2015-2016 ANATOMY OF THE FOREARM

The forearm is the structure and distal region of the upper limb, between the elbow and the wrist. The forearm is covered by skin, the anterior surface usually being less hairy than the posterior surface.

The forearm contains two long bones, the radius and the ulna, forming the radio-ulnar joint. The interosseous membrane connects these bones.

THE SKIN-SENSORY NERVE SUPPLY FROM the anterior and posterior branches of the lateral cut.n.of the forearm,A continuation of the musculocutaneous n. FR0M the anterior and posterior branches of the medial cut.branches of the forearm. ANARROW strip of the skin down the middle of the posterior surface is supplied by the posterior cut.n. of the fore arm.

THE SKIN –SUPERFICIAL VEINS The superficial veins lies in the superficial fascia . THE CEPHALIC VEIN arises from the lateral side of the dorsal venous arch on the back of the hand and winds around the lateral border of the forearm . It ascend into the cubital fossa and up the front of the arm on the lateral side of the biceps . It terminate in the axillary vein. As it ascend up ,it receives a variable numbers of tributaries from the lateral and posterior surfaces of the limb.

THE SKIN –SUPERFICIAL VEINS THE MEDIAN CUBITAL VEIN a branch of the cephalic vein in the cubital fossa, run ward and medially and joins the basilic vein.

THE SKIN –SUPERFICIAL VEINS The basilic vein arise from the medial side of the dorsal venous arch on the back of the hand and winds around the medial border of the forearm. It ascend into the cubital fossa and up the front of the arm on the medial side of the biceps . It terminate by joining the venae comitantes of the brachial artery to form the axillary vein. As it ascend up ,it receives a variable numbers of tributaries from the lateral and posterior surfaces of the limb.

THE SUPERFICIAL LYMPHATIC VESSELS From the thumb and lateral fingers and lateral areas of the hand and forearm follow the cephalic vein to the infra-clavicular group of nodes. Those from the medial fingers and medial areas of the hand and forearm follow the basilic vein to the cubital fossa . Here ,some drain into the supratrochlear L.N. other to the lateral group of the axillary nodes .The efferant vessels from the supratrochlear node also drain into the lateral group of the axillary nodes

FASCIAL COMPARTMENT OF THE FOREARM The forearm is enclosed in a sheath of deep fascia which is attached to the periosteum of the posterior subcutaneous border of the ulna. This fascial sheath together with the interosseous membrane and fibrous intermuscular septa divides up the forearm into a number of compartments each having its own muscles,nerves and blood supply.

In cross-section the forearm can be divided into two fascial compartments. The posterior compartment contains the extensors of the hands, which are supplied by the radial nerve. The anterior compartment contains the flexors, and is mainly supplied by the median nerve. The ulnar nerve also runs the length of the forearm

The interosseous membrane of the forearm (rarely middle or intermediate radioulnar joint) is a fibrous sheet that connects the radius and the ulna. It is the main part of the radio-ulnar syndesmosis, a fibrous joint between the two bones. The interosseus membrane divides the forearm into anterior and posterior compartments, serves as a site of attachment for muscles of the forearm, and transfers forces from the radius, to the ulna, to the humerus. As the forearm moves from Pronation to Supination the Interosseous membrane fibres change from a relaxed state, then become tense in the neutral position and then once again become relaxed as the forearm enters Supination.

Radius head neck radial tuberosity styloid process Ulna coronoid process olecranon process ulnar tuberosity slyloid process Interosseous Membrane

CONTENTS OF THE ANTERIOR FASCIAL COMPARTMENT Muscles in the Anterior Compartment of the Forearm are split into three categories: Superficial Intermediate Deep

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SUPERFICIAL COMPARTMENT The superficial muscles in the anterior compartment are the flexor carpi ulnaris, palmaris longus, flexor carpi radialis and pronator teres. They all originate from a common tendon, which arises from the medial epicondyle of the humerus

FLEXOR CARPI ULNARIS Attachments: Originates from the medial epicondyle with the other superficial flexors. It also has a long origin from the ulna which springs from the medial aspect of the olecranon process of the ulna and the posterior border of the ulna . It passes into the wrist, and attaches to the pisiform carpal bone. Actions: Flexion and adduction at the wrist. Innervation: Ulnar nerve.

PALMARIS LONGUS This muscle is absent is about 15% of the population. Attachments: Originates from the medial epicondyle, attaches to the flexor retinaculum of the wrist. Actions: Flexion at the wrist. Innervation: Median nerve.

FLEXOR CARPI RADIALIS Attachments: Originates from the medial epicondyle. Insertion: attaches to the base of metacarpals II and III. Actions: Flexion and abduction at the wrist. Innervation: Median nerve.

PRONATOR TERES The lateral border of the pronator teres forms the medial border of the cubital fossa, an anatomical triangle located over the elbow. Attachments: It has two origins, one from the medial epicondyle, and the other from medial border of the coronoid process of the ulna. It attaches laterally to the mid-shaft of the radius. Actions: Pronation of the forearm. Innervation: Median nerve.

THE SUPERFICIAL MUSCLES OF THE ANTERIOR FOREARM THE SUPERFICIAL MUSCLES OF THE ANTERIOR FOREARM. INTERMEDIATE COMPARTMENT It can sometimes be classed as a superficial muscle, but in most cadavers it lies between the deep and superficial muscle layers. The muscle is a good anatomical landmark in the forearm – the median nerve and ulnar artery pass between its two heads, and then travel posteriorly. Attachments: It has two heads – one originates from the medial epicondyle of the humerus, the other from the radius from oblique lineon the anterior surface of the radial shaft.

Innervation: Median nerve. Insertion:The muscle splits into four tendons at the wrist, which travel through the carpal tunnel behind the flexor retinaculum, and attache to the middle phalanges of the four fingers. On reaching the proximal phalandes each tendon split into two slips ,these two then unite and the tendon finally divideds again into two slips which are inserted into the sides of the middle phalanx .the corresponding tendon of the flexor digitorum profundus pass through the division of each superficialis tendon and is inserted into the base of the distal phalanx. Actions: Flexes the metacarpophalangeal joints and proximal interphalangeal joints at the 4 fingers, and flexes at the wrist. Innervation: Median nerve.