dermatomes and myotomes

Question 1

what do somites differentiate into and what do these give rise to?

Answer 1

sclerotome- ventral and gives rise to the vertebrae and ribs
dermatomyotome- dorsal and forms the dermis( via dermatomes) and muscle tissue (via myotomes).

Question 2

what is a dermatome

Answer 2

area of skin supplied by a single spinal nerve

Question 3

what does the t10 dermatome supply

Answer 3

umbilicus

Question 4

what does the T4/T5 dermatome supply

Answer 4

nipples

Question 5

what does the L1 dermatome supply

Answer 5

groin

Question 6

what does the C7 dermatome supply

Answer 6

middle finger

Question 7

what does the c6 dermatome supply

Answer 7

thumb
1st finger
forearm

Question 8

what is a neurone/ neuron/ nerve cell

Answer 8

electrically excitable cell that receives, processes and transmits information through chemical and electrical signals.

Question 9

structure of a nerve

Answer 9

enclosed cable like bundle of axons and their supporting cells e.g Schwann cells.
each nerve contains many axons which are each surrounded by a connective tissue called the endoneurium. this consists of an inner sleeve of material called the glycocalyx and a mesh of collagen.
within the endoneurium individual nerve fibres are surrounded by endoneurial fluid. during nerve irritation or injury the amount of endoneurial fluid can increase.
the axons surrounded by endoneurium are bundled together into a fascicle which is wrapped in a connective tissue called perineurium.
the fascicles are then grouped together and surrounded by epineurium.

Question 10

what are blood vessels in nerve cells called

Answer 10

vasa nervorum

Question 11

describe a spinal nerve

Answer 11

mixed nerve that carries motor, sensory and autonomic signals between the body and the spinal cord.
the dorsal nerve root transmits sensory fibres from the sensory receptors to the spinal cord so is an afferent root whereas the ventral nerve root is an efferent root and carries the motor and autonomic fibres that are leaving the spinal cord.

Question 12

what does the spinal cord run through

Answer 12

the vertebral foramen.

multiple vertebral foramina together form the spinal canal.

Question 13

where does the spinal chord start and finish

Answer 13

starts at the inferior margin of the medulla oblongata and ends at the conus medullaris at L2.

Question 14

how do the cervical spinal roots emerge from the vertebral body

Answer 14

cervical spinal roots emerge above the corresponding vertebral body with the exception of the 8th cervical spinal root C8 which emerges between the C7 and T1 vertebrae.

Question 15

how do the corresponding nerve roots exit the thoracic vertebra

Answer 15

exit inferior to the vertebral body.

Question 16

what happens to the spinal nerve after it emerges through the intervertebral foramen

Answer 16

divides into rami
the dorsal ramus supplies the deep muscles and skin of the dorsal trunk.
the ventral ramus supplies the muscles and skin of the upper and lower limbs and also the lateral and ventral trunk.

Question 17

each spinal nerve gives off a tiny meningeal branch. what does this do?

Answer 17

re-enters the spinal canal through the intervertebral foramen.
this supplies the vertebrae, ligaments of the vertebral column , blood vessels and meninges.

Question 18

what happens to the dorsal rami

Answer 18

divide again into medial and lateral branches that supply the skin of the back in a ‘tidy’ segmental manner.

Question 19

what is an axial line

Answer 19

the junction of two dermatomes supplied from discontinuous spinal levels.

Question 20

in the upper limb what marks the pre axial border

Answer 20

cephalic vein

Question 21

in the upper limb what marks the post axial border

Answer 21

basilic vein

Question 22

in the lower limb what marker the pre-axial and post-axial border ?

Answer 22

the great (long) saphenous veins marks the pre-axial border and the small (short) saphenous vein marks the post axial border.

Question 23

what is a myotome

Answer 23

A myotome is the group of muscle fibres supplied by a single spinal nerve.

Question 24

which myotome allows hip flexion

Answer 24

L2

Question 25

which myotome allows knee extension and hip adduction

Answer 25

L3

Question 26

which myotome allows ankle dorsiflexion

Answer 26

L4

Question 27

which myotome allows great toe extension /ankle inversion / hip abduction

Answer 27

L5

Question 28

which myotome allows ankle plantar flexion/ ankle eversion/hip extension?

Answer 28

S1

Question 29

which myotome allows knee flexion/ great toe flexion

Answer 29

S2

Question 30

what is the neural level

Answer 30

lowest level of fully intact sensation and motor function.