A&P 2.12 sacral plexus Flashcards
Sacral plexus
Sciatic nerve - main branch and largest nerve in the body
Pelvis and posterior LE entirely innervated by the branches of the sacral plexus
From ventral rami L4-S4
Composed of tibial and common fibulas nerve wrapped together in a single fascial sheath
Innervates posterior thigh and lateral leg
Sciatic nerve
splits at and becomes
SPLITS AT KNEE TO BECOME TIBIAL (medial - posterior) AND COMMON FIBULAR NERVES
Peroneal nerve
Common FIBULAR nerve
lumbosacrial plexus
Lumbar and sacral plexus are often considered together
Sciatica
Pain along the course of the sciatic nerve (from buttock down posterior and or lateral LE)
Or may be referred from trigger points (most of the time this is at least a component of the pain)
Sciatica may result from
A true neuralgia of the sciatic nerve by
Or trigger points located in the gluteus minimums or piriformis
True neuralgia
2 main causes
Pressure on roots of L5
entrapment of sciatic nerve by pisiform muscle
Pressure on roots of L5 by:
Herniated disc
Osteroarthritis on the lumbosacrial spine
Pressure from the uterus during Px
An improperly administered gluteal intramuscular injection
Trigger points
Trigger points located in the gluteus minimums or piriformis
- cause a pseudo-sciatica where there is no real disturbance to the nerve
At least partially involved in the vast majority of sciatica cases
Nuclei versus ganglia chart
CNS (axons - tracts - white) (cell body- nuclei - grey)
PNS (axons- nerves - white). ( cell bodies - ganglia - grey)
ONLY GANGLIA IN CNS IS THE
ONLY GANGLIA IN CNS IS THE BASAL GANGLIA
Herpes zoster
name & cause
Shingles
Caused by a VIRUS - chicken pox/varicella virus
Lies dormant in the dorsal root ganglia (meeting point for all the sensory neurons in each dermatome
If you had chicken pox, you can get shingles
Herpes zoster
Affects
Affects - the dendrites at the end of sensory neurons along a specific dermatome, blisters break out at nerve endings. Blisters unilaterally.
Herpes zoster
triggers
Triggers - stress, weakened immune system, chemotherapy
Herpes zoster
Symptoms
Symptoms: pain is present before outbreak, for the 2-3 weeks during outbreak, and can last for months after the lesions have healed.
Shingles
Meaning
Latin for belt or girdle
Describing the distribution of blisters around chest or abdomen along a single dermatomal line
Herpes zoster
Treatments
Treatment - anti-viral prescriptions, and will also help stave off Post Herpetic Neuralgia (painful after effects), steroids, antidepressants, anti convulsion, and topical agents
Post Herpetic neuralgia
Pain is the most common complication of shingles. The pain ranges from tenderness, burning, or throbbing to pain is stabbing, shooting or sharp. It can last for months to years
Nerve fiber repair
Mature neurons are typically thought to be incapable of cell division and cannot be replaced. Only option for healing due to damage or disease is repair of those already present.
Nerves can be repaired if
Damage is not too extensive
Cell body and cell membrane (neurilemma) remain intact
Scarring has not occurred
Stages of nerve repair
PNS ONLY
4 stages
Injury resulting in a nerve cut
WALLERIAN DEGENERATION
Remaining NEURILEMMA tunnel from the point of injury to the effector
Neuron’s connection with effector is reestablished
Stages of nerve repair
PNS ONLY
Stage 1
Injury resulting in a nerve cut
Immediately after injury, DISTAL portion of axon degenerates, along with its myelin sheath (WALLERIAN DEGENERATION)
Remaining NEURILEMMA tunnel from the point of injury to the effector: new Schwann cells grow within a tunnel maintaining a pathway for axon regrowrh. Several growing axon sprouts appear. When one of these growing fibers reaches the tunnel, it increases its growth rate. The other sprouts eventually disappear (approximately 1mm per day)
Neuron’s connection with effector is reestablished
Stages of nerve repair
PNS ONLY
Stage 2
Immediately after injury, DISTAL portion of axon degenerates, along with its myelin sheath (WALLERIAN DEGENERATION)
CNS VERSUS PNS repair
Repair in CNS is not as successful in the PNS.
Oligodendrocytes and astrocytes have an inhibiting effect on fiber growthalso the way oligodendrocytes form the myelin sheaths is different.
Stages of nerve repair
PNS ONLY
Stage 3
Remaining NEURILEMMA tunnel from the point of injury to the effector: new Schwann cells grow within a tunnel maintaining a pathway for axon regrowrh. Several growing axon sprouts appear. When one of these growing fibers reaches the tunnel, it increases its growth rate. The other sprouts eventually disappear (approximately 1mm per day)
Stages of nerve repair
PNS ONLY
Stage 4
Neuron’s connection with effector is reestablished
WALLERIAN DEGENERATION
DISTAL portion of axon degenerates, along with its myelin sheath
Glial cells are capable of
Cell division
Quadratus lumborum
A, I, O
Unilateral: ipsilateral flexion, lateral pelvic tilt (to same side)
Bilateral: extension of the spine, fix the ribs during inhalation
O- proximal attachment: 12th rib (internal margin), TP of L1-L4
I- distal attachment: iliac crest (internal lip)
