Muscles and fascias of hand (draw transverse section), tendon sheaths, carpal canal

Muscles of the hand

The muscles of the hand can be divided into three main groups; Thenar muscles, Hypothenar muscles, and muscles of the middle space which are the lumbricals and interossei muscles.

Thenar muscles

1.Abductor pollicis brevis muscle originates form the tuberculum of the scaphoid bone and the retinaculum of the flexor muscle. It inserts onto the base of the proximal phalanx of the thumb. Its main function is the abduction of the thumb and is innervated by the median nerve.

2.Flexor pollicis brevis muscle has two heads the superficial and deep head. It originates from the capitate and trapezoid carpal bones and the retinaculum of the flexor muscle. It inserts onto the lateral part of proximal phalax of the thumb. Its main function is flexion of the metacarpophalangeal joint of the thumb and thumb abduction and opposition. The superficial head is innervated by the median nerve and the deep head is innervated by the ulnar nerve.

3.Musculus opponens pollicis originates from the tuberculum of the trapezius and the retinaculum of the flexor muscle. It inserts onto the metacarpal. The main function is the opposition of the thumb and it is innervated by the median nerve.

4.Adductor pollicis muscle consists of two heads the oblique head and the transverse head. The oblique head originates form the base of the 2nd and 3rd metacarpals. The transverse head originates at the 3rd metacarpal, both heads insert onto the metacarpophalangeal joint of the thumb. Its main function is for the adduction thumb and its innervated by the deep ulnar nerve.

Hypothenar muscles

1.Palmaris brevis muscle originates from the palmar aponeurosis of the ulnar side and inserts onto the skin. It is innervated by the superficial ulnar nerve.

2.Abductor digiti minimi originates from the pisiform bone and the tendon of flexor carpi ulnaris. It inserts at the base of the proximal phalanx of 5th digit. Its main function is the abduction of the 5th digit and it is innervated by the deep ulnar nerve.

3. Flexor digiti minimi brevis originates from the hook of hamate and inserts to the base of the proximal phalanx of the 5th digit. Its main function is the flexion of the metacarpophalangeal joint of the 5th digit and is innervated by the deep ulnar nerve.

4. Musculus opponens digiti minimi originates at the hook of hamate and inserts at the 5th metacarpal. It is usually founs below the abductor digiti minimi and the flexor digiti minimi brevis. Its main function is the addcution oof the 5th digit and is innervated by deep ulnar nerve.

Lumbrical muscles

There are four lumbricals in each hand, each originating from the tendon of the flexor digitorum profundus and insert aponeurosis of each digit. The 2 medial are innervated by the ulnar and 2 lateral by the medial nerve. The main function is the extension of interphalangeal joints and the flexion of the metacarpophalangeal joint.

Interossei muscles

They are found between the metacarpals and are divided into two groups;

1.Dorsal interossei are four muscles, they are attached to the lateral and medial surface of the adjacent metacarpal bones which are facing each other and inset onto the dorsal aponeurosis and base of the proximal phalanx of the finger. Their main function is abduction of the finger away from each other and they are innervated by the deep ulnar nerve.

2.Palmar interossei originate at the 2nd, 4th and 5th metacarpal bases facing the 3rd digit. They insert at the aponeurosis and the proximal phalanx of the associated fingers. Their main function is the adduction of the fingers towards the 3rd digit and they are innervated by the deep ulnar nerve.

Carpal tunnel

Carpal tunnel is a passageway at the forearm to the osteofascisal space at the middle of the palm. It is formed by the deep carpal arch and the flexor retinaculum, more specifically the carpal bones are the dorsal, ulnar and radial borders while the flexor retinaculum is the ventral border.

Contents

The carpal tunnel consists of nine flexor tendons and the median nerve;

1. Ulnarly the 4 tendons of the flexor digitorum superficialis and 4 tendons of the flexor digitorum profundus, are both surrounded by a single synovial sheath. Also the tendon of the flexor pollicis longus in its synovial sheath and the median nerve

2.Radially the flexor carpi radialis tendon with its synovial sheath.