TOPIC 2- 3. The spinal segment. The spinal nerves. The dermatomes and the Head-zones

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How many spinal segments does the spinal cord consist of?

- 8 cervical

- 12 thoracic

- 5 lumbar

- 5 sacral

- 1 coccygeal

How are the organization of the spinal segments in the different areas?

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How many pairs of spinal nerves do we have?

1-2 cm long regions of the spinal cord determined by the spinal rootlets

What are the spinal cord segmented?

Intervertebral foramen

Where does the spinal nerves exit from inside of the vertebral column?

Divides into ventral and dorsal rami

What happens after the spinal nerve has exited through the intervertebral foramen?

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How many cervical vertebraes do we have?

The first spinal nerve exit above C1

- the rest exit below

Does the spinal nerves exit through the superior or inferior side of the vertebra?

C1-C4: cervical plexus

C5-C8: brachial plexus

Role of ventral rami of cervical spinal nerves

C1: suboccipital nerve

C2: greater occipital nerve

C3: third occipital nerve

Which are the dorsal rami of the cervical part of the spinal cord?

- Suboccipital nerve: motor innervation

- Greater occipital nerve and third occipital nerve: skin innervation

What are the roles of the dorsal rami of the cervical part of the spinal cord?

T1: brachial plexus

T12: lumbar plexus

T2-T12: intercostal nerves

What happens with the ventral rami of the thoracic segments?

Muscle and skin innervation of the back

What happens with the dorsal rami of the thoracic segments?

L1-L4: lumbar plexus

L4-L5: give branches to sacral plexus

What happens with the ventral rami of the lumbar segments?

L1-L3: superior cluneal nerves (cutaneous innervation of gluteal region)

What happens with the dorsal rami of the lumbar segments?

Form sacral plexus

What happens with the ventral rami of the sacral segments?

S1-S3 form medial cluneal nerves

What happens with the dorsal rami of the sacral segments?

Posterior femoral cutaneous nerve

From which nerves are the inferior cluneal nerves from?

An area of the skin, that is mainly supplied by a single spinal nerve

What are dermatomes?

The dermatomes may overlap each other

Why may you not notice if one of your dorsal roots are not intact anymore?

Knowing which spinal nerve that is defected

Clinical relevance for knowing the dermatomes?

When the spinal nerve exit the intervertebral foramen it goes around the body

Why are the same dermatome located higher on the back-side than on the front?

C1 only contain motor fibers

Why does not C1 have a dermatome?

An area of skin that is innervated by the same spinal segment as a muscle or viscera

What are head zones?

Painful stimuli to a muscle or viscera may cause pain sensation in the corresponding skin area

- because they are innervated by the same spinal nerve

What is referred pain?

Pain coming from skin is a lot more common than pain from the viscera

Why does the brain misinterpretet visceral/muscular pain as skin pain

Right shoulder, may radiate to the back

What is the head zone of the gall bladder?

At the back between the scapulae

What is the head zone of the pancreas?

Usually felt by heartburn

What is the head zone of the stomach and esophagus?

- Left arm into ulnar innervated areas, especially the 4th finger

What is the head zone of the heart?

Shoulders

What is the head zone of the diaphragm?