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The basic quantities describing a sphere (meaning a 2-sphere, a 2-dimensional surface inside 3-dimensional space) will be denoted by the following variables r {\displaystyle r} is the radius, C = 2 π r {\displaystyle C=2\pi r} is the circumference (the length of any one of its great circles ),
The forearm is the region of the upper limb between the elbow and the wrist. [1] The term forearm is used in anatomy to distinguish it from the arm, a word which is used to describe the entire appendage of the upper limb, but which in anatomy, technically, means only the region of the upper arm, whereas the lower "arm" is called the forearm.
The brachioradialis is a muscle of the forearm that flexes the forearm at the elbow. [1] [2] It is also capable of both pronation and supination, depending on the position of the forearm. [2] It is attached to the distal styloid process of the radius by way of the brachioradialis tendon, and to the lateral supracondylar ridge of the humerus.
The olecranon is situated at the proximal end of the ulna, one of the two bones in the forearm. [1] When the hand faces forward the olecranon faces towards the back (posteriorly). It is bent forward at the summit so as to present a prominent lip which is received into the olecranon fossa of the humerus during extension of the forearm. [2] [3]
De Quervain syndrome causes pain over the styloid process of the radius. [3] [4] This is due to the passage of the inflamed extensor pollicis brevis tendon and abductor pollicis longus tendon around it. [4] [5] The styloid process of the radius is a useful landmark during arthroscopic resection of the scaphoid bone. [6]
Like the extensor digiti minimi (i.e. the extensor of the little finger), the tendon of the extensor indicis runs and inserts on the ulnar side of the tendon of the common extensor digitorum. [2] The extensor indicis lacks the juncturae tendinum interlinking the tendons of the extensor digitorum on the dorsal side of the hand.
The ability to pronate the manus (hand) and forearm in therian mammals is achieved by a rounded head of the radius, which allows it to swivel across the ulna. Supination requires a dorsal glide of the distal radius and pronation a palmar glide in relation to the distal ulna.
The radial artery arises from the bifurcation of the brachial artery in the antecubital fossa.It runs distally on the anterior part of the forearm. There, it serves as a landmark for the division between the anterior and posterior compartments of the forearm, with the posterior compartment beginning just lateral to the artery.