Meninges

(Underneath)Arachnoid MembranePia Matter

Dura Matter

Arachnoid Membrane

Pia Matter

• Made of strong white fibrous tissue• Outer layer of the meninges• Inner periosteum of the cranial bones• Protects inner layers including brain

• Delicate cob-web like• Between Dura matter and Pia matter• Adheres to outer surface of meninges

• Transparent• Adheres to outer surface of the brain and spinal cord• Contains blood vessels

Plexuses

Cervical Plexus(C1 through C4)

Brachial Plexus(C5 through T1)

Lumbar Plexus

Sacral PlexusL4 and L5 throughS1 and S4

Cervical Plexus

Brachial Plexus

• Innervate the muscles and skin of the neck, upper shoulders, and part of the head

• Exiting the plexus, phrenic nerve, which innervates the diaphragm

• Deep within shoulder• Passes from ventral rami of spinal nerves C5 through T1• Beneath clavicle • Toward upper arm• Innervates the lower part of the shoulder and entire arm

Lumbar Plexus

Sacral Plexus

• Made from intermingling fibers from the first four lumbar nerves

• Lumbar region of back• Divides into many branches supplying the thighs

and legs

• Formed fibers from the fourth and fifth lumbar nerves and the first four sacral nerves

• Lies in pelvic cavity on the anterior sirface of the piriformis miuscle

• Forms the sciatic nerce • Through buttocks and back of thigh• Supplies all leg skin

Spinal Cord

Spinal cord lies in the spinal cavity, from the foramen magnum to the lower border of the first lumbar vertebra.

Spinal Cord• Within spinal cavity• From foramen magnum to the lower border of the first

lumbar vertebra• Averages about 18 inches• Conducts information to and from brain• Reflex center for all spinal reflexes