THE MUSCLES OF THE ANTERIOR COMPARTMENT OF FOREARM AND FLEXOR RETINACULUM
LEARNING OBJECTIVES
At the end of the lecture, the student should be able to:
q Describe the muscles of forearm.
q Tell the nerve supply of these muscles.
q Explain actions of the muscles of anterior compartment of forearm.
q Describe attachment and functions of flexor retinaculum
MUSCLES OF THE ANTERIOR COMPARTMENT OF FOREARM
Arranged in two Groups.
q Superficial Group of Muscles.
q Deep Group of Muscles.
SUPERFICIAL MUSCLES
q Pronator teres.
q Flexor carpi radialis.
q Flexor digitorium superficials.
q Palmaris longus.
q Flexor carpi ulnaris.
DEEP MUSCLES
q Flexor digitorium profundus.
q Pronator quaradatus.
q Flexor pollicis longus.
SUPERFICIAL MUSCLES
Have a common origin.
Arise from anterior surface of medial epicondyles.
Three have additional origin also i.e.
Pronator teres,
flexor carpi radials,
flexor digitorium superficials.
PRONATOR TERES
Origin :
A. LARGE SUPERFICIAL HEAD:
1. Common origin.
2. Supra condylar ridge.
B. SMALL DEEP HEAD:
From medial border of the coronoid process of ulna just distal to the tubercle on it.
Insertion :
By flat tendon into the middle of lateral surface of shaft of radius at its most prominent part of its outward convexity.
PRONATOR TERES
NERVE SUPPLY:
Muscular branches of
median nerve.
PRONATOR TERESACTION:
q Pronates the forearm.
q Weak flexor of elbow
FLEXOR CARPI RADIALIS
ORIGIN:
q Common origin.
q Fleshy turn in to long tendon.
q Grooves trapezium.
INSERTION :
On the bases of 2nd and 3rd metacarpals.
NERVE SUPPLY:
median nerve.
FLEXOR CARPI RADIALIS
Actions:
q Flexor and radial abductor of the wrist.
q It is stabilizer of the wrist
FLEXOR DIGITORIUM SUPERFICIALIS
ORIGIN:
q Common origin
q Medial ligament of the elbow.
q Tubercle of the coronoid process of ulna (sublime tubercle).
q Fibrous arch continues the origin across the radius from whole length of anterior oblique line.
Insertion:
q Enters the fibrous flexor sheath.
q divides in two halves
q attached to the margins of the front of the middle phalanges.
FLEXOR DIGITORIUM SUPERFICIALIS
Nerve supply: Median nerve(7,8).
Action: flexor of proximal interphalangeal joints, metacarpophalangeal joints, wrist joint and assists in flexion of elbow.
PALMARIS LONGUS
ORIGIN:
q Common origin.
q Broadens as it passes flexor retinaculum to which it is partially adherent.
q It slits to form longitudinally directed fibers.
Action:
q weak flexor of wrist.
q Anchors the skin and fascia of hand.
FLEXOR CARPI RADIALIS
ORIGIN:
q common origin.
q Wide apponeurosis from the medial border of olecronon process and subcutaneous border of ulna.
q Ulnar nerve lies between humeral and ulnar head.
INSERTION:
q on the pisiform and end by the pisohamate and pisometacarpal ligament into the hamate and 5th metacarpal.
FLEXOR CARPI RADIALIS
NERVE SUPPLY:
Ulnar nerve (C7,8).
ACTION:
It is flexor and ulnar adductor of wrist.
Deep muscles
FLEXOR DIGITORIUM PROFUNDUS
ORIGIN:
• Medial surface of the olecronon.
• Upper three quarters of anterior and medial surface of ulna (including its subcutaneous border and interosseus membrane).
• Tendon of the index finger separates in the forearm.
INSERTION:
• At the base of terminal phalanges of fingers.
NERVE SUPPLY:
• Anterior interosseus branch of median nerve and ulnar nerve
(C 8,T1 little finger side).
ACTION:
• Flexes terminal interphalangeal joint.
• Great gripping muscle.
FLEXOR POLICIS LONGUS
ORIGIN:
Anterior surface of the of the radius below the oblique line and above the insertion of Pronator quaradatus and from interosseus membrane. Tendon forms on ulnar side.
• Passes underneath the flexor retinaculum.
INSERTION:
• at the base of first distal phalanx.
NERVE SUPPLY:
• Anterior interosseus branch of median nerve (C6,7).
ACTION:
• Flexor of interphalangeal joint of thumb.
• Also flexes metacarpophalangeal joint and carpometacarpophalangeal joints of thumb and wrist joint.
PRONATOR QUARADATUS
ORIGIN:
• From a ridge on anterioromedial aspect of ulna.
INSERTION:
• Anterior surface of lower fourth of radius and triangular area above ulnar notch.
PRONATOR QUARADATUS
NERVE SUPPLY:
Anterior interosseus branch of median nerve.
ACTION:
Pronates the forearm and help to hold lower end of radius and ulna together.
FLEXOR RETINACULUM
§ Strong fibrous band.
§ Lies across the carpus bones at proximal part of hand.
§ ATTACHED TO THE,
§ Hook of hamate and pisiform medially.
§ Tubercle of the scaphoid and ridge of trapezium laterally.
• As carpal bones are concave so flexor retinaculum forms carpal tunnel.
• Median nerve and long flexor tendons pass through the capal tunnel.
• Superficialis tendon pass through in two separate rows, middle and ring fingers in frontof the index and Little fingers tendons.
CARPAL TUNNEL SYNDROME.
• Median nerve pass deep between flexor digitorium superficialis flexor carpi radialis when it is liable to compression causing carpal tunnel syndrome.