Engineering Oriented Scaffolds for Directing Neuronal Regeneration
Following nervous system injuries, such as peripheral or spinal cord injuries, severed nerves must regenerate to reinnervate tissues and restore lost-functionality. In many peripheral nerve injuries surgical intervention is required to bridge the gaps cre
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Engineering Oriented Scaffolds for Directing Neuronal Regeneration Merav Antman-Passig and Orit Shefi
6.1 Introduction: Neuronal Regeneration Following Injury 6.1.1 Introduction to the Nervous System The nervous system consists of the brain, spinal cord, and all of the nerves connecting these organs with the rest of the body. The brain and spinal cord are classified as the central nervous system (CNS) and the peripheral nervous system (PNS) constitutes the structures not included in the CNS. Together, the CNS and PNS are responsible for sending and receiving information from and to the body, and of processing these signals. In this chapter we focus primarily on peripheral nerve injuries and touch upon spinal cord injuries.
6.1.1.1
Anatomy of the Spinal Cord
The spinal cord consists of a long tubular structure of nervous tissue enclosed within the vertebral cavity of the spine. The spinal cord relays motor and sensory information between the brain and PNS. Grey matter is located in the center of the spinal cord and continues cell bodies, glial cells and blood vessels, and white matter surrounds the grey matter and consists of myelinated axons through which synaptic connection relay motor and somatosensory information up and down the spinal cord. Axons project from the white matter in bundles, known as fascicles, which exit the encasing bone of the spinal column, and enter the PNS. In the sensory
M. Antman-Passig · O. Shefi () Faculty of Engineering and Bar Ilan Institute of Nanotechnologies and Advanced Materials, Bar Ilan University, Ramat Gan, Israel e-mail: [email protected] © Springer Nature Switzerland AG 2021 B. Bidanda, P. J. Bártolo (eds.), Virtual Prototyping & Bio Manufacturing in Medical Applications, https://doi.org/10.1007/978-3-030-35880-8_6
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pathway peripheral sensory neuron cell bodies are located in the dorsal root ganglia (DRG), with afferent axons projecting into the spinal cord and transmitting sensory information from the periphery.
6.1.1.2
Anatomy of the PNS
The peripheral nervous system is composed of a network of nerves connecting the spinal cord and brain to the entire body. A peripheral nerve is often referred to as an anatomical trunk and consists of axons bundled together within layers of protective tissue. The endoneurium is the innermost connective tissue surrounding individual axons and their Schwann cell sheaths, as well as blood capillaries. The endoneurium is composed predominantly of oriented collagen. Next, the perineurium composed of fibroblasts and collagen surrounds groups of axons and binds them into fascicles. Finally, the epineurium, the outer fibrocollagenous sheath bindings the fascicles into a nerve (Fig. 6.1). A ganglion is a cluster of neuron cell bodies enveloped in an epineurium. Nerves finally branch out and terminate in sensory or motor nerve endings which can innervate different organs and tissues [1, 2].
6.1.1.3
Support Cells of the Nervous System
The nervous system contains non-neuronal cells: the neuroglia
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