Superficial and Intermediate Intrinsic Back Muscles

00:01 We'll start with the superficial and intermediate intrinsic back muscles.

00:07 First we have the splenius capitis and splenius cervicis, which together make up the superficial layer, also known as the spinotransversales.

00:18 A little bit further down we have the spinalis, longissimus and iliocostalis which together make up the intermediate layer, or together we call it the erector spinae.

00:33 Here's the splenius capitis.

00:35 A little bit more zoomed in so we can see its attachments.

00:38 We see we have the spinous processes of C7 to T4, going up to the mastoid process of the temporal bone as well as the lateral 1/3 of the superior nuchal line.

00:51 Nuchal meaning muscles that attach to the neck.

00:55 The innervation of this muscle comes from the posterior rami of these middle cervical nerves.

01:03 And its function is together, they'll draw the head backward or posteriorly, but individually, you could have a rotation to one side or the other.

01:14 Just a bit further down we have the splenius cervicis.

01:18 Cervicis meaning cervical relating more to the neck than the head.

01:23 Here we have attachments to the spinous processes of T3 to T6, going up to the transverse processes of C1 to C3.

01:33 Their innervation here is also from the posterior rami of the lower cervical nerves.

01:40 And the function is again together working to cause neck extension, moving the neck somewhat backwards, but individually they can rotate from one side or the other.

01:53 Now let's look at the iliocostalis, which we can see as cervicis, thoracis, and lamborun going from superior to inferior.

02:04 We have attachments all the way down to the pelvic area with the sacrum and the iliac crest.

02:12 And then all along the angles of the lower 6 to 7 ribs.

02:18 And then by the time we get to the thoracic area, we have the angles of the lower 6 ribs, and the angles, the upper six ribs.

02:27 And by time we get to the cervical area, we have the angles of ribs 3 to 6, all the way up to the transverse processes of cervical vertebra C4 to C6.

02:39 Here we see longissimus with a capitis, cervicis, and thoracis referring to head, neck, and thoracic region.

02:48 Here we have attachments to the sacrum, the spinous and transverse processes of the lumbar vertebra all the way up to the lower you know 9 to 10 or so ribs.

03:01 With cervicis, we see we have the transverse processes of the upper 4 thoracic vertebrae going up to the transverse processes of cervical vertebra 2 to 6.

03:13 And then for capitis, we have the articular processes of the lower cervical vertebra going up to the mastoid process of the temporal bone.

03:23 And now the spinalis, which has a cervicis and a thorasis.

03:27 Again referring to cervical area versus thoracic area.

03:32 And here we have attention to the spinous processes of the upper lumbar and lower thoracic vertebra going up to the spinous processes of the upper thoracic vertebra.

03:42 For cervicis, we have the spinous processes of C7 and variably T1 and T2 up to the spinous processes of cervical vertebra 2, also known as the axis.

03:55 The erector spinae altogether, have innovation from the dorsal branches of the cervical and thoracic spinal nerves in that region.

04:05 And the function is that together, they cause back and neck extension.

04:11 But if they're acting individually on one side or the other, they'll cause lateral flexion to the side that's contracting.