{"id":3046,"date":"2020-12-13T21:20:18","date_gmt":"2020-12-13T19:20:18","guid":{"rendered":"https:\/\/meddists.com\/learn\/pre-clinical\/histology\/neurohistology\/introduction\/peripheral-nerve-layers\/"},"modified":"2021-03-01T00:25:29","modified_gmt":"2021-02-28T23:25:29","slug":"peripheral-nerve-layers","status":"publish","type":"page","link":"https:\/\/meddists.com\/learn\/pre-clinical\/histology\/nervous-system\/introduction\/peripheral-nerve-layers\/","title":{"rendered":"Peripheral nerve layers"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">The nerves at the periphery originate from spinal and cranial nerves, they are arranged in a manner very similar to skeletal muscles &#8212; the functional unit (spinal nerve for instance) can be further down divided into<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Epineurium &#8212; Outer layer<\/li><li>Perineurium &#8212; Middle layer<\/li><li>Endoneurium &#8212; Inner layer<\/li><\/ul>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><a href=\"http:\/\/meddists.com\/wp-content\/uploads\/2019\/01\/1319_Nerve_StructureN1.jpg\" target=\"_blank\" title=\"Peripheral nerve layers\"><img decoding=\"async\" src=\"http:\/\/meddists.com\/wp-content\/uploads\/2019\/01\/1319_Nerve_StructureN1-502x600.jpg\" alt=\"\" class=\"wp-image-8613\"\/><\/a><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Layers of peripheral nerves<\/strong> &#8212; OpenStax &#8212; CC BY-SA 4.0<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Epineurium<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Dense irregular connective tissue binding fascicles to form a common bundle<\/li><li>Contains blood vessels to feed the nerve tissue<ul><li>These blood vessels penetrate into the nerve, but usually, do not reach the endoneurium<\/li><\/ul><\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Perineurium<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Specialized connective tissue around each fascicle<\/li><li>Consists of layers of <strong>perineurial cells<\/strong><ul><li>Squamous cells with basal lamina on both surfaces and tight junctions<\/li><li>Can contract (contain actin filaments)<\/li><li>Typically, 1-2 layers, but in larger nerves, up to 6 layers may be present<\/li><\/ul><\/li><li>Helps form the <strong>blood-nerve barrier<\/strong><ul><li>The blood-nerve barrier is formed by the <strong>tight junctions of the blood vessel endothelium<\/strong>, and the perineurial cells<\/li><\/ul><\/li><li>Typically, no immune cells except mast cells and macrophages are present at this layer<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Endoneurium<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Loose connective tissue around each nerve fiber<\/li><li>Cannot be seen with a normal light microscope<\/li><li>Cells located within &#8212; only fibroblasts, mast cells, macrophages for repair<\/li><li>Metabolite exchange is done through simple diffusion (as mentioned above, this region is poorly vascularized)<\/li><\/ul>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><a href=\"http:\/\/meddists.com\/wp-content\/uploads\/2019\/01\/1319B_Nerve_Mag1.jpg\" target=\"_blank\" title=\"Peripheral nerve layers\"><img decoding=\"async\" src=\"http:\/\/meddists.com\/wp-content\/uploads\/2019\/01\/1319B_Nerve_Mag1-600x291.jpg\" alt=\"\" class=\"wp-image-8614\"\/><\/a><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Endoneurium and perineurium&nbsp;<\/strong>&#8212; OpenStax &#8212; CC BY-SA 4.0<\/p>\n<div id=\"the_titles\" style=\"display:none;\"><\/div>","protected":false},"excerpt":{"rendered":"<p>The nerves at the periphery originate from spinal and cranial nerves, they are arranged in a manner very similar to skeletal muscles &#8212; the functional unit (spinal nerve for instance) can be further down divided into Epineurium &#8212; Outer layer Perineurium &#8212; Middle layer Endoneurium &#8212; Inner layer Layers of peripheral nerves &#8212; OpenStax &#8212; [&hellip;]<\/p>\n","protected":false},"author":23,"featured_media":0,"parent":3028,"menu_order":6,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-3046","page","type-page","status-publish","hentry"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v28.0 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Peripheral nerve layers &#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\/peripheral-nerve-layers\/\" \/>\n<meta name=\"twitter:label1\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data1\" content=\"2 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\\\/peripheral-nerve-layers\\\/\",\"url\":\"https:\\\/\\\/meddists.com\\\/learn\\\/pre-clinical\\\/histology\\\/nervous-system\\\/introduction\\\/peripheral-nerve-layers\\\/\",\"name\":\"Peripheral nerve layers &#8211; 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