Page 388 - Atlas of Histology with Functional Correlations
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SECTION 2 • Peripheral Nervous System
PERIPHERAL NERVOUS SYSTEM
Consists of neurons, neuroglia, nerves, and axons outside the CNS
Cranial nerves arise from the brain and spinal nerves from the spinal cord
Ganglia are accumulations of neurons and are covered by connective tissue
Contains both sensory and motor nerves
Neurons of peripheral nerves can be located in the CNS or in ganglia
CONNECTIVE TISSUE LAYERS IN
PERIPHERAL NERVES
Peripheral nerves are partitioned by layers of connective tissue into fascicles
Outermost connective tissue around the nerve is the epineurium
Perineurium surrounds one or more nerve fascicles and forms a blood–nerve
barrier
Vascular connective tissue layer endoneurium surrounds individual axons
PERIPHERAL NERVES
Nuclei seen between individual axons are Schwann cells and fibrocytes
Schwann cells myelinate and surround individual axons or enclose
unmyelinated axons
Between individual Schwann cells in myelinated axons are the nodes of
Ranvier
Conduction along a myelinated axon is called saltatory conduction
Small satellite cells surround the neurons of PNS ganglia
Satellite cells provide structural support, insulate, and regulate metabolic
exchanges
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