Serratus Posterior Inferior

Remember last week's Serratus Posterior Superior ? Well there is also an inferior!

Serratus Posterior Inferior

Serratus: jagged looking like a knife. Posterior: on the back.  Inferior: below

This muscle lives in your lower back attaching from the lower spine onto the lower ribs and instead of a xmas tree shape (or upside down 'V')  like last week's  Superior,  

Serratus Posterior Inferior is a V- Shape.

Muscle Attachment Points:

breakdown of terminology below:

 

Origin: spinous processes of T11-L2

Insertion: posterior surfaces of ribs 9-12

*spinous processes are the bony bumps that stick out from the back of your spine (aka vertebral column) our spine is divided into segments called vertebrae. T refers to the thoracic spine (mid back where ribs attach) & L refers to our lumbar spine - basically our low back.

(I will fully breakdown the spine in a future post) In conclusion - many many muscles attach to the spinous processes on the vertebrae of our spine :)

Serratus Posterior Inferior

Muscle Actions:

depresses ribs 9-12 at the sc/cs joints

this muscle simply depresses ribs 9-12 during exhalation. It is pretty much stabilizing our lower ribs against the pressure of the pull of the diaphragm.

This subtle movement happens at the sterno-costal and costo-spinal joints*

*our ribs can elevate (rise) and depress (lower) at the front & back of our ribcage. The front is where the sternum (breastbone) & ribs (costals) meet aka sterno-costal joints
And on the back - costo-spinal joints: is where ribs connect to our spine

So for muscle actions I've really been enjoying making little stop-motion vids - however the subtle movement of this particular muscle (which is really a stabilzer more than anything!) is tough to capture! For example see last week's vid for serratus posterior superior (!)

Until our Next Muscle Monday!