Histology
Lab -10-
Shorooq Wessam
Peripheral nervous system
The peripheral nervous system (PNS) consists of neurons , nerves and axons
that are located outside the CNS . these include cranial nerves from the brain
and spinal nerves from the spinal cord , along with their associated ganglia .
Ganglia (singular , ganglion) are small accumulations of neurons that are
located outside the CNS and are surrounded by a connective tissue capsule .
the nerves of the PNS contain both sensory and motor axons . these axons
transmit information between the peripheral organs and the CNS . the neurons
of the peripheral nerves are located either within or outside the CNS in
different ganglia.
Connective tissue layers in the PNS
A peripheral nerve is composed of numerous axons of various sizes
surrounded by several layers of connective tissue that partition the nerve into
several nerve (axon) bundles or fascicles . the outermost connective tissue
layer is the epinerium , which consists of dense irregular connective tissue that
completely surrounds the peripheral nerve . a thinner connective tissue layer ,
Called the perineurium , extends into several and surrounds numerous nerve
fascicles . within each fascicle are individual axon and their supporting cells ,
the neurolemmocytes (Schwann cells) . each exon is surrounded by a loose
connective tissue layer of thin reticular fibers , called the endonerium .
Supporting cells in the PNS
The supportive cells in the PNS are the myeline – forming neurolemmocytes
(Schwann cells) and the satellite cells . satellite cells are small cells that
surround the neuronal cells in paravertebral and peripheral ganglia .
paravertebral ganglia are an interconnected chain of ganglia that are located
parallel to the vertebral column , near the junction of the dorsal and ventral
roots of the spinal nerves . peripheral ganglia are located distally from the
vertebral column , near various visceral organs .
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