Nerve tissue. histology and embryology. Modul IB. Martin Špaček - PDF

Modul IB Nerve tissue histology and embryology Martin Špaček Pictures from: Junqueira et al.: Basic histology Rarey, Romrell: Clinical human embryology Young, Heath:

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Modul IB Nerve tissue histology and embryology Martin Špaček Pictures from: Junqueira et al.: Basic histology Rarey, Romrell: Clinical human embryology Young, Heath: Wheather s functional histology histo_frames.html Development Formation of the notochord (notochordal or head process) inductive influence on the overlying ectoderm Development Nerve tissue develops from the ectoderm At the beginning of the 3rd week the ectoderm overlying the notochord forms the neural plate Neural plate Development neural groove neural folds approach each other in the midline, where they fuse Neural tube is formed This process is known as neurulation Development Neural crest during neurulation a specialized portion of the neural plate separates from the neural tube give rise to heterogeneous array of tissues Development Neural crest during neurulation a specialized portion of the neural plate separates from the neural tube give rise to heterogeneous array of tissues spinal and autonomic ganglia Schwann cells odontoblasts chromaffin cells of of the adrenal medulla pigment cells (melanocytes) meninges Merkel cells Development Histogenesis of the neural tube the wall of the tube consists of the pseudostratified columnar epithelium neuroepithelium formed by 3 zones: 1) ventricular zone progenitor cells 2) intermediate zone neurons migrate toward 3) cortical plate the future gray matter lumen Development Histological differentiation 1. nerve cells (neurons) 2. glia cells connective tissue of the CNS 3. neural crest cells Types of neurons According to the number of processes: Multipolar the most abundant pyramidal cells, Purkinje cells Bipolar visual, auditory system Pseudounipolar sensory ganglia Types of neurons Types of neurons Based on the length of the axon: Golgi type I the axon extends beyond the dendritic tree pyramidal cells, Purkynje cells Golgi type II axon terminates in the immediate area of the cell body stellate cells Components of a neuron Perikaryon (soma) nucleus large, spherical, euchromatic prominent nucleolus synthetic activity endoplasmic ret. Nissl bodies in light microscope highly developed Golgi complex only in the perikaryon transfer and secretory vesicles mitochondria abundant in the axon terminals cytoskeleton neurofilaments, microtubules inclusions lipofuscin, melanin Dendrites Are the receiving surface of the neuron Neurons have numerous dendrites Composition of the cytoplasm is similar to that of the perikaryon Axons Most neurons have only one axon Originate from axon hillock Dependent on the perikaryon for its maintenance axonal transport Axonal Transport Microtubules form tracks within the axon to carry organelles and vesicles Motor Proteins Transport Cargo Proteins related to axon flow include dynein & kinesin they both have two ATPbiding heads & a tail Synapses Enlarged endings of terminal branches Axodendritic Axosomatic Axoaxonic Synapses Presynaptic ending contains synaptic vesicles with neurotransmitters (chemicals that cross the synapse between two neurons) Synaptic cleft a region of extracellular space (20-30 nm) Postsynaptic ending contains receptor sites for neurotransmitters Synaptic transmission N1 cerebrum (HE) N2 cerebrum (Nissl) Cerebellum Cerebellar layers: Molecular layer mostly neuronal fibers Purkynje layer large multipolar neurons Granule cell layer small integrator neurons N4 cerebellum (HE) N4 cerebellum (HE) Neuroglia 10 glial cells for each neuron About half of the volume of nerve tissue Function: provide neurons with structural support and maintain local conditions for neuronal function Staining: silver or gold impregnation, histochemical technique 4 morphologic types The largest I. astrocytes Vascular feet surround and ensheathe all vessels Structural support for nerve tissue Form glial scar I. astrocytes A. protoplasmic granular cytoplasm envelop the surface of nerve cells and blood vessels B. fibrous long processes predominantly in white matter I. astrocytes N8 cerebrum (astrocytes), Antibody Anti-S-100 protein, ABC II. oligodendrocytes Smaller, processes Processes envelop axons and form myelin sheath Are found in both gray and white matter The formation of the myelin sheath is similar to that of Schwann cells in peripheral nerves II. oligodendrocytes III. microglia Phagocytic cells Derived from mesoderm Small cell bodies Their nuclei have elongated shape other neuroglia have spherical Short processes with small expansions thorny appearance III. microglia IV. ependymal cells Epithelial arrangement Line the cavities of the brain and spinal cord Motile cilia (movement of the cerebrospinal fluid) N5 spinal cord (HE) Central canal of spinal cord lined with ependymal cells Nerve fibres Consist of axons enveloped by special sheaths of ectodermal origin Groups of nerve fibres constitute: the tracts of the brain (oligodendrocytes) peripheral nerves (Schwann cells) Fibres: unmyelinated myelinated Unmyelinated fibres CNS axons run free among the other neuronal and glial processes PNS axons are enveloped within simple clefts of Schwann cells Unmyelinated fibres Myelinated fibres myelin formation: in the PNS a single axon is embedded in a Schwann cell the plasma membrane of a Schwann cell wraps in a spiral around the axon Myelinated fibres S Schwann cell nucleolus A axonal cytoplasm M myelin sheath 13 Myelinated axon Myelinated fibres Myelinated fibres nodes of Ranvier gaps between Schwann cells N3 cerebrum (Myelin) Peripheral nervous system nerves nerve fibres grouped in bundles connective tissue coverings: endoneurium perineurium epineurium Nerves Nerves Nerves N7 peripheral nerve (HE) N7 peripheral nerve (HE) Peripheral nervous system Ganglia aggregations of nerve cell bodies outside the CNS a connective tissue capsule each neuronal cell body is surrounded by Schwann celllike satellite cell Two main classes craniospinal (sensory) autonomic (motor) N6 autonomic ganglia (HE) Meninges Dura mater Meninges external meninx dense connective tissue subdural space Arachnoid connective tissue devoid of blood vessels a layer in contact with dura mater system of trabeculae cavities form subarachnoid space (filled with CSF) Pia mater loose connective tissue containing many blood vessels Meninges
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