Dermatomes and Myotomes and segmental innervation Flashcards
Where are the enlargements of the spinal cord?
The cervical and lumbar regions
What is the taper at the end of the spinal cord called?
Conus medullaris
What is meant by the term mixed spinal nerves?
The posterior and the anterior nerve roots
What is the posterior nerve root
Consists of sensory fibres from cell bodies in the spinal/dorsal root ganglion that extend peripherally to sensory endings and centrally to posterior horn of spinal cord grey matter
What is the anterior nerve root
Consists of motor fibres passing from cell bodies in the anterior horn of grey matter in the spinal cord to effector organs in the periphery
What happens as the mixed spinal nerve passes through the intervertebral foramen?
Divides into two branches:
- Posterior/Dorsal Ramus
- Anterior/Ventral Ramus
What does the posterior ramus supply?
- Synovial joints of the vertebral column
- Deep muscles of the back
- Overlying skin (segmental pattern)
What does the anterior ramus supply?
- Anterior and lateral regions of the trunk
- Upper and lower limbs
What does the anterior ramus supply?
- Anterior and lateral regions of the trunk
- Upper and lower limbs
Which ramus forms plexuses?
Anterior
Explain the brachial plexus
- Roots: C5-T1
- Trunks: Superior, Inferior, Middle
- Divisions: All trunks have a posterior and an anterior
- Cords: Medial, Lateral, Posterior
- Branches: Musculocutaneous, Axillary, Radial, Median, Ulnar
Where does the nervous supply to the lower limb come from?
The lumbar plexus (L1-L4) and the sacral plexus (L4-S4)
Where does the lumbar plexus form?
Behind the psoas major muscle
Which nerves emerge medial the psoas major muscle
- Femoral
- Iliohypogastric
- Ilioinguinal
- Lateral cutaneous nerve of the thigh
Which nerves emerge lateral the psoas major muscle
- Femoral
- Iliohypogastric
- Ilioinguinal
- Lateral cutaneous nerve of the thigh
Which nerves emerge medial to the psoas major muscle?
- Obturator nerve
- Lumbosacral trunk
Where does the sacral plexus supply?
- Pelvic region
- Gluteal region
- Perineal region
- Lower limb (via sciatic nerve)
What is a dermatome?
An area of skin supplied my a single spinal nerve
What is an axial line?
The junction between two different dermatomes which are not from adjacent spinal roots
What is the cutaneous distribution of a peripheral nerve?
The area of skin that a peripheral nerve innervates. It normally has nerve fibres from different spinal roots
What is a myotome?
The group of muscles innervated by a single spinal nerve
In which two ways are dermatomes assessed?
- Light touch of cotton wool for example
- Response to pain using a small pin
Which movement is used to assess C5
Elbow flexion
Which movement is used to assess C6
Wrist Extension
Which movement is used to assess C7
Elbow Extension
Which movement is used to assess C8
Finger flexion
Which movement is used to assess T1
Finger abduction
Which movement is used to asses L2
Hip flexion
Which movement is used to assess L3
Knee extension
Which movement is used to asses L4
Ankle dorsiflexion
Which movement is used to assess L5
Great toe extension
Which moment is used to assess S1
Ankle plantar flexion
Which spinal nerve roots are you assessing by neck flexion and extension?
C1 and C2
Which spinal nerve root is assessed by moving the head from side to side?
C3
Which spinal nerve root is assessed by shoulder elevation?
C4
What does shoulder abduction test?
C5
