1. Spinal nerve. Dorsal rami of the spinal nerves.

What are the exceptional dorsal branches that do not follow the general pattern

1. Suboccipital nerve (C1) 2. Greater occipital nerve (C2) 3. 3rd Occipital nerve (C3) 4. Superior cluneal nerve (lateral branches of L1-L3) 5. Middle cluneal nerve (lateral branches of S1-S3)

Describe the branches of a spinal nerve

5 branches after iv-foramena 1. *Meningeal branch* returns through IV-foramen to meninges. 2. *White communicating branch* to sympathetic ganglion of *sympathetic trunk* only at C8-L2 levels bc *intermediolateral ncl* only exists here 3. *The gray communicating branch* unmylineated branch returns to each spinal nerve from the sympathetic trunk ganglia 4. *Dorsal branch* mixed nerve to the dorsal neck and trunk. 5. *Ventral branch* mixed nerve to ventral parts of the neck and trunk

Describe the sensory innervation pattern of the dorsal spinal branches

A line running from the superior nuchal line (cranial) to the mastoid process to the inferior angle of the scapula, to the centre of the iliac crest (lateral) to the coccygeal bone (caudal boundary.)

Describe the greater occipital nerve (pathway and innervation)

Initially mixed nerve, motor innervation for the semispinalis capitis, and lonigssimus capitis. After emergence from the spinal canal it turns around the lower edge of the Obliquus capitis inferior traverses the semispinalis capitis and trapezius. It reaches the occpital region and innervates the skin up to the interauricular line

Describe the inferior cluneal nerves

Innervate the sacral and middle part of the gluteal region

Describe the 3rd occipital nerve

Innervates the nuchal region in the midline region (medial to the greater occipital innervation)

Root of a spinal nerve?

It is a *mixed nerve* formed of two roots. 1. The *ventral root* arises from the *ventrolateral sulcus* of the spinal cord. 2. The *dorsal root* arises from the *dorsolateral* sulcus. Both roots merge at the intervertebral foramen.

Describe the *dorsal root* of the spinal nerve

Represents the sensory part of the spinal nerve. Recieving *somatosensory* information from the skin,musculoskeletal system, and viscerosensory information from the viscera. Dorsal roots consist of *dorsal root ganglia* where peripheral projections reach the periphery and the central projections reach the *dorsal horn gray matter*

Describe the superior cluneal nerves

Sensory branches of the lateral branches of L1-L3 they innervate the superior part of the gluteal skin

Describe the *ventral root* of a spinal nerve

The ventral root represents the *motor* part of the spinal nerve. It is responsible for *somatomotor* innervation of striated muscles, autonomic sympathetic innervation (C8-L2) and parasympathetic innervation (sacral segments)

How many do we have?

There are 31 spinal nerves, a pair corresponding to each spinal segment

Describe the pathway and innervation areas of the dorsal branches

They run dorsally and enter the autochtonous muscles of the back. Then it branches into a medial and lateral branch, both branches contain both motor and sensory fibres. Motor fibres innervate muscles, while the sensory fibres innervate the skin.

Describe the Suboccipital nerve (pathway and innervation)

Thick nerve *only motor fibres* it emerges from the spinal canal thorugh the *posterior atlantooccipital membrane* runs under the vertebral artey and enters the suboccipital triangle- it inn all suboccipital muscles.

How do we organize the spinal nerves?

We divide them based on their point of exit. 1.*Cervical nerves* consist of eight pairs (C1-C8) leave spinal canal through iv-foramena (except C1 which leaves between the occipital bone and atlas) 2.*Thoracic nerves* (T1-T12) 3. *Lumbar nerves* (L1-L5) (last btw L5 and sacrum) 4. *Sacral nerves leave sacral canal via the sacral foramena* Last pair leave the sacral canal through the sacral hiatus.