Dan has taught college Nutrition and Anatomy courses for over 5 years. He has a B.S. in Exercise Physiology from Furman University and a M.S. in Dietetics & Nutrition from Florida International University. He is a Registered Dietitian (RD) and a Certified Exercise Physiologist (EP-C)
Serratus Posterior Muscles
How well are your serratus posterior muscles working? To find out, try this simple at home physical assessment test:
- Stand up with your arms hanging naturally at your sides
- Take a long, deep breath in
- Now blow all of that air out through your mouth
- Bend your back slightly backwards then come back to upright position
- Now turn your back to the right
- Now turn your back to the left
If you were able to complete all of these steps without much difficulty or pain, then your serratus posterior muscles are working pretty well!
The serratus posterior muscles are muscles that are located in the upper and lower parts of the back. These muscles actually consist of two different sections of muscles, which include:
- Serratus posterior superior: a thin, four-sided muscle located in the upper back
- Serratus posterior inferior: a thin muscle located in the lower back
Serratus Posterior Muscles: Innervation
The serratus posterior muscles are innervated by several nerves from the ventral rami. The ventral rami are the nerves that make up the anterior divisions of the spinal nerve. For example, spinal nerves come out of each of the vertebra of the spinal column. Some nerves branch off posteriorly (to the back) while other nerves branch off to the anteriorly (to the front). The ventral rami are the nerves that branch off anteriorly. The following chart describes the specific nerves that innervate each section of the serratus posterior muscles.
|Section of Serratus Posterior Muscles||Innervating nerves|
|Serratus Posterior Superior||Ventral rami of T1 - T5|
|Serratus Posterior Inferior||Ventral rami of T9 - T12|
The 'T' stands for thoracic, which means that these nerves are found in the thoracic region of the spinal column. The thoracic region of the spinal column is located in the back, between the base of the neck and the lower back. There are 12 total thoracic vertebrae.
Serratus Posterior Muscles: Function
The function of the serratus posterior muscles for each section, and the following chart describes the different functions of each section of the muscle (which are the same actions you performed during the physical assessment test at the beginning of the lesson).
|Section of Serratus Posterior Muscles||Function|
|Serratus Posterior Superior||Elevates or raises the ribs which assists in inhalation. As the ribs are elevated, the lungs are able to expand which allows the person to inhale more deeply.|
|Serratus Posterior Inferior|| Extension of the back: backward bend of the back
Lateral rotation of the back: twisting or turning the back to one side
Depression of the lower ribs: aids in exhalation by compressing the lungs
The serratus posterior muscles are made up of two different sections of muscles, one section is located in the upper back (serratus posterior superior) while the other section is located in the lower back (serratus posterior inferior).
These muscles are innervated by the ventral rami of several thoracic (T) vertebrae. The ventral rami are the nerves that branch off the spinal cord anteriorly. The serratus posterior superior is innervated by the ventral rami of the T1-T5 vertebrae, while the serratus posterior inferior is innervated by the ventral rami of the T9-T12 vertebrae.
The serratus posterior superior muscle functions to elevate the ribs which assists with inhalation. The serratus posterior inferior muscle functions to extend the back (bend backwards), laterally rotate the back (turn to the side), and depress the lower ribs which assists in exhalation.
Medical Disclaimer: The information on this site is for your information only and is not a substitute for professional medical advice.
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