pulling away from the body

• Adduction: pulling towards the body

• Medial rotation: rotating towards the centre of the body

• Lateral rotation: rotating away from the body, or towards the sides

NECK

1. Sternocleidomastoid (SCM) 
The most notable of the neck muscles, this muscle forms the familiar V-line around a person’s throat.

The SCM works together with the other neck muscles to stabilize and move the head, though for us artists, it's primary function may just be to look cool (lmao).

It's important to note that this muscle does NOT insert under the jaw, despite how it looks from the front. Instead, it attaches just behind the ears at the back of the skull.

2. Trapezius
The Trapezius, aka the Traps, makes up a big part of the back of the neck as well as the shoulder. From the front, a part of it wraps around the shoulder and attaches onto the clavicle.

In the back of the neck, some people have small protrusions where the spine pushes against the middle of the Traps. This is most often seen in skinny people. Meanwhile, when the Traps are big and bulky, they may form a little valley in the middle of the back of the neck. These are not mutually exclusive though; someone may have a valley with bumps, or neither.

Also, the area of hair on the back of the head usually goes down along the back of the neck, and doesn’t just stop right where the skull meets the neck. This of course comes with a lot of variation depending on the individual.

3. Throat
This area consists primarily of the larynx, including the adam’s apple, plus various minor muscles around it. It’s not important to memorize the individual muscles in this part as an artist, as usually none of them are prominent enough to be visible.

Note, since the main mass of the throat (the larynx) is not a muscle, it doesn’t grow in size alongside other muscles in the neck. When the surrounding muscles are really big, it may even look like the throat is being swallowed up by them.

4. Minor Neck Muscles
This area consists of various small muscles, not too important to memorize as an artist though, since they’re not really distinguishable from the bigger mass of the traps.

For simplicity, it's okay to think of this group as a part of the traps, but if you're aiming for realism, you may want to take the time to study them in detail.

5. Platysma
This muscle is a very thin but broad sheet that wraps across the front of the neck.

Even though this muscle is technically the most superficial (closest to the surface of the skin) among the neck muscle group, it’s so thin that it’s only visible in very specific circumstances. Namely, it contracts when a person is cringing and forms diagonal lines across the neck area. It also tends to be more visible on elderly individuals.

Next Part

Part 2 - Torso: https://www.patreon.com/posts/134307861

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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!