Nervous System - Segmental Innervation of Skin Flashcards
What is a dermatome?
Area of skin supplied by a single spinal nerve.
What happens with dermatomes over the trunk?
They’d ignificantly overlap each other.
What is an axial line?
The line of the junction of two dermatomes supplied from discontinuous spinal levels.
Where do axial lines extend from?
Trunk to limbs.
Where does the anterior axial line run in upper limbs?
Shernal angle across the 2nd costal cartilage, down the front of the limb to the wrist.
Where does the posterior axial line run in the upper limbs?
Vertebra prominent across the back and down the back of the arm, as far as the insertion of deltoid muscle.
Where does C7 supply (dermatome)?
Peripheral extremity of the limn.
Where do cranial disposed segments go to in terms of dermatomes?
Pre-axial border of the limb.
Where do caudally disposed segments go to in terms of dermatomes?
Post-axial border.
Is there overlap between adjacent dermatomes?
Yes.
Is there overlap across axial lines?
No.
How do the dermatomes lie when traced dismally down the front and proximally up the back?
Numerically.
What dermatomes belong to the brachial plexus?
C5-8 and T1.
Is there distortion of the lower limb in terms of dermatome pattern?
Yes.
Where does the anterior axial line run in the lower limb?
- Spirals from the root of the penis/clitoris.
- Goes across the front of the scrotum/labium majus.
- Goes around to the back of the thigh and calf in the midline almost to the heel.
Where does the posterior axial line run in the lower limb?
Fourth lumbar interspace to the back of the thigh down to the head of the fibula (halfway down the calf).
Describe C1 - dermatome?
No skin supply.
Describe C1 - dermatome?
Occipital region and posterior neck.
Describe C3 - dermatome?
Posterior neck and spurs clavicle region.
Describe C4 - dermatome?
Infraclavicular region (over first thoracic interspace) to tip of shoulder above scapular spine.
Describe C5 - dermatome?
Lateral arm (deltoid and below).
Describe C6 - dermatome?
Lateral forearm, thumb, probably index finger.
Describe C7 - dermatome?
Middle finger.
Describe C8 - dermatome?
Ring and little fingers, distal medial forearm.
Describe T1 - dermatome?
Medial elbow (not the axilla).
Describe T2 - dermatome?
Medial arm, axilla, thorax (adjoining C3 + 4).
Describe T3 - dermatome?
Thorax and small extension to the axilla.
Describe T4 - dermatome?
Nipple.
Describe T8 dermatome
Rib margin.
Describe T10 dermatome?
Umbilicus.
Describe T12 dermatome?
Supra-pubic and upper buttock.
Describe L1 dermatome?
Inguinal region, anterior scrotum (labia), upper buttock.
Describe L2 dermatome?
Anterior thigh, upper buttock.
Describe L3 dermatome?
Anterior and medial knee, upper buttock.
Describe L4 dermatome?
Medial leg, medial malleolus, side of foot.
Describe L5 dermatome?
Lateral leg, dorsum, medial side of foot, medial sole, great toe.
Describe S1 dermatome?
Lateral malleolus, lateral side of dorsum and sole. S1 supplies some of the dorsum and sole.
Describe S2 dermatome?
Posterior leg, posterior thigh, buttock, penis.
Describe S3 dermatome?
Sitting area of buttock, posterior scrotum (labia).
Describe S4 dermatome?
Perinatal.
Describe S5 dermatome?
Behind anus and over coccyx.
