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This video is about the superficial muscles of the back, their anatomical layers, origins, insertions, and functions.
Introduction
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Hey What’s up. Meditay here and in this video, we’ll be covering the Superficial muscles of
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the back. Alright. Generally, the muscles of the back consist of superficial muscles
Division of the Superficial Muscles
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and deep muscles. So let’s take a closer look at the superficial muscles.
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These muscles are divided into layers. So, the 1st layer is the most superficial one.
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It consist of the Trapezius, as you see here, and the Latissimus Dorsi.
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The 2nd layer are the Rhomboid Major, Rhomboid Minor and Levator Scapula, and the 3rd layer of
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muscles consists of the Serratus Posterior superior and Serratus Posterior inferior.
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So these are the muscles we’re going to go through throughout this video.
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We’ll start with the 1st Layer, the Trapezius. Now the trapezius Is this large muscle
Trapezius
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that take up the majority of your shoulders. They can also be classified as a cardiothoracic muscle,
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in addition to being one of the superficial muscles of the back.
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Now the Trapezius consists of 3 parts. There’s a Superior Part, a Middle part and an inferior part.
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The superior part will originate from the Superior nuchal line, the external occipital protuberance,
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and the nuchal ligament. It’s then going to insert
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at the Acromial end of the clavicle, as you see here, as well as the acromion of the scapula.
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Then we have the middle part, which originates from the spinous process of the C7-T3 or T4,
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and it’s going to insert at the Spine of the Scapula as you see here, and the acromion.
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Then we have the Inferior Part, which originates from the spinous process of T4-T12
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and insert at the spine of scapula as well. Ok. So what is the function of the Trapezius?
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The Inferior part will pull the shoulder downwards, Middle and superior fibers
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will pull the scapula towards the midline, as well as elevating the scapula. They may also extend the
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head to the side as well in strong contraction. But primarily, they’re associated with movement
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of the scapula. So that is the Trapezius. Next we have the Latissimus Dorsi. And
Latissimus Dorsi
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the latissimus dorsi has several origin points, so let’s go through them one by one.
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It’s first going to originate from the spinous process of T7 to T12. It’s also going to originate
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from the thoracolumbar fascia. And From the Iliac Crest. And from the Inferior surface
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of the 9th to 12th Rib. And the Inferior angle of the Scapula. The fibers are then going to go
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from all of these places and unite to insert at the crest of the lesser tubercle on the humerus,
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as you see here. The overall function of the Latissimus dorsi is to internally rotate,
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adduct and dorsal flex the arm. So that was the 1st layer of the superficial muscles of the back.
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Then if you remove the Trapezius and the Latissimus Dorsi, you’ll get to the 2nd layer,
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which consist of the Rhomboid Major, as you see here. This muscle originates from the
Rhomboid Major
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Spinous process of T1-T4, and insert at the Lower 2/3 of the medial border of Scapula.
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It’s function is to elevate an retract the scapula,
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as well as internal rotation of the scapula. Then we have the Rhomboid Minor. Which is this one.
Rhomboid Minor
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It originates from the Spinous Process of C6-C7, and insert at the Upper 1/3 of the medial border
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of scapula, so it’s superior to the rhomboid major. Its function is also more or less the same,
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which is elevation an retraction of scapula, as well as internal rotation of the scapula.
Levator Scapulae
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Then there’s the Levator Scapulae. This one. It originates from the spinous processes of C1-C6
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and insert at the Superior angle of the Scapula. Its function is to elevate the scapula.
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And that was the 2nd layer of the superficial back muscles. Now. If you remove these three muscles,
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we’ll get to the 3rd and last layer, which consists of the Serratus Muscles. First,
Serratus Posterior Superior
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we have the Serratus Posterior Superior, which is here, underneath the rhomboids. It originates
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from the Spinous Process of C6-T2 and Insert at the External Surface of the 2nd to 5th Ribs.
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Its function is to Elevate the ribs, to help with inspiration by expanding the thoracic cavity so
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that air can come in. The other muscle is the Serratus Posterior Inferior. Which is down here.
Serratus Posterior Inferior
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It originates from the Spinous Processes of T11-L2 and insert at the External Surface of the
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9th-12th ribs. And its function it the opposite of the serratus posterior superior. This one is
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going to pull the ribs down, to aid the process of Expiration, breathing out basically. And that was
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the 3rd layer of the superficial back muscles. In the next video, we’ll go through the
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classification system and all the muscles that are considered a part of the deep back muscles.
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