how are spinal nerves named?
from where they emerge from the spinal cord
how many pairs of spinal nerves are there?
31
what is unique about spinal nerve C8?
-First 7 pairs exit the vertebral canal superior to the vertebrae they’re from, but C8 emerges inferior to the seventh cervical vertebrae between C8 and T1
define ventral root
Contains motor fibers that arise from ventral horn motor neurons and extend to and innervate skeletal muscles
define dorsal root
contain sensory fibers that arise from sensory neurons in the dorsal root ganglia and conduct impulses from the peripheral receptors to the spinal cord
ventral and dorsal roots _________________
combine to form a spinal nerve
what is a plexus?
where do they occur?
an interlacing nerve network of ventral rami
cervical, brachial, lumbar, and sacral regions
__________ unite in ________ then diverge into _________
ventral rami
plexus
peripheral nerves
what are two differences between ventral and dorsal rami
dorsal rami are smaller, more localized
ventral rami take up a larger surface area
dorsal rami supply skin and muscles of posterior body trunk at approximate levels of emergence from the vertebrae
ventral rami supply the rest of the trunk and limbs
Cervical Plexus and Neck
-ventral rami of C1-C5
-supplies muscles of shoulder and neck
-contains phrenic nerve that receives fibers from C3, C4, and C5, this nerve runs inferiorly and supplies both motor and sensory fibers to the diaphragm
Brachial Plexus and Upper Limb
-From ventral rami of C5-C8 + T1
-Divides into 5 major peripheral nerves
The Lumbar Plexus
-From ventral rami of L1-L4
-supplies abdominopelvic region and interior thigh muscles
-contains femoral nerve, the largest nerve in plexus that serves the thigh
The Sacral Plexus
-From ventral rami of L4-S4
-Serves buttock, posterior surface of thigh, all sensory and motor legs of lower legend and foot
-contains sciatic nerve, largest in body
what are the 5 major Peripheral Nerves of the Brachial Plexus?
-Musculocutaneous Nerve
-Median Nerve
-Axillary Nerve
-Radial Nerve
-Ulnar Nerve
Axillary Nerve
-innervates deltoid
-teres minor muscle
-skin and joint capsule of the shoulder
Musculocutaenous Nerve
-supplies motor fibers to the biceps brachii
-brachialis
-coracobrachialis muscles
-cutaneous sensation in the lateral forearm
Median Nerve
-innervates 5 intrinsic muscles of the lateral palm
-motor fibers that pronate the forearm, flex the hand and fingers, and oppose thumb
Radial Nerve
-innervates all the extensor muscles of the upper limb
Ulnar Nerve
-flexor carpi ulnaris
-flexor digitorum profundus
-most intrinsic hand muscles and the skin of the medial aspect of the hand