The palmaris brevis - named from its position in the palm of the hand, and its small size - is a small quadrilateral sheet.

 

Origin

The front of the lower part of the anterior annular ligament above its middle ; and the adjacent part of the palmar fascia at the inner edge of its great central division.

Insertion

The deep surface of the skin and the subcutaneous fat, along the ulnar border of the upper part of the palm.

Structure

Arising by fleshy and short tendinous fibres, this muscle passes in ttransverse fascicuh to its insertion, which is of a similar character to its origin, it belongs to that type of muscle of which the panniculus carnosus in the lower animals is the best example, and lies in the subcutaneous tissue superficial 0 the deep fascia like the platysma myoides and the superficial muscles of the ace.

Nerve-supply

From the inner cord of the brachial plexus (through the first horacic nerve), by filaments from the superficial division of the ulnar nerve which inter the muscle upon its deep aspect near its upper border.

Action

It draws the skin and the superficial fascia of the ulnar border of the hand towards the middle line of the palm, forming a deep dimple or groove upon the upper part of the ulnar border of the hand, and at the same time raising the soft parts into a prominent vertical ridge, the object of which appears to be to prevent the ulnar nerve and artery from being pressed upon when a hard substance is grasped by the hand. It also helps to deepen the cup- shaped hollow when the palm is used to convey fluid to the mouth.

Relations

Superficially, the skin ; deeply, the hypothenar fascia, which separates it from the abductor and flexor brevis minimi digiti, the ulnar vessels and nerve.

Variations

This muscle may be entirely absent.

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