Description

This video covers the muscles of the shoulder joint, including their origins, insertions, functions, and clinical significance.

Muscles of the Shoulder Joint

• Deltoid
• Subscapularis
• Supraspinatus
• Infraspinatus
• Teres Minor
• Teres Major

Deltoid (Musculus Deltoideus)

• Spinal Part
  • Origin: Spine of Scapula (Spina Scapulae)
• Acromial Part
  • Origin: Acromion of Scapula
• Clavicular Part
  • Origin: Clavicle
• Insertion: Deltoid Tuberosity of Humerus (Tuberositas Deltoidei Humeri)
• Function:
  • A: Abduction (Abductio Brachii)
  • C: Internal Rotation (Rotatio Brachii Interna)
  • S: External Rotation (Rotatio Brachii Externa)
  • S+C: Adduction
  • A+C: Flexion
  • A+S: Extension

Subscapularis (Musculus Subscapularis)

• Origin: Subscapular Fossa (Fossa Subscapularis)
• Insertion: Lesser Tubercle + Crest of Humerus (Tuberculum Minus Humeri et Crista Tuberculi Minoris)
• Function: Adduction, Internal Rotation

Supraspinatus (Musculus Supraspinatus)

• Origin: Supraspinous Fossa (Fossa Supraspinata)
• Insertion: Greater Tubercle of Humerus (Tuberculum Majus Humeri)
• Function: Abduction

Infraspinatus (Musculus Infraspinatus)

• Origin: Infraspinous Fossa (Fossa Infraspinata)
• Insertion: Greater Tubercle of Humerus (Tuberculum Majus Humeri)
• Function: External Rotation

Teres Minor (Musculus Teres Minor)

• Origin: Lateral Margin of Scapula (Margo Lateralis Scapulae)
• Insertion: Greater Tubercle of Humerus (Tuberculum Majus Humeri)
• Function: External Rotation, Extension

Teres Major (Musculus Teres Major)

• Origin: Inferior Angle of Scapula (Angulus Inferior Scapulae)
• Insertion: Crest of Lesser Tubercle of Humerus (Crista Tuberculi Minoris Humeri)
• Function:
  • Adduction
  • Extension
  • Internal Rotation

Rotator Cuff Muscles

• Subscapularis (Musculus Subscapularis)
• Supraspinatus (Musculus Supraspinatus)
• Infraspinatus (Musculus Infraspinatus)
• Teres Minor (Musculus Teres Minor)

Function: Stabilizes the Shoulder Joint

Clinical Importance ⚠

• Rotator Cuff Tear
• Tendinitis
• Bursitis

Transcript

Introduction
0:03
What’s up. Meditay here and in this video, we’ll be looking at the muscles of the shoulders,
0:08
which are a part of the upper limb. Alright. So, the muscles of the upper limb are divided into 4
0:13
parts according to their anatomical location. The first group are muscles of the shoulder joint.
0:19
Then we have the muscles of the arm, muscles of the forearm and then the muscles of the hand.
0:24
So again, muscles of the shoulder joint are what we’re gonna focus on today. These are
Division of the Shoulder Muscles
0:28
the Deltoid Muscle, Subscapularis, Supraspinatus, Infraspinatus, Teres Minor and Teres Major. All
0:36
of these muscles surround the shoulder joint. But the supraspinatus, infraspinatus, teres minor and
0:42
subscapularis form the rotator cuff muscles, which allows rotation of the humerus at the shoulder
0:48
joint, they provide stability to the shoulder and prevents dislocation.
0:52
These muscles are clinically important because any rotator cuff injury can cause a dull pain in
0:58
the shoulder, which often worsens when you elevate the arm in a certain way.
1:02
Alright. So let’s talk about these muscles. We’ll add a skeleton to use it as a landmark.
Deltoid
1:07
First we have the deltoid muscle. Which is this large muscle on the shoulder that
1:11
is used as an injection site in the shoulder. This muscle is divided into 3 parts according
1:17
to their place of origin. It’s divided into the Spinal part, Acromial Part,
1:22
and the Clavicular part. So the spinal part originates from the Spine of Scapula, as you
1:27
see here. Acromial part from the acromion of the scapula, and clavicular part from the…. Clavicle.
1:35
Then they all unite and insert at a common region, which is the Deltoid tuberosity of the Humerus.
1:41
The function of the deltoid muscle depends on which muscle fibers contract. For instance,
1:46
if Acromial part contract alone, it abducts the arm. If clavicular part contracts alone, it
1:53
rotates the arm internally, and if the Spinal part contracts alone, it rotates the arm externally. If
2:00
the Spinal part and the Clavicular part contract, they adduct the arm. If the Acromial part and the
2:06
clavicular part contract, they flex the arm. And if the acromial part and the spinal part contract,
2:12
they extend the arm. So that’s the magic behind the deltoid muscle. Awesome.
Subscapularis
2:18
Then we have the subscapularis. And if we look at the scapula anteriorly. Here is the
2:23
subscapular fossa, and here is the subscapular muscle. It originates from the subscapular fossa
2:29
and insert at the lesser tubercle and the crest of the lesser tubercle on the humerus.
2:34
And when this muscle contracts, it adducts the arm and internally rotate the arm.
2:40
So that’s this one. Now let’s look at the scapula from the posterior view. Here, we’ll be able to
Supraspinatus
2:46
see the Supraspinatus, which is this one. It originates from the supraspinous fossa,
2:52
that’s the fossa above the spine of the scapula. And it inserts at the greater tubercle of humerus.
2:58
And when it contracts, it abducts the arm. Pulling it this direction.
3:02
Next, we have the Infraspinatus. Which is here. This one originates from the infraspinous fossa.
Infraspinatus
3:08
And it inserts at the greater tubercle of the humerus. And when it contracts,
3:13
it externally rotates the arm, like this. Then we have the Teres Minor, which is here.
Teres Minor
3:18
This muscle originates from the Lateral Margin of the Scapula and Insert at the greater tubercle of
3:24
the humerus. And when it contracts, it Externally rotates the arm, and extends the arm backwards.
3:31
Our last muscle is the Teres Major, which is here. It originates from the angle of the scapula,
Teres Major
3:37
and then it goes to the front, like you see here, and insert at the crest of the lesser tubercule
3:42
of the humerus. And so when the muscle fibers contract, they pull the arm towards the body,
3:47
so adduction. They extend the arm backwards, and they internally rotates the arm.
3:53
So these are the main muscles of the shoulder. Let’s talk about the rotator cuff a little bit.
Rotator Cuff Muscles
3:59
The rotator cuff muscles are the Subscapularis, Supraspinatus, Infraspinatus, and Teres minor.
4:05
They stabilize the shoulder joint, as you see here. They shoulder joint is actually one of the
4:11
joints in our body that endures a lot of stress all the time, because you’re using your arms
4:16
a lot in day to day basis. Every time you lift something, you fall, or you just move your arms,
4:21
your shoulders are involved, so these muscles stabilizes the joint. And they’re very important
4:27
clinically, because sometimes. The rotator cuff muscles can undergo a rotator cuff tear,
4:33
so a tear in the tendons, or an inflammation of its tendons, called tendinitis, and even the
4:39
bursa of the shoulder can get inflamed, called bursitis. These are a very common diagnosis to
4:44
give for people with shoulder pain. Alright. So that was all the muscles of the shoulder
4:49
joint. In the next video, we’ll be talking about the muscles of the arm.