Muscular Function and Anatomy of the Arms: Major Muscle Groups

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  • 0:06 Axial vs. Appendicular Muscles
  • 1:17 Muscles of the Shoulder
  • 3:29 Muscles that Move the Arm
  • 5:20 Muscles that Move the…
  • 6:05 Lesson Summary
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Lesson Transcript
Instructor: Heather Adewale

Heather has taught reproductive biology and has researched neuro, repro and endocrinology. She has a PhD in Zoology/Biology.

Learning all the muscles of the muscle system can be a pretty daunting task, but we will try and help you by focusing just on the major muscles of the arm in this lesson on arm anatomy.

Axial vs. Appendicular Muscles

The hand bone's connected to the wrist bone, the wrist bone's connected to the...oh wait, wrong system! Okay, so maybe there is no fun song or easy way to remember all the muscles of the muscular system but we're going to help you try! Well, maybe not all the muscles; I think we'll just focus on a few of the more well known, or major, muscles.

But, even though there may not be a song for muscles like there is for bones, they do have something in common: their organization. You see, just like the skeletal system is divided into the axial skeleton (that's the head and vertebral column) and the appendicular skeleton (that's pretty much the rest of the bones), the muscle system is also divided.

Axial muscles are those connected to the axial skeleton, like the muscles found on your back, head and chest. Appendicular muscles are those connected to the appendicular skeleton, such as the muscles found on your arms and legs.

In this lesson, we are going to focus on some of the appendicular muscles of the upper limbs, or 'arms' in layman's terms.

Muscles of the Shoulder

Let's start at the top - that would be the shoulder. The ability to move and rotate your shoulder comes from the presence of numerous muscles, each in charge of different directions of rotations. Some of the main muscles of the shoulder that move the upper arm include the deltoid and the pectoralis major.

The pectoralis major and deltoid muscles
Deltoid and Pectoralis Major

The deltoid is this muscle on the right on the image above, right at the shoulder joint. You could say that this is the muscle that gives your shoulder that rounded shape that it has. It stabilizes and moves the shoulder and arm. The deltoid is the main abductor muscle of the shoulder, meaning it moves the arm away from the center of the body.

The deltoid has three origin points along the scapula and the clavicle - these bones below:

The deltoid originates along the scapula and clavicle.
clavicle and scapula

The origin points are stable and do not move, unlike the insertion point of the muscle, below, which moves the humerus bone of the upper arm.

The insertion point of the deltoid is on the humerus.
deltoid insertion

The antagonist (or opposing muscle) to the deltoid is the pectoralis major. This muscle is located on the upper chest area and is kind of fan-like in shape. Similar to the deltoid, the pectoralis major has multiple origin points, but just one insertion point. The origin points are below, along the clavicle, sternum and abdomen, while the insertion point is on the humerus, also seen below.

The pectoralis major originates are along the clavicle, sternum and abdomen.
pectoralis major origin

The pectoralis major inserts on the humerus.
pectoralis major insertion

So you can see, together the deltoid and pectoralis major work to move the upper arm because both have insertion points on the humerus. And, as you may have guessed, since the pectoralis major is the opposite of the deltoid, its function is to adduct the arm, moving it closer to the center of the body.

Both of these muscles are aided by other muscles around the shoulder, like the pectoralis minor, latissimus dorsi and the teres muscles, helping them raise, lower and rotate the arm.

Muscles that support the deltoid and pectoralis major
Muscles around Shoulders

Muscles That Move the Arm

Beneath the shoulder is the rest of the arm. Just like the deltoid, two of the main muscles of the arms have their origins on the scapula. These are the biceps brachii and triceps brachii, or more commonly referred to as the biceps and triceps. However, unlike the deltoid, these two muscles insert on the bones of the forearm, the radius and ulna.

These muscles work together to move the forearm. The biceps is the agonist, and it inserts on the radius. Contraction of the biceps flexes the arm, moving it toward the humerus and shoulder. The triceps does the opposite. It's the antagonist, and it inserts on the ulna. Contraction of the triceps brings the arm back down, extending it away from the humerus.

The biceps and triceps work to move the forearm.
Biceps and Triceps

While these are probably the most well-known muscles of the arm, they aren't the only muscles producing arm movements. They are assisted by smaller muscles like the brachialis and the brachioradialis, which help initiate and stabilize arm movements.

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