Anterior Axioappendicular Muscles

00:01 For the next topic let's look at the anatomy of the shoulder and very much look at the So, now, let's turn our attention to pectoralis major.

01:19 This is a large flat muscle on the anterior surface of the chest.

01:23 We can see it has the clavicular head. It has a sternocostal head.

01:27 And it also has a small abdominal part we can see there at the bottom.

01:31 We can see that it's going to pass laterally away from the chest wall over towards the humerus.

01:37 And here, we can see attaching to the anterior surface of the medial aspect of the clavicle.

01:43 And also, from the sternum and the six costal cartilages we can see here.

01:48 Here, we can see it referring to the anterior layer of the rectus sheath.

01:53 All of these muscle fibers are going to pass laterally towards the humerus where it attaches to the lateral lip of the intertubercular sulcus.

02:01 Importantly, the brachial plexus has a role to play here in innervating the pectoralis major muscle.

02:09 We'll talk about brachial plexus in much more detail later but coming from the brachial plexus is the lateral pectoral nerve.

02:17 The lateral pectoral nerve is also serve alongside the medial pectoral nerve to go on and supply pectoralis major muscle.

02:25 The function of pectoralis major muscle is to adduct the arm so it helps to pull the arm towards the midline and it also helps to internally rotate the shoulder joint which we can see here.

02:39 It helps to pull the scapular anteroinferiorly.

02:42 So, it very much helps to move the shoulder girdle in an anterior position.

02:47 If we look at pectoralis minor, we see it's very similar to pectoralis major but a smaller version.

02:53 We can see it's originating from the third, fourth, and fifth ribs and it extends superiorly up towards the coracoid process of the scapula.

03:03 This muscle is innervated by the medial pectoral nerve.

03:06 It's not innervated via the lateral pectoral nerve like pectoralis major was.

03:11 So, just one single innervation for pectoralis minor.

03:15 Here, we can see the function of pectoralis minor in stabilizing the scapula.

03:20 And it helps to pull the scapular anteroinferiorly. Let's talk about subclavius muscle.

03:26 This is a very small muscle that sits underneath the clavicle. Hence, subclavius muscle.

03:32 It's running from the first rib all the way up to the middle third of the clavicle and it's supplied by the subclavian nerve.

03:40 This nerve is running again from the brachial plexus.

03:44 The function of the subclavius is to actually stabilize and depress the clavicle.

03:49 So, it helps to hold the clavicle against the axial part of the skeleton.

03:54 We can see it holding it down onto the chest wall there. Let's have a look at serratus anterior.

04:01 So, this muscle is positioned on the posterior aspect of the thoracic cage and it is coming very much from the first through to eighth ribs we can see there on the lateral aspect of the thoracic cage and we can see, it actually forms this serrated edge, hence, its name serratus anterior.

04:19 It passes all the way back to the medial border of the scapula.

04:22 So, you can see how it actually runs between the scapula and the posterior wall of the chest, so, it can - of the thoracic cage, so it can attach to that medial border of the scapula.

04:35 This muscle is innervated by the long thoracic nerve.

04:39 You can see it running down superficial to the muscle and it does actually make this nerve quite vulnerable if you have an exposed lateral chest wall.

04:48 This muscle is important for stabilizing the scapular and it also helps to protract the scapula, that is bring it round and hold it close onto the posterior aspect of the thoracic cage.

05:02 Now, let's have a look at these muscles altogether.

05:05 And we can see that we have pectoralis major here and we can have serratus anterior just underneath it.

05:11 We can see we have deltoid, a muscle we haven't spoken about so far.

05:15 But you're gonna see how this creates an important space, the deltopectoral triangle, a triangle between these two important muscles.

05:24 The cephalic vein as we've spoken about previously passes up through the upper limb and it runs within this space.

05:32 Here, we can see now, pectoralis major has been removed. We have pectoralis minor.

05:37 And we see that muscle passing towards the coracoid process of the scapula.

05:41 It is actually running over the axillary vein, the axillary artery, and the brachial plexus.