Peripheral Nerve Injuries: A Clinical Guide
Peripheral Nerve Injuries: A Clinical Guide is a fully illustrated and informative reference on injuries within the peripheral nervous system. It incorporates new knowledge in molecular and cellular events which underlie the response of nerves to injury,
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The Peripheral Nervous System: Anatomy and Function
Restatement of the facts appears to be warranted by the misconceptions shown by many post graduate students [21].
The nervous system is the mechanism through which the organism is kept in touch with its internal structures and external environments and reacts to changes in them. The central nervous system – the brain and its caudal prolongation the spinal cord – is connected to the periphery by the peripheral nervous system. The latter includes the cranial nerves, the spinal nerves with their roots and rami, the peripheral nerves and the peripheral components of the autonomic nervous system, the sympathetic, parasympathetic and enteric divisions [16]. The peripheral nerves contain motor fibres (to end plates in skeletal muscle), sensory fibres (from organs and endings in skin, muscle, tendon, periosteum, and bone and joint), efferent autonomic fibres (to blood vessels, sweat glands and arrectores pilarum muscle), and visceral afferent fibres. In no other system is so much functional and relay capacity concentrated in so small a volume of tissue. The cervical spinal cord, with a width of about 2 cm and a depth of about 1.5 cm, contains all the apparatus transmitting control of somatic function from the neck down, together with that of control of much visceral function. Because of their greater content of connective tissue, the peripheral nerves have proportionately a lesser functional content, yet severance in an adult’s arm of the median nerve of 5 mm diameter effectively ruins the function of the hand and forearm. Twelve pairs of cranial nerves arise from the brain and brain stem. The second of these, the optic nerves, are in fact prolongations of the central nervous system. Thirty one pairs of spinal nerves – eight cervical, twelve thoracic, five lumbar, five sacral and one coccygeal – arise from the spinal cord. Each spinal nerve leaves or enters the cord by ventral, largely motor, root, and a dorsal sensory root (Figs. 1.1 and 1.2). Each sensory root splits into several rootlets as it approaches the spinal cord; these enter the cord along the line of the posterolateral sulcus. The division of the anterior roots into rootlets is less obvious and takes place nearer the cord. Because in the adult the spinal cord extends caudally only so far as the first lumbar
R. Birch, Peripheral Nerve Injuries: A Clinical Guide, DOI 10.1007/978-1-4471-4613-1_1, © Springer-Verlag London 2013
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The Peripheral Nervous System: Anatomy and Function
Phrenic n.
Dorsal root ganglion C5 Dorsal root ganglion C6 Ventral root C5 Ventral root C6 Dorsal roots C5 Dorsal roots C6
Fig. 1.1 The fifth, sixth cervical nerves avulsed from the spinal cord. The ventral root is easily distinguishable from the dorsal rootlets. Note the dorsal root ganglion, the dural sleeve merging into the epineurium and the spinal nerve itself. The small pieces of tissue on the proximal ends of the dorsal rootlets (below) are probably portions of the spinal cord Dorsal root
Dura mater Arachnoid Pia ma
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