Central Nervous System Histology PDF

HISTOLOGY OF THE CENTRAL NERVOUS SYSTEM Lec. Gözde Öğütçü Near East University Department of Histology and Embryology [email protected] 100 million nerve cells (neurons), assisted by many more glial cells The shape of the neurone and its processes Anatomically; Central nervous system Br...

HISTOLOGY OF THE CENTRAL NERVOUS SYSTEM Lec. Gözde Öğütçü Near East University Department of Histology and Embryology [email protected] 100 million nerve cells (neurons), assisted by many more glial cells The shape of the neurone and its processes Anatomically; Central nervous system Brain (Cerebrum) Spinal cord(Medulla spinalis) Peripheral nervous system Nerve fibers Ganglion • White (white matter) • Gray (gray matter) • The differential distribution of myelin in the central nervous system is responsible for these differences. CELLS OF NERVE TISSUE • Neurons: have many long processes • Glial cells: have short processes, support and protect neurons NEURONS The fuctional unit in both the CNS and PNS is the neuron. Have three main parts: Cell body(perikaryon or soma): Contains the nucleus and organelles Dentrites: Many elongated processes extending from the perikaryon and specialized to receive stimuli from other neurons Axon: is a single long process ending at synapses specialized to generate and conduct nerve impulses to other cells. Three different basic types of neuronal structure: Multipolar neurons: with one axon and two or more dendrites,are the most common. Bipolar neurons: with one dendrite and one axon, comprise the sensory neurons of the retina, the olfactory epithelium and the inner ear. Pseudounipolar (unipolar) neurons: with one process, the axon, that divides close to the cell body into two long axonal branches. The majority of pseudounipolar neurons are sensory neurons located close to the CNS . Multipolar cell Gray matter White matter Outside in the brain and Inside the brain and cerebellum and inside the cerebellum and outside in spinal cord the spinal cord It is gray in color. It is white in color Unmyelinated abundant fibers are Myelinated abundant fibers Neuron (+) Neuron (-) Neuroglia (+) Neuroglia (+) Capillary (+) Capillary (++) Lymphatic capillary (-) Lymphatic capillary (-) are MENINGES (Membranes of the CNS) Three sequential connective tissue membranes, the meninges, cover the brain and spinal cord. • Membranes consist of fibroblasts and collagen fiber bundles. • Outside to the inside: The dura mater is the outermost layer. The arachnoid layer lies beneath the dura. The pia mater is a delicate layer resting directly on the surface of the brain and spinal cord. Duramater Histological structure: White fibrous connective tissue. • Multiple collagen fibrils parallel, few elastic fibrils and fibroblasts. • Small amount of blood vessels and sensory nerves. • Its facing the arachnoid is lined with mesothelial cells. Arachnoid • a cobweb in appearance, is a thin layer • Subarachnoidal space: between the pia and the arachnoid surrounding the brain • filled with cerebrospinal fluid and contains blood vessels. Piamater • In inside of piamater, glia limitans, a thin barrier of astrocyte foot processes associated with basal lamina surrounding the brain and spinal cord. • surrounds the vessels entering the brain tissue • Consist of abundant nerve fibers. Cerebrospinal Fluid (CSF) • The brain ventricles and central canal of spinal cord are filled with cerebrospinal fluid. Some of the cavities filled with CSF enlarged and became the ventricle. • The choroid plexus located in the ventricular wall and synthesizes the CSF. • Mechanical and immunological protection to the brain inside the skull. • Clear, colorless • About 150ml • Less protein, potassium • Na, Cl, Ca, glucose, oxygen • Cell is very rare pulsation of CSF Lumbar puncture Lumbar puncture (LP), also known as a spinal tap, is a medical procedure in which a needle is inserted into the spinal canal, most commonly to collect cerebrospinal fluid (CSF) for diagnostic testing. including infections of the brain or its surrounding meninges. The procedure is typically performed under local anesthesia using a sterile technique. A hypodermic needle is used to access the subarachnoid space and collect fluid. Types Of Neuroglial Cells In CNS Astrocytes: • are the largest of the neuroglial cells. • Astrocytes do not form myelin. • Play important roles in the movement of metabolites and wastes to and from neurons. • They help maintain the tight junctions of the capillaries that form the blood–brain barrier Oligodentrocytes: • Produce myelin in the CNS and are the predominant cell in CNS white matter. • One oligodendrocyte can myelinate many axons Microglia: • Ependymal Cells: • Line central canal of spinal cord and ventricles of brain. • They form a single layer of cuboidal to-columnar cells that have the morphologic and physiologic characteristics of fluidtransporting cells • Unlike a typical epithelium, ependymal cells lack an external lamina. The apical surface of the cell possesses cilia and microvilli. • Produce, monitor & help circulate CSF (cerebrospinal fluid) are phagocytotic cells. • macrophage-like cells that perform immune functions • In the mature brain, microglia facilitate repair by steering the migration of stem cells to the site of inflammation and injury. Blood - Brain Barrier(BBB) • Functional barrier allows tighter control to passage of substances moving from blood into the CNS. • Main structural component of the BBB is the capillary endothelium, in which the cells are tightly sealed together with occluding junctions and surrounded by the basement membrane. • BBB protects neurons and glia from bacterial toxins, infectious agents and other exogenous susbtances and helps maintain stable composition and constant balance of ions in interstitial fluid required for normal neuronal function. Coroid Plexus On the roof of the 3rd and 4th ventricles and in the lateral ventricles, -membrane made by the piamater together with the ependymal cell is called tela koroidea. In the tela koroidea, many finger-shaped protrusions (villus) form and expand the surface, the choroid plexus. Function: to remove water from blood and release it as the CSF. Ependymal cell:simple cubic or pyrismatic shape. CEREBRUM Histologically it consists of white matter or substansia alba and grey matter or substansia grisea. White matter contains the myelinated axon and located in the inner part. Grey matter located in the outer part of the brain, consists of perikaryon or body of neuronal cells. The cortex is highly convoluted, thrown into deep folds which greatly increase the surface area. These convolutions are called gyri and the intervening depressions are sulci. CEREBRAL CORTEX • It is the gray matter overlying white matter • Containing billions of cells • Neurons of the cerebral cortex are of varying shapes and sizes, but the most obvious are pyramidal cells. As the name implies, the cell body is shaped somewhat like a pyramid • Other neurons or to glial cells also present in the cortex. Neuronal Cells In Cortex Betz's pyramidal cells Capilleries Nörons Oligodendrocyte Astrocyte Oligodendrocyte Microglia PURKINJE LAYER • This intermediate layer consists of a single layer of very large Purkinje cells whose cell bodies rest on the innermost granular layer. • The Purkinje cell has a large, prominent, flaskshape cell body with a clear vesicular nucleus. • It has many tree-like dendritic arbor which project into the molecular layer. WHITE MATTER OF CEREBELLUM a branched tree(tree of vital-arbor vitae) in sagittal (longitudinal) section. Neurohistology Staining White matter(myelinated fibers) luxol - fast blue White matter(myelinated fibers) – Weigert(black) Grey Matter of Spinal Cord • Grey matter has a butterfly like shape, located in the inner part of spinal cord and consists of neuron and unmylinated nerve fibers. • The anterior horn contains mostly of multipolar neurons with large polygonal nucleus and large perikaryon and dendrites containing Nissl bodies. Nissl bodies- these regions consist rough endoplasmic reticulum and other polysomes White Matter of Spinal Cord • White matter of spinal cord located in the outer part of spinal cord and consists of bundles of axons having specific functions either motor or sensory for example pain, touch.