Back Anatomy Flashcards
Where is thick and thin skin found?
Skin thicker and tougher on back than on front
Is hairy skin thick or thin?
Thin
Where is thick skin found?
Palms
Bottom of feet
Describe the structure of the vertebral column and its development
Foetal C-shaped curvature > secondary lordotic curves develop in cervical and lumbar regions
What does cervical lordosis allow?
Support of head
What does lumbar lordosis do?
Shift line of gravity forward to help with balance and posture
What are the types of abnormal curves of the vertebral column?
Thoracic exaggerated curvature = kyphosis
Lumbar exaggerated lordosis
Lateral deviation = scoliosis
What is cranial shift?
T1 becomes C8
Gives cervical rib
What is caudal shift?
Extra lumbar vertebra/lumbar vertebra becomes fused with sacrum
What is an extrinsic muscle of the back?
One of attachments on to back
What is an intrinsic muscle of the back?
Both origin and insertion is to back
What is the spatial relationship between extrinsic and intrinsic muscles of the back?
Extrinsic muscles tend to be closer to surface than intrinsic muscles
At what level does the spinal cord end?
L1-2
What is the structure of a typical lumbar vertebra?
Highly vascularised
Articular process projects upwards
L1 > L5 - vertebrae increase in size to support greater load
Contain smooth surface on medial side
What is the significance of the pars interarticularis?
Site of weakness
Common location for fracture
What is the pars interarticularis?
Between inferior and superior facets of articular joints
What do the anterior and posterior sacral foraminae contain?
Nerve roots and vessels
Especially sacral veins
What are sacral veins important for?
Communication between pelvic veins and veins of back for drainage
What is the arterial supply to the lumbar vertebrae?
Posterior intercostal arteries
Lumbar arteries
Lateral sacral arteries
What is the venous drainage of the lumbar vertebrae?
Body drained by basivertebral vein > internal vertebral venous plexus > external vertebral venous plexus
What is the relationship between the internal vertebral venous plexus, and the meninges and vertebral canal?
Extradural but still within vertebral canal
Where are the primary centres of ossification of the vertebrae?
In body and each neural arch = vertebral arch = posterior part of vertebra
When do the primary centres of ossification of the vertebrae appear?
Before birth at 6-8 weeks
Where are the secondary ossification centres of the vertebrae?
5 secondary centres at
- Tips of spinous and transverse processes
- Upper and lower margins of body
When do the secondary ossification centres of the vertebrae close?
Late adolescence
What are the two components of the intervertebral disc?
Annulus fibrosus
Nucleus pulposus
What type of cartilage is the annulus fibrosus?
Fibrocartilage
What is the nucleus pulposus?
Remnant of notochord
What is the main role of the lumbar joints and ligaments?
Limiting range of movement of vertebrae
What are the six types of lumbar joints and ligaments?
Interspinous ligaments Posterior longitudinal ligament Facet joints Intertransverse ligaments Supraspinous ligmant Anterior longitudinal ligmanent
What is the shape of the posterior longitudinal ligament?
Ribbon-like
Then fans out to side when it gets to intervertebral disc
- Provides protection
Goes back to midline
What are the functions of the intervertebral discs?
Absorb weight bearing forces
Allow for stretching and distortion
Why is the ligamentum flavum made of elastic tissue?
For stretching = flexion of back, then recoiling to original shape
Whys is twisting whilst lifting hazardous to the intervertebral disc?
Only 50% of annular fibres positioned to resist load - can’t handle extra movement
Risk of disc prolapse
In which plane is thoracic movement in?
Coronal
In which plane is lumbar movement in?
Sagittal
What are the anterior and posterior rami?
Branches/divisions of spinal nerves, supplying different parts of body
Where the the cell bodies of sensory neurons located?
Dorsal root ganglia
Where are the dorsal root ganglia located?
Intervertebral foramen
What do arteries and veins accompany?
Nerves
Where do nerve roots sit in relation to the bony foramen?
Top
What is the danger of a fracture at thee pars interarticularis of L5?
L5 may slip into pelvis
What are the three types of disc prolapse?
Bulge
Herniation
Extrusion
What is a bulge disc prolapse?
Bulges at a fissure
How can a bulge disc prolapse cause pain?
If it hits outer third, may be pain from recurrent meningeal nerve
What is a herniation disc prolapse?
Herniates out posterior longitudinal ligament
In which direction does a herniation disc prolapse tend to be, and why?
Posterolateral, because of posterior longitudinal ligament being directly posterior
Why is a herniation disc prolapse a common cause of back pain?
Prolapse directs nuclear material towards dorsal root of spinal nerve
What may an extrusion disc prolapse impinge on?
Nerve roots and dorsal root ganglia
How does height change during the day, and why?
Become shorter during day because postures tend to increase loads on lumbar intervertebral discs
Where do all extrinsic muscles of the back act?
All attach to and act on upper limb
What are the extrinsic muscles of the back?
Trapezius
Latissimus dorsi
Rhomboids
Levator scapulae
What is the nerve supply of the extrinsic muscles of the back?
Except for trapezius, innervated by anterior rami of spinal nerves
Do the posterior rami of spinal nerves supply the extrinsic muscles of the back?
No - penetrate them, but don’t supply them, and pass to skin
What is the nerve supply to trapezius?
CN XI = spinal accessory nerve
What are the intermediate muscles of the back?
Serratus
- Posterior
- Superior
- Inferior
What is the function of the intermediate muscles of the back?
Act on ribs - accessory muscles of respiration
What is the nerve supply of the intermediate muscles of the back?
Anterior rami
What are the two groups of deep muscles of the back?
Erector spinae
Transversospinalis
What are the three divisions of erector spinae?
Spinalis
Longissimus
Iliocostalis
What is the function of erector spinae?
Long muscles - prime movers of back = flexion and extension of trunk
What type of contraction occurs in erector spinae?
Concentric = returning flexed trunk to upright position Eccentric = extension of trunk
Where is transversospinalis?
Short muscles - run from lateral to medial across few vertebral segments
What is the function of transversospinalis?
Stabiliser and fixator - limit movement
What is the blood supply of the back?
Superficial veins pass anteriorly
Arteries pass through muscles with dorsal rami to skin
Where does lymph from the skin of the back drain?
Skin above umbilicus drains into axillary nodes
Skin below umbilicus drains into inguinal nodes
What do the posterior rami innervate in the back?
Facet joints
Deep muscles
Overlying skin
What is the reflex muscle spasm?
Protective muscle spasm to prevent facet joint injury
Overlying skin sensitised from irritation of posterior ramus so deep muscles can’t contract
What are the two types of back pain?
Mechanical
Compressive/neurogenic
What is compressive back pain?
When nerve roots that leave spine irritated/pinched
Which nerve root will an L4/5 disc prolapse affect?
One directly below prolapsed disc because nerve root pertaining to above vertebra already exited
= L5
What is spondylosis?
Age-related loss of water in bone > deceased density and increased rigidity of bone
How may spondylosis cause pain?
May cause overgrowth of bone producing osteophytes
Can extend into vertebral foramina and compress exiting nerve roots
