{"id":3047,"date":"2020-12-13T21:20:18","date_gmt":"2020-12-13T19:20:18","guid":{"rendered":"https:\/\/meddists.com\/learn\/pre-clinical\/histology\/neurohistology\/introduction\/meninges\/"},"modified":"2020-12-13T21:58:11","modified_gmt":"2020-12-13T19:58:11","slug":"meninges","status":"publish","type":"page","link":"https:\/\/meddists.com\/learn\/pre-clinical\/histology\/nervous-system\/introduction\/meninges\/","title":{"rendered":"Meninges"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">The structures of the CNS (brain and spinal cord) are covered by several layers of connective tissue; collectively, these connective tissue layers and the spaces between them are referred to as <strong>meninges<\/strong>.<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><a href=\"http:\/\/meddists.com\/wp-content\/uploads\/2018\/02\/Brain_layers.jpg\" target=\"_blank\" title=\"Meninges\" target=\"_blank\" rel=\"noreferrer noopener\"><img decoding=\"async\" src=\"http:\/\/meddists.com\/wp-content\/uploads\/2018\/02\/Brain_layers.jpg\" alt=\"\" class=\"wp-image-2137\"\/><\/a><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Layers of the scalp, skull and brain<\/strong> &#8212;&nbsp;Katie Ahlers &#8212; CC BY-SA 4.0<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The meninges show slight differences in the brain and spinal cord &#8212; we will point them out at each stage.<\/p>\n\n\n<span class=\"block-heading\" id=\"header_1\">\n<h3 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">Pia mater<\/h3>\n<\/span><span class=\"block-content\" id=\"contents_1\">\n\n\n<p class=\"wp-block-paragraph\">The pia mater covers the brain and spinal cord.<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Soft and delicate<\/li><li>Vascular<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Pia mater is located right above the cerebral\/cerebellar cortex, with a subpial space and a thin layer of&nbsp;<strong>glia limitans<\/strong> (see <a href=\"https:\/\/meddists.com\/course\/neurohistology\/lessons\/neuroglial-cells-of-the-cns\/\">Neuroglial cells of the CNS<\/a> lesson) separating them &#8212; thus, pia mater <strong>does not<\/strong> come in direct contact with nerve bodies or fibers.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Pia mater contains collagen fibers (especially collagen type III &#8211;&nbsp;<strong>reticular fibers<\/strong>), elastic fibers and fibroblasts of mesenchymal (mesoderm) origin.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In the spinal cord, pia mater forms triangular extensions called&nbsp;<strong>denticulate ligaments<\/strong>.&nbsp;There are 21 pairs of them, and they function as mechanical support to prevent over-rotation of the spinal cord.<\/p>\n\n\n<\/span><span class=\"block-heading\" id=\"header_2\">\n<h3 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">Arachnoid mater<\/h3>\n<\/span><span class=\"block-content\" id=\"contents_2\">\n\n\n<p class=\"wp-block-paragraph\">The arachnoid covers the pia mater, with a small gap in between &#8212; the subarachnoid space.<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Soft but tougher than pia mater<\/li><li>Loose<\/li><li>Non-vascular<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Arachnoid mater consists of two parts &#8212; a part that forms a spider-web like loosely arranged projections (<strong>trabeculae<\/strong>) that extend to the pia mater through the subarachnoid space, and another part forming a sheet which comes in contact with the dura mater.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Arachnoid mater is derived from the same tissue as the pia mater and they are continuous with each other, and often considered as a single unit &#8212; <strong>pia-arachnoid<\/strong>, also known as&nbsp;<strong>leptomeninges<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The contents of the arachnoid mater are essentially the same as pia mater (collagen, elastic fibers, fibroblasts).<\/p>\n\n\n<\/span><span class=\"block-heading\" id=\"header_3\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title3\">Sub-arachnoid space<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_3\">\n\n\n<p class=\"wp-block-paragraph\">The subarachnoid space is the space formed between the pia mater and the arachnoid mater &#8212; it contains CSF, arachnoid projections (trabeculae) and blood vessels.<\/p>\n\n\n<\/span><span class=\"block-heading\" id=\"header_4\">\n<h3 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">Dura mater<\/h3>\n<\/span><span class=\"block-content\" id=\"contents_4\">\n\n\n<p class=\"wp-block-paragraph\">The dura mater covers the arachnoid mater.<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Thick and tough<\/li><li>Fibroelastic &#8212; dense, irregular connective tissue<\/li><li>Non-vascular<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Dura mater is made from two sublayers &#8212; an outer periosteal (attached to the bone) and an inner meningeal (attached to the arachnoid mater).