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Anterior Axioappendicular Muscles – Anatomy of the Shoulder

by James Pickering, PhD

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    00:00 In this lecture, we're going to look the shoulder region.

    00:03 Specifically the axioappendicular and the scapulohumeral muscles.

    00:10 We're going to look at the shoulder joints and it's range of movement and specifically how the muscles enable the shoulder to move.

    00:19 The anterior and posterior axioappendicular muscles.

    00:23 We'll then look at the scapulohumeral muscles and how some of these formed the rotator cuff coming from the scapula to the humerus.

    00:33 We'll then look at the functional anatomy of these with their origin, insertion and the movements that they can allow the shoulder to perform.

    00:43 The anterior axio-appendicular muscles, what do I mean by axio-appendicular muscles? Well, these muscles that are run from the axial skeleton to the appendicular skeleton.

    00:57 They run from the axial skeleton, the sternum, the ribs, the vertebral column to the appendicular skeleton which in this case is the upper limb, the superior appendicular skeleton, the clavicle, the scapula, the humerus.

    01:14 Here we can see the anterior muscles, we have a whole series of them.

    01:18 We have pectoralis major, we can see here, we can have pectoralis minor, we can see here.

    01:25 We've got subclavius, we can see here and also we've got serratus anterior, we'll come back to that later on.

    01:32 What we can see is the pectoralis major muscle has a number of heads, really it's got two heads, it's got a clavicular head, where it's coming from the clavicle but the axio-appendicular part of it, it's where it's coming from the sternum and the costal margins of the ribs.

    01:53 We can see this muscle, this fan shape muscle is running down towards the shaft of the humerus and we'll see where it attaches on the shaft of the humerus just within the intertubercular sulcus but here not up in between the greater and lesser tubercles, quite distally down on to the shaft of the humerus.

    02:14 We got pectoralis major here.

    02:17 This is a large fan shape muscle that's easily visible once the skin of the anterior chest wall has been reflected.

    02:25 Clavicular head coming from the clavicle and the sternocostal head coming really from the sternum and the costal cartilages.

    02:34 Reflect pectoralis major and we find we have pectoralis minor, we can see pectoralis minor here coming from ribs, three, four and five, we have pectoralis minor running up to the coracoid process of the scapula.

    02:51 Here, it's now important to remember those bony features I was talking about in the first lecture.

    02:57 We can see we've got pectoralis minor, running out towards the coracoid process and that lies deep the pectoralis major.

    03:06 Running underneath the clavicle running from the first rib to that group of subclavius that I spoke about again in the first lecture, on the inferior surface of the clavicle, we've got subclavius muscle we can see here.

    03:22 Running from the external aspect of the first rib, although, I over to the clavicle and here we can see this anterior axio-appendicular muscles.

    03:34 We'll cover serratus anterior in a moment.

    03:37 We can see that the pectoralis major muscle as I mentioned that has two heads and this table really is going to detail their origin and insertion.

    03:48 Its then going to look at the nerve supply and we can cover some functional anatomy here.

    03:53 But here, we've the pectoralis major, we've got the clavicular head and the sternocostal head.

    03:59 We can see where they're attaching as I mentioned previously and these are going to insert into the intertubecular sulcus specifically the lateral lip of it but not between the two tubecals and the nerve supply to this muscle is by the lateral and medial pectoral nerves and these are branches that are coming from the bracheoplexis which we'll see.

    04:23 Here we've got the specific root values, so the specific spinal cord segments that gives rise to those nerves.

    04:33 The function of pectoralis major is it adducts and medially rotates the shoulder joint.

    04:40 So it adducts, it brings the arm, back against the thoracic cavity and it's also revolve in medially rotation the scap -- the shoulder joint.

    04:52 It also pulls the scapula anteriorly so it protracts the pectoral girdle and it pulls the inferiorly as well.

    05:01 So pectoralis major, remember here we can see pectoralis major muscle.

    05:06 Now, we've got pectoralis minor, we can see pectoralis minor like I said coming from ribs, 3 to 5 passing towards the coracoid process of the scapula and this is innovated by the medial pectoral nerves and again we can see this is coming from C8, T1 spinal cord segment.

    05:26 Pectoralis minor is important in stabilizing the scapula so it holds the scapula against the posterior chest wall and it also pulls it anteriorly and inferiorly, a similar function to pectoralis major.

    05:42 If we remind ourselves with subclavius positioned inferior to the clavicle, we can see that it's running from the first rib and the sternum, the junction of those two to the middle third of the clavicle, supply by the subclavian nerve.

    05:58 It stabilizes and depresses the clavicle.

    06:02 We can appreciate that if we see it here coming from the junction of the sternum and the first rib, this is going to be a solid, its origin, this is not going to move and as it muscle contract, it is going to depress the clavicle.

    06:16 The final muscle I want to talk about is serratus anterior and this is somewhat different from the previous muscles I spoke about that were coming from this small anterior aspect of the chest wall.

    06:29 Serratus anterior is coming from this lateral aspect of the chest wall and it's passing backwards towards the medial boarder of the scapula.

