lumbar spine myology

Question 1

what muscles is the lumbar erector spinae made up of (medial to lateral)

Answer 1

spinalis, longissimus, iliocostalis

Question 2

lumbar erector spinae

Answer 2

-Iliocostalis
* Origin: sacrum, iliac crest
* Insertion: all ribs and transverse processes of C6-4
-Longissimus
* Origin: Sacrum, spinous processes of Lx
* Insertion: transverse processes of Lx, ribs, transverse processes of C2-7
-Spinalis
* Origin: Spinous processes of T11 to L2
* Insertion: spinous processes T1-T8
- All 3 =
* Action: extends the spine, controls flexion, lateral
flex & rotation
* Nerve: Dorsal Ramus

Question 3

rectus abdominus (abs)

Answer 3

*Origin- Symphysis Pubis and pubic crest via two tendons
*Insertion- Xiphoid Process, 5th-7th ribs (costal cartilages).
*Action- Flexion of lumbar spine. Or unilateral
flexion if unilateral contraction
*Nerve- Thoraco-abdominal nerve (T7-11) and subcostal (T12)

Question 4

external abdominal oblique

Answer 4

Origin- Ribs 5-12and their costal cartilages. Downwards and medially
Insertion- Outer lip anterior 2/3rds iliac crest, ASIS, linea alba and pubic tubercle
Action: Flexion of the torso or unilateral contraction causes unilateral flexion
Nerve- thoraco-abdominal nerves (T7-11) and subcostal nerve (T12)

(External Obliques – most superficial)

Question 5

internal abdominal oblique

Answer 5

*Origin- Lateral 2/3rds of inguinal ligament and anterior 2/3rds of the iliac crest and the thoracolumbar fascia. Fibres pass vertically
*Insertion- Inferior borders of lower 4 ribs, linea alba and pubic crest
*Action- bilateral = trunk flexion and compresses abdomen. Unilateral = ipsilateral side flexion and rotation
*Nerve- thoracoabdominal (T7-11) and ilioinguinal (L1)

Question 6

transverse abdominus

Answer 6

*Origin- lateral third of inguinal ligament, anterior ⅔ of inner lip of iliac crest, thoracolumbar fascia and inner surface of costal cartilages of lower 6 ribs
*Insertion- linea alba and pubic crest
*Action- compresses the abdominal cavity, acts as a muscular ‘corset’, raises intra-abdominal pressure, coughing/sneezing
*Nerve- thoracoabdominal (T7-11), subcostal (T12) and ilioinguinal (L1)

(Deepest of the 3 abdominal muscles)

Question 7

quadratus lumborum

Answer 7

*Origin- Iliolumbar ligament and adjacent iliac crest
*Insertion- Lower border of 12th rib, transverse processes of
lumbar vertebrae
*Action- unilateral = lateral flex, bilateral = depression of rib
cage/fixes the diaphragm, stabilises pelvis on 1
leg stand
*Nerve- ventral ramus

Question 8

multifidus

Answer 8

*Origin- posterior sacrum, PSIS, aponeurosis of ES and iliac crest
*Insertion- spinous processes of all segments up to the axis
*Action- bilateral = extension of spine, unilateral – ipsilateral side flexion and contralateral rotation, provides proprioceptive feedback due to muscle spindle density, stabilising each segment of the spine
*Nerve- dorsal ramus