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Posts Tagged ‘CNS’

SPINAL NERVES PROPER Immediately distal to the spinal ganglia, ventral and dorsal roots unite to form spinal nerves (see Fig. 43.5, Fig. 15.15). These very soon divide into dorsal and ventral rami, both of which receive fibres from both roots. At all levels above the sacral, this division occurs within the intervertebral foramen. Division of […]

REFERENCES Barson and Sands, 1977. Barson AJ, Sands J: Regional and segmental characteristics of the human adult spinal cord. J Anat 1977; 123:797-803. Bogduk, 2005. Bogduk N: Clinical Anatomy of the L Spine and Sacrum, 4th edn.. Edinburgh, Elsevier Churchill Livingstone, 2005. Broadbent et al., 2000. Broadbent CR, Maxwell WE, Ferrie R, Wilson DJ, Gawne-Cain M, Russell R: Ability of anaesthetists to identify a marked lumbar interspace. Anaesthesia 2000; 55:1122-1126. Carmichael and Gloviczki, 1999. Carmichael SW, Gloviczki P: Anatomy of the blood supply to the spinal […]

INNERVATION VESTIBULOCOCHLEAR NERVE The vestibulocochlear nerve emerges from the cerebellopontine angle (see Fig. 19.3). It courses through the posterior cranial fossa to enter the petrous temporal bone via the internal acoustic meatus, where it divides into an anterior trunk, the cochlear nerve, and a posterior trunk, the vestibular nerve (Fig. 37.12A; see Fig. 27.8). Both […]

NASAL AND OLFACTORY MUCOSAE Nasal mucosa The lining of the anterior part of the nasal cavity and vestibule is continuous with the skin, and consists of keratinized stratified squamous epithelium overlying a connective tissue lamina propria. Inferiorly the skin bears coarse hairs (vibrissae) which curve towards the naris and help to arrest the passage of […]

MEDIAL WALL The medial wall of each nasal cavity is the nasal septum, a thin sheet of bone (posteriorly) and cartilage (anteriorly), that lies between the roof and floor of the cavity (Fig. 32.2D). Bony septum The septum is usually relatively featureless but sometimes exhibits ridges or bony spurs. The posterosuperior part of the septum […]

NEUROGLIA Glial cells which support neurones in the CNS and PNS are derived from three lineages, namely, neuroectoderm, neural crest and angioblastic mesenchyme. In the CNS, cells of the proliferating ventricular zone give rise to astrocytes and oligodendrocytes. After the proliferative phase the cells remaining at the ventricular surface differentiate into ependymal cells, which are […]

MECHANISMS OF NEURAL DEVELOPMENT For more than a century the mechanisms that operate during the development of the nervous system have been studied experimentally. While much has been established, answers to many fundamental questions still remain obscure. In recent years, significant advances in our understanding of the development of vertebrates have come from work on […]

LINEAGE AND GROWTH IN THE NERVOUS SYSTEM Neurones come from three embryonic sources: CNS neurones originate from the pluripotential neural plate and tube, whereas ganglionic neurones originate from the neural crest and ectodermal placodes. The neural plate also provides ependymal and macroglial cells. Peripheral Schwann cells and chromaffin cells arise from the neural crest. The […]

AUTONOMIC NERVOUS SYSTEM Autonomic nerves, apart from the preganglionic motor axons arising from the CNS, are formed by the neural crest. The autonomic nervous system includes the sympathetic and parasympathetic neurones in the peripheral ganglia and their accompanying glia, the enteric nervous system and glia, and the suprarenal medulla. In the trunk at neurulation, neural […]

CENTRAL NERVOUS SYSTEM SPINAL CORD In the future spinal cord the median roof plate (dorsal lamina) and floor plate (ventral lamina) of the neural tube do not participate in the cellular proliferation which occurs in the lateral walls and so remain thin. Their cells contribute largely to the formation of the ependyma. The neuroblasts of […]

AFFERENT CONNECTIONS OF THE CEREBELLUM Mossy fibres and climbing fibres carry the afferent connections of the cerebellum. Mossy fibre systems terminate bilaterally in transversely oriented ‘lobular’ areas; there is considerable overlap amongst the terminations. Climbing fibres from different subnuclei of the inferior olive terminate contralaterally, on discrete longitudinal strips of Purkinje cells. This longitudinal pattern […]

BRAIN STEM RETICULAR FORMATION The brain stem contains extensive fields of intermingled neuronal cell bodies and nerve fibres, which are collectively termed the reticular formation. The reticular regions are often regarded as phylogenetically ancient, representing a primitive nerve network upon which more anatomically organized, functionally selective, connections have developed during evolution. Reticular regions tend to […]