Muscles That Move the Arm Radius and Ulna

Muscles That Move the Arm Radius and Ulna


– [Voiceover] Looking at the muscles that move the arm, the radius and the ulna. We’re looking at the muscles
that move the forearm. First one up is going to be right here. This is going to be the
biceps brachii muscle. Now, this biceps brachii muscle, bi meaning two, that means we have two origins for the biceps brachii. One origin for the short head is going to be the coracoid process. In this view you can see the
coracoid process, right here. The long head though, is going to have an origin from the
supraglenoid tubercle. It also comes off of the lip of the glenoid cavity a little bit. Now, insertion wise, this is going to run all the way down from the origins, all the way down into the
forearm for the insertion. The insertion is going to
be the radial tuberosity. Now the action of the biceps brachii is going to be flexion of the elbow, because it causes the forearm to flex towards the upper arm. We also have a little bit of supination. A little bit of supination in the forearm is helped with the biceps brachii. Its innervation is the
musculocutaneous nerve. The musculocutaneous nerve. Biceps brachii is located
on the anterior side of the upper arm. But the biceps brachii has two other muscles that are synergistic,
or working together with it for flexion at the elbow. One muscle, turn this around. You can see a little bit in the back here. So, anterior, this is posterior back here. But deep to the biceps brachii, is the brachialis muscle. This muscle back here is
the brachialis muscle. Now the brachialis muscle is also going to help with flexion at the elbow. The third muscle of this
synergistic pairing, or synergistic grouping, is going to be your brachioradialis. Now, just to change the
view, just a little bit. If you notice, this is our thumb side. This is the thumb right here. So the brachioradialis muscle. See it running all the
way down through here. Brachioradialis muscle. It also is going to be
helping with forearm flexion. Now, all three of these
muscles, biceps brachii, brachialis, brachioradialis,
are all going to work antagonistically against
the triceps brachii muscle. This muscle, biceps brachii. This muscle right here is the brachialis. And the posterior side, is going to be the triceps brachii. If we turn this around like this, look at the posterior side of the arm now. This posterior side gives
us our triceps brachii. You can notice that this
is the deltoid up here. This is teres major, for orientation. This is going to be the
medial border of the scapula. So our triceps brachii. The triceps brachii will
originate, again three heads. In the triceps brachii we
have the infraglenoid tubercle of the scapula, that’s the long head. Infraglenoid tubercle, scapula. The lateral head is the
posterior shaft of the humerus. Obviously we’re looking more towards the proximal portion
of the posterior shaft. And then the medial head is also the posterior shaft of the humerus. But it’s distal to the radial groove. So it’s a little bit
more of a further aspect. Little bit more down. So we have the triceps brachii. The triceps brachii, tri meaning three. Three heads, so three origins. The long head is the
infraglenoid tubercle. The lateral head is going to be the posterior shaft of the humerus. And then the medial head is also the posterior shaft of the humerus. But it’s going to be the posterior shaft of the humerus, distal
to the radial groove. But even with all three origins, they’re going to come down and insert into one insertion right down here, right near the elbow. This is actually the elbow right here. The insertion for the triceps brachii is the olecranon, so we’re looking at the olecranon of the ulna. Or olecranon process. Now, as far as actions
go, the triceps brachii is going to be a forearm extensor. So it can cause extension at the elbow. Forearm extensor. And the innervation is the radial nerve. Innervation is the radial nerve. Now if we stay in the region of the elbow. If we just turn this a little bit, so again we’re back on a view now more of the anterior side. So here is our biceps brachii. This is our brachioradialis. This muscle right here, see how it’s diving deep under the brachioradialis. If we take off the brachioradialis, you can notice this muscle coming down and all the way over here. This is going to be your pronator teres. The pronator teres muscle. It’s action is pronation of the forearm. So pronator teres, like it sounds is pronation of the forearm. Moving from the pronator teres. There is a second muscle
that is synergistic. It’ll help with pronation. If we slide this over a little bit. Now see down in the wrist. We’re going to notice that right here there’s a very deep
muscle underneath here. Under these tendons, under
this muscle right here. Very deep muscle called
the pronator quadratus. Pronator quadratus has the muscle fibers running from radius and
ulna, back and forth. Running across the wrist. This is going to allow for
pronation of the forearm also. Pronator quadratus. Here is a different view
of the pronator quadratus. If you’re looking right
here in this figure, you can see how the deep muscle is running between the radius and the ulna. Here’s the radius, moving
over to the ulna here. Pronator quadratus. If we go back up into
the elbow region again. Now, we move back up into the elbow. This muscle again is your pronator teres. We have our biceps brachii. Remember, we’ve removed the
brachioradialis from here. This muscle that is right on this side, we’re on the radial side, this muscle is going to be the supinator muscle. The supinator is going
to have an action of supination of the forearm. The supinator muscle. That means it’s working antagonistically to the pronator teres
and then down the wrist, the pronator quadratus. The last muscle to cover in this group is going to be the anconeus muscle. This muscle right here
is the anconeus muscle. Now, helpful orientation,
this muscle right here is the supinator muscle. So we’re on the posterior side of the arm, right at the elbow. This anconeus muscle is going to have an action that controls ulnar abduction, so A-B-duction, during forearm pronation. If you’re trying to think of what is that, well ulnar abduction,
you’re taking the ulna and moving it away from center line, away from the body. That occurs as you go through pronation of the forearm; that takes the ulna, which is on the fifth digit side, and it will be pulled away from the body as the radius comes closer
to the midline at the wrist. So the anconeus muscle, controlling ulnar abduction during forearm pronation.

3 Replies to “Muscles That Move the Arm Radius and Ulna”

  1. this video helped me as a starting point to understand my transverse fracture in my arm and what muscles I need to work on afterwards around my radius and ulna that broke.

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