Anatomy - Back Muscles

what are the two subcategories of extrinsic muscles?

superficial and intermediate

what is the function of superficial extrinsic muscles?

produce and control limb movements

what is the function of intermediate extrinsic muscles?

elevation and depression of ribs during respiration

what is the function of intrinsic muscles?

specifically act on the vertebral column, producing its movements, and maintaining posture

what are the superficial extrinsic muscles?

• trapezius

• latissimus dorsi

• levator scapulae

• rhomboids (major and minor)

what are the intermediate extrinsic muscles?

serratus posterior (superior and inferior)

what are layers of the deep intrinsic muscles?

• superficial

• intermediate

• deep

where doe superficial extrinsic muscles receive their nerve supply from?

anterior ramus of the cervical nerves

what do the superficial extrinsic muscles act on?

the upper limb

where does the trapezius muscle receive its motor fibers from?

the spinal accessory nerve (CN 11)

where doe intermediate extrinsic muscles receive their nerves supply from?

the intercostal nerves

what describes the trapezius muscle?

broad, flat, triangular, most superficial

what is the origin of the trapezius muscle?

skull, ligamentum nuchae, and spinous processes of C8-T12

where does the trapezius muscle insert?

clavicle, acromion, spine of scapula

what innervates the trapezius muscle?

CN XI, proprioceptor, fibers from C3 and C4

what is the action of the trapezius mucle?

• upper fibers elevate and rotate scapula

• middle fibers retract scapula

• lower fibers depress scapula

what describes the latissiumus dorsi?

covers a wide area of the lower part of the back

what is the origin of the latissiumus dorsi?

broad: spinous processes of T6-T12, thoracolumbar fascia, iliac crest, and the inferior three ribs

where does the latissimus dorsi insert?

tendon attaches to the intertubercular sulcus of the humerus

what innervates the latissimus dorsi?

thoracdorsal nerve (C6-C8)

what is the action of the latissimus dorsi?

extends, adducts, and medially rotates the upper limb

what is the origin of the minor rhomboid?

spinous processes of C7-T1

where does the minor rhomboid insert?

medial scapula at spine

what is the origin of the major rhomboid?

spinous processes of T2-T5

what is the insertion of the major rhomboid?

medial scapula below spine base

what innervates the major and minor rhomboids?

dorsal scapular nerve

what is the action of the major and minor rhomboids?

retracts and rotates the scapula

where are the rhomboids located in respect to each other?

minor is superior to major

what is the origin of the levator scapulae?

transverse processes of C1-C4 vertebrae

where does the levator scapulae insert?

medial border of the scapula

what innervates the levator scapulea?

dorsal scapular nerve (C5) + fibers from C3/4

what is the action of the levator scapulae?

elevates the scapula

what is the origin of the serratus posterior superior?

ligamentum nuchae, spinous processes C7-T3

what is the insertion of the serratus posterior superior?

superior aspect of ribs 2-5

what innervates the serratus posterior superior?

fibers from T1-T4

what is the action of the serratus posterior superior?

elevates the ribs

what is the origin of the serraturs posterior inferior?

spinous processes of T11-L2

what is the insertion of the serratus posterior inferior?

inferior aspect of ribs 9-12

what innervates the serratus posterior inferior?

fibers from T9-T12

what is the action of the serratus posterior inferior?

depresses the ribs

an injury to the accessory nerve will affect what muscle?

trapezius

how does an injury to the accessory nerve present clincally?

• drooping of the shoulder

• inability to raise arm above the head

• weakness in attempting to raise the shoulder

an injury to the thoacodorsal nerve will affect what muscle?

latissimus dorsi

how will an injury to the thoacodorsal nerve present clinically?

inability to pull the body upright when climbing or doing a pull up

the intrinsic (deep) muscles of the back are innervated by what?

the posterior ramus of the spinal nerves

what is the origin of the splenius capitis?

lower aspect of the ligament nuchae and processes of C7-T3/4 vertebrae

where does the splenius capitis insert?

mastoid process and occipital bone of the skull

what innervates the splenius capitis?

C3/C4

what is the action of the splenius capitis?

rotates head to the same side

what is the origin of the splenius cervicis?

spinous processes of the T3-T6 vertebrae

where does the splenius cervicis insert?

transverse process of C1-3/4

what innervates the splenius cervicis?

lower cervical nerves

what is the action of the splenius cervicis?

rotates head to the same side

what are the muscles that make up the erector spinae?

• iliocostalis

• longissimus

• spinalis

what is the function of the erector spinae?

primary extensors and lateral flexors of the vertebral column

where is the erector spinae located?

lies parallel to the vertebral column between spinous processes and angles of the ribs

what is the origin of the erector spinae?

a broad, thick tendon attached to the sacrum, the spinous processes of the lumbar and lower thoracic vertebrae, and the iliac crest

what deep intrinsic muscles make up the transversospinales?

• semispinalis

• multifidus

• rotatores

what is the origin of the semispinalis?

the transverse processes of C4-T10

where does the semispinalis insert?

the spinous processes of C2-T4 and occipital bone of skull

what is the action of the semispinalis?

extends and contralaterally rotates the head and vertebral column

what is the origin of the multifidus?

sacrum, posterior iliac spine, common tendinous origin of the erector spinae, mammillary processes of lumbar vertebrae, transverse processes of T1-T3 and articular processes of C4-C7

what does the multifudus attach to?

the vertebral spinous processes

what is the action of the multifidus?

stabilizes the column

what is the origin of the rotatores?

vertebral transverse processes

where does the rotatores insert?

lamina and spinous processes of the vertebrae above

what is the action of the rotatores?

extension/rotation of the spine, stabilizes vertebra, proprioception

what is the most superficial deep intrinsic muscle?

semispinalis

what muscle is the deepest of the deep intrinsic muscles and is most prominent in thoracic region?

rotatores

what are the minor deep intrinsic muscles?

• interspinales

• intertransversarii

• leavatores costarum

what describes the interspinales?

spans between adjacent spinous processes and acts to stabilize the vertebral column

what describes the intertransversarii?

spans between adjacent transverse processes and acts to stabilize the vertebral column

what is the origin of the leavatores costarum?

the transverse processes of C7-T11w

where does the leavatores costarum attach?

to the rib immediately below

what is the action of the leavatores costarum?

elevates the ribs

what is the suboccipital triangle?

small, deep triangle at the base of the skull

what are the contents of the suboccipital triangle?

vertebral artery/vein and suboccipital nerve

what is the medial border of the suboccipital triangle?

rectus capitis posterior major

what is the lateral border of the suboccipital triangle?

obliquus capitis superior

what is the inferior border of the suboccipital triangle?

obliquus capitis inferior