Dermatomes And Myotomes Of The Upper Limb Flashcards
What do somites differentiate into?
Sclerotome
Dermatomyotome
What does a sclerotome form?
Vertebrae and ribs
What does dermatomyotome form?
Muscle and dermis of skin
What does skin and muscle derived from a single dermatomyotome have in common?
Spinal nerve supply
What is a myotome?
Group of muscles supplied by a single spinal nerve
What is a Dermatome?
Area of skin supplied by a single spinal nerve
What is a spinal nerve made up of?
Both sensory and motor axons
Where are spinal nerves found?
Intervertebral Foramen
Where do the C1-C7 cervical nerves emerge with respect to their associated vertebrae?
Above their vertebrae
Where does the C8 spinal nerve exit the spinal canal?
Between C7 and T1
Below C7 above T1
Where do the T1-L5 spinal nerves exit with respect to their corresponding vertebrae?
Below their vertebrae
Where do the S1-S4 spinal nerves exit?
Via 4 pairs of sacral foramina
Where does the S5 and Co1 spinal nerves exit?
Via sacral hiatus posteriorly
What are the names of the bones where the C1 spinal nerve emerges between?
Occipital bone and atlas (C1)
What do spinal nerves branch into once they’ve emerged from the spinal cord?
Posterior/dorsal ramus
Anterior/ventral ramus
What part of the body do the anterior/ventral rami supply?
Muscles and skin of upper and lower limbs
Lateral and ventral trunk (Front and sides)
What part of the body do the posterior/dorsal rami supply?
Deep muscles and skin of dorsal trunk
There is a junction between C4 and T2, how do the C5-T1 nerve roots supply the upper limbs?
Via the Brachial plexus
What spinal nerve roots make up the Brachial plexus?
C5-T1
Where is the C4 Dermatome?
Top of chest spans towards shoulders
Where is the C5 dermatome?
RADIAL ASPECT (Lateral portion of arm when in anatomical position)
From the shoulder, stops just before elbow joint
Where is the C6 Dermatome?
Cross elbow joint from arm to forearm
RADIAL aspect (Lateral aspect) of forearm and supplies THUMB and INDEX finger
Where is the C7 dermatome?
The MIDDLE FINGER
C7 to heaven
Where is the C8 dermatome?
RING and LITTLE finger
Moves slightly onto ULNAR aspect of forearm
Where is the T1 Dermatome?
ULNAR aspect of the forearm just past the elbow joint/cubital fossa
Where is the T2 Dermatome?
ULNAR aspect of the arm and the UPPER chest
What is the name of the structure where rearrangement of the ventral rami of spinal nerves occur producing peripheral nerves?
Plexuses
What often makes up a peripheral nerve?
Axons from several spinal nerves
Axons from one spinal nerve can enter multiple peripheral nerves
What peripheral nerves does C6 supply?
Musculocutaneous nerve
Axillary
Radial nerve
Median nerve
What are the spinal nerve roots supplying the musuculocutaneus nerve?
C5, C6 and (C7)
C7 has very little contribution
What is special about the C5 fibres that supply the musculocutaneous nerve?
They are all motor fibres
No sensory input from C5
What are peripheral nerve territories?
Areas of skin supplied by the peripheral nerves
They are NOT the same as Dermatome
What plexus is responsible for peripheral nerve formation in the upper limbs?
Brachial plexus
What plexus is responsible for peripheral nerve formation in the lower limbs?
Lumbosacral plexus
What spinal nerves make up the femoral nerve? (Lumbosacral plexus)
L2, L3, L4
What are the 2 major branches of the femoral nerve?
Anterior femoral cutaneous nerve
Saphenous nerve
Where does the saphenous nerve cover?
Medial leg below the knee
Where does the anterior Femoral cutaneous nerve cover?
Knee and anterior thigh
What are the 5 spinal nerve roots that supply the upper limbs via the brachial plexus?
C5
C6
C7
C8
T1
What is the function of the C5 myotome?
Shoulder ABduction
Shoulder external rotation
What is the function of the C6 myotome?
Elbow Flexion
Wrist extension
Supination (Neutral position then turn palm to the ceiling)
What is the function of the C7 myotome?
Elbow extension
Wrist Flexion
Pronation (opposite of supination)
What is the function of the C8 myotome?
Finger Flexion
Finger extension
What is the function of the T1 myotome?
Finger ABduction
Finger ADduction
