13.4 Spinal nerves and plexuses Flashcards
What are the three layers that surround the spinal nerves
Epineurium—outermost; network of collagen fibers
2. Perineurium—middle layer; separates nerve into fascicles (axon bundles)
3. Endoneurium—innermost; surrounds individual axons
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What is a nerve plexuses
It is a complex interwoven network of nerve fibers.
What are the four major nerve plexuses
- Cervical plexus
- Brachial plexus
- Lumbar plexus
- Sacral plexus
Describe the cervical plexus
Includes anterior rami of spinal nerves at C1-C5 and innervates scalp behind ear, neck, and diaphragm
What are the major cervical plexus nerves
– Phrenic nerve—from C3–C5; controls diaphragm
– Lesser occipital nerve
– Great auricular nerve
– Transverse cervical nerve
– Supraclavicular nerves
Describe the brachial plexus
It is anterior rami of C5-T1 and it innervates the pectoral girdle, upper back , upper limb
Describe the division of the brachial plexus
The rami first divide into three trunks called the superior, middle and inferior. Then trunks re-sort their axons to form three cords called lateral, posterior and medial cords
What are major brachial plexus nerve
Musculocutaneous nerve (lateral cord)
– Median nerve (lateral and medial cords)
– Ulnar nerve (medial cord)
– Axillary nerve (posterior cord)
– Radial nerve (posterior cord)
Describe the lumbar plexus
includes anterior rami of spinal nerves from T12 - L4
What the major nerves of the lumbar plexus
- Iliohypogastric nerve
- Ilio-inguinal nerve
- Femoral nerve
- Obturator nerve
- Genitofemoral nerve
- Lateral femoral cutaneous nerve
Describe the sacral plexus
Includes anterior rami of spinal nerves L4–S4
What are the major nerves of the sacral plexus
Sciatic nerve
* Superior and inferior gluteal nerves
* Pudendal nerve
What are the two branches of the sciatic nerve
- Fibular nerve (common fibular nerve)
- Tibial nerve
