dermatome and myotomes

Question 1

• what does the somite contain?
• what do these turn into?

Answer 1

sclerotome, dermatome and myotome

sclerotome = vertebrae and ribs

dermatome = dermis

myotome = muscle

Question 2

where does the nerve supply come from?

Answer 2

neural tube contains percursors for nervous system - each dermatomyotome as a specficic spinal nerve and takes tht nerve supply with them

Question 3

what do skin and muscle from a single dermatomyotome have in common?

Answer 3

derived from same spinal nerve

Question 4

what is a spinal root?

what does the ventral root have?

dorsal?

Answer 4

roots connect the spinal nerve to the spinal cord

ventral root = motor/efferent nerve fibres

dorsal root = sensory/afferent fibres

Question 5

what is a spinal nerve?

what does it mark?

how many are there?

Answer 5

• it is a brief area where motor and sensory nuerones mix in the intervertebral foramen
• it marks the division between PNS and CNS
• 31 pairs

Question 6

what spinal structure does the spinal nerves leave from?

what does the spinal cord run down?

Answer 6

intervertebral foramina

vertebral foramina

Question 7

• where does the spinal cord start and end?
• where do the roots of inferior segments decend the spine

Answer 7

starts - inferior margin of medulla oblongata

ends - L2 at conus medullaris

Question 8

where do the spinal nerves emerge with respiect to their vertebrae?

Answer 8

C1-7 = above corresponding vertebrae

T1-L5 = below

S1-S4 = sacral foramina

S5 and Co1 = sacral hiatus

Question 9

• what are rami?
• what do these rami supply?
• what other branch does the spinal nerve give off?

Answer 9

the spinal nerve divides in to ventral and dorsal rami

dorsal = deep muscle and skin of dorsal trunk

ventral = muscle and skin of upper and lower limbs, lateral and ventral trunk (bigger area than dorsal)

meningeal branch - supplies vertebrae, ligamnets, blood vessels, meningies

Question 10

what does the dorsal ramus divide into?

what manner does it supply skin and muscle in?

Answer 10

medial and lateral branch

simple segmented mannor - tidy

it supplies the narrow strip if muscle and skin in line with intervertebral foramina

Question 11

what mannor does the ventral ramus supply the skina nd muscle?

Answer 11

complexxxx - segmented for the trunk (T2-12)

eners plexus to supply limbs

Question 12

what plexus supplies the arm?

what plexus supplies the leg?

Answer 12

brachial plexus

lumbo sacral plexus

Question 13

what dermatome map do we use?

Answer 13

foerster map

Question 14

• what is a myotome?
• what is a dermatome?

Answer 14

group of muscles supplied y a single spinal nerve

an area of skin supplied by a single spinal nerve

Question 15

what is the difference between a motor unit and a myotome?

Answer 15

a motor unit is a sngle. motor neurone and the miscle fibres it supplies

1 spinal nerve supplies many motor units

Question 16

myotome functions of upper limb!

learn red

Answer 16

Question 17

myotome functions of lower limb!

learn red

Answer 17

Question 18

what is hiltons law?

example

Answer 18

the nerve crossing a joint supplies: the muscles acting on it, the skin over the insertion of those muscles and the joint itself

e.g. femoral nerve- crosses knee

supplies quadriceps femoris to extend the knee and the skin over the knee

e.g. L3

the myotome for knee etension is L3, L3 s=dermatome is also over the knee

Question 19

what happens if you damage the femoral nerve in the groyne ?

Answer 19

paralysis of muscles supplied by femoral nerve distal to site of injury

anaethesia in skin of femoral nerve and its branches

Question 20

why would there be some sensation in dermatomes that are injured?

what stops this?

Answer 20

there is functional overlaps between adjacent dermatomes meaning some of the dermatomes next to the injued area may produce minimal sensation

axial line = junction of 2 dermatomes from discontinuous spinal levels? honestly fuck knows

Question 21

what is an axial line?

what 2 axial lines do you have?

Answer 21

• the junction of 2 dermatomes supplied from discontinous spinal levels

anterior and posterior

they mark the centre of dorsal and ventral comparments of the limb

Question 22

why do the pre axial borders change to post axial borders?

what direction do the limbs rotate?

where are the pre axial and post axial borders?

Answer 22

because of the limbs rotaion in develoment in pregnancy

lower = inwards

upper =outwards

upper limb: cephalic vein = pre, basilic vein = post

lower limb: pre = long sphenous vein, post = short saphenous vein

Question 23

spinal nerves Vs peripheral nerves

exmple?

Answer 23

peripheral nerves can often contain neurones from many spinal nerves - fibres from one spinal nerve can enter many peripheral nerves

ulna nerve is made of C8 and T1

Question 24

what are peripheral nerve territories?

Answer 24

areas of the skin supplied by peripheral nerves

they often overlap with sections of multiple dermatomes that are consistent with their spinal nerve content