Chapter 13 A&P

Lumbar Plexus

Arises from lumbar segment of spinal cord Innervates pelvic girdle and lower limbs Axon from ventral rami of spinal nerves T12-L4 Genitofemoral nerve, lateral femoral cutaneous, femoral nerve

What are dorsal roots?

Axon of neurons, bring sensory info into spinal cord

Where is the epidural space

Between dura mater and walls of the vertibral canal (contains areolar tissue, blood vessels, and protective padding)

Where does the adult spinal cord end?

Between vertebrae L1 and L2

Pia mater

Bound to underlying neural tissue

How is white matter organized in spinal cord?

Posterior white columns, anterior white columns, lateral white columns, anterior white commisure

Sacral Plexus

Sacral segments of spinal cord Axons from ventral rami of spinal nerves Sciatic nerve, Pudendal nerve

How is grey matter organized in spinal cord?

Sensory nuclei, motor nuclei, posterior gray horn, anterior gray horn, lateral gray horn, anterior white commissure

What are spinal meninges? What are their functions

Series of specialized membranes surrounding the spinal cord, provide necessary physical stability and shock absorption

What is a dermatome?

Specific bilateral region of the skin surface monitored by a single pair of spinal nerves. Damage or infection of spinal nerve or dorsal root ganglia produces loss of sensation in corresponding regions of skin

What is a mixed nerve?

Spinal nerves classified as mixed nerves that contain both afferent (sensory) and efferent (motor) fibers

Cervical Plexus

Ventral rami of spinal nerves C1-C5. Innervates muscles of neck and extends into thoracic cavity Phrenic is major nerve

How many pairs of spinal nerves are there?

31

How many cervical nerves are there?

8

What is a tract? (fasciculus)

A bundle of axons in CNS that is somewhat uniform in diameter, myelination, and propagation speed

Ascending tract

Carries sensory info towards brain

What is a nerve plexus?

Complex interwoven network of nerves

What are ventral roots?

Contain axons of motor neurons that extend into the peripheral nervous system to control somatic and visceral effectors

Descending tract

Conveys motor commands to spinal cord

Where is grey matter the greatest in the spinal cord?

In segments of the spinal cord dedicated to the sensory and motor control of the limbs

Endoneurium

Innermost layer of delicate connective tissue, extends from perineurium and surrounds individual axons

Brachial Plexus

Innervates pectoral girdle and upper limb contributes from ventral rami of spinal nerves C4-T2 Musculocutaneus nerve, ulnar nerve, axillary nerve, radial nerve

What are dorsal ganglia?

Located near spinal cord, contain cell bodies of sensory neurons

Perineurium

Middle layer extends inward from epineurium

Arachnoid mater

Middle meningial layer, subarachnoid space filled with CSF acts as shock absorber and diffused medium for dissolved gases, nutrients, chemical messengers and waste

Dura Mater

Outermost covering, provide longitudinal stability fuses with periosteum of occipital bone

Epineurium

Outermost layer of spinal cord, dense network of collagen