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Which muscle group is primarily responsible for the extension of the spine?
Which feature distinguishes the internal oblique muscle in terms of force production?
What is the main role of the transverse abdominis?
What is the function of the deep muscles of the back, particularly the transversospinal group?
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Which of the following describes the unilateral contraction in the context of muscle activation?
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Which muscles are primarily activated during trunk flexion?
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Which joint primarily allows for significant axial rotation in the cervical spine?
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What is the consequence of the facet orientation in the lumbar spine?
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During axial rotation of the thoracic spine, what occurs on the side opposite to the rotation?
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What primary function does the sacroiliac joint serve in relation to the spine?
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What is the primary function of the transverse foramen in the cervical vertebrae?
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Which cervical vertebra is characterized by having no spinous process?
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What type of movements does spinal coupling involve?
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Which activities are most critically impacted by the sacroiliac joint resulting in pain?
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How do the orientations of the superior and inferior articular facets of the cervical spine affect its function?
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What is the main role of the uncinate processes found on cervical vertebrae C3 to C6?
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What structure acts as a fulcrum for rotation and facilitates approximately 50% of cervical rotation?
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Which statement best describes the unique structural feature of the C2 vertebra?
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Which vertebrae contribute to the formation of the atlanto-occipital joint?
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What differentiates the cervical spine from the thoracic and lumbar regions regarding the vertebral components?
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What is the orientation of the most spinous processes in the thoracic region?
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Which feature distinguishes the lumbar spine's spinous process from that of the thoracic spine?
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What is the primary role of the nucleus pulposus within the intervertebral disc?
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What distinguishes the orientation of superior and inferior articular facets in the lumbar spine?
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What consequence may result from dehydration of the intervertebral disc?
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What is the function of the vertebral endplate?
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What type of joints are the facet joints in the thoracic region referred to as?
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Which characteristic of the lumbar spine's vertebral bodies is notable in comparison to the thoracic or cervical spines?
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What is the role of the annulus fibrosis in the intervertebral disc?
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What type of symptoms might indicate nerve impingement due to issues with intervertebral discs?
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Study Notes
Unilateral Contraction
- One side of the body is activated
- Extension, lateral flexion, and axial rotation occur
Erector Spinae Group
- Spinalis, Longissimus, Iliocostalis
- Extends spine and assists lateral flexion
Transversospinal Group
- Semispinalis, Multifidus, Rotators
- Provides stability and control
- Fine motor control due to crossing fewer intervertebral junctions
- Multifidi important for low back pain due to altered timing and intramuscular fat
Short Segmental Group
- Interspinalis, Intertransversarius
- Fine motor control over one intervertebral segment
Anterior-Lateral Trunk Muscles
- Rectus Abdominis (superficial)
- Flexion of the trunk
- Tendinous intersections creates "six-pack"
- External Oblique
- Originates on ribs and runs inferiorly and medially
- Assists flexion and lateral flexion
- Activates in a "pocket" orientation
- Internal Oblique
- Originates on iliac crest and runs superiorly and medially
- Largest physiological cross-sectional area
- Generates significant isometric force
- Transverse Abdominis
- "Corset Muscle"
- Compresses abdomen and stabilizes lower back
Role in Stabilization
- Deep abdominal muscles (internal oblique, transverse abdominis) activate before prime movers (e.g., anterior deltoid)
- Stabilizes spine before movement
Flexion and Lateral Flexion
- Rectus abdominis, external oblique, internal oblique assist in trunk flexion
- Left lateral flexion involves left side muscles
- Right lateral flexion involves right side muscles
- Muscle with largest moment arm creates greatest effect on movement
Unilateral Activation and Movements
- Right external oblique activation produces right lateral flexion
- Internal oblique activation produces lateral flexion on the same side
Cervical Spine Osteology
- Cervical spine composed of seven vertebrae (C1-C7)
- Unique features separate cervical from thoracic and lumbar spine
Basic Osteologic Features
- Spinous Process
- Lamina
