Superficial and Intermediate Muscles of the Back

INSTRUCTOR: In this video, we will be discussing the superficial and intermediate muscles of the back. We will also show visible nerves innervating these muscles. Lastly we will touch on the visible ligaments of the spinal column. To begin, the superficial muscles of the back include the trapezius, the latissimus dorsi, the rhomboid major, rhomboid minor, and lastly the levator scapulae.

Starting with the trapezius, this muscle originates superiorly on the occipital bone and spans anteriorly on the spines of the thoracic vertebrae. It inserts on the scapula and functions to fix, rotate, and elevate the scapula. The trapezius is innervated by the accessory nerve and can be seen on a section here. This is the accessory nerve.

Next is the latissimus dorsi. Shown here and here this muscle originates on the lower thoracic to sacral vertebrae and the iliac crest.

It inserts on the humerus and it functions to aduct, extend, and medially rotate the arm. The latissimus dorsi is innervated by the thoraccodorsal nerve. This nerve originates from the brachial plexus, which we will review with you in the next unit. Here is the thoraccodorsal nerve.

The next three muscles in the superficial compartment of the back are all inserting on the scapula. They are all innervated by the dorsal scapular nerve, and they're located deep to the trapezius muscle. Starting with the rhomboid major this muscle originates on the spinous process of thoracic vertebrae.

It inserts on the scapula, and its function is to retract and downwardly rotate the scapula.

Next is the rhomboid minor. This muscle originates on the spinous process of T1, and inserts on the scapula.

Like the rhomboid major its function is to also retract and downwardly rotate the scapula.

Finally we have the levator scapulae. This muscle originates on the transverse process of cervical vertebrae and is going to insert all the scapula, just like the rhomboid major and minor. Its function is to elevate the scapula and laterally flex the neck.

Let's review these muscles one more time. Here we have the levator scapulae, rhomboid minor, and rhomboid major.

Now let's move on to the intermediate muscles of the back. This includes the serratus posterior inferior, and serratus posterior superior. Both muscles are innervated by the [INAUDIBLE] of spinal nerves. Starting with the serratus posterior inferior.

This muscle originates on the spinous process of vertebrae in the lumbar region. It inserts on the lower ribs and the function of this muscle is to depress the ribs it attaches to.

Next is the serratus posterior superior. This muscle is located deep to the rhomboid major and minor.

It originates on the spinous process of vertebrae in the upper thoracic region. It is going to insert on the upper ribs. The function of this muscle is to elevate the ribs it attaches to.

Now let's review the ligaments of the spinal column that are visible. The first is the supraspinous ligament. This is going to connect the spinous process of each vertebrae and will span the entire vertebral column. In the cervical region, the supraspinous ligament is thickened and is referred to as the ligamentum nuchae. Once again, the ligamentum nuchae will span the cervical region of the spinal column.

Now let's do one more review of the muscles we have learned today. First is the trapezius. Then the latissimus dorsi. And deep to the trapezius is the rhomboid major, rhomboid minor, levator scapulae.

Lastly are the intermediate muscles of the back. First we have serratus posterior superior located under the three muscles I've just identified. And located deep to the latissimus dorsi will be the serratus posterior inferior. This concludes the superficial and intermediate muscles of the back.