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When viewed at a position along the positive z-axis, the ¼ turn from the positive x-to the positive y-axis is counter-clockwise. For left-handed coordinates, the above description of the axes is the same, except using the left hand; and the ¼ turn is clockwise. Interchanging the labels of any two axes reverses the handedness.
The reason for the clockwise standard for most screws and bolts is that supination of the arm, which is used by a right-handed person to tighten a screw clockwise, is generally stronger than pronation used to loosen. Sometimes the opposite (left-handed, counterclockwise, reverse) sense of threading is used for a special reason.
This corresponds to a counterclockwise twist for the right forearm and a clockwise twist for the left (when viewed superiorly). In the forearm, this action is performed by pronator quadratus and pronator teres muscle .
The muscle is inserted onto the radial sesamoid bone of the metacarpophalangeal joint. It acts to flex, adduct, and abduct the thumb, and is therefore also able to oppose the thumb. The superficial head is innervated by the median nerve, while the deep head is innervated by the ulnar nerve (C8-T1). [6]
In these dances the follower's right arm is normally used to lead a turn (most commonly by the leader's left arm, but sometimes by the leader's right arm when a cross-hand or "handshake" position is used), an inside turn is normally a left (counter-clockwise) turn, while an outside turn is a right (clockwise) turn.
The metacarpophalangeal joints (MCP) are situated between the metacarpal bones and the proximal phalanges of the fingers. [1] These joints are of the condyloid kind, formed by the reception of the rounded heads of the metacarpal bones into shallow cavities on the proximal ends of the proximal phalanges. [1]
The terms are derived from the Latin words for "left" (sinister) and "right" (dexter). Other disciplines use different terms (such as dextro-and laevo-rotary in chemistry, or clockwise and anticlockwise in physics) or simply use left and right (as in anatomy). Relative direction and chirality are distinct concepts.
Examples of a pivot joint include: Proximal radioulnar joint; Distal radioulnar joint; Median atlanto-axial joint; In contrast, spherical joints (or ball and socket joints) such as the hip joint permit rotation and all other directional movement, while pivot joints only permit rotation.