    06:40 Here we can see the medial boarder of the scapula, remember this is the lateral boarder and this serratus anterior muscle, it's got this nice serrated edge which gives its name coming from the ribs here we can see rib 2, 3, 4, 5, 6, 7, 8, 9 running all the way along the chest wall.

    07:02 We can see it's running between the chest wall and the scapula.

    07:07 This impression here is just a shading through the scapula.

    07:11 It runs between the scapula and the chest wall to attach to the medial surface.

    07:16 We can see here serratus anterior, coming from the external surface of ribs 1 to 8.

    07:23 We can see have the fibers passing through the medial boarder of the scapula, see it passing in between the scapula and the posterior chest wall, it is innovated via the long thoracic nerve and the long thoracic nerve is going through running down in this direction.

    07:44 We can see the long thoracic nerve running down in this direction.

    07:48 The long thoracic nerve coming from spinal cord segments C6 and C7.

    07:55 It's involved in protracting the scapula so it can pull the scapula forward and hold it against the posterior thoracic wall.

    08:03 This is important if you were to say push off from a wall.

    08:07 If you are leaning against the wall and pushing off, then you need the scapula to be anchored against the posterior chest wall.

    08:14 If that's anchored against the posterior chest wall then you'll be able to move backwards, if it isn't, if there's damage say to the long thoracic nerve then this serratus anterior cannot contract, it cannot hold the scapula against the posterior, thoracic wall and then when you push off, this scapula actually pushes out into the skin of the back and you have something called winged scapula.

    08:40 So damage to thoracic nerve via trauma of a knife attack in to the axilla or breast surgery or removing of lymph nodes for cancer treatment, can damage the long thoracic nerve and lead to winged scapula.

    08:54 If we have to look at these in the more anatomical arrangement then here we can see, we've got pectoralis major here, we can see we've got serratus anterior sitting underneath it here, we can see that that fan shape pectoralis major is passing towards the arm and we've got this muscle here, deltoid, which will cover in the few moments time.

    09:18 But what we can see is that between pectoralis major here and deltoid, we have this deltopectoral triangle and that in trianglism important as it receives the cephalic vein.

    09:32 As we mentioned the previous lecture, the cephalic vein passing up towards the axillary vein, runs in the deltoid triangle and here we have the formation of deltopectoral triangle.

    09:45 Here we can se pectoralis major and we can see serratus anterior.

    09:49 If we reflect pectoralis major over here on this side of this screen we can see here the reflected cottage of pectoralis major.

    09:58 We can see it's cottage here as it's running down attaching to the intertubecular sulcus and we can see pectoralis minor.

    10:07 What we can see directly beneath pectoralis minor is a blood vessel here, another blood vessel here and a yellow nerve.

    10:17 This indicate the auxiliary artery and the auxiliary vein and the brachial plexus and these are running deep within the axilla running deep to pectoralis minor, we can see them running along here and we look at these in the next lecture.

    10:32 Here we can see pectoralis major, we can see once it's reflected, we can see pectoralis minor and here we're gonna see some of the digits of serratus anterior.


    About the Lecture

    The lecture Anterior Axioappendicular Muscles – Anatomy of the Shoulder by James Pickering, PhD is from the course Upper Limb Anatomy.


    Included Quiz Questions

    1. Its origin is from the second and third ribs
    2. It has a clavicular head
    3. It has a sternocostal head
    4. It is a fan-shaped muscle
    5. It is attached to the greater tubercle of the humerus
    1. It arises from third, fourth and, fifth ribs
    2. It arises from the first rib
    3. It arises from the coracoid process
    4. It arises from the sternum
    5. It arises from the humerus
    1. Adducts and medially rotates the shoulder joint
    2. Adducts and laterally rotates the shoulder joint
    3. Abducts and laterally rotates the shoulder joint
    4. Abducts and medially rotates the shoulder joint
    5. Pulls scapula inferiorly
    1. Serratus anterior
    2. Subclavius
    3. Pectoralis major
    4. Pectoralis minor
    5. External intercotal muscles
    1. C5, 6, 7
    2. T1
    3. C8
    4. T2
    5. C4
    1. Cephalic veins
    2. Basilic veins
    3. Superior vena cava
    4. Carotid veins
    5. Inferior vena cava
    1. C7, C8, and T1
    2. C1 and C2
    3. C3 and C4
    4. C4 and C5
    5. C6 and C7

    Author of lecture Anterior Axioappendicular Muscles – Anatomy of the Shoulder

     James Pickering, PhD

    James Pickering, PhD


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    Outstanding
    By Victoria W. on 04. December 2018 for Anterior Axioappendicular Muscles – Anatomy of the Shoulder

    So well organized and clearly explained! The way you organize the material makes anatomy reasonable... the puzzle pieces fit.

     
    So Important to have
    By Yara de P. on 31. October 2018 for Anterior Axioappendicular Muscles – Anatomy of the Shoulder

    I am really enjoying this, helps me understand better and it makes it possible to review after I have had a lecture at my university or even before.