Gateways in the Posterior Wall of the Axilla

00:01 So, now, let's look at some important spaces on the posterior aspect of the axilla or gateways as they're described here.

00:12 So, looking at the posterior aspect of the axilla, we have a number of muscular structures included.

00:18 Here, we're looking at the posterior aspect of it, so, we're looking at the axilla from behind the individual.

00:24 And we can see a number of important spaces. So, here, we can see the quadrangular space.

00:29 Here, we can see the triangular space. And then, inferiorly, we have the triangular interval.

00:37 Now, these are important spaces or gateways as they allow structures that are found within the axilla to pass posteriorly out of the axilla into the posterior aspect of the arm and surrounding region.

00:50 So, let's have a look at these structures in a bit more detail.

00:54 So, let's look at the boundaries of the quadrangular space.

00:57 So, we see the quadrangular space highlighted here in green.

01:01 Superiorly, we have teres minor. Medially, we have the long head of triceps brachii.

01:08 Inferiorly, we have teres major. And then, laterally, we have the shaft of the humerus.

01:15 So, for the quadrangular space as its name implies, it has four sides and we've got four muscles that form its boundaries.

01:22 Teres minor, teres major, superiorly, inferiorly, the long head of triceps brachii medially and then, the shaft of the humerus laterally.

01:32 Passing through this space, so, passing from the axilla to the posterior aspect of the arm, we have a number of important structures. We have the axillary nerve.

01:41 And then, we have the posterior circumflex humeral artery and its neighboring vein.

01:47 So, these are passing out of the axilla to the posterior aspect of the arm via the quadrangular space.

01:53 The two arterial, the venous and arterial structure here runs around the surgical neck of the humerus.

02:00 And therefore, fractures at this location cause damage to those blood vessels.

02:04 Also, increasing in muscle mass can also lead to compression of these nerves and blood vessels.

02:12 Looking at the triangular space which is located more medially, we have similar boundaries.

02:18 Superiorly, we have the teres minor muscle and inferiorly, we have teres major.

02:24 And now, this time, the long head of triceps brachii forms the lateral boundary.

02:29 But as its name suggests, the triangular space, there are only three landmark structures here.

02:36 Superiorly, teres minor, inferiorly, teres major, and laterally, we have the long head of triceps brachii.

02:42 Passing through this space, we have the circumflex scapular artery.

02:48 As you'll see, it is accompanied by its neighboring vein.

02:52 So, where there's an artery passing through this space, you'll also find the neighboring vein as well.

02:58 Most inferiorly of these three spaces, again, it has three boundaries because it's triangular in shape.

03:03 We have the triangular interval. Superiorly, we have teres major forming its superior boundary.

03:09 And then, medially, again, we're recognizing the long head of triceps brachii.

03:14 And then, laterally, we have the shaft of the humerus.

03:18 And we can see this forming the lateral aspect of the triangular interval.

03:24 Passing through the triangular interval, again, from the axilla through to the posterior aspect of the arm, we find an important nerve.

03:34 Here, we can see the radial nerve that's passing through this space to run alongside the humerus, supplying important structures in the posterior aspect of the arm.

03:44 And here, we can see the deep brachial artery as well passing from the axilla down into the posterior aspect of the arm.

03:52 So, there important spaces that allow structures to pass from the axilla to the posterior aspect of the arm.