{"id":3477,"date":"2020-12-29T12:47:54","date_gmt":"2020-12-29T11:47:54","guid":{"rendered":"https:\/\/meddists.com\/learn\/pre-clinical\/anatomy\/upper-limb\/bones\/radius-and-ulna\/"},"modified":"2021-11-30T19:42:13","modified_gmt":"2021-11-30T17:42:13","slug":"radius-and-ulna","status":"publish","type":"page","link":"https:\/\/meddists.com\/learn\/pre-clinical\/anatomy\/upper-limb\/bones\/radius-and-ulna\/","title":{"rendered":"Radius and ulna"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\"><div class=\"intro\">The radius and ulna are two parallel bones found in the forearm.<\/div><\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><a href=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/02\/radius_ulna.png\" target=\"_blank\" title=\"Radius and ulna\"><img decoding=\"async\" src=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/02\/radius_ulna-463x600.png\" alt=\"\" class=\"wp-image-23852\"\/><\/a><figcaption><strong>The radius and ulna<\/strong> (Credit: OpenStax, CC BY-SA 4.0)<\/figcaption><\/figure><\/div>\n\n\n<span class=\"block-heading\" id=\"header_1\">\n<h3 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Description<\/h3>\n<\/span><span class=\"block-content\" id=\"contents_1\">\n\n\n<p class=\"wp-block-paragraph\">In an anatomical presentation (when the hands are extended and the palm is facing the viewer) the radius is lateral and the ulna is medial.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">They are inverse in measures, resulting from the position of the head: the radius is small proximally (head) and large distally, while the ulna is large proximally and small distally (head).<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">These two bones articulate with the humerus at the elbow joint and with the carpal bones at the wrist joint. They can be divided into <strong>proximal ends<\/strong>, <strong>middle parts,<\/strong>&nbsp;and <strong>distal ends<\/strong>.<\/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 title1\">Proximal ends<\/h3>\n<\/span><span class=\"block-content\" id=\"contents_2\">\n\n<\/span><span class=\"block-heading\" id=\"header_3\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">Radius<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_3\">\n\n\n<p class=\"wp-block-paragraph\">The <strong>proximal end of the radius<\/strong>&nbsp;consists of:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>The <strong>head<\/strong>, a thick disc-shaped structure with a concave circular superior surface that articulates with the capitulum. Medially, it articulates with the <strong>radial notch<\/strong> on the <strong>proximal end of the ulna<\/strong>.<\/li><li>The <strong>neck<\/strong>, a short and narrow cylinder of bone that lies between the previous and following structure of the radius.<\/li><li>The <strong>radial tuberosity<\/strong>, a large blunt projection on the medial surface of the radius with a <strong>roughened surface<\/strong> for the insertion of the biceps brachii tendon.<\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_4\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">Ulna<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_4\">\n\n\n<p class=\"wp-block-paragraph\">The <strong>proximal end of the ulna<\/strong> is much larger than the radial one, consists of:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>The <strong>olecranon<\/strong>, a large projection of bone that articulates with the trochlea through the <strong>trochlear notch<\/strong>. It has a large roughened impression on its superior surface for the insertion of the triceps brachii muscle. The posterior surface is shaped triangularly, forming the <strong>\u201ctip of the elbow\u201d<\/strong>.<\/li><li>The <strong>coronoid process<\/strong>, an anterior projection that helps to form the <strong>trochlear notch<\/strong>.<ul><li>It presents the <strong>radial notch<\/strong>, which articulates with the head of the radius. Inferior to this, there is a fossa that allows the radial tuberosity to move during pronation and supination. The posterior margin of this fossa presents the <strong>supinator crest<\/strong>.<\/li><li>The <strong>tuberosity of the ulna<\/strong> is found on the anterior surface of the coronoid process and allows the insertion of the brachialis muscle.<\/li><\/ul><\/li><\/ul>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><a href=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/02\/elbow_joint3.png\" target=\"_blank\" title=\"Radius and ulna\"><img decoding=\"async\" src=\"https:\/\/meddists.com\/wp-content\/uploads\/2020\/02\/elbow_joint3-600x489.png\" alt=\"\" class=\"wp-image-23864\"\/><\/a><figcaption><strong>Medial view of the left elbow joint<\/strong><\/figcaption><\/figure><\/div>\n\n\n<\/span><span class=\"block-heading\" id=\"header_5\">\n<h3 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Middle parts<\/h3>\n<\/span><span class=\"block-content\" id=\"contents_5\">\n\n\n<p class=\"wp-block-paragraph\">The middle parts of the radius and ulna consist of their shafts.<\/p>\n\n\n<\/span><span class=\"block-heading\" id=\"header_6\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">Radius<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_6\">\n\n\n<p class=\"wp-block-paragraph\">The shaft of the radius is a triangular continuation of the radial tuberosity and neck, has <strong>three borders<\/strong> (anterior, posterior, and interosseous) and <strong>three surfaces<\/strong> (anterior, posterior, and lateral).<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>In the superior third, the <strong>oblique line of the radius<\/strong>, belonging to the anterior border, crosses the shaft diagonally from medial to lateral.<\/li><li>The posterior border can be detected only in its middle third.