Extensors

The extensor carpi radialis longus (eks-ten'sor kar-pi' ra"de-a'lis long'gus) runs along the lateral side of the forearm, connecting the humerus to the hand. It extends the hand at the wrist and assists in abducting the hand (figs. 9.31 and 9.32).

The extensor carpi radialis brevis (eks-ten'sor kar-pi' ra"de-a'lis brev'is) is a companion of the extensor carpi radialis longus and is located medially to it. This muscle runs from the humerus to metacarpal bones and extends the hand at the wrist. It also assists in abducting the hand (figs. 9.31 and 9.32).

The extensor carpi ulnaris (eks-ten'sor kar-pi' ul-na'ris) is located along the posterior surface of the ulna and connects the humerus to the hand. It extends the hand at the wrist and assists in adducting it (figs. 9.31 and 9.32).

The extensor digitorum (eks-ten'sor dij"i-to rum) runs medially along the back of the forearm. It connects the humerus to the posterior surface of the phalanges and extends the fingers (figs. 9.31 and 9.32).

A structure called the extensor retinaculum consists of a group of heavy connective tissue fibers in the fascia of the wrist (fig. 9.31). It connects the lateral margin of the radius with the medial border of the styloid process of the ulna and certain bones of the wrist. The retinaculum gives off branches of connective tissue to the underlying wrist bones, creating a series of sheathlike compartments through which the tendons of the extensor muscles pass to the wrist and fingers.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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