So now, we’re going to look at the
glenohumeral joints or the shoulder joints
between the head of the humerus and the glenoid
cavity or the glenoid fossa on the head of
the scapula. And we can see on the screen, we’ve
got numerous images which show different views
of this joint. So here we can see a section
through the joint. We can see we've got the head
of the humerus here, and we’ve got the glenoid
cavity. We can see the shallow glenoid cavity
and the relatively large head of the humerus.
Here, we can see a lateral view. We can see
the glenoid cavity and how it’s deepened via
this glenoid labrum. And then we can see
some of the ligaments that are helping to support
this joint. So if we look at the articulation,
then as I mentioned, we have this large humeral
head. But it’s running up against this shallow
glenoid cavity. Now, although this allows
increased range of movements, it means there’s
reduced stability. So when we look at the
hip joints in the lower limb lectures, you’ll
see that the equivalent of the glenoid cavity,
the acetabulum is very deep, and it actually
holds the vast majority of the head of the
femur. Here, we’ve only got a very shallow
glenoid cavity for that large humeral head.
The glenoid cavity has reinforced this deepened
by this fibrocartilagenous glenoid labrum.
We can see the glenoid labrum here. We can
see it running all the way around the glenoid
cavity. And this serves to deepen that recess
which the head of the humerus sits. We can
see we’ve got the glenoid labrum running
around here, helping to deepen that cavity.
The humeral head is held in the cavity, if
you remember, by the tonic contraction of
the rotator cuff muscles. This scapulohumeral
muscle passing from the scapula to the
humerus, the supraspinatus, infraspinatus,
subscapularis, and teres minor muscles. The
base old contraction, the tonic contraction
of this muscle actually pulls the head against
the glenoid cavity, and this actually helps
to stabilize the joint. The fibrous capsule
of the glenohumeral joint is relatively loose.
This allows the increased mobility. If it
was tight, then you wouldn’t have as much
mobility, and it’s running from the glenoid
cavity to the anatomical neck of the humerus.
So we can see we’ve got the anatomical neck
of the humerus here. Remember, it’s between
the tubercles of the humerus
and the head of the humerus, and it attaches
here to the perimeter of the glenoid cavity.
Superiorly, the joint is actually reinforced
because we have the tendon of long head of
biceps. And here we can see the tendon of
long head of biceps. Remember, it’s passing
through the intertubercular sulcus, the
intertubercular groove between the two tubercles.
It’s running up, over the head of the humerus
to attach to the supraglenoid tubercle.
And this along with the acromion helps to reinforce
the joints superiorly. Inferiorly, the joint
is very loose, and there is no reinforcements
inferiorly of the capsule. And if the humerus
is to dislocate at the glenohumeral joint,
it typically will be an inferior dislocation.
The head is then pulled forwards via the action
of pectoralis major muscles. So let’s have
a look at the ligaments to support it. Well,
we have the glenohumeral ligaments. The glenohumeral
ligaments, we can see here, are found anteriorly
and they strengthen the joint anteriorly.
We can see we’ve got superior, a medium, and
an inferior part of the glenohumeral ligament,
and these are running here. Here, we can see
the tendon of subscapularis passing to the
lesser tubercle, one of the rotator cuff muscles,
and that will be coming from the subscapular
fossa. Here, we can see the anterior view of
the joint. So we can see the coracoid process
here as well. But here, we have the glenohumeral
ligament, superior, medium, and inferior,
we can see lying anteriorly to reinforce the
joint. We also have the coracohumeral ligament.
The coracohumeral ligament passes from the
coracoid process to the greater tubercle of
the humerus. And this is a strong band. It
strengthens the joint again superiorly.
So we can see the coracohumeral joints running
across here to the coracoid process and it
passes to the greater tubercle of the humerus.
It strengthens it superiorly. We also have
the transverse humeral ligament. And this
bridges the intertubercular groove. It attaches
to the greater and lesser tubercle. So we
can see it running over here. And it creates
that tunnel for the long head of biceps to pass
through. We also have a complex arrangement
that again is very strong and it prevents
superior dislocation. And this is known as
the coracoacromial arch. We have the coracoid
process, we have the acromion, and we have
the coracoacromial ligament. Remember, the
coracoacromial ligament helping to augment
supports the acromioclavicular joint. Well,
it actually forms a roof over the superior
aspect of the glenohumeral joint. And this
serves to prevent superior dislocation.
Movements at the glenohumeral joints are flexion-extension,
abduction, adduction, we’ve got rotation,
and we’ve also got circumduction. And these
movements cover a wide range and they’re
possible due to the high number of muscles
that enable these movements. And also the
loose fibrous capsule and the arrangement
of the head of the humerus onto the glenoid
cavity, these allow a high range of movement.