ANATOMY & PHYSIOLOGY A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z                    HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site humerus Posterior (I) and anterior (II) view of the right humerus. Illustration: Gray's Anatomy The long bone of the upper arm of humans and other tetrapod vertebrates. The humerus extends from the scapula, or shoulder-blade, where it articulates at the glenoid cavity, to the elbow. A notch, called the olecranon cavity, on the posterior roughened end of the humerus, provides the point of articulation for the ulna, one of the bones of the forearm. Detailed anatomy The head of the humerus at the proximal end forms slightly less than a sphere. Its articular surface covered by hyaline cartilage faces upwards, inwards and slightly backwards. The curvature of the head is not reciprocal to that of the glenoid cavity. This means that only a small area of the head is in contact with the scapula at any one time. The anatomical neck is the slight constriction just behind the head. The surgical neck is the first narrowing on the shaft below the expanded proximal end. The lesser tubercle projects forwards from just beyond the anterior part of the anatomical neck. The greater tubercle is the most lateral part of the proximal humerus, producing the rounded contour of the shoulder. The shaft of the humerus is roughly cylindrical proximally, becoming triangular distally. About mid-way down the shaft on the lateral aspect is a rough area, the deltoid tuberosity. Curving around the posterior aspect of the upper half of the shaft is the spiral groove. The distal expanded end of the humerus carries articular surfaces for the ulna and radius and attachments (the epicondyles) for the forearm muscles. Laterally and anteriorly the capitulum forms a small hemisphere, articulating with the discoid radial head. Anteriorly in the middle third of the distal expansion the pulley-shaped trochlea articulates with the trochlear notch of the ulna. The medial third is formed into the medial epicondyle, the common origin of the flexors of the forearm. Depressions are present in the anterior aspect, above the trochlea and capitulum for the ulna (coronoid fossa) and above the capitulum for the radius (radial fossa). Similarly a depression is present above the trochlea on the posterior aspect for the olecranon process of the ulna (olecranon fossa). Related category    • ANATOMY AND PHYSIOLOGY Source: Faculty of Medicine, Memorial University of Newfoundland Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP