L23-24: Deep Back I-II Flashcards
(42 cards)
Discuss embryological development of the deep back muscles
Mesoderm – paraxial mesoderm bilaterally – somites, which form muscles of trunk
- Somite – sclerotome and a myo-dermatome
- Myotome gives rise to myoblast cells that form muscles of trunk
- Myotomes: a.) epaxial (dorsal) division, b.) hypaxial (ventral) division
a. ) epaxial division - supplied by dorsal rami
- gives rise to deep extensor muscles of back
b. ) hypaxial division - supplied by ventral rami
- gives rise to infrahyoid, flexor muscles of vertebral colum, quadratus lumborum
What feature of deep back muscles allows for smooth movement of vertebral column during flexion, extension and rotation?
- Origins and insertions of different muscles overlap
Function of deep back muscles
- Maintain posture, balance, produce flexion, extension and rotation of back
- Support most of body weight (which sits anterior to vertebral column)
What are the only muscles innervated by the dorsal primary rami?
- Intrinsic back muscles
Describe 4 groups of intrinsic muscles of back
- ) Splenius group: post midline of back and proceed laterally and superiorly to their insertion
- ) Erector spinae group: arise from post midline or more laterally and run longitudinally
- ) Transversospinalis group: arise laterally, but travel toward midline to their insertion
- ) Suboccipital group: responsible for movement of head and neck only
Three layers of intrinsic back muscles
- ) superficial layer: erector spinae and splenius muscles
- ) intermediate layer: semispinalis and multifidus
- ) deep layer: segmental muscles and supoccipital muscles
List muscles found in each group of the intrinsic back muscles
- ) splenius: splenius capitis, splenius cervicis
- ) erector spinae: iliocostalis, longisimus, spinalis
- ) transversospinalis: semispinalis, multifidus, segmental muscles (interspinalis, intertransversarii and rotators)
- ) suboccipital: oblique capitis inferior, oblique capitis superior, rectus capitis posterior major, rectus capitis posterior minor
Muscles of the splenius group
- splenius capitis
- splenius cervicis
Three columns of the erector spinae muscle group. Which is most medial? Lateral? What bony structures are each associated with?
1.) Iliocostalis: cervicis, thoracis, lumborum
2.) Longissimus: capitis, cervicis, thoracis
3.) Spinalis: usually only has thoracic part, can have cervicis and lumbar
From lateral to medial: I Love Spaghetti – Iliocostalis (associated with ribs), longissimus (associated with transverse processes) and spinalis (associated with spinous processes)
Action of erector spinae muscle group?
- Bilaterally, they extend head and vertebral column
- Unilaterally, they flex head and vertebral column
- Chief extensor of vertebral column
Three muscle masses of transversospinalis muscles? Divisions of each if any? Do these lie superficial or deep to erector spinae muscle group?
- Seminspinalis: capitis, cervicis and thoracis
- Multifidus
- Segmental muscles: interspinalis (lacking in thoracic), intertransversarii (lacking in thoracic), rotatores (long and short)
These muscles are deep to erector spinae muscles, with segmental muscles being deepest
Two sets of rotatores muscles? How many vertebrae does each span?
- ) Long rotatores (longus): skips vertebra
2. ) Short rotatores (brevis): does not skip vertebra
Name suboccipital muscles. What does this muscle group connect?
- Oblique capitis inferior and superior, rectus capitis posterior major and minor
- Connects the skull to the atlas and axis
Borders of suboccipital triangle
- Oblique capitis inferior
- Oblique capitis superior
- Rectus capitis posterior major
What is contained in the suboccipital triangle?
- Vertebral artery: courses across floor of triangle enters skull through foramen magnum
- Dorsal ramus of C1 (suboccipital nerve)
Which muscle is part of the suboccipital muscle group, but doesn’t act as border of suboccipital triangle?
- Rectus capitis posterior minor
Innervation of suboccipital muscles
- Dorsal ramus of C1 known as suboccipital nerve
What does the greater occipital nerve innervate? What ramus is it? Course?
- Dorsal ramus of C2
- Emerges from below oblique capitis inferior muscles (outside suboccipital triangle) cross the muscle and travels obliquely across the triangle to the back of the skull
- Provides sensory innervation to the posterior part of the scalp, no muscles are innervated by it
Describe which muscles perform the following actions of the vertebral column: A.) flexion B.) extension C.) lateral flexion D.) rotation
- A.) Flexion: ant trunk muscles and gravity with back muscles as antagonists to provide smooth movement
- B.) Extension: all deep muscles (chief = erector spinae) except intertransversarii
- C.) Lateral flexion: intertransversarii, splenius capitis and cervicis rotate head to same side and laterally flex neck, erector spinae unilaterally, opposite side muscles gradually relax to provide smooth movement
- D.) Rotation: multifidi, rotatores, semispinalis all rotate the trunk to opposite side, splenius capitis and erector spinae extend trunk and help rotate to same side.
Which back muscles rotate atlas and turns face to same side?
- Oblique capitis inferior, rectus capitis posterior major and minor
Which back muscles extend head bilaterally and flex it to the same side unilaterally?
- Oblique capitis superior, rectus capitis posterior major and minor
Which of the following muscles are derived from the epaxial division? A. infrahyoid B. flexor muscles of back C. deep extensor muscles of back D. quadratus lumborum E. B&C
- C
The fibers of the following muscle/muscle groups proceed superiorly and medially A.) erector spinae B.) rotators C.) transversospinalis D.) splenius E.) B&C
- E
What muscle represents the lateral division of the sacrospinalis (aka erector spinae)? A.) Iliocostalis B.) Longissimus capitis C.) Longissimus cervicis D.) Spinalis
- A