- Pedicle
Unique Cervical Spine Features
Transverse Foramen
- Passage for vertebral artery (supplies blood to brain)
Articular Facets
- Large facets for movement
- Superior facets face superiorly and posteriorly
- Inferior facets face inferiorly and anteriorly
- Facets affect direction and type of motion
Uncinate Processes
- Vertical projections on C3-C6
- Provides stability in vertical and frontal plane
Key Cervical Vertebrae
C1 (Atlas)
- "Atlas" refers to the Greek god who holds the world, as this vertebra supports the head
- No spinous process (posterior tubercle instead)
- Large transverse processes for muscle attachment
- Concave superior articular facets accommodate occipital condyles of the cranium
Atlanto-Occipital (AO) Joint
- Formed between C1 and occiput
- Allows for approximately 50% of cervical flexion and extension
C2 (Axis)
- Prominent vertical projection called Dens (odontoid process)
Atlantoaxial (AA) Joint
- Formed between C1 and C2
- Acts as a fulcrum for rotation
- Allows for about 50% of cervical rotation
- Flat facets and vertical dens facilitate rotation
Thoracic and Lumbar Spine Osteology
- Thoracic spine contains 12 vertebrae (T1-T12)
- Lumbar spine contains 5 vertebrae (L1-L5)
Thoracic Spine Features
Spinous Processes
- Oriented inferiorly in most thoracic vertebrae (T6-T8 especially)
Facet Joints
- Superior facets face posteriorly
- Inferior facets face anteriorly
- Apophyseal or zygapophyseal joints
Lumbar Spine Features
Vertebral Body
- Larger than thoracic or cervical spine to support greater weight-bearing
Spinous Process
- Projects directly posteriorly
Mammillary Processes
- Attachment site for multifidus muscles (enhanced stability and movement)
Articular Facets
- Superior facets are vertical and slightly concave
- Inferior facets are vertical and slightly convex
- L1 superior facet articulates with L2 inferior facet
Interbody Joints
- Between two vertebral bodies
- Vertebral endplate
- Intervertebral disc
Intervertebral Disc
- Central nucleus pulposus (gel-like shock absorber)
- Annulus fibrosis (15-25 concentric layers of collagen fibers for stiffness and support)
Intervertebral Disc Function
- Shock absorption through nucleus pulposus
- Must remain hydrated (dehydration leads to reduced shock absorption and potential arthritis)
Common Intervertebral Disc Issues
- Dehydration due to aging, injury, or disease
- Loss of shock absorption
- Bone-on-bone contact
- Osteophyte (bone spur) formation impinging on nerves
Nerve Impingement Symptoms
- Radicular symptoms (tingling, numbness, warmth, or weakness along affected nerve distribution)
Vertebral Endplate
- Continuity between intervertebral disc and vertebral body
- Fibrocartilage (inner) binds strongly to annulus fibrosis
- Calcified cartilage (outer) binds to vertebral body
- Supplies nutrients (oxygen, glucose) to nucleus pulposus and annulus fibrosis (lack blood vessels)
Spinal Movement
- Flexion: Anterior/superior slide
- Extension: Posterior/inferior slide
- Axial Rotation: Contralateral slide
Atlanto-Occipital (AO) and Atlanto-Axial (AA) Joints
- AO joint (convex on concave): Flexion, extension, lateral flexion
- AA joint (flat surfaces): Significant axial rotation
Thoracic Spine (T1-T12)
- Facet orientation: 15 degrees off the frontal plane
- Flexion/Extension: Superior/anterior slide during flexion; posterior/inferior slide during extension
- Axial Rotation: Contralateral slide
- Lateral Flexion: Opposite movement on each side; inferior slide on flexed side
Lumbar Spine (L1-L5)
- Facet orientation: 25 degrees off the sagittal plane
- Flexion: Superior/anterior slide
- Extension: Inferior/posterior slide
- Limited axial rotation due to facet orientation
Spinal Coupling
- Associated movements in different planes (e.g., lateral flexion coupled with axial rotation)
- Used to assess spinal mechanics during movement
Sacroiliac Joint (SI Joint)
- Primary interface between axial skeleton (spine) and appendicular skeleton (lower extremities)
- Ilium (pelvis) and sacrum
- Not palpable directly, but can be approximated
- Common source of chronic low back pain (25% of cases)
Horizontal Plane Motion
- External oblique: Rotation on opposite side
- Internal oblique: Rotation on same side
Head and Neck Muscles and Movements
- Sternocleidomastoid (SCM)
- Originates on mastoid process, sternum, and clavicles
- Unilateral activation:
- Ipsilateral lateral flexion
- Contralateral axial rotation
- Bilateral activation:
- Upper cervical spine extension
- Mid to lower cervical spine flexion
- Protracts head and neck
- Scalene Muscles
- Anterior, middle, and posterior scalene
- Originate on transverse processes of cervical vertebrae
- Insert on first and second ribs
- Elevate ribs (assist ventilation)
- Assist cervical flexion if arms are fixed
- Clinical Applications
- Hyperactive scalenes may indicate respiratory issues (COPD)
- Scalene muscle hypertrophy can compress the brachial plexus (thoracic outlet syndrome)
- Longus Colli
- Extends from C1 to T3
- Stabilizes spine and assists cervical flexion
- Longus Capitis
- Originates on occipital bone
- Inserts on transverse processes of mid to lower cervical spine
- Helps correct forward head posture (exercises like longus coli nod)
- Splenius Muscles
- Splenius cervicis and splenius capitis
- Originates from the spinous processes of the upper thoracic vertebrae
- Inserts on the mastoid process (capitis) and transverse processes of the cervical vertebrae (cervicis)
- Ipsilateral: Lateral flexion, rotation, and extension of the head and neck
- Splenius Muscles
- Splenius cervicis and splenius capitis
- Originates from the spinous processes of the upper thoracic vertebrae
- Inserts on the mastoid process (capitis) and transverse processes of the cervical vertebrae (cervicis)
- Ipsilateral: Lateral flexion, rotation, and extension of the head and neck
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