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Anterior Axioappendicular Muscles – Anatomy of the Shoulder

by James Pickering, PhD
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    00:01 In this lecture, we’re going to look at the shoulder region specifically the axio-appendicular and the scapulohumeral muscles. So we are going to look at the shoulder joint and its range of movement and specifically have the muscles enable the shoulder to move, the anterior and posterior axio-appendicular muscles. We then look at the scapulohumeral muscles and how some of these form the rotator cuff coming from the scapula to the humerus. 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. So the anterior axio-appendicular muscles. What do I mean by axio-appendicular muscles? Well these are muscles that run from the axial skeleton to the appendicular skeleton. So 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 And here we can see the anterior muscles we have a whole series of them. We have pectoralis major, we can see here. We have pectoralis minor, we can see here. We have got subclavius, we can see here and also we have got serratus anterior. We will come back to that later on.

    01:32 What we can see is the pectoralis major muscle has a number of heads, really it has got two heads. It has got clavicular head where its coming from the clavicle. But the axio- appendicular parts of it, is 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 will 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 onto the shaft of the humerus. So we have got pectoralis major head.

    02:17 This is a large fan shape muscle that is easily visible once the skin of the anterior chest wall has been reflected. Clavicular head coming from the clavicle and a sternocostal head coming really from the sternum and the costal cartilages. Reflect pectoralis major and we have find we have pectoralis minor. We can see pectoralis minor here. Coming from ribs 2, 3, and 4, we have pectoralis minor running up to the coracoid process of the scapula.

    02:52 So here its now important to remember those bony features I was talking about in the first lecture. We can see we have got pectoralis minor running up towards the coracoid process and that lies deep to pectoralis major. Running underneath the clavicle, running from the first rib to that groove for subclavius that I spoke about again in the first lecture.

    03:17 On the inferior surface of the clavicle we have got subclavius muscle we can see here.

    03:23 Running from the sternal aspect of the first rib all the way over to the clavicle.

    03:30 And here we can see this anterior axio-appendicular muscles. We will cover serratus anterior in a moment. We can see that the pectoralis major muscle as I mentioned that has two heads.

    03:44 And this table really is going into detail the origin and insertion is then going to look at the nerve supply and we can cover some functional anatomy here. But here with the pectoralis major we have got the clavicular head and the sternocostal head. We can see where there they are attaching as I mentioned previously. And these are going to insert into the intertubercular sulcus, specifically the lateral lip of it, but not between the two tubercles. The nerve supply to this muscle is via the lateral and medial pectoral nerves and these are branches that are coming from the brachial plexus which we'll see. Here we have got the specific root values.

    04:26 So the specific spinal cord segments that give rise to those nerves. The function of pectoralis major is, it adducts and medially rotates the shoulder joint. So it adducts, it brings the arm back against the thoracic cavity and it's also involved in medially rotating the scapular shoulder joint. It also pulls the scapula anteriorly, so it protracts the pectoral girdle and it pulls it inferiorly as well. So it’s pectoralis major.

    05:03 Remember here we can see pectoralis major muscle. Now we have got pectoralis minor. We can see pectoralis minor like I said coming from ribs 3-5 passing towards the coracoid process of the scapula and this is innervated via the medial pectoral nerves. And again we can see this is coming from C8, T1 spinal cord segment. Pectoralis minor is important in stabilizing the scapula, so it holds the scapula against the posterior chest wall and also pulls it anteriorly and inferiorly, a similar function to pectoralis major. If we remind ourselves of 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 supplied by the subclavian nerve. It stabilizes and depresses the clavicle. We are going to 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 is not going to move, and as its muscles contract, it is going to depress the clavicle. The final muscle I want to talk about is serratus anterior.

    06:21 And this is somewhat different from the previous muscles I spoke about. They were coming from this small anterior aspect of the chest wall. Serratus anterior is coming from this lateral aspect of the chest wall and it's passing backwards towards the medial border of the scapula.

    06:40 So here we can see the medial border of the scapula and this is the lateral border.

    06:45 And this serrated anterior muscle has 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. We can see it is running between the chest wall and the scapula. So this impression here is just a shading through the scapula. It runs between the scapula and the chest wall to attach to the medial surface. So we can see here, serratus anterior coming from the external surface of ribs 1-8. We can see we have the fibers passing to the medial border of the scapula, see it passing in between the scapula and the posterior chest wall.

    07:36 It is innervated via the long thoracic nerve. And the long thoracic nerve is going to be running down in this direction. So 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. Its involved in protracting the scapula, so it can pull the scapula forward and hold it against the posterior thoracic wall. This is important if you were to say push off from the wall. If you lean against the wall and pushing off, then you need the scapula to be anchored against the posterior chest wall. If that is anchored against the posterior chest wall, then you will be able to move backwards. If it isn't, if there is damaged state 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, the scapula actually pushes out into the skin of the back and you have something called winged scapula. So damage to the thoracic nerve via trauma when knife attacked into the axilla or breast surgery or removal of lymph nodes for cancer treatment, can damage the long thoracic nerve and leads to winged scapula. If you have look at these in a more anatomical arrangement, then here we can see we have got pectoralis major here. We can see we have got serratus anterior sitting underneath here. We can see that the fan shaped pectoralis major is passing towards the arm and we have got this muscle here, deltoid which we'll cover in a few moments of time. But what we can see is that between pectoralis major here and deltoid, we have this deltopectoral triangle. And that triangle is important as it receives the cephalic veins. As we mentioned in the previous lecture, the cephalic vein passing up towards the axillary vein runs in the deltopectoral triangle.

    09:41 And here we have the formation of the deltopectoral triangle. So here we can see pectoralis major and we can see serratus anterior. If we reflects pectoralis major over here on this side of the screen we can see here the reflected cartilage of pectoralis major. We can see its cartilage here as it is running down attaching to the intertubercular sulcus and we can see pectoralis minor. What we can see directly beneath pectoralis minor is a blood vessel here and another blood vessel here and a yellow nerve. These indicate the axillary artery, the axillary vein and the brachial plexus. And these are running deep within the axilla, running deep to pectoralis minor.

    10:27 We can see them running along here and we'll look at these in the next lecture.

    10:33 So here we can see pectoralis major, we can see once it's reflected, we can see pectoralis minor and here we can see some of this 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 second and third ribs
    2. It has a clavicular head
    3. It has a sternocostal head
    4. It is fan shaped muscle
    5. It is attached to the shaft 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. C 5, 6, 7
    2. T 1
    3. C 8
    4. T2
    5. C 4
    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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