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