<\/li><li>Linking both parallel bones, the <strong>interosseous membrane<\/strong> attaches to the sharp interosseous border.<\/li><li>Its anterior and posterior surfaces are smooth, while the lateral one presents an <strong>oval roughening<\/strong> for the attachment of the pronator teres.<\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_7\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">Ulna<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_7\">\n\n\n<p class=\"wp-block-paragraph\">Similar to the radius, the shaft of the ulna is a triangular continuation of its large proximal end with three borders and three surfaces (anterior, posterior, and <strong>medial<\/strong>).<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>The anterior border is smooth, while the posterior one is sharp and can be palpable.<\/li><li>Linking both parallel bones, the <strong>interosseous membrane<\/strong> attaches to the sharp interosseous border.<\/li><li>Its anterior surface presents a <strong>prominent linear roughening<\/strong> for the attachment of the <strong>pronator quadratus muscle<\/strong>.<\/li><li>The medial surface is smooth, while the posterior one is rough for the attachment of different muscles.<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Besides, a thin <strong>interosseous membrane<\/strong> connects the radius (medially) and the ulna (laterally), providing space for blood vessels to pass into both compartments of the forearm and more support, without restricting pronation and supination movements between these two bones.<\/p>\n\n\n<\/span><span class=\"block-heading\" id=\"header_8\">\n<h3 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title1\">Distal ends<\/h3>\n<\/span><span class=\"block-content\" id=\"contents_8\">\n\n<\/span><span class=\"block-heading\" id=\"header_9\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">Radius<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_9\">\n\n\n<p class=\"wp-block-paragraph\">The <strong>distal end<\/strong>, which is broad and flattened anteroposteriorly.<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Its anterior and posterior surfaces are wide, while the medial and lateral surfaces are narrow.<\/li><li>The anterior surface is smooth; the posterior surface has a <strong>large dorsal tubercle<\/strong>, acting as an anchor (pulley) for the <strong>extensor pollicis longus muscle<\/strong>.<\/li><li>The medial surface has a prominent facet, the <strong>ulnar notch<\/strong>, which articulates with the head of the ulna; and the lateral surface projects distally as a <strong>radial styloid process<\/strong>.<\/li><li>It has two <strong>articular facets<\/strong> that articulate with the <strong>scaphoid<\/strong> and <strong>lunate carpal bones<\/strong>.<\/li><\/ul>\n\n\n<\/span><span class=\"block-heading\" id=\"header_10\">\n<h4 class=\"wp-block-heading\" class=\"wp-block-heading\" class=\"title_collection title2\">Ulna<\/h4>\n<\/span><span class=\"block-content\" id=\"contents_10\">\n\n\n<p class=\"wp-block-paragraph\">The <strong>distal end<\/strong>, which is small, has a rounded<strong> head<\/strong>:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Its anterolateral and distal parts are covered by <strong>articular cartilage<\/strong>.<\/li><li>From its posteromedial aspect, the cone-shaped <strong>ulnar styloid process<\/strong> appears to project distally.<\/li><li>The ulna does not participate in the wrist joint.<\/li><li>A <strong>radio-ulnar joint<\/strong> forms between the ulna (lateral articular surface of the head) and the radius (ulnar notch).<ul><li>A triangular, fibrous <strong>articular disc<\/strong> separates this joint from the wrist joint, having points of attachment in both bones.<\/li><li>A <strong>synovial membrane<\/strong>, covered by a <strong>fibrous capsule<\/strong>, covers this joint externally.<\/li><\/ul><\/li><\/ul>\n<\/span><div id=\"the_titles\" style=\"display:none;\"><h3 class=\"wp-block-heading\" class=\"wp-block-heading\">Description<\/h3><h3 class=\"wp-block-heading\" class=\"wp-block-heading\">Proximal ends<\/h3><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Radius<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Ulna<\/h4><h3 class=\"wp-block-heading\" class=\"wp-block-heading\">Middle parts<\/h3><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Radius<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Ulna<\/h4><h3 class=\"wp-block-heading\" class=\"wp-block-heading\">Distal ends<\/h3><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Radius<\/h4><h4 class=\"wp-block-heading\" class=\"wp-block-heading\">Ulna<\/h4><\/div>","protected":false},"excerpt":{"rendered":"<p>Description In an anatomical presentation (when the hands are extended and the palm is facing the viewer) the radius is lateral and the ulna is medial. They are inverse in measures, resulting from the position of the head: the radius is small proximally (head) and large distally, while the ulna is large proximally and small [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":5854,"menu_order":4,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-3477","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>Radius and ulna &#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\/anatomy\/upper-limb\/bones\/radius-and-ulna\/\" \/>\n<meta name=\"twitter:label1\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data1\" content=\"4 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\\\/anatomy\\\/upper-limb\\\/bones\\\/radius-and-ulna\\\/\",\"url\":\"https:\\\/\\\/meddists.com\\\/learn\\\/pre-clinical\\\/anatomy\\\/upper-limb\\\/bones\\\/radius-and-ulna\\\/\",\"name\":\"Radius and ulna &#8211; 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