<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In the skull, the two sublayers are fused, while in the spinal cord they are separated by a space &#8212; the <strong>epidural space<\/strong>, which contains loose connective tissue and a venous plexus. The epidural space is a frequent site of anesthetic injections.<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><a href=\"http:\/\/meddists.com\/wp-content\/uploads\/2019\/01\/Epidural_Anesthesia1.png\" target=\"_blank\" title=\"Meninges\" target=\"_blank\" rel=\"noreferrer noopener\"><img decoding=\"async\" src=\"http:\/\/meddists.com\/wp-content\/uploads\/2019\/01\/Epidural_Anesthesia1-600x360.png\" alt=\"\" class=\"wp-image-8697\"\/><\/a><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Meningeal layers in the spinal cord<\/strong> &#8212;&nbsp;Blausen.com staff (2014) &#8212; CC BY-SA 4.0<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><a href=\"http:\/\/meddists.com\/wp-content\/uploads\/2019\/01\/Layers_of_the_scalp_and_meninges1.png\" target=\"_blank\" title=\"Meninges\"><img decoding=\"async\" src=\"http:\/\/meddists.com\/wp-content\/uploads\/2019\/01\/Layers_of_the_scalp_and_meninges1-600x600.png\" alt=\"\" class=\"wp-image-8696\"\/><\/a><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Meningeal layers in the brain&nbsp;<\/strong>&#8212;&nbsp;Frank Gaillard &#8212; CC BY-SA 4.0<\/p>\n\n\n<\/span><span class=\"block-heading\" id=\"header_5\">\n<h2 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Demonstration<\/h2>\n<\/span><span class=\"block-content\" id=\"contents_5\">\n\n\n<p class=\"wp-block-paragraph\">Usually, we can only see the remnants of the meninges. Since they are rich in reticular fibers, we can use silver impregnation techniques showing them in black, or&nbsp;Masson trichrome which will show them in blue\/green.<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><a href=\"http:\/\/meddists.com\/wp-content\/uploads\/2019\/01\/cerebellum_pia.png\" target=\"_blank\" title=\"Meninges\"><img decoding=\"async\" src=\"http:\/\/meddists.com\/wp-content\/uploads\/2019\/01\/cerebellum_pia-300x222.png\" alt=\"\" class=\"wp-image-8580\"\/><\/a><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Pia mater in the cerebellum (black arrow),&nbsp; H&amp;E<\/strong> &#8212; Adapted from the work of&nbsp;Michael Bonert &#8212; CC BY-SA 4.0<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><a href=\"http:\/\/meddists.com\/wp-content\/uploads\/2019\/01\/Screenshot_5.png\" target=\"_blank\" title=\"Meninges\"><img decoding=\"async\" src=\"http:\/\/meddists.com\/wp-content\/uploads\/2019\/01\/Screenshot_5-300x172.png\" alt=\"\" class=\"wp-image-8581\"\/><\/a><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Pia mater in the cerebellum (red arrow), reticular fibers are shown in black, silver impregnation<\/strong>&nbsp;&#8212; Adapted from the work of Berkshire Community College &#8212; CC BY-SA 4.0<\/p>\n<\/span><div id=\"the_titles\" style=\"display:none;\"><h3 class=\"wp-block-heading\" class=\"wp-block-heading\">Pia mater<\/h3><h3 class=\"wp-block-heading\" class=\"wp-block-heading\">Arachnoid mater<\/h3><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Sub-arachnoid space<\/h4><h3 class=\"wp-block-heading\" class=\"wp-block-heading\">Dura mater<\/h3><h2 class=\"wp-block-heading\" class=\"wp-block-heading\">Demonstration<\/h2><\/div>","protected":false},"excerpt":{"rendered":"<p>The structures of the CNS (brain and spinal cord) are covered by several layers of connective tissue; collectively, these connective tissue layers and the spaces between them are referred to as meninges. Layers of the scalp, skull and brain &#8212;&nbsp;Katie Ahlers &#8212; CC BY-SA 4.0 The meninges show slight differences in the brain and spinal [&hellip;]<\/p>\n","protected":false},"author":23,"featured_media":0,"parent":3028,"menu_order":7,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-3047","page","type-page","status-publish","hentry"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.8 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Meninges &#8211; Meddists<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/meddists.com\/learn\/pre-clinical\/histology\/nervous-system\/introduction\/meninges\/\" \/>\n<meta name=\"twitter:label1\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data1\" content=\"3 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/meddists.com\\\/learn\\\/pre-clinical\\\/histology\\\/nervous-system\\\/introduction\\\/meninges\\\/\",\"url\":\"https:\\\/\\\/meddists.com\\\/learn\\\/pre-clinical\\\/histology\\\/nervous-system\\\/introduction\\\/meninges\\\/\",\"name\":\"Meninges &#8211; 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