MSK Session 4 (Lecture 4.1) Flashcards
What is the adult nervous supply to the dermis and muscle of a dermatomyotome?
Spinal segmental nerve
Where does the spinal cord start?
Medulla in the brain
Where does the spinal cord end?
Ends at conus medullaris where it forms a ligament = filum terminale.
Ends around L2/L3
What are the two important features of a vertebrae in relation to the spinal cord?
1) Vertebral foramen
2) Inter-vertebral foramen
Where does the S.C run through the vertebral column? What does it form?
Vertebral foramina forming spinal canal
What does the spinal cord give off through the inter-vertebral foramina?
Pair of right and left nerves at each vertebral level called spinal nerves.
What are the spinal nerves also known as?
Segmental nerves
What is special about the spinal nerves emerging in the cervical spine?
S.N. emerge superior to their corresponding vertebral level.
What is special about the spinal nerves emerging in the non-cervical spine?
S.N. emerge inferior to their corresponding vertebral level.
What are the levels of the spinal cord including numbers?
C1-7 T1-T12 L1-L5 S1-S5 Coccygeal root
What is a neural level?
Segment of nerve tissue emerging from the spinal cord. I.E. the nerve level (NOT VERTEBRAL LEVEL)
Where are the two enlargements of the spinal cord?
Cervical and lumbar bulges
What are segmental nerves also known as?
Mixed spinal nerves
What does each spinal segmental nerve comprise of?
1) Dorsal roots (sensory or afferent)
2) Ventral roots (efferent) - motor (skeletal muscle) and autonomic (smooth muscle, glands)
What is a ramus?
Branch
What is the difference between the size of the dorsal and ventral rami?
Dorsal (posterior) is smaller while to ventral (anterior) is larger
What does the dorsal ramus divide into?
Medial and lateral branches
Which spinal segments supply the lower limb?
Lumbar and Sacral (L1-S4)
What are the two separate network of nerves that supply the lower limb?
Lumbar plexus (L1-L4) and Sacral plexus (L4-S4)
Where does the lumbar plexus form?
Behind the psoas major muscle
Where do the nerves emerge from the lumbar plexus?
Medial or lateral to the borders of the psoas major muscle.
What are the nerves emerging lateral to psoas?
Femoral (L2-L4)
Iliohypogastric
Ilioinguinal
Lateral cutaneous nerve of the thigh
What are the nerves emerging medial to psoas?
Obturator nerve
Lumbrosacral
What is the sacral plexus composed of?
Lumbosacral trunk (half of L4 & all L5) Sacral spinal segmental outflow
Where does the sacral plexus form? Where does it lie in relation to?
Pelvic cavity
Lies in relation to piriformis
What does the sacral plexus supply?
Pelvic region
Gluteal region
Perineal region
Lower limb via sciatic nerve
What is a dermatome?
Area of skin supplied by sensory nerve fibres from a single spinal nerve (neural level)
Which part of the body does not have a dermatome?
Anterior face (supplied by a CN)
Why is overlap of dermatomes useful?
Damage to 1 nerve does not render loss of function to the area.
Also reduces probability of skin patches without natural sensory nerve supply
What is the axial line?
Line of junction of two dermatomes supplied from discontinuous spinal levels
Where are the axial lines marked on the upper and lower limb?
Upper - cephalic & basilic veins
Lower - great saphenous & small saphenous veins
What are sensory nerve territories?
Sensory divisions of terminal nerves of the brachial plexus supply the skin in territorial domains
